Oxygen Atom Of Water Molecule Research Articles

The anisotropy of molybdenite planes: Analysis based on the adsorption behaviors of reagent and H2O

Multiple planes with different properties are exposed after the comminution of molybdenite because of the anisotropy of molybdenite. Study on the properties of different planes is of great significance to enhance the comprehensive utilization of molybdenite, especially in flotation. In order to explore the properties of different planes, the two main planes of molybdenite (basal plane and edge plane) are respectively taken as the research object in this paper, and the properties of planes are expressed using DFT through the adsorption behaviors of a new reagent named DTC-CTS and water molecules. The results show that edge plane has higher activity than basal plane. This is because there are exposed molybdenum atoms on the edge plane, and the sulfur atoms in DTC-CTS and oxygen atoms in water molecules are easy to react with the exposed molybdenum atoms. While the activity of basal plane is low because of the hinderance effect of sulfur atoms in the skin layer. The different adsorption behaviors of water molecules on molybdenite planes verified the hydrophobicity of different planes. In addition, the results also show that the water can affect the DTC-CTS adsorption on edge plane. Water can enhance interaction between single-bond sulfur atom and molybdenum atom, and weaken the interaction between double-bond sulfur atom and molybdenum atom on edge plane.

Constructing Unsaturated Ru Atom Arrays Confined in Mn Oxides to Boost Neutral Water Reduction.

Recently, Ru single atoms supported on carbon nanomaterials have demonstrated ultrahigh activity for acid hydrogen evolution reaction (HER), however their neutral HER activity remains low due to the sluggish kinetics for both the water dissociation step to generate H* intermediates and subsequent H* recombination in neutral electrolytes. Here, we synthesize ordered low-coordinated Ru atom arrays confined in Mn oxides (i.e., Li4Mn5O12) for concurrently boosting the water dissociation and H* recombination, thus achieving a 6-fold HER activity enhancement than commercial Pt/C in neutral media. Control experiments indicate that low-coordinated Ru atoms with strong affinity to oxygen atoms of water molecules facilitate the water dissociation to rapidly generate H*. More importantly, both electrochemical and theoretic results uncover that the array-like structure allows the activation of two water molecules on two adjacent Ru atoms for enabling direct H*-H* recombination via the Tafel step, while isolated Ru atoms can only activate water one by one for recombining H* via the sluggish Heyrovsky step. Clearly, this work paves new avenues to boosting the electrocatalytic activity by constructing ordered metal atoms assembles with controllable coordination environments.

Constructing Unsaturated Ru Atom Arrays Confined in Mn Oxides to Boost Neutral Water Reduction

Recently, Ru single atoms supported on carbon nanomaterials have demonstrated ultrahigh activity for acid hydrogen evolution reaction (HER), however their neutral HER activity remains low due to the sluggish kinetics for both the water dissociation step to generate H* intermediates and subsequent H* recombination in neutral electrolytes. Here, we synthesize ordered low‐coordinated Ru atom arrays confined in Mn oxides (i.e., Li4Mn5O12) for concurrently boosting the water dissociation and H* recombination, thus achieving a 6‐fold HER activity enhancement than commercial Pt/C in neutral media. Control experiments indicate that low‐coordinated Ru atoms with strong affinity to oxygen atoms of water molecules facilitate the water dissociation to rapidly generate H*. More importantly, both electrochemical and theoretic results uncover that the array‐like structure allows the activation of two water molecules on two adjacent Ru atoms for enabling direct H*–H* recombination via the Tafel step, while isolated Ru atoms can only activate water one by one for recombining H* via the sluggish Heyrovsky step. Clearly, this work paves new avenues to boosting the electrocatalytic activity by constructing ordered metal atoms assembles with controllable coordination environments.

