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Coupled-cluster theory (CCSD(T)) extrapolated to the complete basis set limit was used for examining the thermochemical parameters of trifluoromethanol. Energy barrier of 28.7 kcal/mol was observed in a six-membered ring dimer.

Anti-Stokes Raman scattering is used for monitoring vibrational energy redistribution in liquid nitromethane and perdeuterated nitromethane after ultrafast infrared (IR) excitation of either the symmetric or asymmetric CH- or CD-stretch transitions. The results have predicted the slow interconversion among CH-stretch excitations and the slower relaxation of the asymmetric CH-stretch.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine administration has been used, in various mammalian species, as an experimental model of Parkinson's disease. The pathogenesis for such pharmacologically induced Parkinson's disease involves 1-methyl-4-phenylpyridinium (MPP+), the active metabolite of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. This metabolite produces rapid degeneration of nigrostriatal dopaminergic neurons, which causes the parkinsonian syndrome. In this work, we show that injection of MPP+ into the presynaptic terminal of the squid giant synapse blocks synaptic transmission without affecting the presynaptic action potential or the presynaptic calcium currents. These effects of MPP+ were mimicked by the injection of an active form of caspase-3 and prevented by inhibitors of caspase-3 and protein kinase C [delta]. Ultrastructurally, MPP+-injected synapses showed a dramatic reduction in the number of neurotransmitter vesicles at the presynaptic active zone, as compared with control synapses. Otherwise, normal docking and clathrincoated vesicles were observed, albeit at much reduced numbers. These results indicate that MPP+ acutely reduces presynaptic vesicular availability, not release, and that MPP+-induced pathogenesis results from presynaptic dysfunction that leads, secondarily, to dying-back neuropathy in affected neurons. MPP+ | Parkinson's disease | presynaptic terminal | synaptic potentials | voltage clamp

Hepatic folate, methyl group, and homocysteine metabolism are interrelated pathways that when disrupted are associated with numerous pathologies. Maintenance of normal methyl group and homocysteine homeostasis is dependent on the balance between: S-adenosylmethionine (SAM)-dependent transmethylation, which utilizes methyl groups and produces homocysteine; remethylation of homocysteine back to methionine by folate-dependent and -independent mechanisms; and homocysteine catabolism via the transsulfuration pathway. Recent studies have demonstrated that hormonal imbalance is a factor in the control of key proteins that regulate these pathways. A diabetic state is characterized by increased expression of specific methyltransferases that utilize SAM-derived methyl groups and produce homocysteine. Although the supply of methyl groups from the folate-dependent 1-carbon pool appears to be diminished under diabetic conditions, the increased production of homocysteine is compensated for by stimulation of folate-independent remethylation and catabolism by transsulfuration, resulting in hypohomocysteinemia. Similar changes have been observed with glucocorticoid administration and in a growth hormone-deficient model, which can be prevented by insulin and growth hormone treatment, respectively. Taken together, these reports clearly indicate that hormonal regulation is a major factor in the metabolic control of folate, methyl groups, and homocysteine, thereby providing a potential link between the pathologies associated with these pathways and hormonal imbalance.

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 methyl-deficient model of endogenous hepatocarcinogenesis in rodents is unique in that dietary omission rather than the addition of chemical carcinogens leads to tumor formation. Thus, the biochemical and molecular events predisposing to cancer in this model result from chronic metabolic stress and provide an ideal model system to study progressive alterations that occur during carcinogenesis. Moreover, epigenetic alterations imposed by this diet are believed to be 1 of the main mechanisms responsible for malignant transformation of rat liver cells. In this study we examined the changes in global histone modification patterns in liver during hepatocarcinogenesis induced by methyl deficiency. Feeding animals the methyl-deficient diet (MDD) led to progressive loss of histone H4 lysine 20 trimethylation (H4K2Ome3), H3 lysine 9 trimethytation (H3K9me3), and histone H3 lysine 9 (H3K9ac) and histone H4 lysine 16 (H4K16ac) acetylation. A considerable decrease of H4K2Ome3 and H3K9ac was also detected in liver tumors induced by MDD. In contrast, liver tumors displayed an increase in H3K9me3 and H4K16ac. To determine the possible mechanism of alterations of histone modifications, we analyzed the expression of histone-modifying enzymes in liver during hepatocarcinogenesis. The expression of Suv4-2Oh2 and RIZ1 histone methyltransferases (HMTs) steadily decreased along with the development of liver tumors and reached its lowest level in tumor tissue, whereas the expression of Suv39-h1 HMT and histone acetyltransferase 1 (HAT1) substantially increased in tumors. These results illustrate the complexity and importance of histone modification changes in the etiology of hepatocarcinogenesis induced by MDD. J. Nutr. 137: 216S-222S, 2007.

