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Carbonyl Species (carbonyl + species)
Selected AbstractsUnexpectedly Superior Enantioselectivity for trans-Stilbene cis-Dihydroxylation over Anchored Triosmium Carbonyl Species in Confined Al-MCM-41 Channels.CHEMINFORM, Issue 35 2005Valerie Caps Abstract For Abstract see ChemInform Abstract in Full Text. [source] Rate constant estimation for C1 to C4 alkyl and alkoxyl radical decompositionINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 4 2006H. J. Curran Rate coefficients for alkyl and alkoxy radical decomposition are important in combustion, biological, and atmospheric processes. In this paper, rate constant expressions for C1C4 alkyl and alkoxy radicals decomposition via ,-scission are recommended based on the reverse, exothermic reaction, the addition of a hydrogen atom or an alkyl radical to an olefin or carbonyl species with the decomposition reaction calculated using microscopic reversibility. The rate expressions have been estimated based on a wide-range study of available experimental data. Rate coefficients for hydrogen atom and alkyl radical addition to an olefin show a strong temperature curvature. In addition, it is found that there is a correlation between the activation energy for addition and (i) the type of atom undergoing addition and (ii) whether this radical adds to the internal or terminal carbon atom of the olefin. Rate coefficients for alkoxy radical decomposition show a strong correlation to the ionization potential of the alkyl radical leaving group and on the enthalpy of reaction. It is shown that the activation energy for alkyl radical addition to a carbonyl species can be estimated as a function of the alkyl radical ionization potential and enthalpy of reaction. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 250,275, 2006 [source] A tandem MS precursor-ion scan approach to identify variable covalent modification of albumin Cys34: a new tool for studying vascular carbonylationJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 11 2008Giancarlo Aldini Abstract We developed a liquid chromatography electrospray ionisation multi-stage mass spectrometry (LC-ESI-MS/MS) approach based on precursor-ion scanning and evaluated it to characterize the covalent modifications of Cys34 human serum albumin (HSA) caused by oxidative stress and reactive carbonyl species (RCS) adduction. HSA was isolated and digested enzymatically to generate a suitable-length peptide (LQQCPF) containing the modified tag residue. The resulting LQQCPF peptides were identified by LC-ESI-MS/MS in precursor-ion scan mode and further characterized in product-ion scan mode. The product ions for precursor-ion scanning were selected by studying the MS/MS fragmentation of a series of LQQCPF derivatives containing Cys34 modified with different ,,,-unsaturated aldehydes and di and ketoaldehydes. We used a Boolean logic to enhance the specificity of the method: this reconstitutes a virtual current trace (vCT) showing the peaks in the three precursor-ion scans, marked by the same parent ion. The method was first evaluated to identify and characterize the Cys34 covalent adducts of HSA incubated with 4-hydroxy-hexenal, 4-hydroxy- trans -2-nonenal (HNE) and acrolein (ACR). Then we studied the Cys34 modification of human plasma incubated with mildly oxidized low-density lipoproteins (LDL), and the method easily identified the LQQCPF adducts with HNE and ACR. In other experiments, plasma was oxidized by 2,2'-azobis(2-amidinopropane) HCl (AAPH) or by Fe2+/H2O2. In both conditions, the sulfinic derivative of LQQCPF was identified and characterized, indicating that the method is suitable not only for studying RCS-modified albumin, but also to check the oxidative state of Cys34 as a marker of oxidative damage. Copyright © 2008 John Wiley & Sons, Ltd. [source] Intervention strategies to inhibit protein carbonylation by lipoxidation-derived reactive carbonylsMEDICINAL RESEARCH REVIEWS, Issue 6 2007Giancarlo Aldini Abstract Protein carbonylation induced by reactive carbonyl species (RCS) generated by peroxidation of polyunsaturated fatty acids plays a significant role in the etiology and/or progression of several human diseases, such as cardiovascular (e.g., atherosclerosis, long-term complications of diabetes) and neurodegenerative diseases (e.g., Alzheimer's disease, Parkinson's disease, and cerebral ischemia). Most of the biological effects of intermediate RCS, mainly ,,,-unsaturated aldehydes, di-aldehydes, and keto-aldehydes, are due to their capacity to react with the nucleophilic sites of proteins, forming advanced lipoxidation end-products (ALEs). Because of the emerging deleterious role of RCS/protein adducts in several human diseases, different potential therapeutic strategies have been developed in the last few years. This review sheds focus on fundamental studies on lipid-derived RCS generation, their biological effects, and their reactivity with proteins, with particular emphasis to 4-hydroxy- trans -2-nonenal (HNE)-, acrolein (ACR)-, malondialdehyde (MDA)-, and glyoxal (GO)-modified proteins. It also discusses the recently developed pharmacological approaches for the management of chronic diseases in which oxidative stress and RCS formation are massively involved. Inhibition of ALE formation, based on carbonyl-sequestering agents, seems to be the most promising pharmacological tool and is reviewed in detail. © 2006 Wiley Periodicals, Inc. Med Res Rev, 27, No. 6, 817,868, 2007 [source] Characterization of the Oxidation States of Supported Gold Species by IR Spectroscopy of Adsorbed COCHEMIE-INGENIEUR-TECHNIK (CIT), Issue 6 2007M. Mihaylov Dr. Abstract The use of IR spectroscopy of adsorbed CO for determination of gold speciation on supported gold catalysts is reviewed. Different ionic and metallic sites (Au3+, Au+, Au0, and Au,) can be differentiated on the basis of the frequency and stability of their surface carbonyl species formed after CO adsorption. In addition, the study of CO adsorption and reaction with other gases can provide unique information on the mechanisms of catalytic reactions with participation of CO. Finally, results from complementary techniques such as X-ray absorption spectroscopy, also useful for determination of gold oxidation state, are briefly considered. [source] Variable-Temperature Infrared Spectroscopy Studies on the Thermodynamics of CO Adsorption on the Zeolite Ca,YCHEMPHYSCHEM, Issue 12 2008Barbara Bonelli Dr. Abstract Variable temperature FT,IR spectroscopy (in the range of 298,380 K) is used to study the thermodynamics of formation of Ca2+,,,CO carbonyl species upon CO adsorption on the faujasite-type zeolite Ca,Y, and also the (temperature-dependent) isomerization equilibrium between carbonyl and isocarbonyl (Ca2+,,,OC) species. The standard enthalpy and entropy changes involved in formation of the monocarbonyl species resulted to be ,H0=,50.3 (±0.5) kJ,mol,1 and ,S0=,186 (±5) J,mol,1,K,1, respectively. Isomerization of the (C-bonded) Ca2+,,,CO carbonyl to yield the (O-bonded) Ca2+,,,OC isocarbonyl involves an enthalpy change =+11.4 (±1.0) kJ,mol,1. These results are compared with previously reported data for the CO/Sr,Y system; and also, a brief analysis of enthalpy,entropy correlation for CO adsorption on zeolites and metal oxides is given. [source] | ||||||||||