Synthesis and characterization of indazole derived Schiff base ligands and their metal complexes: Biological and computational studies

Indazoles represent one of the most important heterocycles in drug molecules. Therefore, in the pursuit of potent biological agents, a series of ligands (HL1-HL4) and their corresponding transition metal complexes [M(L1-L4)2(H2O)2] were synthesized by the condensation reaction of 6-aminoindazole with various derivatives of salicylaldehyde. Further, the compounds underwent characterization through several physicochemical (TGA, powder XRD, SEM, EDAX) and spectroscopic techniques (FT-IR, UV–Vis, NMR, mass spectrometry, ESR). These techniques suggested hexacoordinated stereochemistry of the metal complexes, where ligands chelate via oxygen atom of phenolic ring, azomethine nitrogen and oxygen atom of water molecules in 1:2 (M:L) molar ratio. The thermal stability of the complexes was demonstrated by thermal analysis revealing three step decompositions leaving behind metal oxide as an end residue. The surface morphology of the ligands was distinct from metal complexes as revealed by SEM analysis, while mapping images demonstrated the simultaneously existence of the elements. While, to ascertain the nature of the obtained compounds (crystalline or amorphous), powder X-ray investigation was conducted by utilizing a wavelength of 1.54 Å. The compound’s antioxidant potential was assessed through DPPH assays and anti-inflammatory activity was evaluated using BSA denaturation inhibition assay, while their antimicrobial potential was evaluated against six microbial strains (E. coli, S. aureus, P. aeruginosa, B. subtilis, C. albicans, A. niger) by serial dilution approach. The performed biological evaluations revealed that the complexes are more efficient in controlling infectious ailment in comparison of ligands. HL2 (2) and its Cu(II), Zn(II) complexes (11, 12) exhibited potent antimicrobial activity (MIC value: 0.0047, 0.0048 µmol/mL against B. subtilis) and potent anti-inflammatory efficacy (IC50 value: 6.7 ± 0.044, 6.9 ± 0.036 µM). All the complexes exhibited potent antioxidant activity and their is enhancement in the activity of Schiff base ligands upon complexation, complex (19) demonstrated the greatest activity with IC50 value 2.1 ± 0.059. Additionally, the ADMET score provided a robust indication of the compounds’ drug-like behaviour. Furthermore, the biological effectiveness of the highly microbial potent ligand HL2 (2) and its complexes (9–12) was demonstrated through computational studies. The binding studies exposed that complexes (11, 12) exhibited lowest binding energy at −7.8, −7.9 kcal/mol. While, DFT study emphasized that complex (12) exhibits the highest electrophilicity index value (6.359), suggesting its affinity for binding with biological molecules and also revealed that complexes exhibit greater potency compared to the ligands and could potentially be utilized as drugs for combatting pathogen-induced malformations.

HydraProt: A New Deep Learning Tool for Fast and Accurate Prediction of Water Molecule Positions for Protein Structures.

Water molecules are integral to the structural stability of proteins and vital for facilitating molecular interactions. However, accurately predicting their precise position around protein structures remains a significant challenge, making it a vibrant research area. In this paper, we introduce HydraProt (deep Hydration of Proteins), a novel methodology for predicting precise positions of water molecule oxygen atoms around protein structures, leveraging two interconnected deep learning architectures: a 3D U-net and a Multi-Layer Perceptron (MLP). Our approach starts by introducing a coarse voxel-based representation of the protein, which allows for rapid sampling of candidate water positions via the 3D U-net. These water positions are then assessed by embedding the water-protein relationship in the Euclidean space by means of an MLP. Finally, a postprocessing step is applied to further refine the MLP predictions. HydraProt surpasses existing state-of-the-art approaches in terms of precision and recall and has been validated on large data sets of protein structures. Notably, our method offers rapid inference runtime and should constitute the method of choice for protein structure studies and drug discovery applications. Our pretrained models, data, and the source code required to reproduce these results are accessible at https://github.com/azamanos/HydraProt.

