Light-harvesting Molecules Research Articles

Closed-loop transfer enables artificial intelligence to yield chemical knowledge.

Artificial intelligence-guided closed-loop experimentation has emerged as a promising method for optimization of objective functions1,2, but the substantial potential of this traditionally black-box approach to uncovering new chemical knowledge has remained largely untapped. Here we report the integration of closed-loop experiments with physics-based feature selection and supervised learning, denoted as closed-loop transfer (CLT), to yield chemical insights in parallel with optimization of objective functions. CLT was used to examine the factors dictating the photostability in solution of light-harvesting donor-acceptor molecules used in a variety of organic electronics applications, and showed fundamental insights including the importance of high-energy regions of the triplet state manifold. This was possible following automated modular synthesis and experimental characterization of only around 1.5% of the theoretical chemical space. This physics-informed model for photostability was strengthened using multiple experimental test sets and validated by tuning the triplet excited-state energy of the solvent to break out of the observed plateau in the closed-loop photostability optimization process. Further applications of CLT to additional materials systems support the generalizability of this strategy for augmenting closed-loop strategies. Broadly, these findings show that combining interpretable supervised learning models and physics-based features with closed-loop discovery processes can rapidly provide fundamental chemical insights.

Molybdenum Disulfide Nanoparticle Enhancing Photosynthesis in Solanum Lycopersicum

AbstractPhotosynthesis is a dynamic, complex, photo‐catalytic process that plays a key role in the growth and development of plants. It converts solar energy to chemical energy by precise organisation of light harvesting molecules in the photosynthetic system. Artificially imitating such systems is difficult due to the complexity of different cascades associated with photosynthesis. Nanoparticle mediated photocatalytic complexes have been shown to improve photosynthesis efficiency. Nanomaterials, such as molybdenum disulfide (MoS2) efficiently capture sunlight and assist in photosynthesis enhancement and nanosheets offer an additional advantage of increased surface area for sunlight harnessing. Foliar nutrition supplementation provides high yield potential to crops and their application in small doses improves the photosynthesis and elevates the plant performance. This study aims at mapping the efficiency of facile one‐pot hydrothermally synthesized MoS2 nanosheets in enhancing the photosynthetic ability of tomato plants. The treatments included the supplementation and absence of molybdenum source to plants. Physiological features (root length, shoot length, biomass), biochemical parameters (antioxidant activity), photosynthesis parameters (carbon assimilation, stomatal conductance, transpiration rate, water use efficiency, chlorophyll and carotenoid content), uptake and translocation of MoS2 nanosheets were evaluated. Increases of 22.07 %, 49.95 % and 18.56 % in net photosynthetic rate, water use efficiency and chlorophyll content respectively, were observed in MoS2_Nano treated plants compared with untreated plants. These nanosheets improved plant photosynthesis parameters and enhanced photosystem efficiency without inducing phytotoxicity. This study demonstrates the promise of such approaches towards enhanced plant photosystem efficiency, leading to improved agricultural productivity, particularly in the regions with less sunlight.

Functionalized nitrogen-enrich graphene as a highly efficient photocatalyst for oxidative cyclization of thioamide and degradation of Dye

Functionalized photocatalysts have shown to be an effective method for oxidative cyclization processes and the degradation of organic poisons like chemicals and dyes. In this study, we report the facile, environmentally friendly, room-temperature (RT) synthesis and development of a graphene-based visible light active photocatalyst (NenG-RhB) which is thermodynamically converted to nitrogen-enriched graphene (NenG) covalently bonded to a light-harvesting RhB molecule [9-(2-Carboxyphenyl)-6-(diethylamino)-N, N‑diethyl-3H-xanthen-3-iminium chloride)]. The NenG-RhB photocatalyst is extremely effective, resulting in good oxidative cyclization of aromatic thioamide (92.5 %) and degradation efficiency of industrial orange G (97.29 %) under solar light. The current research focuses on the invention and implementation of a nitrogen-enrich graphene-based photocatalyst for direct solar medicinal chemical synthesis and industrial dye degradation in wastewater using solar light.

Generalized biomolecular modeling and design with RoseTTAFold All-Atom.