The intimate relation between amino acids and protein and nitrogen requirements is well recognized. Nutrition research has focused on the capacity of food to meet the need for nitrogen and indispensable amino acids (IAA) and led to the conclusion that the quality, not just the quantity, of protein is critical. This is especially relevant in regard to the sulfur amino acids (SAA) methionine and cysteine because of the increased understanding of their relation to chronic diseases (e.g., cardiovascular disease, dementia, cirrhosis), immunomodulation, DNA transcription, and RNA translation. Considerable effort has been expended to determine whether and to what extent cysteine can spare the requirement for the IAA methionine. In vivo studies in humans generally concur that the dietary requirement of the SAA ranges between 13 and 16 mg x [kg.sup.-1] x [d.sup.-1], but how much can be met by cysteine relative to methionine remains controversial. This review examines the current status of in vivo estimates of methionine and cysteine requirements in human adults and considers needs beyond what is necessary for protein synthesis. Factors influencing the utilization of methionine and cysteine, especially those conditions that lead to toxicity on the one hand or beneficial effects on the other, are discussed. Data on alternative dietary sources of methyl groups (e.g., betaine, choline, phosphatidylcholine, S-adenosylmethionine, S-methylmethionine) or sulfur (e.g., N-acetylcysteine or L-2-oxothiazolidine-4-carboxylic acid) support a role for the SAA 'beyond protein.' Other pathways may influence the specific requirement for methionine and/or cysteine, especially when the person is challenged by disease, inadequate availability of food, or environmental stress. KEY WORDS: * methionine * cysteine * methyl groups * sulfur amino acid requirement * amino acids

Atmospheric field measurement and modeling studies have long noted discrepancies between observation and predictions of OH and H[O.sub.2] concentrations in the atmosphere. Novel photochemical mechanisms have been proposed to explain these differences. Although inclusion of these additional sources improves agreement, they are unable to fully account for the observations. We report and demonstrate the importance of weak electronic absorption features, normally ignored or not measured, in contributing to significant OH radical production. Experiments on methyl hydroperoxide, a prototypical organic peroxide in large abundance in the troposphere, highlights how photochemistry in the neglected electronic absorption tail makes an important addition to the tropospheric OH budget. The present results underscore the need to measure absorption cross sections for atmospheric molecules over a wider dynamic range, especially over the wavelength regions where the solar flux is high, to fully quantitate their contributions to atmospheric photochemistry. absorption cross section | atmospheric photochemistry | electronic absorption | methyl hydroperoxide | photodissociation

The wave profiles for single-crystal cyclotetramethylene tetranitramine are analyzed. The analysis reveals that the rise times vary with porosity and grain size, which suggests that plasticity is important for granular HMX as well as for a single crystal.

The electron-transfer rate constant is measured in two U-shaped donor-bridge-acceptor molecules over a wide range of temperature in acetonitrile and N-methylacetamide (NMA). The electron-transfer rate at high temperature can be well described by a nonadiabatic model of the reaction but at low temperatures the rate in NMA becomes controlled by the solvent.

An approach based on relaxation-optimized spectroscopy and multiplet simplification that improves both the resolution and sensitivity of methylene group NMR studies is presented. The approach is applicable both to small molecules and biological macromolecules.

The organolithium addition protocol using methyllithium is applied in an enantiodivergent fashion to the preparation of both enantiomers of 1-(2-hydroxyphenyl)ethylamine, which is used as an efficient chiral auxillary for the synthesis of natural products in the laboratory. The synthetic utility of this methodology involving diastereoselective methyl addition is demonstrated by further application to the asymmetric synthesis of a new type of calcium receptor agonist (calcimimetics), (R)-(+)-NPS R-568 and its thio analogue.

An Escherichia coli strain engineered for expression of the ribABGH genes of Bacillus subtilis is shown to produce 100 mg of the riboflavin precursor 6,7-dimethyl-8-ribityllumazine per liter of minimal medium. Growth of recombinant strain in medium supplemented with [U-(super 13)C(sub 6)]glucose and/or (super 15)NH(sub 14)Cl as single sources of carbon and/or nitrogen afforded 6,7-dimethyl-8-ribityllumazine labeled with C(super 13) and/or N(super 15).

Photochemical reduction of several 4-picolyl- and N-methy-4-picolinium esters is examined using product analysis, laser flash photolysis, and fluorescence quenching. It is demonstrated that the radical (anions) formed in these reactions readily fragment t yield a carboxylic acid and a 4-pyridylmethyl radical intermediate.

