Secondary Structural Units Research Articles

Engineering Internal and External Low-Coordination Atoms in Nickel-Organic Framework Nanoarrays to Promote the Electrochemical Oxygen Evolution Reaction.

Monometallic nickel-organic frameworks based on a carboxylated ligand [2,6-naphthalenedicarboxylic acid (Ni-NDC)] have abundant and uniformly distributed single-atom Ni sites, enabling superior oxygen evolution reaction (OER) activity. In theory, most of the Ni atoms inside Ni-NDC microcrystals are coordinatively saturated except for the surface. Therefore, there are no accessible low-coordination atoms (LCAs) as electrocatalytic sites for the OER. One effective way is to expose more LCAs by preparing self-supporting Ni-NDC nanoarrays (Ni-NDC NAs) with hierarchical secondary structural units. Another effective method is to create more internal LCAs by removing partial ligands or coordination atoms attached to the Ni atoms. Herein, by combining the two strategies, we engineered LCAs in the interior and exterior of Ni-NDC to synergistically accelerate the OER. In brief, ultrathick "brick-like" Ni-NDC NAs were first prepared with dissolution and coordination effects of NDC on self-sacrificial templates of "agaric-like" nickel hydroxide nanoarrays [Ni(OH)2 NAs]. Subsequently, dual-coordinated NDC was partially replaced by monocoordinated 2-naphthoic acid (NA). The Ni-NDC NAs were further tailed into ultrathin "liner leaf-like" nanoneedle arrays (LCAs-Ni-NDC NAs). As a consequence, the LCAs-Ni-NDC NAs have more internal and external LCAs, which can deliver an OER performance that is superior to that of Ni-NDC NAs.

Characteristics of Jurassic Source Rocks and Evaluation of Hydrocarbon Resources in Tarim Basin, western China

Jurassic strata in Tarim are significant for their hydrocarbon-rich content. However, the distribution of hydrocarbon source rocks in this region is uneven, and the conditions for hydrocarbon accumulation vary significantly among the different structural elements. Therefore, it is essential to investigate the distribution of Jurassic source rocks, the evolution history of hydrocarbon generation, and the mechanisms influencing hydrocarbon accumulation for effective hydrocarbon exploration and development. To achieve this, seismic, geologic, drilling, logging, and testing data were integrated to analyze the distribution and quality of hydrocarbon source rocks, the evolution of hydrocarbon generation, and the factors influencing hydrocarbon accumulation in Jurassic hydrocarbon source rocks in Tarim Basin. The study revealed that the Jurassic effective hydrocarbon source rock centers are mainly located in the piedmont areas of Kuqa depression, southwest depression, and southeast depression, as well as Yingjisu sag and Manjiaer sag in the eastern Tarim area. Based on a comprehensive evaluation and comparison of the potential of Jurassic hydrocarbon potential in each secondary structural unit, it is concluded that Kuqa Depression has the most favorable exploration zone due to its excellent hydrocarbon accumulation conditions and abundant hydrocarbon resources. Although the overall exploration potential of the southwest depression is lower than that of the Kuqa depression, the hydrocarbon resources potential of the piedmont thrust belt and the associated depression is very high. Similarly, the eastern part of the Manjiaer sag and the Altun piedmont zone of the southeastern depression still have promising exploration prospects, although the overall exploration potential of the eastern Tarim area and the southeastern depression is not as good as the former two.

Multi-stages of Paleozoic deformation of the fault system in the Tazhong Uplift, Tarim Basin, NW China: Implications for hydrocarbon accumulation

