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Mid-infrared pump-probe spectroscopy is used to study the vibrational relaxation and orientational dynamics of HDO molecules in aqueous solutions of tetramethylurea (TMU). The results shows that at high TMU concentrations the structure of the solution becomes hetergeneous with the water molecules present in the form of clusters in the TMU matrix.

The Jumonji C domain is a catalytic motif that mediates histone lysine demethylation. The Jumonji C-containing oxygenase JMJD2A specifically demethylates tri- and dimethylated lysine-9 and lysine-36 of histone 3 (H3K9/36me3/2). Here we present structures of the JMJD2A catalytic core complexed with methylated H3K36 peptide substrates in the presence of Fe(II) and N-oxalylglycine. We found that the interaction between JMJD2A and peptides largely involves the main chains of the enzyme and the peptide. The peptide-binding specificity is primarily determined by the primary structure of the peptide, which explains the specificity of JMJD2A for methylated H3K9 and H3K36 instead of other methylated residues such as H3K27. The specificity for a particular methyl group, however, is affected by multiple factors, such as space and the electrostatic environment in the catalytic center of the enzyme. These results provide insights into the mechanisms and specificity of histone demethylation. demethylase | oxygenase | JmjC | epigenetic | chromatin

The synthesis, structures and the pseudorotation of the derivatives of Cyclotetraphosphinophosphonium ions are described. The frameworks of the cations in the solid state are found to be the snapshots of different conformational isomers within the solution-phase pseudorotation process.

The oxidation of 4-methylcatechol and 3,4-dihydroxyphenylacetic acid by [O.sub.2] is examined. Results presents that the catechol quinine promotes catechol oxidation by participating in comproportionation to yield the semiquinone, which is more readily oxidated by [O.sub.2].

The reaction mechanism of a novel methylidene penem, which inhibited a class C [beta]-lactamase GC1 is analyzed. A quantum chemical modeling is used to describe the form of a seven-membered ring complex and tautomerism between intermediates.

A Car-Parrinello molecular dynamics study of 4,5-dimethyl-2-(N,N-dimethylaminomethyl)-phenol, a Mannich base, is used to investigate the vibrational properties in solution of its intramolecular hydrogen bond. The dynamic behavior of this hydrogen-bonded system will help in studying hydrogen bond dynamics in biological systems.

The study describes the synthesis, as well as the electronic structure of Bis(4-cyano-2,2,6,6-tetramethyl-3,5-heptanedionato)copper(II), a metal-organic copper spin-1/2 moleculewith a comparatively small magnetic moment. The results show that this molecule has a gap between the highest and the lowest unoccupied molecular orbital, even after being well screened in its photoemission final state.

The structures of two unusual atlas-sphere dithioether silver clusters consisting of [Ag.sub.12][S.sub.6] clusters linked by bis(methylthio)methane ligands are presented. The clusters are associated through the bis(methylthio)methane ligands in a double-chain one-dimensional (1D) coordination polymer and the pentafluoropropionate complex has utilized silver-coordinated water molecules, thus forming hydrogen bonds that connect adjacent chains in a 2D coordination network.

The structural characterization of Rhodobacter sphaeroides dimethyl sulfoxide (DMSO) reductase reduced with trimethylarsine is presented and shown that it is structurally analogous to the physiologically relevant dimethyl sulfide reduced DMSO reductase. The similarity of the trimethylarsine and dimethyl sulfide complexes has indicated that the dimethyl sulfide reduced enzyme consists of a classical coordination of DMSO with no special elongation of the S-O bond.

The reactions of laser-ablated group 3 metal atoms with methyl halides are carried out in excess of Ar during condensation and the matrix infrared spectra studied. The results have reconfirmed that the number of valence electrons on the metal is important for agnostic interaction in simple methylidene complexes.

Temperature-dependent electronic circular dichroism (CD) spectra are described for (R)-(+)-3-methylcyclopentanone (R3MCP) in various solvents. Optical rotation (OR) measurements for R3MCP in cyclohexane solution in the visible region have displayed excellent agreement with OR DFT calculations of the equatorial and axial methyl conformers.

