Electron Transfer in Biological Systems

An Innovation is something original, new and important in whatever field that breaks the market or society. The driving force behind much of the recent boom in biology science is technological development. There are immense diversity and rapid evolution of technologies with relevance to (or impact on) the life sciences enterprise. Nanotechnology, Biotechnology synergistic combination create novel opportunities for scientists, industrialists and researchers to explore the aspects of biological and chemical diversity that cannot be accessed through natural mechanisms or processes. In the beginning of the 21st century, scientific discovery and its understanding is playing an important role in meeting the challenges-related to environment, human health, economic conditions, effecting societies everywhere. Indeed it is reasonable to say that we are entering the age of Biology. To meet the changing societal and environmental needs, improve the quality of human life, promoting health, preventing diseases and ensuring adequate food possibility of new energy sources, Genetic engineering and biotechnology plays a vital role as biological agent making it potent or damaging. The threat of old infectious diseases is persisting where, these diseases are the second largest killers in the world. In addition to this the new emerging diseases are posing serious problems. New communicable diseases and drug-resistant infectious diseases are also increasing. Because of sedentary life, diseases like diabetes, cardiovascular diseases, obesity is now the leading cause of death in developing and industrial World. An average of one new infectious disease and twenty drug-resistant diseases are appearing every year. In addition to that some old diseases such as cholera, Tuberculosis, chikungunya, yellow fever etc., reappeared. More than 1100 epidemics have identified. About 75% of emerging pathogens are zoonotic. Current infection risks are NDM-1-an enzyme that can make a variety of bacteria resistant to most drugs, many forms of influenza- (H5N1) avian flu such as Mutant avian flu is produced intentionally-a bio weapon. New problems may come from unregulated synthetic biology laboratories of the future. Future use of genetic data software and Nanotechnology will help to detect and treat disease and the genetic or molecular level. With all multifaceted problems in the world today, there is a need of imperative innovations in biological sciences. This book describes the updates on the methodologies and recent trends in Biological Research, challenges and opportunities. The book will help postgraduate students and researchers to explore the recent research and techniques in Biological Sciences which help them to reach their objectives and goals.

Multi-step electron transfer is increasingly recognized as a means for moving charge in biological systems over long distances rapidly. Many postulated multi-step mechanisms rely on the formation of organic radicals (amino-acid radicals, nucleobase radicals) as intermediate electron or ?hole? carriers. In this thesis, the multi-step mechanism for electron transfer in both proteins and DNA is investigated. These two systems form a natural complement; the role of electron transfer in DNA with regard to lesion repair is still unknown, as are the electron transfer events in the proteins that mediate the repair. Rhenium-labeled mutant Pseudomonas aeruginosa azurins serve as model systems for this phenomenon in proteins. The photo-active rhenium label in these azurins can be oxidized by a flash/quench reaction to provide a potent oxidant capable of generating a variety of radicals in the protein matrix. Three mutants (with one tryptophan residue each) were constructed to investigate the effect of tryptophan radicals on charge transfer in proteins. The properties of tryptophan radicals in three protein environments have been investigated; including a kinetically stable tryptophan radical that persists for more than 5 hrs at room temperature. The variation in these radicals plays a significant role in their effect on the oxidation of the remote copper center in azurin. The stable radical greatly reduces the rate of electron transfer from copper relative to the rhenium-labeled wild-type analogs, while another radical plays no role in copper oxidation. In order to examine multi-step electron transfer in DNA, a series of photo-active ruthenium and rhenium-thymine complexes were constructed. By attaching the metal complexes at the sugar of the deoxyribonucleic acid, they were incorporated into DNA strands by solid-state synthetic techniques. Two different ruthenium-labeled DNA strands were produced in this way; one with a single guanine base and one with two side by side guanine bases. The strand containing a guanine-guanine sequence showed formation of a guanine radical by EPR under flash/quench conditions, while the strand containing a single guanine remained EPR silent. These strands represent an excellent template to examine a system which may or may not exhibit multi-step charge transfer.

Photosynthesis is frequently represented as an interaction between outputs of NADPH and ATP from light reactions and their use in CO2 fixation via the CBB cycle, or dark reactions. However, the action of light energy in photosynthesis is to drive a redox reaction. Redox reactions involve a change in the oxidation states of atoms with a reduction of one chemical and a complementary oxidation of another through the transfer of electrons. Photosynthesis uses the products of the redox reaction, but if these are not utilized, which may occur under high light conditions, then reactive oxygen species (ROS) can form and damage cell contents and tissues. Control of the photosynthesis system has components that operate to reduce excess redox reactions whilst maintaining competence for CO2 fixation in conditions of fluctuating light flux. This involves processes protecting against damage from high light flux and the repair of damage that does occur. Control around PSII involves both reduction of transfer of light excitation to PSII through action involving protective pigments and damage of PSII itself, which reduces electron flow, and is gradually repaired. Control around PSI through cyclical electron flow is an essential component because its action produces ATP even though linear electron flow (from PSII) is reduced and this ATP may be essential for the repair process of PSII. Control of photosynthesis does not achieve homeostasis in CO2 fixation, or an optimum rate; it protects and repairs both the light and dark cycle systems.