The Tazhong Uplift is an important petroliferous secondary structure unit in the Tarim Basin and has undergone multiple structural deformation. In the current study, we use 3D and 2D seismic data to investigate the nature of the fault system in the Tazhong Uplift. The deformation of the Cambrian sedimentary rocks in the Tazhong Uplift is generally neglected but noted in this study. We found that the Lower–Middle Cambrian rocks are involved in thrust faults. NE-trending weak zones acted as accommodation faults formed at the connective positions and bends of the deep thrust faults. The Middle Cambrian compressional stress stemmed from the northeastern margin of the Tarim Block, pointed SW, and caused the uprising of the Tabei Uplift. The second deformation occurred in the Late Ordovician. In this instance, the compressional stress stemmed from the SW direction of the Tazhong Uplift, which originated from the amalgamation of the Western Kunlun Terrane and Tarim Block. The main strike–slip fault surfaces and subordinate faults developed along the weak zones generated in the Middle Cambrian. The collision that occurred in the southeast part of the Tarim Block in the Middle Silurian to Middle Devonian resulted in the third deformation. The representative structures that occurred during this compressive deformation were the intensive NEE-trending thrust faults in the southeast of the Tazhong Uplift. The three stages of deformation played different and important roles in hydrocarbon accumulation. These strike–slip faults holding the high-productivity hydrocarbon wells generally experienced early-stage Cambrian deformation, had wide fracture damage zones in the Ordovician carbonate rock strata, and had weak en echelon faults in the Silurian to Middle Devonian clastic rocks.

A Review of the Application of Metal-Organic Frameworks in the Absorption, Storage and Release of Methane

Natural gas, which mainly consists of methane, is a good fuel for vehicles. Metal-organic frameworks (MOF) have attracted much attention as a new group of adsorbent materials in natural gas storage. MOF structures form various networks by connecting secondary structural units composed of metal ions and organic binders. These regular materials have high porosity and have high design capabilities. This feature has made MOFs suitable for special applications in trapping and absorbing various materials. The investigation of these materials has focused on the absorption of pure methane, although natural gas contains a small amount of larger hydrocarbons such as ethane and propane, which have greater absorption than methane. This Manuscript presents an overview of the current state of the metal-organic framework for methane storage.

Luminescence intensity-tunable X-ray scintillation based on zirconium-based metal-organic frameworks

The low-energy ultraviolet or visible photons can be produced by the interaction between the scintillator materials and ionizing radiation. For this reason, scintillator materials are widely used as radiation detectors, which are prevalently utilized in different applications such as nuclear medicine imaging, homeland security, high-energy physics, oil drilling explorations, etc. Herein, a high-atomic-number (Z) zirconium-based metal-organic framework nanoflower material CJLU-1 (Zr6(μ3-O)4(μ3-OH)4(OH)6(TCA)2(H2O)6) (H3TCA = tri-carboxylic acids 4,4′,4″-nitrilotribenzoic acid) was synthesized and can effectively convert X-ray into visible light. CJLU-1 is composed of secondary structural unit hexagonal Zr metal cluster and connected by TCA ligands. The photo luminescence spectra (PL) emission peak and excitation peak of CJLU-1 are at 470 nm and 395 nm respectively. CJLU-1 exhibited radioluminescence (RL) peak with a maximum at 480 nm under steady-state excitation with X-rays. Moreover, by accommodating different guest molecules such as xylene and RhB in the same MOF material, intensity-tunable X-ray scintillation can be facilely achieved, providing a new class of scintillating materials with luminescence intensity tunability. The high-Z hexagonal Zr clusters, which are arranged in an orderly fashion, absorb and interact with the ionizing radiation and sensitize the adjacent organic ligands TCA to produce efficient RL. This work contributes to the development of high-Z zirconium-based MOFs and RL intensity-tunable scintillation materials towards future practical nuclear sensing applications.

Introducing VO2+ Group in Phosphomolybdic Acid and Supporting on MOF-808 for Efficient Oxidative Desulfurization.

Herein, by introducing a VO2+ group into the microstructure of phosphomolybdenic acid (PMA) and loading it onto MOF-808, a series of composite catalysts were obtained by reducing the V element with Vitamin C (ascorbic acid). V atoms exist in the secondary structural units of phosphomolybdic acid as [VO(H2O)5]H[PMo12O40]. Surprisingly, the VC-VO-PMA/MOF-808 completely removed DBT and 4,6-DMDBT from the simulated oil in 12 min. The EPR and XPS results verify the electronic structure and valence state of V4+ in the composites. The oxygen vacancy and V4+ generated by VC modification in VC-VO-PMA/MOF-808 have positive effects on the oxidation desulfurization (ODS) activity. Based on the design of the microstructure and electronic structure, this study provides a new paradigm for the development of readily available and efficient ODS catalysts.