Spectroscopic studies, antimicrobial activity, and computational investigations of hydrazone ligands endowed metal chelates

Our current efforts are aimed to synthesize 16 complexes of Co (II), Ni (II), Cu (II), and Zn (II) metal ions from heterocyclic hydrazone ligands by condensation reaction of 2,6‐diacetylpyridine with hydrazide derivatives to find out combating agent against microorganism diseases. The synthesized compounds were precisely characterized by various physicochemical and spectroscopic techniques like FT‐IR, UV–Vis, 1H and 13C NMR, magnetic susceptibility, ESR, mass spectrometry, powder XRD, TGA, and SEM that suggested the octahedral geometry of the complexes coordinating via enolic oxygen atoms, azomethine nitrogen atom, pyridine ring nitrogen atom of the hydrazone ligands, and oxygen atom of water molecule. The thermal stability of the complexes was demonstrated by thermal analysis revealing two‐step decompositions leaving behind metal oxide as an end residue. By using serial dilution method, the compounds (1–20) were tested for in vitro antimicrobial activity against four bacterial and two fungal pathogens. Among all the synthesized compounds, complex 16 was most active against B. subtilis, whereas complexes 13, 14, and 15 were most efficient for C. albicans. Moreover, the biological efficacy of H2L3 (3) ligand and its (13–16) complexes were demonstrated by computational methods like molecular docking, MESP, DFT, and ADMET studies that highlight that complexes have more potency than the ligands and may be employed as effective drug for pathogen‐induced malformations.

Synthesis, Spectroscopic Characterization, and X-ray Structure of the Co-crystal Copper(II) Complex of the Dissymmetrical 1-(2 hydroxy-3-methoxybenzylidene)-5-(pyridin-2 ylmethylene) Carbnohydrazide Ligand

In the pentanuclear title complex, bis{<i>μ</i>₂-1-(2-oxido-3-methoxybenzylidene)-5-(pyridin-2-ylmethylene)carbonohydrazide}-1<i>κ</i>⁴<I>O</I>,<I>N</I>,<I>N</I>’,<I>N</I>’’:2<i>κ</i>²<I>O</I>,<I>N</I>;2<i>κ</i>²<I>O</I>,<I>N</I>:3<i>κ</i>⁴<I>O</I>,<I>N</I>,<I>N</I>’,<I>N</I>’’-1,2,3-tricopper(II) bis{[1-(2-oxido-3-methoxybenzylidene)-5-(pyridin-2-ylmethylene)carbonohydrazide]-<i>κ</i>⁴<I>O</I>,<I>N</I>,<I>N</I>’,<I>N</I>’’-copper(II)} tetraperchlorate tetrahydrate (1), two monocationic mononuclear units and one dianionic trinuclear unit co-exist. The Cu<SUP>II</SUP> centers in the mononuclear units as well as the two terminal Cu<SUP>II</SUP> centers in the trinuclear unit are located in the N₃O cavity of the ligand and are coordinated to a phenolate oxygen atom, to a pyridine nitrogen atom, to an imino nitrogen atom and to a hydrazinyl nitrogen atom. The third central Cu(II) atom in the trinuclear unit, which is hexacoordinated, is located in N₂O₄. The metal center is coordinated to two ligand molecule through one imino nitrogen atom one oxygen atom of a carbonyl moiety per ligand and two oxygen atom of water molecules. The tetracoordinated copper(II) ions are situated in distorted square planar environments, while the hexacoordinated copper(II) is located in octahedral geometry. In the mononuclear units, as well as in the trinuclear units, the methoxy oxygen atoms remain uncoordinated. Each atom of the uncoordinated perchlorate anions is disordered over two sets of sites in a 0.5 ratio. Four free water molecules are also present. In the crystal, the trinuclear cationic unit and the mononuclear cationic units are assembled into infinite layers. These layers are held together via electrostatic interactions, forming a three-dimensional structure.