Byline: T. Srinivasan Introduction Electrons are one of the fundamental particles postulated in physics and one of the early evolutes after the big bang, when universe started to expand and evolve into galaxies and star systems. Electrons exist in all matter, both as bound electrons and as free electrons. In biological systems, electrons play an important role in oxidation-reduction reactions.[sup][1] In this small book, Szent–Gyorgyi has argued that a biologist deals normally with three levels of living systems, namely, macroscopic, microscopic, and molecular levels. The last and the most important level is the most subtle too and is the electronic level. At this level, we look for electronic exchanges that take place at the subatomic plane. Electronic configurations at this level provide many faceted properties to the cells. He recalls his ideas in this area as follows: “The main actors of life had to be electrons whereas the clumsy and unreactive protein molecules had to be the stage on which the drama of life was enacted” (1, p. 5). This fascinating and insightful statement made in the early part of last century was received with scepticism; in fact, it presupposed many later discoveries and was thus much ahead of its time. He goes on to state that “Taking out electrons irreversibly is killing” (1, p. 18). The above narration by a leading scientist provides a basis for investigating electron transfer mechanism in biology. For life to emerge, certain conditions are required one of them being maintenance of low entropy (increasing negentropy). It should be noted that increase in entropy signifies increased disorder in a system, while the term negentropy signifies a measure of order. The system should be able to absorb energy from the environment and provide a negentropic milieu for sustenance of life processes. It is said that in the energy cycle within an organism, electrons are passed from hydrocarbons to oxygen.[sup][2] This energy cycle is the driving mechanism for maintaining life processes in cells. At present, a great deal work is taking place on redox imbalances in the body. Redox is a chemical reaction in which the oxidation states of atoms are changed. We know, for example, that oxidation (losing an electron) of a biomolecule could results in many health problems. Further, reactive oxygen species along with reactive nitrogen species are considered as one of the major contributing factors for oncogenesis or cancer production. It is said that “Oxidative stress induces a cellular redox imbalance which has been found to be present in various cancer cells compared with normal cells; the redox imbalance thus may be related to oncogenic stimulation.”[sup][3] Further, it is observed that unremitting inflammation is one of the basic problems related to acute as well as chronic diseases. Research in this area suggests that effects of inflammation could be reduced through earthing the body.[sup][4] This is a simple procedure, connecting the body to the ground which is a rich source of electrons. On grounding the body, electrons find an easy path to enter the body and perhaps able to neutralize the oxidative stress. Water is a major electron provider inside the body and let us reviews what has been reported so far in the role of water in health and disease. Water has a major role to play in all living systems. In the body, liquid water seems to display as charged particles and coherent domains (CD) are established through trapping of specific electromagnetic frequencies. …