Synthetic 3-O-methylmannose containing polysaccharide (sMMPS) were designed and synthesized. The procedure involves five glycosidations and produces sMMP-8-, 12-, and 16mers and it was found that the synthetic and natural MMPs exhibit almost similar properties.

Synthetic 6-O-methyl-D-glucose containing polysaccharides (sMGPs) were designed and synthesized from [alpha], [beta] and [gamma]-cyclodextrins (CDs). Results show that the amount of Mukaiyama acid required in the sMGP series increased with an increase of substrate size.

A study to determine the differences between the spectroscopic data of the isolated and synthetic samples of the marine natural product (+)-elisabethadione and (+)-elisabethamine was conducted. Results concluded that the published NMR spectral data for natural (+)-elisabethadione do not fit the assigned structure and raises doubt about the (+)-elisabethamine structure.

Matrix isolation infrared spectroscopy is used to study the conformations of dimethoxydimethylsilane (DMDMS) by trapping the silane in argon and nitrogen matrixes. Natural bond analysis has indicated that the charge-transfer hyperconjugative interactions have determined the conformational preferences in the molecule.

The high-level ab initio electronic structure theory is used to calculate the heats of formation of diphosphene (cis- and trans-[P.sub.2][H.sub.3]), phopshinophosphinidene (singlet and triplet [H.sub.2]PP) and diphosphine ([P.sub.2][H.sub.4]), and those of the [P.sub.2]H and [P.sub.2][H.sub.3] radicals ensuing from PH bond cleavages. The calculated results for the hydrogenation reactions have shown that substitution of an organic substituent for H improves the energetics, suggesting that secondary diphosphines and diphosphenes are potential candidates for use in a chemical hydrogen storage system.

The confocal Raman Spectra of isolated single poly(3-methylthiophene) (P3MT) nanotubes prepared by the electrochemical polymerization method are described. The spectra confirm a complete polymerization to the level of individual nanotubes while subtle differences in the Raman spectra obtained from different positions of the nanotubes was detected.

The [super 1]H NMR investigation is employed to measure the thickness of the pre-molten surface layer formed at the interface of octamethylcyclotetrasiloxane (OMCTS) to the matrix in controlled pore glasses with different pore diameters. The study reveals that the surface layer thickness highly depends on the curvature of the pore wall and the solid-liquid interface, as OMCTS itself is a weakly polar molecule with close to spherical shape.

A study demonstrates the regulation of the channel opening process by the alternate splicing method, which generates flip and flop variants of GluR3 receptors by controlling the rate of the channel closing. The analysis presents the differences in the channel opening kinetics of the [alpha]-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), which may also be extensively used for future studies.

Asymmetric reduction of ketimines with trichlorosilane, which could be catalyzed by N-methylvaline-derived Lewis-basic formamides, is described. The results reveal that appending a fluorous tag simplifies the isolation procedure, while preserving high enantioselectivity.

The morphological structures of asymmetric poly(ethylene oxide)-b-poly(1,1'-dihydroperflurooctyl methacrylate) (PEO-b-PFOMA) thin films are examined upon annealing in a compressible fluid, supercritical C[O.sub.2]. The strong affinity between PFOMA and C[O.sub.2] is found which induce phase segregation when annealing PEO-b-PFOMA films at the same temperature as compared with vacuum.