Np(V) dicyanamide complexes with electroneutral N-donor ligands

Abstract Three new complexes of Np(V) dicyanamide with electroneutral N-donor ligands have been synthesized and structurally characterized: two with terpyridine derivatives: [(NpO2)(Cl-Terpy)(DMA)(N(CN)2)]·0.5DMA (1), [(NpO2)(TPTZ)(N(CN)2)(H2O)]·2H2O·CH3OH (2) and a dimeric complex with bipyridine [(NpO2)(Bipy)(N(CN)2)(H2O)]2·2(CH3OH) (3). In compounds 1–3, the coordination polyhedra of Np atoms are pentagonal bipyramids with “yl” oxygen atoms in apical positions. The equatorial plane of the bipyramids is formed by nitrogen atoms of the anions [N(CN)2]− and N-donor electroneutral ligands (Cl-Terpy, TPTZ, Bipy) and the oxygen atom of water molecule (1, 3) or DMA (2). In compounds 1 and 2, the [N(CN)2]− anions manifest themselves as monodentate ligands, and in compound 3 dicyanamide is a bidentate-bridging ligand.

Simulation of the CO2 hydrate-water interfacial energy: The mold integration-guest methodology.

The growth pattern and nucleation rate of carbon dioxide hydrate critically depend on the precise value of the hydrate-water interfacial free energy. There exist in the literature only two independent experimental measurements of this thermodynamic magnitude: one obtained by Uchida et al. [J. Phys. Chem. B 106, 8202 (2002)], 28(6)mJ/m2, and the other by Anderson and co-workers [J. Phys. Chem. B 107, 3507 (2003)], 30(3)mJ/m2. Recently, Algaba et al. [J. Colloid Interface Sci. 623, 354 (2022)] have extended the mold integration method proposed by Espinosa and co-workers [J. Chem. Phys. 141, 134709 (2014)] to deal with the CO2 hydrate-water interfacial free energy (mold integration-guest or MI-H). Computer simulations predict a value of 29(2)mJ/m2, in excellent agreement with experimental data. The method is based on the use of a mold of attractive wells located at the crystallographic positions of the oxygen atoms of water molecules in equilibrium hydrate structures to induce the formation of a thin hydrate slab in the liquid phase at coexistence conditions. We propose here a new implementation of the mold integration technique using a mold of attractive wells located now at the crystallographic positions of the carbon atoms of the CO2 molecules in the equilibrium hydrate structure. We find that the new mold integration-guest methodology, which does not introduce positional or orientational information of the water molecules in the hydrate phase, is able to induce the formation of CO2 hydrates in an efficient way. More importantly, this new version of the method predicts a CO2 hydrate-water interfacial energy value of 30(2)mJ/m2, in excellent agreement with experimental data, which is also fully consistent with the results obtained using the previous methodology.

Crystal architecture, DFT and Hirshfeld surface analysis of novel ‘double open-end spanner’ type dimer derived from 4-aminoantipyrine

A novel synthetic route where 4-aminoantipyrine dimerizes through an azo group with the introduction of a new pyrazole ring to obtain (E)-6-((1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)diazenyl)-1-methyl-2-phenyl-1,5-dihydropyrazolo[4,3-c]pyrazol-3(2H)-one and characterized by single crystal X-ray diffraction technique. Title compound shows mass spectrum with molecular ion peak at m/z 469. The monoclinic crystal lattice was developed by arranging two organic molecules facing antiparallel to each other held together by two water molecules through strong hydrogen bonds. Spectral analysis, NBO analysis, electronic, geometric and thermochemical investigation were done using density functional theory at B3LYP level employing 6-311++G(d,p) basis set. A detailed investigation of intermolecular interactions through three-dimensional Hirshfeld surface analysis and corresponding two-dimensional fingerprint plots revealed that the organic crystal structure is stabilized by the gluing effect of water molecules thereby decreasing the intermolecular distance of organic molecules. The association in organic crystal involves predominantly CO—H, NH—O close contacts along with other weak interactions. Strong hydrogen bonds are found in the range 1.98 ± 0.06 Å. The oxygen atoms of water molecules facing opposite directions involved in ‘double open-end spanner’ dimer are kept at a distance of 6.633 Å. 3D topology of energy frameworks is analyzed. The intermolecular interactions are quantified and presented by mapping electrostatic potential and presenting close contacts through dnorm, shape index and curvedness parameters.

