57744-87-3Relevant academic research and scientific papers
Comparison of liquid chromatography-isotope ratio mass spectrometry (LC/IRMS) and gas chromatography-combustion-isotope ratio mass spectrometry (GC/C/IRMS) for the determination of collagen amino acid δ13C values for palaeodietary and palaeoecological reconstruction
Dunn, Philip J. H.,Honch, Noah V.,Evershed, Richard P.
experimental part, p. 2995 - 3011 (2012/05/20)
Results are presented of a comparison of the amino acid (AA) δ13C values obtained by gas chromatography-combustion-isotope ratio mass spectrometry (GC/C/IRMS) and liquid chromatography-isotope ratio mass spectrometry (LC/IRMS). Although the primary focus was the compound-specific stable carbon isotope analysis of bone collagen AAs, because of its growing application for palaeodietary and palaeoecological reconstruction, the results are relevant to any field where AA δ13C values are required. We compare LC/IRMS with the most up-to-date GC/C/IRMS method using N-acetyl methyl ester (NACME) AA derivatives. This comparison involves the analysis of standard AAs and hydrolysates of archaeological human bone collagen, which have been previously investigated as N-trifluoroacetyl isopropyl esters (TFA/IP). It was observed that, although GC/C/IRMS analyses required less sample, LC/IRMS permitted the analysis of a wider range of AAs, particularly those not amenable to GC analysis (e.g. arginine). Accordingly, reconstructed bulk δ13C values based on LC/IRMS-derived δ13C values were closer to the EA/IRMS-derived δ13C values than those based on GC/C/IRMS values. The analytical errors for LC/IRMS AA δ13C values were lower than GC/C/IRMS determinations. Inconsistencies in the δ13C values of the TFA/IP derivatives compared with the NACME- and LC/IRMS-derived δ13C values suggest inherent problems with the use of TFA/IP derivatives, resulting from: (i) inefficient sample combustion, and/or (ii) differences in the intra-molecular distribution of δ13C values between AAs, which are manifested by incomplete combustion. Close similarities between the NACME AA δ13C values and the LC/IRMS-derived δ13C values suggest that the TFA/IP derivatives should be abandoned for the natural abundance determinations of AA δ13C values.
Stable Nitrogen Isotope Analysis of Amino Acid Enantiomers by Gas Chromatography/Combustion/ Isotope Ratio Mass Spectrometry
Macko, Stephen A.,Uhle, Maria E.,Engel, Michael H.,Andrusevich, Vladimir
, p. 926 - 929 (2007/10/03)
The analysis of the stable nitrogen isotope compositions of individual amino acid stereoisomers through the use of gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) is presented. Nitrogen isotopic compositions of single amino acids or of their enantiomers is possible without the labor-intensive and time-consuming preparative-scale chromatographic procedures required for conventional stable isotope analysis. Following hydrolysis and derivatization, single-component isotope analysis is accomplished on nanomole quantities of each of the stereoisomers of an amino acid, utilizing the effluent stream of gas chromatographic separation. Nitrogen isotope fractionation is minimal during acylation of the amino acid, with no additional nitrogen being added stoichiometrically to the derivative. Thus, the isotopic composition of the nitrogen in the derivative is that of the original compound. Replicate stable nitrogen isotope analyses of 11 amino acids, and their trifluoroacetyl (TFA)/isopropyl (IP) ester derivatives, determined by both conventional isotope ratio mass spectrometry (IRMS) and GC/C/IRMS, indicate that the GC procedure is highly reproducible (standard deviations typically 0.3-0.4‰) and that isotopic differences between the amino acid and its TFA/IP derivative are, in general, less than 0.5‰.
Separation of Enantiomeric Amino Acid Derivatives on Axially Chiral 1,1'-Binaphthyl-2,2'-bis(N-decylcarboxamide) as a Stationary Phase for Capillary Gas Chromatography
Oi, Shuichi,Ochiai, Yoshiro,Miyano, Sotaro
, p. 1575 - 1576 (2007/10/02)
Axially chiral 1,1'-binaphthyl-2,2'-bis(N-decylcarboxamide) was utilized as a chiral stationary phase for capillary gas chromatographic separation of enantiomers.This stationary phase showed efficient differentiation for amino acid derivatives allowing complete separation of eleven N-trifluoroacetyl amino acid isopropyl esters.
Stable carbon isotope analysis of amino acid enantiomers by conventional isotope ratio mass spectrometry and combined gas chromatography/isotope ratio mass spectrometry
Silfer,Engel,Macko,Jumeau
, p. 370 - 374 (2007/10/02)
The application of a combined gas chromatography/isotope ratio mass spectrometry (GC/IRMS) method for stable carbon isotope analysis of amino acid enantiomers is presented. This method eliminates the numerous preparative steps integral to the isolation of amino acids and amino acid enantiomers from protein hydrolyzates that precede δ13C analysis by conventional isotope ratio mass spectrometry. Unlike hydrocarbons, amino acids require derivatization prior to GC/ IRMS analysis. Replicate δ13C analyses of trifluoroacetyl (TFA) isopropyl ester derivatives of 22 amino acids by IRMS revealed that the derivatization process is reproducible, with an average error (1 standard deviation) of 0.10‰ ± 0.09 ‰. The average analytical error for analysis of amino acid derivatives by GC/IRMS was 0.26‰ ± 0.09‰. In general, absolute differences between IRMS and GC/IRMS analyses were less than 0.5‰. The derivatization process introduces a distinct, reproducible isotopic fractionation that is constant for each amino acid type. The observed fractionations preclude direct calculation of underivatized amino acid δ13C values from their respective TFA isopropyl ester δ13C compositions through mass balance relationships. Derivatization of amino acid standards of known stable carbon isotope compositions in conjunction with natural samples, however, permits computation of the original, underivatized amino acid δ13C values through use of an empirical correction for the carbon introduced during the derivatization process.
Nucleophilic Substitution Reactions of Alkyl Halides By Using New Polymer-Supported Reagents Containing Hemin
Saito, Kiyoshi,Harada, Kaoru
, p. 2562 - 2566 (2007/10/02)
A new polymer reagent consisting of hemin, divinylbenzene, and 2-methyl-5-vinylpyridine was synthesized by suspension copolymerization.Substitution reactions of primary, secondary, and tertiary alkyl halides with the hemin copolymer combined with cyanide, azide, and thiocyanate ions were given satisfactory yields.This reaction mechanism was revealed to be a SNi type on the basis of stereochemical study.The hemin copolymer was not only a polymer-supported reagent with functional capabilities, but also served to separate the product from the reaction mixture.
The Structure of a Toxic Octapeptide from the Larvae of Sawfly
Williams, Dudley H.,Santikarn, Sitthivet,Angelis, Francesco De,Smith, Richard J.,Reid, David G.,at al.
, p. 1869 - 1878 (2007/10/02)
The amino acid sequence of an octapeptide from sawfly (Lophyrotoma interrupta) larvae, which acts as a liver toxin, has been determined as C6H5COAla-Phe-Val-Ile-Asp-Asp-Glu-Gln.The amino acids, Ala, Phe, Asp5, and Glu7 residues, have the D absolute configuration.