Open AccessCCS ChemistryRESEARCH ARTICLES22 Oct 2022Decrypting the Influence of Axial Coordination on the Electronic Microenvironment of Co-N5 Site for Enhanced Electrocatalytic Reaction Bingyu Huang†, Senhe Huang†, Chenbao Lu, Longbin Li, Judan Chen, Ting Hu, Dirk Lützenkirchen-Hecht, Kai Yuan, Xiaodong Zhuang and Yiwang Chen Bingyu Huang† Institute of Polymers and Energy Chemistry (IPEC), College of Chemistry and Chemical Engineering, Nanchang University, Nanchang 330031 , Senhe Huang† Themeso-Entropy Matter Lab, School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240 , Chenbao Lu Themeso-Entropy Matter Lab, School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240 , Longbin Li Institute of Polymers and Energy Chemistry (IPEC), College of Chemistry and Chemical Engineering, Nanchang University, Nanchang 330031 , Judan Chen Institute of Polymers and Energy Chemistry (IPEC), College of Chemistry and Chemical Engineering, Nanchang University, Nanchang 330031 , Ting Hu School of Materials Science and Engineering, Nanchang University, Nanchang 330031 , Dirk Lützenkirchen-Hecht Faculty of Mathematics and Natural Sciences-Physics Department, Bergische Universität Wuppertal, Wuppertal D-42119 , Kai Yuan *Corresponding authors: E-mail Address: [email protected] E-mail Address: [email protected] E-mail Address: [email protected] Institute of Polymers and Energy Chemistry (IPEC), College of Chemistry and Chemical Engineering, Nanchang University, Nanchang 330031 , Xiaodong Zhuang *Corresponding authors: E-mail Address: [email protected] E-mail Address: [email protected] E-mail Address: [email protected] Themeso-Entropy Matter Lab, School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240 and Yiwang Chen *Corresponding authors: E-mail Address: [email protected] E-mail Address: [email protected] E-mail Address: [email protected] Institute of Polymers and Energy Chemistry (IPEC), College of Chemistry and Chemical Engineering, Nanchang University, Nanchang 330031 Institute of Advanced Scientific Research (iASR), Key Lab of Fluorine and Silicon for Energy Materials and Chemistry of Ministry of Education, Jiangxi Normal University, Nanchang 330022 https://doi.org/10.31635/ccschem.022.202202241 SectionsSupplemental MaterialAboutAbstractPDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareFacebookTwitterLinked InEmail Metal porphyrins are star molecules that possess well-defined coordination metal centers for versatile catalytic reactions. However, most previous work has focused on the correlations between in-plane symmetric configuration of metal-N4 sites and their catalytic performance. Addressing the catalytic contribution of additional axial coordination to such symmetric configuration remains a challenge. Theoretical calculations revealed that axially anchoring an extra pyridine on the tetra-coordinated cobalt porphyrin (Co-N4) to construct penta-coordinated cobalt porphyrin (Co-N5) renders cobalt a higher electron density, thereby favoring the rate-determining O2 adsorption/activation and reducing the oxygen electroreduction barrier. Therefore, a well-defined Co-N5 site is rationally introduced into the azo-linked polymer framework for a fundamental structure–catalytic performance correlation study. As-prepared Co-N5 catalyst exhibits a 26 mV positive shift in half-wave potential compared with the pyridine-free Co-N4 counterpart, discloses a markedly higher power density (141.4 mW cm−2), and possesses better long-term durability (over 160 h cycles) in a Zn-air battery. Moreover, such a Co-N5 catalyst also showcases potential applications for CO2 reduction with high CO2-to-CO conversion faradic efficiency and better selectivity than the Co-N4 counterpart because coordination of the fifth pyridine evokes electronic localization that suppresses a competitive side reaction. This work proves the positive electrocatalytic contribution of axial penta-coordination on well-defined metal-porphyrin-based catalysts and offers atomic understanding of the structure–performance correlation on single atom catalysts for future catalyst design. Download figure Download PowerPoint Introduction Currently, many advanced electrocatalysts have been developed to facilitate the sluggish kinetics of the multiple-electron transfer process in energy conversion reactions, such as the oxygen reduction reaction (ORR) and CO2 reduction reaction (CO2RR).1–4 Due to maximized atom utilization, mainstream research has focused on the isolated transition metal/nitrogen coordinated (M-N-C) single-atom catalysts (SACs) with high catalytic activity and selectivity.5–9 Despite extensive investigations, the rational design and controllable and precise synthesis of M-N-C catalysts continues to be the main obstacle to multiple-electron transfer processes.10–12 The preparation of M-N-C catalysts normally needs high-temperature pyrolysis to increase the graphitization degree for better conductivity.13–17 Unfortunately, the pyrolysis process inevitably evokes metal aggregation due to the thermal decomposition of metal precursors and high surface energy of single metal atoms, posing challenges for maintaining atomic-metal isolation.13,18,19 The inhomogeneity and indistinction of the catalytic environment of carbonaceous materials give rise to tremendous difficulties in simultaneously enhancing the catalysts' activity and selectivity. In addition, the inherently less-defined active sites formed after pyrolysis leaves an ambiguous structure–performance relationship and seriously precludes us from exploring the in-depth mechanism for different electrocatalytic reactions.20–24 Therefore, the above-mentioned challenges stimulate the vigorous search for developing cost-effective and high-performance pyrolysis-free electrocatalysts with well-defined active sites. Transition-metal macrocycles, such as cobalt porphyrins, which possess the distinct tetra-coordinated cobalt porphyrin (Co-N4) site, have been heavily studied.25–28 Benefitting from the production of fewer radical oxygen species during the electrocatalytic process, the Co-N4 structure is more robust and advantageous for electrocatalysis of ORR.16,20,29–31 However, the representative plane-symmetric electron configuration of Co-N4 is not the optimal structure for the chemisorption and activation of reactants.32–34 Breaking the structure symmetry with penta-coordination to regulate the charge redistribution of Co-N4 sites could promote the electrocatalytic process, but the accurate synthesis of this structural motif is still a noteworthy challenge. Besides, the role of penta-coordination and the exact local microenvironment of such active sites have not yet been ascertained.35,36 In view of this, offering a model catalyst as an ideal platform is urgently required to elucidate the contribution of axial penta-coordination on catalytic activity, selectivity, and durability of Co-N4 sites. In this work, we probed the positive effect of axial pyridinic penta-coordinated cobalt porphyrin (Co-N5) to achieve optimized electronic localization on the Co-N5 site for boosting ORR through density functional theory (DFT) calculations as well as electrochemical analysis. DFT calculations indicate Co-N5 with axial pyridinic coordination possesses obviously higher electronic density on the Co center in comparison with Co-N4. Taking advantage of the electronic-push effect of penta-coordination, the ORR rate-determining step of O2 adsorption/activation can be significantly promoted, ensuring better ORR performance of Co-N5 than the Co-N4 model. Hence, we innovatively designed and synthesized an azo-linked polymer framework with atomically dispersed electron-rich Co-N5 sites for ORR through a pyrolysis-free axial-pyridinic coordination strategy. The Co-N5 catalyst displays impressive ORR performance with a more positive half-wave potential of 0.811 V and lower Tafel slope of 39 mV dec−1 than the Co-N4 counterpart (0.785 V and 50 mV dec−1), which support the theoretical predictions. Encouragingly, such a penta-coordination-induced electronic localization strategy also promises the potential for improving the CO2-to-CO conversion faradic efficiency and selectivity of electrocatalytic CO2 reduction. This work provides new design strategies toward well-defined single-atom electrocatalysts with axial coordination and offers new models for fundamentally understanding the catalytic mechanism of asymmetric coordination systems. Experimental Methods Synthesis of [email protected] catalysts First, 20 mg (27.3 μmol) of CoTAPP and 80 mg of G-py were redispersed in 20 mL of dimethyl sulfoxide (DMSO). Then, the mixture was stirred for 15 h to ensure CoTAPP was fully coordinated to G-py. Immediately after the coordination, 35.2 mg (0.11 mmol, 4 equiv to CoTAPP) of PhI(OAc)2 was added to the mixed solution, and the mixture was stirred for 24 h. The resultant precipitate was filtered and washed with DMSO, methanol, deionized water, and ethanol for three times, and dried at 60 °C overnight. [email protected] was harvested as a black powder (86.8 mg, 87% yield). [email protected] and [email protected] were prepared with a procedure similar to [email protected] Experimental details, materials characterization methods, and synthesis of other samples are available in the Supporting Information. Results and Discussion Theoretical calculations and catalytic mechanism Based on cobalt porphyrin, two models with different coordination environments, axial pyridinic Co-N5 model and Co-N4 model were designed (Figure 1a and Supporting Information Figure S1). The elementary steps and corresponding ORR adsorption configurations on the two models are presented in Supporting Information Figure S2. The Gibbs free energies at different potentials for all elementary steps were evaluated to illustrate how the penta-coordination affects intrinsic ORR activity. As given in Figure 1b, all elementary steps are distinctly downhill at U = 0 V, thus the reaction is exothermic and able to proceed spontaneously. When the potential rises to 1.23 V, the rate-determining step of Co-N4 is the first step (* + O2 + H2O + e− → *OOH + OH−) with a high energy barrier of 0.34 eV. In contrast, the final release step (*OH + e− → OH− + *) of the Co-N5 model is the rate-determining step, and its free energy can be distinctly reduced to only 0.26 eV. The thermodynamic limiting potentials, which represent the maximum potential to ensure all steps downhill are 0.97 and 0.89 V for Co-N5 and Co-N4 models, respectively (Figure 1c and Supporting Information Figure S3), revealed the Co-N5 model requires the minimum overpotential to drive the oxygen reduction. This result implies that the axial pyridine coordination plays a crucial role in regulating the ORR intermediates adsorption strength and decreasing the reaction barrier of the rate-determining step. Similarly, axial pyridine coordination can also alter the Fe electronic microenvironment, thereby enhancing the catalytic activity of the Fe-N5 model ( Supporting Information Figures S4–S7), further validating the universality of additional axial coordination. Figure 1 | (a) DFT calculation models of Co-N5 and Co-N4 for the electrochemically catalyzed ORR. (b) Free energy diagrams at U = 0 V and U = 1.23 V, and (c) free energy diagrams for the thermodynamic limiting potentials of Co-N5 model and Co-N4 model. (d) PDOS of Co atom for Co-N5 model (top) and Co-N4 model (bottom); the d-band center is denoted by the dashed gray line. Differential charge density distribution after O2 absorption on (e) Co-N5 model and (f) Co-N4 model. Download figure Download PowerPoint To further study axial coordination induced changes in the Co center's electronic configuration and interaction with oxygen-containing intermediates, projected density of states (PDOS) was conducted. The axial coordination obviously tunes the Co 3d orbital according to the PDOS in Figure 1d. The d-band center of the Co-N5 model at −1.59 eV is closer to the Fermi level than that of Co-N4 at −1.76 eV, thereby leading to an increase in O-containing intermediates' adsorption.37 The enhanced adsorption ensures subsequent ORR steps proceed through a more efficient four-electron pathway. Hence, the thermodynamic onset potentials improvement can be ascribed to fine-tuned adsorption strength of the ORR intermediates, which directly determines the activity and selectivity of catalysts. In addition, the higher PDOS near the Fermi level represents more abundant charge carriers and better electronic conductivity for the Co-N5 model. During the ORR process, the activated Co d orbitals and their hybridization with O p orbitals co-determine the adsorption strength for oxygen-containing adsorbates.38–42 After O2 adsorption and *OH formation, the increased overlapping degree of the strong σ-bond that originates from the Co dz2 orbital and O p orbital, along with the decreased O2 antibonding orbital filling degree that appears above the Fermi level for Co-N5 model, can be observed. It theoretically suggests that the extra fifth pyridine coordination assures