Alkyl sulfate monoesters are involved in cell signaling and structure. Alkyl sulfates are also present in many commercial detergents. Here, we show that monomethyl sulfate acts as an efficient alkylating agent in water, reacting spontaneously with oxygen nucleophiles >100-fold more rapidly than do alkylsulfonium ions, the usual methyl donors in living organisms. These reactions of methyl sulfate, which are much more rapid than its hydrolysis, are insensitive to the nature of the attacking nucleophile, with a Bronsted [[beta].sub.nuc] value of -0.01. Experiments at elevated temperatures indicate a rate constant of 2 x [10.sup.-11] [s.sup.-1] for the uncatalyzed hydrolysis of methyl sulfate at 25[degrees]C ([t.sub.1/2] = 1,100 y), corresponding to a rate enhancement of [approximately equal to] [10.sup.11]-fold by a human alkylsulfatase. Equilibria of formation of methyl sulfate from methanol and sodium hydrogen sulfate indicate a group transfer potential ([DELTA][G'.sub.pH7]) of -8.9 kcal/mol for sulfate ester hydrolysis. The magnitude of that value, involving release of the strong acid HS[O.sup.-.sub.4], helps to explain the need for harnessing the free energy of hydrolysis of two ATP molecules in activating sulfate for the biosynthesis of sulfate monoesters. The 'energy-rich' nature of monoalkyl sulfate esters, coupled with their marked resistance to hydrolysis, renders them capable of acting as sulfating or alkylating agents under relatively mild conditions. These findings raise the possibility that, under appropriate circumstances, alkyl groups may undergo transfer from alkyl sulfate monoesters to biological target molecules. group transfer potential | methyl transfer | sulfate monoester

The new aspect of polymorphism in oligothiophene compound 5,5'''-bis[(2,2,5,5-tetramethyl-1-aza-2,5-disila-1-cyclopenthyl)ethyl]-2,2':5',2':5',2''-quaterthiophene is reported in two forms, namely form-I, which is a more stable phase obtained as-synthesized materials, and form II, which is a less stable phase obtained by a solid-melt-solid transformation from form-I. The solid-solid transformation from form-II to form-I is observed in the range between room temperature and melting point, thus concluding that concluded that the system of two polymorphs is monotropic.

Copper(I) chloro complexes are synthesized with a family of ligands, [HL.sup.R] [[HL.sup.R] = N(2-pyridylmethyl)acetamide, R = null; 2-phenyl-N-(2-pyridylmethyl)acetamide, R = Ph; 2,2-dimethyl-N(2-pyridylmethyl)propionamide, R = Me3; 2,2,2-triphenyl-N-(2-pyridylmethyl)acetamide, R = Ph3)]. All of the ligands, each with different substituent groups on the amide exhibit similar monodentate coordination modes when combined with CuCl to form [Cu.sup.I] complexes.

The NMR solution structures of the binary complex of HPPK with the MgATP analogue MgAMPCPP and the ternary complex with MgAMPCPP and the HP analogue 7,7-dimethyl-6-hydroxymethylpterin are reported. Results indicate that in the binary complex HPPK.MgAMPCPP, loop 2 and 3 can assume multiple conformations in slow exchange on the NMR chemical shift as evidenced by multiple sets of NMR signals.

Spin trapping by 5,5-dimethylpyrroline-N-oxide (DMPO) is used for the detection of radicals in Fenton media in the presence and absence of Nafion perfluorinated ionomers. The formation and trapping of solvent-derived free radicals in ethanol and in methanol is one of the major limitations of DMPO as a spin trap for radical identification in Fenton media, but for water as solvent, the method can be useful when the polymer is treated at higher than ambient temperatures.

The structural analysis of natural protein fibers with mixed parallel and antiparallel [beta]-sheet structures by solid-state NMR is described. The differences found in NMR parameters for tripeptides may be applied to assign the parallel and antiparallel [beta]-sheet [.sup.13.C] resonances in the asymmetric and broad methyl spectra of [3-.sup.13.C]-Ala silk protein fiber of a wild silkworm Samia cynthia ricini.

The structure and acidity of the dimethylhalonium ions were studied at the Density Functional Theory level of calculations. Results indicated that upon proton transfer to form the dimethylhalonium ylide, the C-X-C bond angle increases and there are modifications in the C-X bond lengths, indicative of hyperconjugation between the electron pair with the C-X antibonding orbital.

The synthesis and catalytic activity of lanthanide monoamido complexes supported by a beta-diketiminate ligand are reported. The resulting complexes have displayed good catalytic activity for the polymerization of methyl methacrylate and epsilon-caprolactone.