Structures of 18-crown-6/Cs+ complexes in aqueous solutions by wide angle X-ray scattering and density functional theory

• The oxygen atoms of 18-crown-6 and the hydrogen atoms of water molecule form strong hydrogen bonds in aqueous solution. • Cs + is located directly above the 18-crown-6 ring plane, about 1.15 Å from the centroid of 18-crown-6. • The higher the concentration of CsCl, the lower the complexation percentage of 18-crown-6 to Cs + . • Cs + complexing with 18-crown-6 mainly hydrates with four water molecules. Wide angle X-ray scattering (WAXS) and density functional theory (DFT) were employed to study the structures of aqueous 18-crown-6/CsCl solutions with CsCl concentrations of 0.25, 0.50 and 1.00 mol·L -1 . The empirical potential structure refinement (EPSR) modelling was adopted to get the pair distribution functions (PDFs), coordination numbers ( CN ), coordination number distributions (CND), angle distribution functions (ADFs), independent gradient model (IGM) and spatial density functions (SDFs) for the 18-crown-6 hydration, the complexation of 18-crown-6 and Cs + , the hydration of 18-crown-6/Cs + complex, and the association of Cl - and 18-crown-6/Cs + complex. Judging from the distance and orientation of water molecules, and the IGM between 18-crown-6 and water molecules, the oxygen atoms of 18-crown-6 (Oc) and the hydrogen atoms of water molecules (Hw) form strong hydrogen bonds, and these water molecules were distributed on both sides of the 18-crown-6 ring plane. However, the hydrogen atoms of 18-crown-6 (Hc) hardly form hydrogen bonds with the oxygen atoms of water molecules (Ow). Cs + is located directly above the 18-crown-6 ring plane of 0.35 to 2.05 Å away from the centroid of 18-crown-6, and forms 18-crown-6/Cs + complex with six Oc at r Cs + - O c = 3.06 Å. When the concentrations of CsCl are 0.25, 0.50 and 1.00 mol·L -1 , the complexation percentage of 18-crown-6 to Cs + are about 100%, 58% and 54%, respectively. No classic 2:1 “sandwich” 18-crown-6/Cs + complex structure was found in the solutions we surveyed. Both interaction energies and solvation stability energies reveal that the hydrates of 18-crown-6/Cs + complexes were formed in aqueous solutions. Cs + uncomplexed with 18-crown-6 hydrates with eight water molecules in aqueous solution, while Cs + can also hydrate with about four water molecules when it complexes with 18-crown-6. The results of atomic pair distances, the dipole distance of water molecules, the SDF and the IGM indicate that although water molecules can be located on both sides of the 18-crown-6 ring plane when the hydrates are formed, they hydrate with Cs + on the side where Cs + only existed. Cs + of 18-crown-6/Cs + complex associates with Cl - with the r Cs + - Cl - = 3.79 Å by electrostatic attraction.

Crystal-structure studies of 4-phenyl-piperazin-1-ium 4-eth-oxy-benzoate monohydrate, 4-phenyl-piperazin-1-ium 4-meth-oxy-benzoate monohydrate, 4-phenyl-piperazin-1-ium 4-methyl-benzoate monohydrate and 4-phenyl-piperazin-1-ium tri-fluoro-acetate 0.12-hydrate.