a tighter connection between Co centers and O2 ( Supporting Information Figures S8 and S9), thus enabling higher ORR selectivity towards the four-electron pathway.43 As verified by charge density differences ( Supporting Information Figure S10), obvious asymmetrical charge distribution caused by axial coordination can be found for the Co-N5 model in comparison with the symmetric Co-N4 model. An apparent charge accumulation on the Co center is found to form the electron-rich Co-N5 site due to the electronic-push effect of axial pyridine. As expected, the O2 only absorbs on the individual Co center (Figure 1e,f), which can provide superior ORR electrocatalytic sites. Furthermore, the axial pyridine can construct an electronic pathway that renders adequate charge transfer to oxygen molecules from the conductive graphene layer. In general, the electron-rich Co-N5 site promises stable chemisorption and activation of O2, which facilitates O–O bond cleavage, thus offering better selectivity for the four-electron reduction pathway. Therefore, the axial-pyridine coordination-induced electronic localization strategy is viable to efficaciously enhance the ORR kinetics. Synthesis and structural characterization To experimentally confirm the calculation results and demonstrate the significance of penta-coordination architecture in ORR, an azo-linked penta-coordinated cobalt porphyrin-based polymer (CoTAPP-Azo) anchored on pyridine functionalized graphene (G-py) ([email protected]) was synthesized. The synthesis route and structure of [email protected] and the counterpart [email protected] (directly grown CoTAPP-Azo on pristine graphene) are schematically revealed in Figure 2a. Tetrakis(4-aminophenyl) porphyrin (TAPP) was first chelated with cobalt cation to obtain CoTAPP ( Supporting Information Figure S11). TAPP coordinating with Fe (FeTAPP) and Ni (NiTAPP) were also successfully obtained using the same procedure. The formation of CoTAPP, FeTAPP, and NiTAPP were confirmed by mass spectrometry ( Supporting Information Figure S12) and Fourier-transform infrared (FTIR) spectroscopy ( Supporting Information Figure S13). The successful pyridine functionalization in G-py was confirmed by thermogravimetric analysis ( Supporting Information Figure S14), Raman spectroscopy ( Supporting Information Figure S15), and X-ray photoelectron spectroscopy (XPS) ( Supporting Information Figure S16). Subsequently, CoTAPP was anchored on G-py through axial pyridine coordination; following an azo-coupling reaction, [email protected] was finally obtained (see details in Supporting Information Scheme S1). For comparison, FeTAPP-based polymer hybridized with G-py ([email protected]) and graphene ([email protected]) and NiTAPP-based polymer hybridized with G-py ([email protected]), were synthesized by similar routes. Figure 2 | (a) Synthetic route of CoTA[email protected]y and [email protected] (b) HAADF-STEM image of [email protected] (c) High-resolution Co 2p XPS spectra of [email protected] and [email protected] Download figure Download PowerPoint The morphology of [email protected] was first identified by scanning electron microscopy (SEM). Compared with the thin-layered sheet structure of G-py, a thicker layer was observed, indicating G-py was covered by CoTAPP-Azo ( Supporting Information Figures S17 and 18). The transmission electron microscopy (TEM) image of [email protected] also presented representative lamellar plate morphology ( Supporting Information Figure S18c). To further discern the structural features at the atomic level, high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) was carried out. HAADF-STEM images and the corresponding energy dispersive spectroscopy (EDS) of [email protected] indicated homogeneous spatial distribution of C, N, Co elements ( Supporting Information Figure S19). The abundant bright points (highlighted by red circles) offer direct evidence for the uniform distribution of single Co atoms (Figure 2b). Similarly, [email protected], [email protected], and [email protected] all exhibited similar lamella morphology with homogeneously distributed elements ( Supporting Information Figures S20–S22). The chemical structures of [email protected] were preliminarily examined by FTIR spectroscopy ( Supporting Information Figure S23). Compared with CoTAPP, the corresponding FTIR spectrum of [email protected] displayed a significant intensity increase of N=N stretching signals (1570 cm−1, 1215 cm−1) along with an obviously weakened N–H peak at 3400 cm−1, proving the successful polymerization of CoTAPP. The increased ID/IG ratio of 0.94 for [email protected] to 1.07 for [email protected] in the Raman spectra ( Supporting Information Figure S24) verifies surface lattice interference caused by penta-coordination. X-ray diffraction (XRD) confirmed that G-py was coated by CoTAPP-Azo, and the absence of crystalline cobalt species diffraction peaks demonstrated the highly dispersed state of Co atoms ( Supporting Information Figure S25), agreeing well with the HAADF-STEM observations. [email protected] and [email protected] both show similar XRD patterns ( Supporting Information Figures S26 and S27). Furthermore, XPS was extracted to unravel the nature of the chemical bonding of [email protected] and [email protected] ( Supporting Information Figures S28–S31). Compared with [email protected], the N 1s XPS spectrum for [email protected] displayed an obvious pyridinic N peak (398.3 eV, Supporting Information Figure S29). The C 1s XPS spectrum of [email protected] showed that the C–N peak shifts to higher binding energy (BE) than that of [email protected] (ΔBE = 0.4 eV), revealing the decreased electron density of C atom. In the Co 2p spectra (Figure 2c), [email protected] underwent a shift to lower BE for Co 2p3/2 (780.3 eV) and Co 2p1/2 (795.6 eV) peaks, relative to that of [email protected] (780.8 and 796.0 eV for Co 2p3/2 and Co 2p1/2, respectively), providing evidence for the electronic localization on the Co with penta-coordination.44,45 This result confirms that axial pyridine ligands act as channels between G-py and CoTAPP-Azo and boost the charge transfer from graphene to Co centers, which is consistent with the electron-rich Co-N5 model in theoretical calculations. Importantly, similar phenomena were found in [email protected] and [email protected], suggesting the universality of such an electron localization approach. The UV–vis spectrum of [email protected] revealed a clear porphyrin Soret band at 448 nm ( Supporting Information Figure S32). Interestingly, an appreciable peak change to 438 nm in [email protected] was observed due to the penta-coordination-induced electron transfer. Meanwhile, photoluminescence spectroscopy was conducted to explore the charge separation behaviors ( Supporting Information Figure S33). Significantly increased quenching occurred in [email protected] compared with [email protected], further demonstrating that axial pyridine can enhance the charge transfer between G-py and CoTAPP-Azo. The work function, which represents the minimum energy needed to draw one inner electron from the nucleus, was obtained by ultraviolet photoelectron spectroscopy. [email protected] showed a 0.51 eV shift to higher BE than [email protected] in the second electron cut-off edge ( Supporting Information Figure S34). Hence, with respect to 4.49 eV for [email protected], the smaller work function for [email protected] (3.98 eV) indicated that the electrons are more likely to be activated and transferred outward.46,47 We assessed the porosity of the samples by nitrogen physisorption isotherms ( Supporting Information Figure S35). [email protected] and [email protected] both displayed the typical type-IV isotherms with an evident hysteresis loop, indicative of the coexistence of micropores and mesopores. The Brunauer–Emmett–Teller specific surface areas for [email protected] and [email protected] were calculated to be 506.6 and 440.3 m²/g, respectively. Pore size distribution demonstrated by nonlocalized DFT showed the pore widths centered at 1.9 and 4.8 nm for [email protected] ( Supporting Information Figure S36). These results demonstrate the improved surface area and hierarchical porous structure of [email protected], which are conducive to increase the quantity of accessible active sites and enhance the mass transport. To investigate the local coordination environment of the Co center, X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) analyses were examined. The stronger white-line peak intensity of [email protected] (7727 eV) compared with [email protected] was assigned to the larger coordination number of the Co center for [email protected] than [email protected] (Figure 3a).48 The quantitative fits ( Supporting Information Table S1) showed a Co atom in [email protected] was straightforwardly connected by N atoms with a coordination number of 5.1 and the average bond length of 1.98 Å. From the Co K-edge Fourier-transformed EXAFS spectra (Figure 3b), the first shell peak for [email protected] around 1.43 Å corresponded to the Co–N scattering path, accompanying the absent Co–Co peak at 2.18 Å, jointly signifying the isolated Co atoms' configuration. [email protected] displayed an obviously positive shift for the Co–N first shell in than [email protected], suggesting an Co–N bond length caused by the to the EXAFS results (Figure and Supporting Information Figures and in to an of for [email protected], the first shell intensity for [email protected] was enhanced with an to revealing the larger number of N coordination The was also for the coordination In Figure the intensity maximum at for [email protected] was assigned to Co–N Co–Co and corresponding coordination was demonstrating the of the Co The shift of [email protected] maximum compared with that of CoTAPP is caused by the in [email protected] Hence, on and EXAFS as well as the XPS we that [email protected] by Co-N5 sites was successfully synthesized. Figure | (a) Co K-edge spectra and (b) the of Co K-edge EXAFS spectra of [email protected] with Co and CoTAPP as (c) The corresponding EXAFS of [email protected] model with Co N and C (d) of [email protected] in comparison with Co and CoTAPP. Download figure Download PowerPoint Electrocatalytic ORR performance To how axial penta-coordination affects ORR [email protected] and [email protected] were first evaluated with a In ( Supporting Information Figure significant peaks in for [email protected], but a peak was observed in The (Figure and Supporting Information Figure that [email protected] the ORR performance with the most positive half-wave potential of 0.811 V which is 26 mV more positive than that of [email protected] (0.785 V These results indicate that [email protected] possesses superior catalytic performance that from the electron localization caused by pyridine penta-coordination. in comparison with [email protected], the density for [email protected] was enhanced because the axial pyridine as between G-py and CoTAPP-Azo, thus boosting the charge transfer from graphene to CoTAPP layer. Figure 4 | (a) ORR of [email protected] and [email protected] catalysts at (b) Tafel (c) density by electrochemically active surface and (d) comparison of Tafel and for [email protected] and [email protected] catalysts. (e) The of [email protected] and [email protected] and after (f) and power density specific for Zn-air at and long-term performance of Zn-air at a density of using [email protected], [email protected], and as catalysts. Download figure Download PowerPoint To further into the reaction kinetics of [email protected], the at from to were ( Supporting Information Figure The ( Supporting Information Figure which were from at different potentials, revealed the toward the of Based on the the number for [email protected] was which with the This proves that the Co-N5 site a four-electron pathway towards ORR, [email protected] has a smaller of ( Supporting Information Figure We the enhanced ORR selectivity to the Co-N5 configuration that can be with because of the effect between Co and pyridinic the resultant O–O bond with stronger stretching is thus providing higher selectivity for four-electron ORR. [email protected] has a more positive than [email protected] ( Supporting Information Figures that ORR activity can be improved by microenvironment through extra axial penta-coordination on different metal Moreover, the Tafel slope of 39 mV dec−1 the process of [email protected] for oxygen reduction (Figure and Supporting Information Figure by the of electrochemical spectroscopy ( Supporting Information Figure the decreased in the for [email protected], indicating the optimized and electron toward ORR kinetics. In addition, [email protected] exhibited the electrochemically active surface area ( Supporting Information Figure which is conducive to more active sites. density with an in the ORR can be found (Figure the intrinsic activity for [email protected] For further comparison, the performance density Tafel density and for different electrocatalysts are (Figure and