Deep-learning methods have revolutionized protein structure prediction and design but are presently limited to protein-only systems. We describe RoseTTAFold All-Atom (RFAA), which combines a residue-based representation of amino acids and DNA bases with an atomic representation of all other groups to model assemblies that contain proteins, nucleic acids, small molecules, metals, and covalent modifications, given their sequences and chemical structures. By fine-tuning on denoising tasks, we developed RFdiffusion All-Atom (RFdiffusionAA), which builds protein structures around small molecules. Starting from random distributions of amino acid residues surrounding target small molecules, we designed and experimentally validated, through crystallography and binding measurements, proteins that bind the cardiac disease therapeutic digoxigenin, the enzymatic cofactor heme, and the light-harvesting molecule bilin.

Digital quantum simulation of non-perturbative dynamics of open systems with orthogonal polynomials

Classical non-perturbative simulations of open quantum systems' dynamics face several scalability problems, namely, exponential scaling of the computational effort as a function of either the time length of the simulation or the size of the open system. In this work, we propose the use of the Time Evolving Density operator with Orthogonal Polynomials Algorithm (TEDOPA) on a quantum computer, which we term as Quantum TEDOPA (Q-TEDOPA), to simulate non-perturbative dynamics of open quantum systems linearly coupled to a bosonic environment (continuous phonon bath). By performing a change of basis of the Hamiltonian, the TEDOPA yields a chain of harmonic oscillators with only local nearest-neighbour interactions, making this algorithm suitable for implementation on quantum devices with limited qubit connectivity such as superconducting quantum processors. We analyse in detail the implementation of the TEDOPA on a quantum device and show that exponential scalings of computational resources can potentially be avoided for time-evolution simulations of the systems considered in this work. We applied the proposed method to the simulation of the exciton transport between two light-harvesting molecules in the regime of moderate coupling strength to a non-Markovian harmonic oscillator environment on an IBMQ device. Applications of the Q-TEDOPA span problems which can not be solved by perturbation techniques belonging to different areas, such as the dynamics of quantum biological systems and strongly correlated condensed matter systems.

Transformation of PMMA from sunlight-blocking to sunlight-activated coupled with DNH photocatalytic platform for oxidative coupling of amines and generation/regeneration of LDC/NADH.

The photocatalytic oxidation and generation/regeneration of amines to imines and leucodopaminechrome (LDC)/NADH are subjects of intense interest in contemporary research. Imines serve as crucial intermediates for the synthesis of solar fuels, fine chemicals, agricultural chemicals, and pharmaceuticals. While significant progress has been made in developing efficient processes for the oxidation and generation/regeneration of secondary amines, the oxidation of primary amines has received comparatively less attention until recently. This discrepancy can be attributed to the high reactivity of imines generated from primary amines, which are prone to dehydrogenation into nitriles. In this study, we present the synthesis and characterization of a novel polymer-based photocatalyst, denoted as PMMA-DNH, designed for solar light-harvesting applications. PMMA-DNH incorporates the light-harvesting molecule dinitrophenyl hydrazine (DNH) at varying concentrations (5%, 10%, 20%, 30%, and 40%). Leveraging its high molar extinction coefficient and slow charge recombination, the 30% DNH-incorporated PMMA photocatalyst proves to be particularly efficient. This photocatalytic system demonstrates exceptional yields (96.5%) in imine production and high generation/regeneration rates for LDC/NADH (65.27%/78.77%). The research presented herein emphasizes the development and application of a newly engineered polymer-based photocatalyst, which holds significant promise for direct solar-assisted chemical synthesis in diverse commercial applications.

Pore-Confined π-Chromophoric Tetracene as a Visible Light Harvester toward MOF-Based Photocatalytic CO2 Reduction in Water.

Integrating photoactive π-chromophoric guest molecules inside the MOF nanopore can result in the emergence of light-responsive features, which in turn can be utilized for developing photoactive materials with inherent properties of MOF. Herein, we report the confining of π-chromophoric tetracene (TET) molecules inside the nanospace of postmodified Zr-MOF-808 (Zr-MOF) with MBA molecules (MBA = 2-(5'-methyl-[2,2'-bipyridine]-5-yl)acetic acid) for effectively utilizing its light-harvesting properties toward photocatalytic CO2 reduction. The confinement of the TET molecules as a photosensitizer and the covalent grafting of a catalytically active [Re(MBA)(CO)3Cl] complex, postsynthetically, result in a single integrated catalytic system named Zr-MBA-TET-Re-MOF. Photoreduction of CO2 over Zr-MBA-TET-Re-MOF showed the evolution of 805 μmol g-1 CO with 99.9% selectivity after 10 h of continuous visible light irradiation in water without any additional sacrificial electron donor and having the apparent quantum efficiency of 1.3%. In addition, the catalyst demonstrated an appreciable activity even under direct sunlight irradiation in aqueous medium with a maximum production of 362.7 μmol g-1 CO, thereby mimicking artificial photosynthesis. Moreover, electron transfer from TET to the catalytic center was supported by the formation of photoinduced TET radical cation, as inferred from in situ UV-vis spectra, electron paramagnetic resonance (EPR) analysis, and transient absorption (TA) studies. Additionally, the in situ diffuse reflectance infrared Fourier transform (DRIFT) measurements support that the photoreduction of CO2 to CO proceeds via *COOH intermediate formation. The close proximity of the light-harvesting molecule and catalytic center facilitated facile electron transfer from the photosensitizer to the catalyst during the CO2 reduction.