In this study, four new piperazinium salts, namely, 4-phenyl-piperazin-1-ium 4-eth-oxy-benzoate monohydrate, C9H9O3·C10H15N2·H2O (I); 4-phenyl-piperazin-1-ium 4-meth-oxy-benzoate monohydrate, C10H15N2·C8H7O3·H2O (II); 4-phenyl-piperazin-1-ium 4-methyl-benzoate monohydrate, C10H15N2·C8H7O2·H2O (III); and 4-phenyl-piperazin-1-ium tri-fluoro-acetate 0.12 hydrate, C10H15N2·C2F3O2·0.12H2O (IV), have been synthesized. The single-crystal structures of these compounds reveal that all of them crystallize in the triclinic P space group and the crystal packing of (I)-(III) is built up of ribbons formed by a combination of hydrogen bonds of type N-H⋯O, O-H⋯O and other weak inter-actions of type C-H⋯O and C-H⋯π, leading to a three-dimensional network. In the crystal of (IV), the cations and the anions are connected by C-H⋯O, N-H⋯O and C-H⋯F hydrogen bonds and by C-H⋯π inter-actions, forming sheets which in turn inter-act to maintain the crystal structure by linking through the oxygen atoms of water mol-ecules and van der Waals inter-actions, giving the whole structure.

Evaluation of transport mechanism of ascorbic acid through cyclic peptide-based nanotubes: A molecular dynamics study

Cyclic peptide nanotubes (CPNTs) are potential candidates for drug delivery, separation and recovery technologies, as well as self-assembling nanomaterials. In this study, we investigated the L-ascorbic acid transport behaviour through two CPNTs using computational studies, including quantum calculations, molecular docking and steered molecular dynamics (SMD) simulations. Two cyclic peptide nanotubes 8 × [L-Gln-(D-Leu-L-Trp) 4-D-Leu-] (QLWL) and 8 × [(D-Ala-L-Ala) 5] (AA), embedded in a fully hydrated membrane composed of DPPC/POPC/POPS/cholesterol, were considered. Our findings from SMD simulations revealed that ascorbic acid moves differently in AA nanotube compared to QLWL nanotube. The analysis of the number of hydrogen bonds shows that the hydrogen atoms of ascorbic acid hydroxyl groups form more hydrogen bonds compared to oxygen atoms with water molecules and the CPNTs. This result was supported using the calculations of radial distribution functions of various atoms of the ascorbic acid near the oxygen atom of water molecules and carbonyl groups of the CPNTs during the transport pathway in the lumen of each CPNTs. Entropy calculations show that the configurational entropy of ascorbic acid in the transport pathway is not monotonous, and it changes due to variable behaviour when the molecule moves throughout CPNTs. The interactions that the nanotubes form with their environment play an important role in the binding energy of ascorbic acid with each of the peptide ring that the binding energy value is significant for each of the peptide rings with ascorbic acid. These informations can be useful to future applications and studies in the field of nanoscience and nanotechnology, such as drug delivery and nanosensors.

Ferrocenylimine-based homoleptic metal(II) complexes: Theoretical, biocompatibility, in vitro anti-proliferative, and in silico molecular docking and pharmacokinetics studies

Three new ferrocenylimine-based homoleptic metal(II) complexes with general formula [M(L)2(H2O)2](ClO4)2 (1‒3), where L = trans-4-(ferrocenylideneamino)-1,5-dimethyl-2-phenyl-1H-pyrazol-3(2H)-one, and M = Ni2+, Cu2+ and Zn2+ have been synthesized and characterized by spectroscopic methods. The spectral and theoretical studies revealed the distorted octahedral (Oh) geometry for the synthesized complexes with the involvement of azomethine nitrogen, carbonyl oxygen and oxygen atom of water molecules in coordination to metal(II) ion. The UV–vis and cyclic voltammetric techniques were employed to understand the reduction behaviour of copper(II) complex (2) in ascorbic acid. The in vitro biocompatibility studies show the risk-free nature of complexes to NHDF (normal human dermal fibroblast) cell line up to the concentration level of 100 µg/mL. In vitro anti-proliferative activity was investigated on two human cancerous MCF-7 (breast adenocarcinoma) and HepG2 (hepatoma), and one non-cancerous NHDF (normal human dermal fibroblast) cell lines by MTT reduction assay. The complexes showed higher anti-proliferative activity and biocompatibility without showing any toxicity towards normal cell lines. The docking studies indicated H-bonding, π-pair and hydrophobic interactions between complexes and protein molecules (VEGF, EGF and CEA receptors). In addition, the pharmacokinetics properties were analyzed using Lipinski's ʹrule of fiveʹ and the ADMET (Absorption, Distribution, Metabolism, Excretion and Toxicity) properties, which predicted the drug-likeness and bio-activity of the synthesized complexes.