The interactions and feedbacks among plants, animals, microbes, humans, and the environment ultimately form the world in which we live. This world is now facing challenges from a growing and increasingly affluent human population whose numbers and lifestyles are driving ever greater energy demand and impacting climate. These and other contributing factors will make energy and climate sustainability extremely difficult to achieve over the 20-year time horizon that is the focus of this report. Despite these severe challenges, there is optimism that deeper understanding of our environment will enable us to mitigate detrimental effects, while also harnessing biological and climate systems to ensure a sustainable energy future. This effort is advanced by scientific inquiries in the fields of atmospheric chemistry and physics, biology, ecology, and subsurface science - all made possible by computing. The Office of Biological and Environmental Research (BER) within the Department of Energy's (DOE) Office of Science has a long history of bringing together researchers from different disciplines to address critical national needs in determining the biological and environmental impacts of energy production and use, characterizing the interplay of climate and energy, and collaborating with other agencies and DOE programs to improve the world's most powerful climate models. BER science focuses on three distinct areas: (1) What are the roles of Earth system components (atmosphere, land, oceans, sea ice, and the biosphere) in determining climate? (2) How is the information stored in a genome translated into microbial, plant, and ecosystem processes that influence biofuel production, climate feedbacks, and the natural cycling of carbon? (3) What are the biological, geochemical, and physical forces that govern the behavior of Earth's subsurface environment? Ultimately, the goal of BER science is to support experimentation and modeling that can reliably predict the outcomes and behaviors of complex biological and environmental systems, leading to robust solutions for DOE missions and strategic goals. In March 2010, the Biological and Environmental Research Advisory Committee held the Grand Challenges for Biological and Environmental Research: A Long-Term Vision workshop to identify scientific opportunities and grand challenges for BER science in the coming decades and to develop an overall strategy for drafting a long-term vision for BER. Key workshop goals included: (1) Identifying the greatest scientific challenges in biology, climate, and the environment that DOE will face over a 20-year time horizon. (2) Describing how BER should be positioned to address those challenges. (3) Determining the new and innovative tools needed to advance BER science. (4) Suggesting how the workforce of the future should be trained in integrative system science. This report lays out grand research challenges for BER - in biological systems, climate, energy sustainability, computing, and education and workforce training - that can put society on a path to achieve the scientific evidence and predictive understanding needed to inform decision making and planning to address future energy needs, climate change, water availability, and land use.