The supramolecular structures of aggregates of three different OPV-PERY-OPV arrays (OPV = oligo(p-phenylene vinylene), PERY = perylene bisimide) in methylcyclohexane (MCH) is characterized in terms of H- and I-type aggregates using absorption spectroscopy and molecular mechanics calculations. The results show that a balance between molecular properties and intermolecular interactions is vital to the photophysics of self-assembled architectures of functional molecules.

The synthesis and characterization of two new anhydrous pip polymers containing the tin(II) and copper(II) ions namely [Sn(pcp)]and [Cu(pcp)] is presented. It is observed that there is a significant interaction with a C-C bond of one phenyl ring caused by the lone pair of tin(II) and the [Cu(pcp)] complex displays the polymeric columnar structure formed by two intersecting sinusoidal ribbons of Cu(II) ions bridged by the bifunctional phosphinate ligands.

Attempts to apply the (super 1)H NMR ABX method for assignment of stereochemistry of beta-hydroxy ketones to aldols 4-10 deriving from alpha-methyl aldehydes lacking beta-branches reveals that the presence of a beta-branch in the aldehyde reaction partner is necessary so that the average chemical environment of Ha and Hb is different for the Felkin and anti-Felkin aldols. This analysis provides provides a rational basis for application of the (super 1)H NMR ABX pattern analysis to other beta-hydroxy ketone derivatives.

The second-order Moller-Plesset perturbation theory and the conductor-like polarized continuum model investigating the mechanism of phosphine-catalyzed hydroalkoxylation of the methyl vinyl ketone, is presented. Results showed generation of the base in the first stage of the reaction and hydroalkoxylation of the methyl vinyl ketone catalyzed by the base in the second stage.

Quantum chemistry and RRKM/master equation calculations are used to characterize the effect of the vinyl group on the chemistry of the methyl vinyl carbonyl oxide. Natural bond order analysis revealed that the vinyl group weakens the C=O bond of the carbonyl oxide, also dioxole formation, which has a CBS-QB3 reaction barrier of 13.9 kcal/mol, and it is found to be favored over vinyl hydroperoxide formation, dioxirane formation, and collisional stabilization.

The bonding property of the CH/pi interaction in organic crystals are investigated by the means of a periodic ab initio method. Computational evidence of the existence of the cooperative effect of (CH(sp (super 2))/pi interaction in crystals is presented.

The displacements of the methyl substituents away from the metal and out of the cyclopentadienyl ring plane are compared in sterically crowded (C5Me5)3M complexes vs sterically normal f-element complexes in an attempt to evaluate the utility of this parameter in predicting unusual (C5Me5)(super 1-) ring reactivity. The methyl displacement values of sterically crowded complexes overlap with those in the other complexes, which demonstrates that the basis of the structural distortions is complex.

Benzalacetone analogues of naphth[1,2-a]azulene, naphth[a]azulenes and naphth [2,3-a]azulene were synthesized from 2-(5-methyl-2-furyl)-1-tropylionaphthalene, 1-(5-methyl-2-furyl)-2-tropylionaphthalene and 2-(5-methy-2-furyl)-3-tropylionaphthalene respectively. Single-crystal X-ray work on the napth[1,2-a]azulene derivative revealed that its tetracyclic system exhibited deformation from planarity similar to that of benzo-[c]phenanthrene.

One-color resonant two-photon ionization (1C-R2PI), two-color resonant two-photon ionization (2C-R2PI), and mass-analyzed threshold ionization (MATI) spectra of selected isomers of deuterium-substituted p-methoxyphenol (p-methoxyphenol-d1) is reported. It is found that hydrogen/deuterium (H/D) exchange only occurs in the OH and OCH3 parts for both the cis and trans conformers.

A practical synthesis of benzisoxazole and its conversion to alpha-aryloxyisobutyric acid using 1,1,1-trichloro-2-methyl-2-propanol is developed. A highly reactive, short-lived intermediate derived from chloretone is detected by ReacIR and its half-life determined to be ~5 min.