The diastereofacial selectivity of 2-methyl-5-X-adamant-2-yl cations toward methanol is investigated in the gas phase at 750 Torr and in the 40-120 degreeC temperature range and compared with that of I(sub F) (X = F) and I(sub Si) (X = (CH(sub 3))(sub 3)Si) measured previously under similar conditions. Detailed analysis of the energy surface of the I(sub Me) (X = CH(sub 3)) ion reveals that the activation barrier of its syn addition to methanol is significantly lower than that of the anti attack.

Reactivity, kinetic and thermodynamic studies for reactions of a rhodium(II) bimetalloradical with H2, and with the methyl C-H bonds for a series of methyl substrates CH(sub 3)R (R=H, CH(sub 3), OH, C00(sub 6)H(sub 5)) using an m-xylyl diether tethered diporphyrin ligand is reported. The results reveal that bimolecular reactions involving the intramolecular use of two metalloradical centers and preorganisation of the four-centered transition state, result in large rate enhancements.

Electronic absorption (Abs) and magnetic circular dichroism (MCD) spectroscopic techniques to probe cofactor/enzyme active site interactions in the Co(super 3+)Cbl 'ground' state for Methylmalonyl-CoA mutase (MMCM) reconstituted with both the native cofactor AdoCbl and its derivative methylcobalamin are analyzed. The results indicate that the dominant contribution to the enzymatic Co-C bond activation presumably comes through stabilization of the Co2+Cbl/Ado post-homolysis products.

The proteolysis data indicate that in acid solution human growth hormone (hGH) adopts a partly folded state characterized by a local unfolding of the first minihelix (residues 38-47) encompassing the Phe44-leu45 peptide bond. It is suggested that MGs may have a physiological significance and play a role in ligand binding and translocation across membrane as well as in protein aggregation phenomena.

The vacuum ultraviolet laser single-photon zero kinetic energy (ZEKE) photoelectron spectrum of the [X.sup.2][E.sub.3/2] ground electronic state of the methyl bromide cation is reported. The spectrum is dominated by the origin hand [0.sup.0.sub.0] of the transition [X.sup.2][E.sub.3/2] [left arrow] [X.sup.1][A.sub.1]. In addition, the [2.sup.1.sub.0] band and the [3.sup.1.sub.1] hot band are observed. All observed bands show similar rotational contours. Simulation of the rotational contour of the origin band yields the first ionization energy of methyl bromide (85 031.2 [+ or -] 1.0 [cm.sup.-1]) and the rotational constants of the cation in its ground electronic state. Key words: methyl bromide, vacuum ultraviolet laser, single-photon excitation, zero kinetic energy photoelectron spectroscopy.

Byline: I. N. Stan'kov (1), A. A. Sergeeva (1), V. B. Sitnikov (1), I. D. Derevyagina (1), O. T. Morozova (1) Abstract: Procedures were developed for the determination of trace isobutyl S-2-(N,N-diethylamino)ethyl methylphosphonothioate (IBDAEMP) in soil and construction materials by gas chromatography at a level of 1 x 10.sup.--9%. The procedures are based on the extraction of IBDAEMP from test materials using an aqueous solution of monoethanolamine or chloroform saturated with ammonia, the back extraction of IBDAEMP into hexane, the evaporation of the hexane solution (with an addition of HCl) to dryness, the treatment of the residue with a solution of silver nitrate in methanol for obtaining O-isobutyl O-methyl methylphosphonate, and gas-chromatographic separation on an open tubular column with the HP--5MS chemically modified stationary phase with flame-photometric detection. Author Affiliation: (1) State Research Institute of Organic Chemistry and Technology, sh. Entuziastov 23, Moscow, 111024, Russia Article History: Registration Date: 06/10/2004

A simple united-atom second-order potential model for dimethylmethylphosphonate (DMMP) is designed to reproduce molecular conformations and physical properties, such as the liquid density, heat of evaporation, and thermal expansion coefficient of the pure liquid used. It is concluded that the average lifetime of hydrogen bonds does not exceed rotation correlation time of individual water molecules, thus indicating that there are no long-living DMMP.H2O complexes in the aqueous solutions.

A torsional dependence of electron spin-spin exchange coupling in trimethylenemethane (TMM)-type dinitroxide biradicals is described. This torsional dependence is compared with an analogous series of TMM-type bis(semiquinone) biradicals.

The assignment of methyl (super 13)C and (super 1)H chemical shifts from Ile, Leu, and Val residues in high molecular weight proteins, and it is studied using new NMR experiments. Results show that the size of the proteins increases significantly and highlights the possibility of using side-chain methyl groups for probing the molecular structure and dynamics in high molecular weight systems.