Some redox chemistry and biochemistry of p-benzoquinones are summarised. In particular, the behaviour of quinols and quinones at electrode surfaces and in solution, together with the mechanism of reduction of soluble cytochrome c by quinols, produces a model of electron transfer relevant to biological systems. In such a model the biological transfers occur by collisional reactions of the quinone and quinol with the protein donors and acceptors. After collision, the detailed reactions occur via bound enzyme intermediates but electronic mobility between the donors and acceptors is provided by diffusional mobility of the quinone molecules. Such considerations have allowed a detailed investigation of the redox reactions of quinols with a complex biological multiprotein system, the bc complex. A probable mechanism of electron transfer into and through this complex is presented, together with some discussion of the mechanism of energy transduction which would operate in the intact biological system.

In 1998, computer scientist Ehud Shapiro returned to the Weizmann Institute in Rehovot, Israel, as a group leader after a five‐year break as a software entrepreneur. At the peak of the Internet boom, it would have been easy to find an exciting topic to pursue in computer science. Instead, Shapiro became interested in the origin of life and began to train himself in molecular biology, which eventually sparked his idea to build computers from biological molecules. His team first constructed a molecular Turing machine based on DNA, restriction nuclease and ligase to perform simple computations (Benenson et al , 2001), soon followed by a more sophisticated system that performs stochastic computations using mRNA molecules as input (Benenson et al , 2004). What seems merely to be the intellectual interest of an Israeli computer scientist—using biological compounds and systems to create logical circuits—has in fact become the hottest area in the biological sciences: synthetic biology. Other engineers are also dropping their soldering guns for micropipettes to rewire genes and genomes with the aim of reprogramming living organisms. “Synthetic biology is the other side of the coin of systems biology,” commented Victor de Lorenzo, Vice Director of the National Centre of Biotechnology in Madrid, Spain. “What you want is to create or recreate systems that have some properties of life from engineering principles.” This includes a range of techniques from recombinant cloning, to synthesizing genomes de novo , to creating completely new entities such as Shapiro's artificial systems. However, more interesting than the technology itself is the ability to create artificial metabolic and regulatory pathways and to test their viability in living systems. It allows scientists to probe the complexity of an organism's innards and thus derive further insights into how cells work. As George Church, Professor of Genetics at Harvard Medical School …

The search for a non-precious-metal based, oxygen reduction reaction (ORR) catalysts for fuel cells has grown due to rising prices of the catalysts used today which is derived from their scarcity. Although very active, platinum, which is considered to be the state-of-the-art catalyst for ORR, is not used in biological systems almost at all, especially not in processes which involve the catalysis of ORR. One of the reasons may be availability, another may be reaction selectivity. Instead, biological systems usually use transition metal complexes to catalyze such reactions. These are normally a part of an elaborate system of electron donors, electron acceptors and electron mediators, described in electron transfer chains and cycles. Since the beginning of the search for non-precious-metal catalyst, one family of catalysts has always been interesting as a possible candidate to replace precious metal catalysts – transition metal macrocycles (TMMs). This is due to the significant roles these macrocycles play in biological systems, which in many cases involve ORR catalysis.In the past years we have worked on the study of the interaction between various TMMs and redox active molecules known as electron donors in catalytic cycles. The interaction between quinones and other possible electron donors such as imidazoles and thiophenes have shown to enhance the ORR activity of TMMs. Figure 1 shows an RRDE measurement obtained with cobalt porphyrin (CoTPPS) interacting with hydroquinone on the surface of carbon electrode. In comparison to its ORR activity without the hydroquinone layer on the carbon (not shown), the CoTPPS’s half wave potential is shifted by more than 400mV to a more positive potential. This shift is attributed to the interaction with the electron donor.In this talk, we will present our most recent work on the study of the interaction between TMMs and electron donors and its effect on ORR electrocatalysis.