Effect of Dipyridamole on Membrane Energization and Energy Transfer in Chromatophores of Rba. sphaeroides.

Effect of dipyridamole (DIP) at concentrations up to 1 mM on fluorescent characteristics of light-harvesting complexes LH2 and LH1, as well as on conditions of photosynthetic electron transport chain in the bacterial chromatophores of Rba. sphaeroides was investigated. DIP was found to affect efficiency of energy transfer from the light-harvesting complex LH2 to the LH1–reaction center core complex and to produce the long-wavelength (“red”) shift of the absorption band of light-harvesting bacteriochlorophyll molecules in the IR spectral region at 840-900 nm. This shift is associated with the membrane transition to the energized state. It was shown that DIP is able to reduce the photooxidized bacteriochlorophyll of the reaction center, which accelerated electron flow along the electron transport chain, thereby stimulating generation of the transmembrane potential on the chromatophore membrane. The results are important for clarifying possible mechanisms of DIP influence on the activity of membrane-bound functional proteins. In particular, they might be significant for interpreting numerous therapeutic effects of DIP.

Molecular interactions in DNA-scaffolded energy transfer systems

Natural photosynthetic systems utilize quantum coherent effects to enhance energy transfer efficiency when light-harvesting molecules are closely interacting. These natural photosynthetic complexes enable molecular packing and interaction by precise scaffolding within a protein environment. We compare these natural photosynthetic systems to light-harvesting systems which utilize synthetic DNA nanotechnology. DNA nanotechnology enables a similar level of control of molecular interactions when using rational attachment of photoactive dyes to DNA scaffolding.

Nanomaterials for enhancing photosynthesis: interaction with plant photosystems and scope of nanobionics in agriculture

The complex process of photosynthesis requires precise arrangements of light harvesting molecules in the photosynthetic system.

Synthesis of orthogonal push-pull chromophores via click reaction of arylynamines.

Herein, we report a catalyst-free 'click' reaction: metal-free [2 + 2] cycloaddition-retro-electrocyclisation (CA-RE) of arylynamines with the sluggish acceptor tetracyanoquinodimethane (TCNQ) to provide orthogonal electron-push-pull light-harvesting small molecules: N-heterocyclic dicyanoquinodimethane-substituted methylene malononitriles. Ynamines are reactive alkynes and tend to induce over-reactions with the CA-RE adducts. The reactivity of arylynamines was balanced properly by ensuring the electron-density of the nitrogen atom was delocalised more over the aromatic rings than the triple bond.

"Candidatus Chlorobium masyuteum," a Novel Photoferrotrophic Green Sulfur Bacterium Enriched From a Ferruginous Meromictic Lake.