Construction of Submicron Spherical ZSM-48 Zeolite: Crystallization Mechanism and Catalytic Application

Morphology control of zeolite with a one-dimensional channel, especially for ZSM-48 zeolite, is a great challenge due to its inherent characteristics of growth along the main channels. How to shorten the diffusion path of molecules is crucial to alleviating the diffusion limitation. Here, a direct synthesis route for submicron (500 nm) spherical ZSM-48 zeolite was developed with the assistance of F– ions at low crystallization temperature. Through detailed investigation of the role of F– ions and the crystallization mechanism using various characterization techniques, a reliable formation mechanism of spherical ZSM-48 zeolite was proposed. First, F– ions addition shortens the induction period by promoting the dissociation rearrangement of aluminosilicate precursors, which promotes the preferential formation of secondary structural units. Moreover, F– ions induce the formation of ZSM-48 spheres by promoting surface silanol group condensation. ZSM-48 spheres with sizes of 500–2500 nm can be successfully obtained by regulating the crystallization temperature. In m-xylene isomerization, submicron spherical ZSM-48 zeolite exhibits significantly improved stability compared with the conventional one. Moreover, the selectivity for p-xylene is much higher than that of a typical ZSM-5 zeolite (68% vs 48%). The excellent catalytic performance of submicron spherical ZSM-48 highlights not only the positive impact of shortened channels for mass transfer but also its potential as a new catalyst for m-xylene isomerization.

Structural Insights into the Antiparallel G-Quadruplex in the Presence of K+ and Mg2+ Ions.

G-Quadruplex (GQ) is a secondary structural unit of DNA, formed at the telomere region of the chromosome with a high guanine content. It is reported that the GQs can hinder many biological processes. Thus, research thrives to explore the structural stability of GQs. Studies based on circular dichroism (CD) and nuclear magnetic resonance (NMR) experiments established the vital role of cations such as K+ and Mg2+ in the stability of antiparallel G-quadruplexes (AGQs). However, there is a need to understand how stability in AGQ is attained in the presence of cations. Here, we employed molecular dynamics (MD) simulations, steered MD (SMD) simulations, and QM/MM calculations to understand the biophysical and electronic bases of the stability imparted to AGQs via cation binding. Our results showed that Mg2+ prefers to bind in the plane with the guanine tetrad, whereas K+ binds in between the AGQ tetrads. Thus, three Mg2+ cations or two K+ ions are needed to stabilize an AGQ molecule, where each and every tetrad binds to Mg2+ more robustly with a higher binding affinity. SMD revealed that the traversal of K+ through the AGQ central channel required less force than that of Mg2+, illustrating the presence of more strong interactions between Mg2+ and AGQ tetrads compared to K+. The stabilization in the AGQ tetrads due to cation binding is reassessed by employing ab initio simulations. Mixed QM/MM calculations confirmed that Mg2+ binds strongly to AGQ compared to K+, and it induces higher interactions between the guanine tetrads. However, K+ binding to AGQ induces a higher stabilization energy than Mg2+ binding to AGQ tetrads. Despite the higher binding energy, Mg2+ binding imparts lower stabilization to AGQ due to its unfavorable fermionic quantum energy.

Reductionist insights into how chaperone charge influences RNA folding.