Light-driven conversion of chemical substances has attracted much attention with respect to the photogeneration of valuable chemicals and the photodegradation of pollutants. Covalent organic frameworks (COFs), which are crystalline porous polymers, have attracted much attention as novel platforms for photo-energy conversion materials because of their unique physiological properties, including their nano-porous structure, high design flexibility and visible light absorption. In addition, as COFs possess abundant hetero atoms with a lone electron pair, such as N, O and S, they can support metal atoms via coordination bonds and exhibit various functions originated from supported metals. For example, our group has recently demonstrated metal-doped COFs (M-COFs) exhibited various unique elctrocatalytic functions depending on the metal species. Cu- and Ni-doped COFs serve as the electrocatalysts for oxygen reduction reaction (ORR) [1] and carbon dioxide reduction (CRR) [2], respectively. In this study, we newly synthesized various metal-doped bipyridine-linked COFs (bpy-COF) and evaluated their photoelectrocatalytic activity. First, the details in the photo-induced charge transfer process were investigated using photoelectrochemical action spectrum, photoluminescence and in situ spectroscopy by employing the ORR mediated by Cu sites doped in bpy-COF (Cu-bpy-COF) as a model system. We subsequently attempted to expand metal-doped COFs as the photo electrocatalysts for CRR toward the application in artificial photosynthesis.First, we physically characterized our Cu-bpy-COF using various X-ray technics. The X-ray diffraction (XRD) pattern of Cu-bpy-COF exhibited a peak at 2q = 3.5° and 26.5°, which are assignable to (100) and (001), respectively. These XRD patterns indicated that the COFs have the microporous structure. The surface elemental composites calculated by X-ray photoelectron spectroscopy (XPS) shows that the atomic ratio of Cu atom was 1.8 %, and Cu/N ratio was 0.13. Then, we analyzed Cu-2p XPs and XANES spectra to determine the oxidation state of Cu atoms. The Cu 2p3/2 XPS peaks generated by Cu-bpy-COF at 932.7 eV corresponded to the Cu(II). The Cu K-edge XANES spectra show that the absorption edges of the Cu-bpy-COF were 8980 eV, which is similar to that of CuO. These results indicate that that the Cu(II) oxidation state was dominant in Cu-bpy-COF.Then, we investigated the photoelectrochemical ORR property of Cu-bpy-COF. The photocurrent was measured under the monochromated light. Interestingly, the value of the cathodic photocurrent corresponded with ORR was drastically increased by the deposition of Cu in bpy-COF. The incident-photon-to-current-efficiency (IPCE) was also calculated. The resulting IPCE for Cu-bpy-COF clearly corresponded to the absorption spectrum of Cu-bpy-COF. These results clearly indicate that the photocurrent was originated due to the photo absorption of Cu-bpy-COF. Then, we investigated the detailed electron transfer mechanism of Cu-bpy-COF in the presence of O2. Photoluminescence and gas-phase in situ X-ray absorption spectra show that the photo-excited electrons in the bpy-COF film were transferred to oxygen via the Cu atom. The remained holes in the valence band reached to the ITO electrode, generating the cathodic photocurrent. At the conference, we will also present the photoelectrocatalytic CO2 reduction reactions (CRR) using M-COF for the application toward artificial photosynthesis.Reference:[1] K.Iwase, T.Yoshioka, S.Nakanishi, K.Hashimoto, K.Kamiya, Angew. Chem. Int. Ed. 2015, 54, 11068-11702.[2] P.Su, K Iwase, T.Harada, K.Kamiya, S.Nakanishi., Chemical Science. 2018, 9, 3941-3947.[3] K.Dey, M.Pal, K.C.Rout, S.Kunjattu, A.Das, R.Mukherjee, U.K.Kharul, R. Banerjee. J. Am. Chem. Soc. 2017, 139, 13083-13091.

Early-career researchers: answering the most important scientific questions of our time.