Anoxygenic phototrophic bacteria can be important primary producers in some meromictic lakes. Green sulfur bacteria (GSB) have been detected in ferruginous lakes, with some evidence that they are photosynthesizing using Fe(II) as an electron donor (i.e., photoferrotrophy). However, some photoferrotrophic GSB can also utilize reduced sulfur compounds, complicating the interpretation of Fe-dependent photosynthetic primary productivity. An enrichment (BLA1) from meromictic ferruginous Brownie Lake, Minnesota, United States, contains an Fe(II)-oxidizing GSB and a metabolically flexible putative Fe(III)-reducing anaerobe. “Candidatus Chlorobium masyuteum” grows photoautotrophically with Fe(II) and possesses the putative Fe(II) oxidase-encoding cyc2 gene also known from oxygen-dependent Fe(II)-oxidizing bacteria. It lacks genes for oxidation of reduced sulfur compounds. Its genome encodes for hydrogenases and a reverse TCA cycle that may allow it to utilize H2 and acetate as electron donors, an inference supported by the abundance of this organism when the enrichment was supplied by these substrates and light. The anaerobe “Candidatus Pseudopelobacter ferreus” is in low abundance (∼1%) in BLA1 and is a putative Fe(III)-reducing bacterium from the Geobacterales ord. nov. While “Ca. C. masyuteum” is closely related to the photoferrotrophs C. ferroooxidans strain KoFox and C. phaeoferrooxidans strain KB01, it is unique at the genomic level. The main light-harvesting molecule was identified as bacteriochlorophyll c with accessory carotenoids of the chlorobactene series. BLA1 optimally oxidizes Fe(II) at a pH of 6.8, and the rate of Fe(II) oxidation was 0.63 ± 0.069 mmol day–1, comparable to other photoferrotrophic GSB cultures or enrichments. Investigation of BLA1 expands the genetic basis for phototrophic Fe(II) oxidation by GSB and highlights the role these organisms may play in Fe(II) oxidation and carbon cycling in ferruginous lakes.

Dye-TiO2/SiO2 assembly photocatalysis for blue light-initiated selective aerobic oxidation of organic sulfides

Previous attempts of incorporating TiO2 with porous SiO2 (TiO2/SiO2) to elevate the photocatalytic activity within the visible region have encountered with limited success. Therefore, light-harvesting molecules like alizarin red S (ARS) could be assembled onto TiO2/SiO2 to circumvent this bottleneck. Herein, a series of TiO2/SiO2 with different molar ratios were fashioned by the sol–gel and ensuing calcination method. Thereafter, ARS was conveniently assembled onto these TiO2/SiO2 under reaction conditions of selective aerobic oxidation of sulfides under the illumination of 460 nm blue light-emitting diodes (LEDs). Moreover, a redox mediator TEMPO ((2,2,6,6-tetramethylpiperidin-1-yl)oxyl) could boost the electron transfer from the light-excited ARS to sulfides which in turn alleviates the destruction of ARS assembled on TiO2/SiO2 (molar ratio, 1/3). The more abundant surface hydroxyl groups of SiO2 than TiO2 could ameliorate selectivities for sulfoxides. A wide range of organic sulfides can be converted into sulfoxides with above 90% selectivities and conversions over ARS-TiO2/SiO2 assembly and 2 mol% TEMPO. The positive involvement of an insulator like SiO2 represents a way forward both in scope and in depth for dye-semiconductor photocatalysis during selective transformations.

A new ultrafast energy funneling material harvests three times more diffusive solar energy for GaInP photovoltaics

There is no theoretical limit in using molecular networks to harvest diffusive sun photons on large areas and funnel them onto much smaller areas of highly efficient but also precious energy-converting materials. The most effective concept reported so far is based on a pool of randomly oriented, light-harvesting donor molecules that funnel all excitation quanta by ultrafast energy transfer to individual light-redirecting acceptor molecules oriented parallel to the energy converters. However, the best practical light-harvesting system could only be discovered by empirical screening of molecules that either align or not within stretched polymers and the maximum absorption wavelength of the empirical system was far away from the solar maximum. No molecular property was known explaining why certain molecules would align very effectively whereas similar molecules did not. Here, we first explore what molecular properties are responsible for a molecule to be aligned. We found a parameter derived directly from the molecular structure with a high predictive power for the alignability. In addition, we found a set of ultrafast funneling molecules that harvest three times more energy in the solar's spectrum peak for GaInP photovoltaics. A detailed study on the ultrafast dipole moment reorientation dynamics demonstrates that refocusing of the diffusive light is based on ∼15-ps initial dipole moment depolarization followed by ∼50-ps repolarization into desired directions. This provides a detailed understanding of the molecular depolarization/repolarization processes responsible for refocusing diffusively scattered photons without violating the second law of thermodynamics.

Directing charge transfer in perylene based light-harvesting antenna molecules.

Directing energy and charge transfer processes in light-harvesting antenna systems is quintessential for optimizing the efficiency of molecular devices for artificial photosynthesis. In this work, we report a novel synthetic method to construct two regioisomeric antenna molecules (1-D2A2 and 7-D2A2), in which the 4-(n-butylamino)naphthalene monoimide energy and electron donor is attached to the perylene monoimide diester (PMIDE) acceptor at the 1- and 7-bay positions, respectively. The non-symmetric structure of PMIDE renders a polarized distribution of the frontier molecular orbitals along the long axis of this acceptor moiety, which differentiates the electron coupling between the donor, attached at either the 1- or the 7-position, and the acceptor. We demonstrate that directional control of the photo-driven charge transfer process has been obtained by engineering the molecular structure of the light-harvesting antenna molecules.