Non-coding RNAs are composed of modular secondary and tertiary structural units that themselves must form complex 3D structures for the entire RNA to fold and perform its biological function. However, the high density of negative charges associated with the phosphate backbone gives rise to substantial amounts of electrostatic repulsion, contributing to the large energetic barrier between unfolded and folded states. RNA folding chaperones (RFCs) are proteins that help lower this energy barrier by transiently interacting with RNA. Recent work has shown that some RFCs can function as macromolecular counterions for their RNA clients, thereby screening backbone electrostatic repulsion. However, the fundamental principles associated with how RFCs assist folding is largely unexplored. Here, we reduce RFCs to their smallest cationic constituents and then systematically “re-build” RFCs from these components (e.g., NH4+→ Lys→ polyK10→ RFC). We use single-molecule FRET to determine how these counterions influence both the relative population abundance and mean FRET efficiency of the folded and unfolded states of small model RNAs. From these studies, we have begun to determine aspects of RFCs that contribute to chaperoning RNA folding, such as net cationic charge and charge distribution. Here, we show that cationic amino acids (e.g., Lys and Arg) bind to RNA with apparent Kd values (appKd) on the order of 100 mM, which are comparable to those associated with their characteristic functional groups (e.g., ammonium and guanidinium). Further, increasing the net cationic charge of a counterion systematically decreases the appKd over several orders of magnitude. We also show a correlation between the decrease in appKd and a decrease in the folding free energy barrier. We then compare our observations of these polypeptide chaperones to the behavior of known RFCs (e.g., protamine, H1, and HCV nucleocapsid protein) with the small model RNAs.

Two new 5-mercapto-1-phenyl-1H-tetrazole-based Cu(I) coordination polymers with double layer structures: Crystal structures, substituent effects and sensing responses to NACs

During the construction of coordination compounds, a minor variation in the steric and electronic characteristics of the substituent on a ligand might have a great impact on the structures and properties of the target compounds. To investigate this issue, two new coordination polymers with double layer structures, [Cu2(MPTZ)I]n (1) and {[Cu(MHPTZ)]·0.5H2O}n (2), have been successfully synthesized through the reactions of CuI and the sulfhydryl tetrazole derivatives (HMPTZ ​= ​5-mercapto-1-phenyl-1H-tetrazole and HMHPTZ ​= ​5-mercapto-1-(4-hydroxyphenyl)- 1H-tetrazole) and characterized by single crystal X-ray diffraction, powder X-ray diffraction, elemental analysis, infrared spectra and thermogravimetric analysis. In compounds 1 and 2, both (MPTZ)- and (MHPTZ)- coordinate with four Cu(I) ions with distorted tetrahedral geometry in the same coordination modes (μ4-1қN3, 2қN4, 3қS1, 4қS1) to construct the similar two-dimensional (2D) double-layer structures, however, different substituents on ligands have important effects on the introduction of iodide ions and supramolecular forces. For compound 1, a 2D inorganic wavy (CuI)n cationic double-layer structure containing Cu2I2 secondary structural unit with the Cu⋯Cu distance of 2.65 ​Å is observed, but I¯ anions are not involved in the coordination with Cu(I) in compound 2. The difference in crystal structures and compositions of compounds 1 and 2 leads to changes of their fluorescence properties. Compound 1 shows the apparent yellow emission with the maximum at 558 ​nm when exciting at 352 ​nm, which shows sensitive luminescence quenching response to nitrobenzene compounds. However, fluorescent signals of compound 2 were not monitored under UV illumination or on fluorescence spectrophotometer. The results indicate that a minor variation in the substituent on a ligand has a great impact on the structures and properties of the target coordination compounds.

Superior Iodine Uptake Capacity Enabled by an Open Metal-Sulfide Framework Composed of Three Types of Active Sites

Superior Iodine Uptake Capacity Enabled by an Open Metal-Sulfide Framework Composed of Three Types of Active Sites

Formation process of organic template-free chabazite zeolite membrane and its separation performance of water-rich mixtures