Currently, about 80% of chemical and biological science research in the world is claimed by the discipline of biochemistry. The major reason for this lion share is that biochemistry forms a strong foundation on which stands the whole model of all biological and medical sciences. That is why the spectrum of teaching and research activity in biochemistry embraces large number of fields such as molecular biology, food and nutrition, cell biology, microbiology, toxicology, immunology, agriculture, veterinary science, botany, zoology, medicine and many others. So much so that the hierarchy of evolution of life on earth from a-biotic to biotic environment is traced back and interpreted in terms of systematic construction of biomolecules such as fatty acids and lipids, amino acids and proteins, sugars and carbohydrates from inorganic compounds. All these dimensions of biochemistry highlight the importance of this discipline in the world particularly in the developing countries; the major reference for this article is to examine the current directions of research in these countries and suggest a future road map that will target the present and future problems encountered by them. The enquiry reveals that most of the experts in developing countries undertake research that leads to publication in journals of international repute with high impact factor without examining its utility on the soil where it is being conducted. This type of research is usually the basic research which cannot be conducted without involvement of highly expensive machines and instruments. The developing countries, in the first instance, lack requisite capital to purchase these necessities. Many purchase them on loan through bi-lateral agreements or knock the doors of some international aid disbursing organizations. The net result is that research activity keeps going without its utility in solving the national problems. What actually required is a research targeted at national problems to offer appropriate solutions and that is the applied research. Thus the enquiry was lodged in the light of published results of the attempts of different research groups of author to examine the following dimensions of the problem stricken areas to identify what appropriate research projects the experts in the developing world should undertake to target their national problems to seek appropriate solutions: Disposal of wastewaters: sewage, garbage, industrial effluents with a target of cleanliness of environment. Techno-economic disposal of agricultural waste. Techno-economic disposal of solid waste. Rationalization of the use of oriental/traditional medicines on scientific. Production of the products of micro-organisms to dispose of waste and extract along with that the economic benefits. Indigenous production of plant and animal enzymes to reduce import under national substitution policy. Microbial leaching of ores and minerals for indigenous production of highly expensive metals such as uranium, etc. Preservation of foodstuffs such as raw vegetables and fruits for off-season use and avoiding their spreading in the environment to cause a large number of environmental problems. Preservation of foodstuffs such as raw vegetables and fruits for off-season use and avoiding their spreading in the environment to cause a large number of environmental problems. Currently, about 80% of chemical and biological science research in the world is claimed by the discipline of biochemistry. The major reason for this lion share is that biochemistry forms a strong foundation on which stands the whole model of all biological and medical sciences. That is why the spectrum of teaching and research activity in biochemistry embraces large number of fields such as molecular biology, food and nutrition, cell biology, microbiology, toxicology, immunology, agriculture, veterinary science, botany, zoology, medicine and many others. So much so that the hierarchy of evolution of life on earth from a-biotic to biotic environment is traced back and interpreted in terms of systematic construction of biomolecules such as fatty acids and lipids, amino acids and proteins, sugars and carbohydrates from inorganic compounds. All these dimensions of biochemistry highlight the importance of this discipline in the world particularly in the developing countries; the major reference for this article is to examine the current directions of research in these countries and suggest a future road map that will target the present and future problems encountered by them. The enquiry reveals that most of the experts in developing countries undertake research that leads to publication in journals of international repute with high impact factor without examining its utility on the soil where it is being conducted. This type of research is usually the basic research which cannot be conducted without involvement of highly expensive machines and instruments. The developing countries, in the first instance, lack requisite capital to purchase these necessities. Many purchase them on loan through bi-lateral agreements or knock the doors of some international aid disbursing organizations. The net result is that research activity keeps going without its utility in solving the national problems. What actually required is a research targeted at national problems to offer appropriate solutions and that is the applied research. Thus the enquiry was lodged in the light of published results of the attempts of different research groups of author to examine the following dimensions of the problem stricken areas to identify what appropriate research projects the experts in the developing world should undertake to target their national problems to seek appropriate solutions: 1. Disposal of wastewaters: sewage, garbage, industrial effluents with a target of cleanliness of environment. 2. Techno-economic disposal of agricultural waste. 3. Techno-economic disposal of solid waste. 4. Rationalization of the use of oriental/traditional medicines on scientific. 5. Production of the products of micro-organisms to dispose of waste and extract along with that the economic benefits. 6. Indigenous production of plant and animal enzymes to reduce import under national substitution policy. 7. Microbial leaching of ores and minerals for indigenous production of highly expensive metals such as uranium, etc. 8. Preservation of foodstuffs such as raw vegetables and fruits for off-season use and avoiding their spreading in the environment to cause a large number of environmental problems.

Investigating DNA-Mediated Charge Transport by Time-Resolved Spectroscopy

If we examine the objectives of the American Institute of Biological Sciences and the National Association of Biology Teachers with only the slightest bit of objectivity, we see two organizations in which the mutual commitments far outweigh the differences. In several areas where emphases differ, the strength of one organization would offset the weakness of the other. It is not obvious to the membership and leaders of both AIBS and NABT that these two organizations need each other's support? Could joint planning and cooperative programs help both organizations to meet the needs of teachers and researchers in the biological sciences? Could both organizations in concert, and through the power of numbers, speak more effectively as one voice concerning the needs for private and public support for basic research in biology, and the national need for excellence in the teaching of the biological sciences? And would removing the duplication of effort, at a time when money is scarce, through the sharing of responsibilities make economic sense to members and potential members of both organizations? Cooperative efforts could strengthen the national conventions of both organizations. In areas of basic research in biology, the AIBS meetings are excellent because they make it possible for those who conduct -the research and those who teach the biological sciences to interact and become better informed. But over the years the AIBS meetings have not provided strong programs for teachrs of biology. Because of this general weakness in the total program of AIBS, the number of secondary and college teachers attending meetings has dwindled. At the same time, the NABT conventions have been especially designed for those who devote a major portion of their time to the teaching of the biological sciences and to demonstrating new methods of teaching biology. NABT conventions have suffered from a lack of participation by research scientists who are enthusiastic about reaching leachers to ensure that their data will be properly taught by well-informed teachers. Here we see just one example of how closer cooperation would strengthen both organizations. Nothing but good could come out of AIBS playing an active, well-defined role in planning a portion of the NABT conventions and NABT designing strong biological education programs to present at AIBS meetings. It would also be to the advantage of both organizations to carefully schedule the national meetings so that they are in different parts of the country each year. This would help attendance, save energy and money, and allow each organization to advertise in the journal of the other. This, again, would present a solid front for the biological sciences. AIBS and NABT should join in organizing and sponsoring activities at the state level. Due to a lack of communication, several state or regional organizations may hold meetings with similar programs one week apart in the same city, or there may not be meetings in some states for several years. Cooperative planning and leadership at the national level can correct this situation. Joint efforts in communicating with Congress and federal funding agencies, as well as activities relating to the protection of the rights of teachers and researchers in sensitive areas are equally important to both organizations. Separately, neither organization speaks for the biological sciences; but together they can speak with one voice. The editors of BioScience and The American Biology Teacher have good records of cooperation and communication, and with encouragement from their respective Executive C mmittees the quality of the content in both journals would be improved. By working to eliminate duplication in reviewing of books and audiovisual materials, the two journals could cover a broader range of topics, and use of the available space more effectively. The joint planning of special publications could provide a wide variety of materials and in formation for the total audience. The times are right for the kinds of cooperation I have described. The Executive Committees of both organizations are communicating, and seem to be receptive to some of these ideas. New Executive Directors in both organizations are enthusiastic and open to changes in attitude and organization. The financial advantages far outweigh the disadvantages. AIBS and NABT need each other, and our individual members need both organizations.

Journal Article AIBS and NABT: A Time for Cooperation Get access Jack L. Carter, Jr. Jack L. Carter, Jr. Department of Biology, Colorado College, Colorado Springs, CO 80903 Search for other works by this author on: Oxford Academic Google Scholar BioScience, Volume 30, Issue 4, April 1980, Pages 221–222, https://doi.org/10.2307/1307872 Published: 01 April 1980