The stoichiometry of the reduction of coenzyme F430 pentamethyl ester is examined by three independent methods. The experiments demonstrate that the reduction of coenzyme F430M to the species having almost identical UV-vis and EPR spectra as MCR(sub red1) is a one-electron process and therefore inconsistent with a reduction of the macrocycle chromophore.

The independent generation of 5-(2'deoxycytidinyl)methyl radical and that this radical can give rise to the predicted novel intrastrand cross-link lesion in dinucleoside monophosphates of d(mCG) and D(GmC) is reported. The 5-(2'-deoxycytidinyl)methyl radical can be specifically generated by 254-nm irradiation of 5-(phenyl-thiomethyl)-2'-deoxycytidine in dinucleoside monophosphates d(mCSPLG) and D(GmCSPL).

Phase transitions in nonpolymeric fluid mixtures at negative pressures are studied. The results reveal that there is an intimate relation between pressures and the isotopic content of the solvent.

The spectra of C8H4 and C10H5 are observed in a butadiyne/argon discharge under the same conditions as those whereby C7H2 and C9H3 are found to dominate the spectroscopy. The results are discussed in terms of the chemistry of plasmas and the interstellar medium.

Based on pulse radiolysis measurements in acid solution and supported by ab initio molecular orbital calculations, the mechanistic details of H atom reaction with the methyl viologen dication, MV(super 2+) in aqueous solutions is discussed. In all cases of H addition, a reduction in conjugation and increase in radical dipole moment is obtained.

The effect of the mixed-ring silyl methyl complex in bromobenzene-d5 resulted in the zwitterionic hafnium silyl structure, which is constant for a minimum of 12 h in the solution. It is the omicron-bond metathesis is quite significant in the creation of novel catalytic alterations.

The consequences of the aromatic consistency at the speed of [1,5]-hydrogen moves in a sequence of carbo-and heterocyclic dihydroaromatic compounds which were approximately calculated by the B3LYP divided by 6-31G. The Marcus theory can be effectively used for different pericyclic shifts like the [1,5]-shifts that comprise of the transmission of chlorine and methyl.

The combination of experimental and theoretical methods, allowed unraveling the magnetic properties of the novel cationic tungsten(IV) complexes in solid state and in solution. The presented methodology provides strong guidelines for future studies in the field of solution and solid-state magnetochemistry.

Electrochemical reduction of p-methyl-, p-methoxy-, and 3,5-dinitrophenyl thiocyanates, p-methyl- and p-methoxyphenyl disulfides were investigated in the acetronitrile at an inert electrode. The series of compounds revealed a striking change in the reduction cleavage mechanism of the S-CN bond in thiocyanates as a function of the substituent on the aryl ring in the aryl thiocyanate.

The kinetics of the reaction between OH and pyridine, all three picoline isomers, all six lutidine isomers, and all three ethylpyridine isomers are experimentally investigated. The atmospheric implications of the findings are discussed in terms of the role of pyridinated compounds in the ionic composition of the troposphere are discussed.

The kinetics of hydroxyl radical trapping by some nitrones and the decay of their corresponding spin adduct and correlation of these experimental results with theoretical calculations is reported. The results suggest that hydroxyl radical trapping by 5-d3emethyl -1-pyrroline N-oxide (DMPO) is significantly slower compared to the trapping rate of spin traps 5-ethoxycarbonyl-5-methyl-1-pyrrolilne N-oxide (EMPO) , 5-butoxycarbonyl-5-methyl-1-pyrroline N-oxide (BocMPO) and many more.

The photodissociation dynamics of methacrylonitrile (H2C=C(CH3)CN) at 193nm and of 2-butenenitrile for comparison are investigated by measuring rotationally resolved laser induced fluorescence spectra of the CN fragments. It was found that the photodissociation of the compounds occurs from the ground electronic state after internal conversion from the initial pi right arrow pi(super *) transition.

Dissociations of aminoketyl radicals and cation radicals derived from beta-alanine N-methylamide, N-acetyl-1,2-diaminoethane, N(sub alpha)-acetyl lysine amide, and N(sub alpha)-glycyl glycine amide are investigated by combined density functional theory and Moller-Plesset perturbational calculations. The facile N-C(sub alpha) bond dissociation in thermalized ions indicates that it is unnecessary to invoke the hypothesis of non-ergodic behavior for electron capture dissociation intermediates.

A sensitive 3D NMR pulse scheme, (H)C(CA)NH-COSY is presented for the assignment of 13C(super delta1) IIE chemical shifts in large perdeuterated, methyl protonated proteins. The experiment presented utilizes COZY-based transfer steps and refocuses undesirable 13C-13C scalar couplings that degrade the efficiency of TOCSY transfers.