The growth process of chabazite seed crystal transformed into chabazite zeolite membrane in an organic template-free and fluoride-containing synthesis gel was investigated in details. The characterization results showed that the formation process of organic template-free chabazite zeolite membrane included the processes of seed crystal dissolution and chabazite crystal reconstruction. In the first process of seed dissolution into amorphous, the secondary building units (D6Rs) of CHA framework were completely destroyed except for the presence of a small number of 4Rs. While the amorphous contained many primary building units (TO4) as the nucleation sites in the second process of chabazite crystal reconstruction, which nucleated rapidly again under the promotion of fluorine anion. With the further prolongation of crystallization time, the regenerated secondary structural units connected together to reconstruct the framework structure of chabazite zeolite, and gradually grew into a continuous and dense membrane layer with the cross-linking growth of chabazite zeolite. In addition, chabazite zeolite membrane exhibited high permeation flux and excellent long-term hydrothermal stability for the separation of water-rich mixtures. For 50 wt% EtOH/H2O and 50 wt% IPA/H2O binary mixtures at 348 K, the stable permeation fluxes of the membranes were as high as 13.50 kg m−2 h−1 and 14.80 kg m−2 h−1, respectively.

The Structural Rule Distinguishing a Superfold: A Case Study of Ferredoxin Fold and the Reverse Ferredoxin Fold.

Superfolds are folds commonly observed among evolutionarily unrelated multiple superfamilies of proteins. Since discovering superfolds almost two decades ago, structural rules distinguishing superfolds from the other ordinary folds have been explored but remained elusive. Here, we analyzed a typical superfold, the ferredoxin fold, and the fold which reverses the N to C terminus direction from the ferredoxin fold as a case study to find the rule to distinguish superfolds from the other folds. Though all the known structural characteristics for superfolds apply to both the ferredoxin fold and the reverse ferredoxin fold, the reverse fold has been found only in a single superfamily. The database analyses in the present study revealed the structural preferences of - and -units; the preferences separate two -helices in the ferredoxin fold, preventing their collision and stabilizing the fold. In contrast, in the reverse ferredoxin fold, the preferences bring two helices near each other, inducing structural conflict. The Rosetta folding simulations suggested that the ferredoxin fold is physically much more realizable than the reverse ferredoxin fold. Therefore, we propose that minimal structural conflict or minimal frustration among secondary structures is the rule to distinguish a superfold from ordinary folds. Intriguingly, the database analyses revealed that a most stringent structural rule in proteins, the right-handedness of the -unit, is broken in a set of structures to prevent the frustration, suggesting the proposed rule of minimum frustration among secondary structural units is comparably strong as the right-handedness rule of the -unit.

Gelation properties and protein conformation of grass carp fish ball as influenced by egg white protein.

Dried egg white powder (EWP) and purified ovalbumin (OVA, 98%) were used as supplements to improve grass carp (GC) fish balls (FB) quality. The effects of EWP and/or OVA contents on the gel strength, water holding capacity (WHC), moisture migration and distribution, and rheological properties of GC-FB, as well as on myofibrillar protein (MfP) structures in the GC-FB were evaluated. The results showed that with the increase of EWP addition from 0 to 4% (w/w), the gel strength, and WHC of the GC-FB samples were increased from 34.28 to 66.63 N × mm, and 83.02 to 88.36%, respectively, but the increases were insignificant between 3 and 4% EWP-added GC-FBs (p > .05). As the EWP increased, the T2 relaxation time shifted toward lower values, indicating a general decline in water mobility. The effects of EWP on rheological properties were insignificant. Addition of OVA and/or EWP led to changes in secondary structural units in the FB, with α-helix (27.53%) reaching the highest value in OVA-added GC-FB, β-sheet (46.07%) reaching the highest value in GC-FB, and β-turn (33.54%) reaching the highest value in EWP-added GC-FB, respectively. Raman spectroscopy revealed that OVA-added GC-FB had the lowest hydrophobic interlinkages. Protein pattern analysis suggested that the OVA (1.58%) might contribute to the decrease in the myosin heavy chain band intensity through cross-linked with MfP. These results suggested that EWP could improve the quality of GC-FBs and OVA played an important role with MfP gelation.

Relation between Morphology and Porous Structure of SAPO-11 Molecular Sieves and Chemical and Phase Composition of Silicoaluminophosphate Gels.