Synthesis and Complexation Properties of 2-Hydroxy-5-methoxyphenylphosphonic Acid (H3L1). Crystal Structure of the [Cu(H2L1)2(\u041d2\u041e)2] Complex

2-Hydroxy-5-methoxyphenylphosphonic acid (H3L1) and the complex [Cu(H2L1)2(H2O)2] were synthesized and characterized by IR spectroscopy, thermogravimetry, and X-ray diffraction analysis. The polyhedron of the copper atom is an axially elongated square bipyramid with oxygen atoms of phenolic and of monodeprotonated phosphonic groups at the base and oxygen atoms of water molecules at the vertices. The protonation constants of the H3L1 acid and the stability constants of its Cu2+ complexes in water were determined by potentiometric titration. The protonation constants of the acid in water are significantly influenced by the intramolecular hydrogen bond and the methoxy group. The H3L1 acid forms complexes CuL‒ and CuL24‒ with Cu2+ in water.

Interaction of amino acid functional group with water molecule on methane hydrate growth

Kinetic inhibitor-amino acid exhibits a promising advantage in preventing the hydrate formation. In this work, adsorption behaviors of amino acid including glycine, serine and valine on methane hydrate surface are investigated by the density functional theory (DFT). It is found that the nitrogen/oxygen and hydrogen atoms in hydrophilic groups of amino acid prefer to attach the hydrogen and oxygen atoms of water molecules in hydrate simultaneously to achieve a more stable adsorption mode. The adsorption energy of hydrophobic groups is lower than that of hydrophilic groups. Meanwhile, molecular dynamics (MD) simulations are carried out to analyze the inhibition effect of glycine, serine and valine. It is observed that the strongest interaction appears between the hydrophilic groups of serine and methane hydrate surface. The hydrophobic group-methyl of valine weakens the interaction of amino and carboxyl groups with water molecules, whereas increases the disturbance of water molecules.

SYNTHESES OF COBALT AND CADMIUM COORDINATION POLYMERS COMPOSED OF DICARBOXYLATE AND BIS(4-(1H-IMIDAZOL-1-YL)PHENYL)METHANONE LIGANDS

Two coordination polymers {[Co(L1)2(H2O)2](fdc)(H2O)2.5}n (1) and [Cd(L1)(tpdc)(H2O)]n (2) (L1 = bis(4-(1H-imidazol-1-yl)phenyl)methanone, H2fdc = furan-2,5-dicarboxylic acid, H2tpdc = thiophene-2,5-dicarboxylic acid) are synthesized and structurally characterized by IR, EA, and single crystal X-ray diffraction analyses. In 1, Co1 has a distorted octahedral geometry with two oxygen atoms of water molecules and four nitrogen atoms from four L1 ligands to give a distorted octahedral coordination geometry. The [Co(L1)2]2 units are bridged by L2 ligands to form 1D chains. In 2, Cd1 is seven-coordinated by four O atoms from two tpdc2– ligands, one O atom from a coordinated water molecule, and two N atoms from two distinct L1 ligands. Complex 2 possesses a 4-connected net topology with the point symbol {44·62}.

Potassium-induced partial inhibition of lactoperoxidase: structure of the complex of lactoperoxidase with potassium ion at 2.20Å resolution.

