Reference

Chiral morphing and enantiomeric quantification in mixtures by mass spectrometry

Chiral morphing and enantiomeric quantification in mixtures by mass spectrometry. Wu, Lianming; Meurer, Eduardo Cesar; Cooks, R. Graham ( Department of Chemistry, Purdue University, West Lafayette, IN 47907, USA). Analytical Chemistry, 76(3), 663-671 (English) 2004 American Chemical Society. CODEN: ANCHAM. ISSN: 0003-2700. DOCUMENT TYPE: Journal CA Section: 9 (Biochemical Methods) A novel mass spectrometric method is introduced for rapid and accurate chiral quantification by examg. a tetracoordinated transition metal complex into which a ref. and a fixed ligand are incorporated simultaneously with the analyte. Chiral anal. is performed by measuring the dissocn. kinetics of these trimeric cluster ions [(MII + Lfixed - H)(ref*)(An)]+ (MII = a transition metal ion, Lfixed = chiral peptide fixed ligand, ref* = chiral ref. ligand, and An = chiral analyte) in an ion trap mass spectrometer. The ratio of the product ion branching ratios measured when a pair of pure chiral fixed ligands and chiral ref. ligands (LDfixed/ref*D and LLfixed/ref*L; or LDfixed/ref*L and LLfixed/ref*D) are employed in sep.Several reagents with their cas registry numbers 1115-78-2 and 7440-50-8 are used here. expts. is related, via the kinetic method formalism, to the enantiomeric compn. of the chiral mixt. This fixed-ligand quotient ratio (QRfixed) is logarithmically proportional to enantiomeric purity allowing construction of a calibration curve for chiral anal. when the analyte is only available in one form of known optical purity. There are reciprocal relationships when switching the chirality of the fixed/ref. ligands. Improved quantification accuracy (due to simplified dissocn. kinetics) and ready construction of two or more single-point calibration curves allow data to be cross-checked and represent an advantage of this approach. These features and the matrix tolerance of the kinetic method are demonstrated using the QRfixed method for detns. of enantiomeric excess of the drug DOPA in the presence of the co-drug compd. L-carbidopa. The chiral selectivity of DOPA was found to vary from 0.0581 to 0.337 using this method, depending on the choices of fixed-ligand and ref. chirality. The av. relative errors are less than 1.2%. The potential of chiral morphing (changing chiral centers in the ligands) to further refine the chiral interactions and hence to maximize chiral recognition is shown. .

Long range vibrational interactions as conformational probes

Long range vibrational interactions as conformational probes. Diem, Max (Hunter Coll., City Univ. New York, New York, NY 10021, USA). Raman Spectrosc., Proc. Int. Conf., 8th, 721-2. Edited by: Lascombe, Jean; Huong, Pham V. Wiley: Chichester, UK. (English) 1982. CODEN: 50HVAT.There are some commonly used reagents with their cas registry numbers 1115-78-2 and 1948-31-8 in this article. DOCUMENT TYPE: Conference CA Section: 34 (Amino Acids, Peptides, and Proteins) Section cross-reference(s): 22 The Raman spectra of diastereomeric mols. H-D-Ala-L-Ala-OH and H-L-Ala-L-Ala-OH are virtually the same, with differences occurring only at ~350, 1100, and 1340 cm-1. The results are discussed in terms of splitting of a-H deformations. .