The formation of silicoaluminophosphate gels using boehmite, Al isopropoxide, and di-n-propylamine as a template of silicoaluminophosphate gels as well as their subsequent crystallization into SAPO-11 molecular sieves was studied in detail using X-ray fluorescence spectroscopy (XRF), powder X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and N2 adsorption–desorption methods. The effect of the chemical and phase composition of silicoaluminophosphate gels on the physicochemical properties of SAPO-11 molecular sieves was shown. The secondary structural units that the AEL lattice is composed of were found to be formed at the initial stage of preparation involving aluminum isopropoxide. Several approaches to control their morphology and secondary porous structure are also proposed.

Controllable Preparation of Cubic Zeolite A and Application of Langmuir Model in Carbon Dioxide Adsorption.

A large amount of remaining fly ash has been piled up or landfilled, which not only a waste of land resources but also results in a series of environmental problems. Therefore, using fly ash to produce high value-added products is a win-win development orientation between human beings and nature. In this study, zeolite A is successfully synthesized using a hydrothermal method using fly ash. Additionally, it is at 1.0 mol·L−1 of the alkali concentration that the crystallinity of zeolite A reaches the maximum value, about 96.6%. FTIR research shows that the main secondary structural unit D4R vibration band of zeolite A appears at 555 cm−1. The results of the SEM study indicate the structure of zeolite A is cubic. The TEM results show that the crystal structure of the zeolite A belongs to the body-centered cubic structure. Meanwhile, the positively charged sodium ions cooperate with the silicon oxygen tetrahedron and the aluminum oxygen tetrahedron to form the zeolite A skeleton. Carbon dioxide adsorption equilibrium study shows that the maximum adsorption capacity of zeolite A of 46.5 mL·g−1 is significantly higher than the maximum adsorption capacity of commercial-grade zeolite 4A of 39.3 mL·g−1. In addition, the application of the Langmuir model in the adsorption of carbon dioxide by commercial-grade zeolite 4A and zeolite A is studied, which not only extends the application of zeolite A, but can be further extended to other zeolite materials as well. Meanwhile, the adsorption process belongs to the Langmuir model, which is a single layer adsorption on an ideal surface.

Structural characteristics and formation mechanisms of Bayanhushu Sag in Hailar Basin, north‐east China: A study based on structural physical simulation

The Hailar Basin, located in north‐east China, is a typical continental rifted basin that contains oil and gas. The basin formation process comprised several stages of construction and reformation with complex formation mechanisms. The Bayanhushu (BYHS) Sag is a secondary structural unit in the south‐west Hailar Basin with a significant resource potential, but its current poor exploration and insufficient understanding of the structural evolution characteristics are restricting further oil and gas exploration. Therefore, the study of the structural evolution of the BYHS Sag plays a pivotal role in the future exploration and development of oil and gas. There are different hypotheses on the formation mechanisms and structural evolution of the BYHS Sag. To further understand the evolutionary history of the BYHS Sag, a structural physical simulation experiment was used based on the structural interpretation and geometric analysis of a seismic section. Inversion validation was then undertaken by the 2DMove equilibrium profile recovery technology. It was found that the formation process of the BYHS Sag was mainly controlled by the western Adunchulu Fault. Faults on the section developed in succession from top to bottom. The fault plane experienced multiple changes, thus forming a special seat‐shaped structural pattern. Structural inversion occurred twice during the evolution of the sag. The compressive stress during the tectonic inversion mainly acted in a SE direction. It is inferred that this was related to the subduction of the Palaeo‐Pacific Plate under the Eurasian Plate and the intermittent compression caused by the transmission of stress of the arc–continent collision.