Lactoperoxidase, a heme-containing glycoprotein, catalyzes the oxidation of thiocyanate by hydrogen peroxide into hypothiocyanite which acts as an antibacterial agent. The prosthetic heme moiety is attached to the protein through two ester linkages via Glu258 and Asp108. In lactoperoxidase, the substrate-binding site is formed on the distal heme side. To study the effect of physiologically important potassium ion on the structure and function of lactoperoxidase, the fresh protein samples were isolated from yak (Bos grunniens) colostrum and purified to homogeneity. The biochemical studies with potassium fluoride showed a significant reduction in the catalytic activity. Lactoperoxidase was crystallized using 200mM ammonium nitrate and 20% PEG-3350 at pH 6.0. The crystals of LPO were soaked in the solution of potassium fluoride and used for the X-ray intensity data collection. Structure determination at 2.20Å resolution revealed the presence of a potassium ion in the distal heme cavity. Structure determination further revealed that the propionic chain attached to pyrrole ring C of the heme moiety, was disordered into two components each having an occupancy of 0.5. One component occupied a position similar to the normally observed position of propionic chain while the second component was found in the distal heme cavity. The potassium ion in the distal heme cavity formed five coordinate bonds with two oxygen atoms of propionic moiety, Nε2 atom of His109 and two oxygen atoms of water molecules. The presence of potassium ion in the distal heme cavity hampered the catalytic activity of lactoperoxidase.

Syntheses of cobalt and cadmium coordination polymers composed of dicarboxylate and bis(4-(1H-imidazol-1-yl)phenyl)methanone ligands

Two coordination polymers {[Co(L1)2(H2O)2](fdc)(H2O)2.5}n (1) and [Cd(L1)(tpdc)(H2O)]n (2) (L1 = bis(4-(1H-imidazol-1-yl)phenyl)methanone, H2fdc = furan-2,5-dicarboxylic acid, H2tpdc = thiophene-2,5-dicarboxylic acid) are synthesized and structurally characterized by IR, EA, and single crystal X-ray diffraction analyses. In 1, Co1 has a distorted octahedral geometry with two oxygen atoms of water molecules and four nitrogen atoms from four L1 ligands to give a distorted octahedral coordination geometry. The [Co(L1)2]2 units are bridged by L2 ligands to form 1D chains. In 2, Cd1 is seven-coordinated by four O atoms from two tpdc2– ligands, one O atom from a coordinated water molecule, and two N atoms from two distinct L1 ligands. Complex 2 possesses a 4-connected net topology with the point symbol {44·62}.

Misconception Profile of High School Student on Electrolyte and Non-Electrolyte Solution Using Pictorial-Based Two-Tier Multiple Choices Diagnostic Test

&lt;p&gt;The development and study had been done to determine misconceptions profile of class X high school students in Kuningan West Java on electrolyte and non-electrolyte solutions using descriptive methods. The instrument used was a pictorial-based two-tier multiple choices diagnostic test consisted 18 questions. The instrument had been tested for its feasibility with the CVR and CVI values was one, and the Cronbach's Alpha (reliability) value for the whole item was 0.706. The items were applied to class X students in schools with high, medium and low category. Based on the results of the application, the most common misconceptions of students on electrolyte and non-electrolyte solutions was that when dissolved in water, ionic compounds would be ionized into ions, oxygen atom in water molecule interacted with anions and hydrogen atoms in water molecule interacted with cations (37.78%). The misconceptions of class X high school students on electrolyte and non-electrolyte solution in high and low category schools in Kuningan had a significant difference. Based on the one-way ANAVA test, the significance level &amp;lt; 0.05, there was 0.045. The misconception of class X high school students in Kuningan on electrolyte and non-electrolyte solutions based on gender differences did not have a significant difference. Based on results of t test, the significance level &amp;gt; 0.05, there was 0.755.&lt;/p&gt;