A tetra L-prolinylmethyl derivative of a tetra-sulfonated calix[4]resorcarenes is an effective chiral NMR solvating agent for water-soluble compounds with phenyl, pyridyl, bicyclic aromatic, or indole rings. The effectiveness of a calix[4]resorcarenes prepared from N-methyl-L-alanine as a chiral NMR discriminating agent is compared to the L-prolinylmethyl derivative. for other types of water-soluble organic salts is described.

The beta-carbolinone core structure present in a variety of alkaloids was efficiently prepared from 5-oxo-1,2,3,5-terahydroindolozine-6-trifluoromethanesulfonate precursors. Allylation of methyl 6-hydroxy-5-oxo-1,2,3,5-tetrahydroindolizine-8-carboxylate gave the corresponding ethers, which subsequently underwent thermal Claisen rearrangement to afford the C-allyl products in high yields.

Gas-phase H/D exchange experiments with CD3OD and D2O and quantum chemical ab initio G3(MP2) calculations is conducted on protonated histidine and protonated histidine methyl ester in order to elucidate their bonding and structure. Results reveal that the proton fluctuates between the amino and imidazole groups in the protonated form across an almost vanishing barrier.

A density functional investigation into the structure and vibrational properties of the recently synthesized, novel, Zn(I)-containing species decamethyldizincocene is performed. The analysis is in agreement with the general structural properties of the experimental results.

A study investigates the kinetic resolution of a range of methyl-substituted 1-oxaspirol[2.5]octanes by yeast epoxide hydrolase (YEH) from Rhodotorula glutinis. The structural determinants of substrate specificity and stereoselectivity of YEH toward these substrates appears to be the configuration of the epoxide ring and the substitution pattern of the cyclohexane ring.

The conformations and properties of benzimidazole cavitand with four benzimidazole flaps are studied by (super 1)H NMR. The benzimidazole cavitand could form very stable vase structures with an enforced concave cavity by intermolecular hydrogen bonding with four hydroxyl-containing molecules, X-OH, such as methanol, acetic acid, and trifluoroacetic acid.

A report that regioselective distal bond cleavage of methylenecyclopropanes is accomplished, irrespective of the structure of the substituent R(super 1), by using the cyclic amides. The selectivity of the respective ring-opening position depends on the substituents of methylenecyclopropanes.

A series of three-dimensional (3D) novel coordination polymers M(bpdc)1.5(H2O).0.5DMF (where M=Tb, Ho, Er or Y) is synthesized by reaction of the rare earth ions (M(super 3+)) with 4,4'-biphenyldicarboxylic acid (H2bpdc) in a mixed solution of N,N'-dimethylformamide (DMF) and C2H5OH. These polymers possess the same 3 dimensional architectures and crystallize in monoclinic space group C2/c.

N,N',N'-[Tris(trimethylysilyl)]hydrazino-diphenylphosphane, (TMS)2N-(TMS)N-PPh2, and N,N',N'-[tris(trismethylsilyl]hydrazino-phenyl(chloro)phosphane, (TMS)2N-(TMS)N-P(Cl)Ph2, are obtained in the reaction of bis-[lithium-tris(trimethylsilyl)hydrazide] with Ph(sub n)PCl(sub 3-n) (n = 1,2). The structure and bonding of both species are discussed on the basis of experimentally observed and theoretically obtained data.

A simple strategy is described for the induction of chiral mesomorphic superstructures through noncovalent association between functionalized monomers. The introduction of a suitable chiral diacid, (R)-3-methyladipic acid, is responsible for the formation of H-bonds that preserve the structural integrity of this organization through the formation of a supramolecular polymeric structure.

A series of basket-shaped nongeminally substituted halo-alkyl-phenyl cyclophosphazenes were prepared from the cis isomer of [Me(Ph)PN]3, 2, via deprotonation of the methyl groups and treatment with halogen-containing electrophiles. Also, the mono- and dibromoalyl derivatives were isolated.