Clustering and Differentiation of glr-3 Gene Function and Its Homologous Proteins

In order to adapt to the low temperature environment, organisms transmitexcitement to the central system through the thermal sensing system, whichis a classic reflex reaction. The cold receptor GLR-3 perceives cold and produces cold avoidance behavior through peripheral sensory neurons ASER.In order to further understand the gene encoding of the cold sensing glr-3gene and the evolution of its homologous gene group function and proteinfunction, the nucleotide sequence and amino acid sequence of the glr-3gene and its homologous gene in 24 species were obtained and compared.By clustering with the GRIK2 gene sequence of Rana chensinensis, the bioinformatics method was used to predict and sequence analyze the change ofgene, evolution rate, physical and chemical properties of protein, glycosylation sites, phosphorylation sites, secondary structure and tertiary structureof protein. The analysis results show that the glr-3 gene and its homologousgene have obvious positive selection effect. The protein prediction analysisshowed that the glr-3 gene and its homologous genes encoded proteinsin these 25 species were hydrophilic proteins, and the proportion of sidechains of aliphatic amino acids was high. The transmembrane helix waswidespread and there were more N-glycosylation sites and O-glycosylationsites. The protein phosphorylation sites encoded were serine, threonine andtyrosine phosphorylation sites. Secondary structure prediction showed thatthe secondary structure units of the encoded protein were α-helix, β-turn,random coil and extended chain, and the proportion of α-helix was the largest. This study provides useful information on the evolution and function ofthe cold sensing gene glr-3 and its homologous genes.

Lessons from combined experimental and theoretical examination of the FTIR and 2D-IR spectroelectrochemistry of the amide I region of cytochrome c.

Amide I difference spectroscopy is widely used to investigate protein function and structure changes. In this article, we show that the common approach of assigning features in amide I difference signals to distinct secondary structure elements in many cases may not be justified. Evidence comes from Fourier transform infrared (FTIR) and 2D-IR spectroelectrochemistry of the protein cytochrome c in the amide I range, in combination with computational spectroscopy based on molecular dynamics (MD) simulations. This combination reveals that each secondary structure unit, such as an alpha-helix or a beta-sheet, exhibits broad overlapping contributions, usually spanning a large part of the amide I region, which in the case of difference absorption experiments (such as in FTIR spectroelectrochemistry) may lead to intensity-compensating and even sign-changing contributions. We use cytochrome c as the test case, as this small electron-transferring redox-active protein contains different kinds of secondary structure units. Upon switching its redox-state, the protein exhibits a different charge distribution while largely retaining its structural scaffold. Our theoretical analysis suggests that the change in charge distribution contributes to the spectral changes and that structural changes are small. However, in order to confidently interpret FTIR amide I difference signals in cytochrome c and proteins in general, MD simulations in combination with additional experimental approaches such as isotope labeling, the insertion of infrared labels to selectively probe local structural elements will be required. In case these data are not available, a critical assessment of previous interpretations of protein amide I 1D- and 2D-IR difference spectroscopy data is warranted.

Fourth order sequence and its distribution characteristics determined by well - seismic combination in Wuerxun depression

Wuerxun depression is a secondary structural unit of Beier lake depression in Hailaer basin. It is located in the middle of the basin and has a high degree of exploration, with the gradual deepening of exploration degree, the previous studies on sequence division and sedimentary facies cannot meet the requirements of high-precision exploration. In this paper, the Nantun Formation is divided into three third-order sequences and eight fourth-order sequences through the study of high-resolution sequence stratigraphy in Wuerxun depression, in the study, firstly, multiple exploration wells with complete sequence development are selected in Wunan area of Wuerxun depression, because Wuerxun depression on the whole is characterized by complex structural features, multiple provenances, short provenances and rapid phase transformation, so we should try our best to make the distribution of preferred wells in all the fourth order structural zones, in order to facilitate the next step of stratigraphic correlation between the structural zones and the whole region. After that, the original sequence of all the selected wells is further subdivided according to the rock and electrical characteristics of single well, and a set of scheme for dividing the fourth-order sequence is determined. Finally, through the tracing of seismic horizon between exploration wells and the fine comparison of well and well seismic in the development area, the traceability and comparability of the newly divided fourth-order sequence are determined, and a set of reasonable fourth-order sequence division scheme in Wuerxun depression is finally determined, which effectively guides the geological oil and gas exploration deployment and lays a solid foundation.