The energies of the preferred conformations of four 7a-methyl octa(or hexa)hydrocyclopenta[d][1,3]oxazines, five 8a-methyl octa(or hexa)hydro[3,1]benzoxazinone, all cis-fused, are investigated by DFT methods. A methodology for determining the conformational equilibria of systems that is comparable in many respects to experimental approaches such as variable-temperature NMR to the use of model coupling constant values, when available, from analogous compounds is provided.

A concise synthesis of (+)-geissoschizine, a biosynthetic precursor of a variety of monoterpenoid indole alkaloids, from D-tryptophan is performed as a critical prelude to achieving the first biomimetic, enantioslective synthesis of the sarpagine alkaloid (+)-Na-methylvellosimine. The approach to (+)-geissonschizine is designed to address the dual problems of stereocontrolled formation of the E-ethylidene moiety.

Determination of the molecular sizes of higher aggregates of dimethlcuprates (Me2CuLi, Me2CuLi.Lil, and Me2CuLi.LiCN) and bis[(trimethylsilyl)methyl]cuprates ((Me3SiCH2)(sub 2)CuLi, ((Me3SiCH2)(sub 2)CuLi.Lil, and ((Me3SiCH2)(sub 2)CuLi.LiCN) in diethyl ether (Et2O) was done by pulsed field gradient (PFG) NMR diffusion measurements. Diffusion coefficients show molecular sizes larger than dimers, and the aggregation extent depends on steric hindrance, salt effects, and sample concentration.

Molecular dynamics of polycrystalline alpha-L-fucopyranose and methyl alpha-L-fucopyranoside are investigated using (super 13) C and (super 1) H spin relaxation times over a range of temperature (90-400 K). The proton second moment showed a reduction to a lower value at about 150 K due to the rotation of methyl groups.

In a study of the reaction system methylaluminoxane (MAO)/(C5H5)2ZrMe2, the size of the ion pair [(C5H5)2Zr(u-Me)2AIMe2]+ [Me-MAO]- was determined by pulsed filed-gradient NMR of its cationic moiety. MAO contains various species that produce Me-MAO- anions with different Lewis basicities.

A kinetic reactor system is described which couples pulsed laser photolytic production of radicals with continuous laser excitation cavity ring-down spectroscopic detection in the near-infrared (NIR). The atmospherically relevant alkyl peroxy radicalEs ethyl peroxy (C2H5O2) and methyl peroxy (CH3O2) are monitored via their structured absorbance spectra in the NIR near 1.3 mum.

The transient birefringence in the room-temperature ionic liquids (RTILs), 1-alkyl-3-methylimidazolium bis((trifluoromethyl)sulfonyl)imides, [C(sub n) mim]NTf2 with n = 2, 4, 5, 6, 8, 10 (C2, C4, C5, C6, C8, C10), is studied using optically heterodyne-detected Raman-induced Kerr effect spectroscopy (OHD-RIKES). It is found that the intemolecular vibrational spectra for the RTILS obtained form the reduced OHD-RIKES extend from 0 to 200 cm(sub -1).

The production of clean samples of CH3OO radicals in cryogenic matrices is described using a tandom pair of supersonic nozzles. The polarization spectroscopy provides new information that makes many of the fundamental assignments of the CH3OO radical more definite.

Infrared and Raman spectra of pinosylvin are recorded and the vibrational frequencies with the corresponding infrared intensities are compared with the results of ab initio calculations utilizing the DFT method with the Becke3P86 functional and the 6-31G(D) basis set.

Quantum mechanical electronic structure calculations are used to determine equilibrium geometries, energetics and normal-mode frequencies for stationary points along the minimum energy reaction path for the reaction of methyl radicals with chlorine molecules. The results are used to measure the rate coefficient, employing both extended RRKM theory and quasi-classical trajectory techniques.

The room temperature vapor phase overtone spectra of ortho-, meta-, and para-xylene are studied in the CH stretching region. The difference in the methyl band profiles in o-xylene, and in m- and p-xylene are ascribed mainly to differences in the torsional potential and the dipole moment function.

A variety of S-alkylated products are prepared by alkylation of methyl thioethers [ MeSB12 H11] (super 2-) (5), [1-(MeS)-2(7,12) -Me2s) B12H10] (super -1) (6-8), and [1,2(7,12)-(MeS)2 B12H10] (super 2-) (9,11) with alkyl halides and tosylates in acetonitrile. Several derivatives of methyl thioethers 5-11 are characterized by single-crystal X-ray diffraction.