Aerobic Barley Mg-protoporphyrin IX Monomethyl Ester Cyclase is Powered by Electrons from Ferredoxin.

Chlorophyll is the light-harvesting molecule central to the process of photosynthesis. Chlorophyll is synthesized through 15 enzymatic steps. Most of the reactions have been characterized using recombinant proteins. One exception is the formation of the isocyclic E-ring characteristic of chlorophylls. This reaction is catalyzed by the Mg-protoporphyrin IX monomethyl ester cyclase encoded by Xantha-l in barley (Hordeum vulgare L.). The Xantha-l gene product (XanL) is a membrane-bound diiron monooxygenase, which requires additional soluble and membrane-bound components for its activity. XanL has so far been impossible to produce as an active recombinant protein for in vitro assays, which is required for deeper biochemical and structural analyses. In the present work, we performed cyclase assays with soluble and membrane-bound fractions of barley etioplasts. Addition of antibodies raised against ferredoxin or ferredoxin-NADPH oxidoreductase (FNR) inhibited assays, strongly suggesting that reducing electrons for the cyclase reaction involves ferredoxin and FNR. We further developed a completely recombinant cyclase assay. Expression of active XanL required co-expression with an additional protein, Ycf54. In vitro cyclase activity was obtained with recombinant XanL in combination with ferredoxin and FNR. Our experiment demonstrates that the cyclase is a ferredoxin-dependent enzyme. Ferredoxin is part of the photosynthetic electron-transport chain, which suggests that the cyclase reaction might be connected to photosynthesis under light conditions.

Efficacious elimination of intramolecular charge transfer in perylene imide based light-harvesting antenna molecules.

Two light-harvesting antenna molecules were obtained by positioning naphthalene monoimide energy donors at the imide position, instead of the bay positions, of perylene imide energy acceptors. Such rational design resulted in a complete suppression of parasitic intramolecular charge transfer without compromising the desired ultrafast rates of excitation energy transfer.

Bacterial elimination via the photodynamic activity of a fullerene/light-harvesting antenna molecule assembled system integrated into liposome membranes.

Ease of transmission and exceptionally high mortality rates make pathogen-based infections an ongoing global threat. Herein, a facile bacterial elimination process is described which is based on the photodynamic activity of fullerenes composed of light-harvesting antenna molecules integrated into liposome membranes. This was done to expand the absorption capabilities of fullerene derivatives. Efficient energy transfer from the photoactivated antenna molecules to the fullerenes enhanced antimicrobial activity without any harmful lytic activity against red blood cells even under irradiation.

Extension of π Conjugation System By Functionalization of the Beta Position of Porphyrin

Porphyrin is a macrocyclic light harvesting molecule that absorbs the light in visible region of the electromagnetic spectrum. Extension of π-conjugation causes the red shifting of the absorbance and adding more fused aromatic rings in to the main macrocycle is a common way to achieve that goal. Heck Coupling reaction can be used to introduce fused aromatic rings in to the β position of porphyrin. π-extended porphyrins possess different and interesting photophysical , Optoelectronic and Physicochemical properties . Aromatic ring fused porphyrins open wide range of applications including in Molecular Rods, Bio sensors, near Infra-red dyes, Photodynamic therapy etc. In here, we are reporting the use of Heck coupling reaction to synthesis β - extended porphyrin and their red shifted light absorbing properties using its UV-Vis absorption spectrum.

Enhancement of photosynthesis in Synechococcus bacillaris by sponge-derived Ageladine A.

This study is a proof of concept that the sponge derived pyrrole-imidazole alkaloid Ageladine A acts as an additional light harvesting molecule for photosynthesis of symbionts of marine sponges. The absorbance of Ageladine A is in the UV range and fluoresces blue, matching the blue absorbance of chlorophyll a. A joint modeling and experimental approach demonstrates that Ageladine A increases photosynthetic O2 production of Synechococcus bacillaris WH5701 (CCMP1333), when the cells are exposed to UV light, which is marginally used for photosynthesis. Due to the presence of Ageladine A, production of O2 increased 2.54 and 3.1-fold, in the experiments and the model, respectively.