Peptides enantiomers

Desai,M.J., Armstrong, D.W. (2004). Analysis of native amino acid and peptide enantiomers by high-performance liquid chromatography/atmospheric pressure chemical ionization mass spectrometry. J. Mass. Spec. 39, 177-187. 

R)-DNB-Leu molecule also binds to the selector via an ion-pairing mechanism, but it cannot be stabilized by 71-71 stacking interaction that is apparently of crucial importance for the chiral discrimination. In summary, the enantiodiscrimination is achieved by cooperative multiple contact interactions, such as ion pairing, hydrogen bonding, and n-n stacking [62]. A mechanistically similar enantiodiscrimination process of peptide enantiomers on CSP 56 has been proposed [83]. 

Maier, N. M., Rissanen, K., Lindner,W. Direct high-performance liquid chromatographic separation of peptide enantiomers Study on chiral recognition by systematic evaluation of the influence of structural features of the chiral selectors... 

Czerwenka, C., Zhang, M. M., Kaehlig, H., Maier, N. M., Lipkowitz, K. B., Lindner,W. Chiral Recognition of Peptide Enantiomers by Cinchona Alkaloid Derived Chiral Selectors Mechanistic Investigations by Liquid Chromatography, NMR Spectroscopy, and Molecular Modeling, J. Org. Chem., 2003, 68, 8315-8327. 

IIOS. Mason, G. Tranter, Energy inequivalence of peptide enantiomers from parity non-conservation, J. Chem. Soc. Chem. Commun. (1983) 117-119. 

Stereoselectivity. The chiral center of lipids is located in the head group region. Thus, it is possible that peptide-membrane interactions are stereoselective. The stereoselectivity may be the same as that observed pharmacologically, preferring the natural peptide enantiomers, or it may be the opposite. 

Siifl F, Poppitz W, Saenger-van de Griend C, Scriba GKE (2001) Influence of the amino acid sequence and nature of the cyclodextiin on the separation of small peptide enantiomers by capillary electrophoresis using randomly substituted and single isomer sulfated and sulfonated cyclodextrins. Electrophoresis 22 2416-2423... 

Siifl F, Kahle C, Holzgrabe U, Scriba GKE (2002) Studies on the chiral recognition of peptide enantiomers by neutral and sulfated f -cyclodextrin and heptakis-(2,3-di-0-acetyl)P-cyclodextrin using capillary electrophoresis and nuclear magnetic resonance. Electrophoresis 23 1301-1307... 

Czerwenka C, Lammerhofer M, Lindner W (2003) Structure-enantioselectivity relationships for the study of chiral recognition in peptide enantiomer separation on cinchona alkaloid-based chiral stationary phases by HPLC influence of the N-tenninal protecting group. J Sep Sci 26 1499-1508... 

The infrared spectra of optically active peptide enantiomers are identical (e.g. D, D and L, L isomers) but there may be differences in the spectra of isomers where the optical activity differs at different asymmetric carbons (e.g. D, L and L, D isomers). The use of polarised infrared radiation can be helpful in peptide studies - for example, to determine the orientation of... 

Czerwenka C, Zhang MM, Kahlig H, Maier NM, Lipkowitz KB, Lindner W. Chiral recognition of peptide enantiomers by cinchona alkaloid derived chiral selectors mechanistic investigations by liquid chromatography, NMR spectroscopy, and molecular modeling. J. Org. Chem. 2003 68 8315-8327. 

Use of D-amino acids in the synthesis of a hairpin loop portion from the CD4 receptor provides a stable CD4 receptor mimic, which blocks experimental allergic encephalomyelitis (144). This synthetic constmct is not simply the mirror image or enantiomer of the CD4 hairpin loop, but rather an aH-D-constmct in the reverse sequence, thus providing stereochemicaHy similar side-chain projections of the now inverted backbone (Fig. 11). This peptide mimetic, unlike its aH-L amino acid counterpart, is resistant to en2yme degradation. As one would expect, the aH-D amino acid CD4 hairpin loop, synthesi2ed in the natural direction, the enantiomer of the natural constmct, is inactive. 

This amide, readily formed from an amine and the anhydride or enzymatically using penicillin amidase, is readily cleaved by penicillin acylase (pH 8.1, A -methylpyrrolidone, 65-95% yield). This deprotection procedure works on peptides, phosphorylated peptides, and oligonucleotides, as well as on nonpeptide substrates. The deprotection of racemic phenylacetamides with penicillin acylase can result in enantiomer enrichment of the cleaved amine and the remaining amide. An immobilized form of penicillin G acylase has been developed. ... 

The improvements in resolution achieved in each deconvolution step are shown in Figure 3-3. While the initial library could only afford a modest separation of DNB-glutamic acid, the library with proline in position 4 also separated DNP derivatives of alanine and aspartic acid, and further improvement in both resolution and the number of separable racemates was observed for peptides with hydrophobic amino acid residues in position 3. However, the most dramatic improvement and best selectivity were found for c(Arg-Lys-Tyr-Pro-Tyr-(3-Ala) (Scheme 3-2a) with the tyrosine residue at position 5 with a resolution factor as high as 28 observed for the separation of DNP-glutamic acid enantiomers. 

A mixed 4x4 peptide library consisting of 16 members was again prepared from the earlier-shown two families of building blocks 9-12 (all l enantiomers) and... 

Racemization of the native L-amino acid in peptides and proteins to the D-enantiomer generally results... 

Phenylthiocarbamoyl derivatives of 18 chiral amino acids were separated on a C8 column connected in series to a phenylcarbamoylated (3-cyclodextrin column (Iida et al., 1997). The Cg column separated the derivatized amino acids from one another entering the chiral column. Under this configuration several enantiomers of adjacent amino acids coeluted resulting in poor resolution. However, this configuration was successful in determining the amino acid sequence and chirality of the amino acids in a D-amino acid containing peptide. 

Chiral stationary phases for the separation of enantiomers (optically active isomers) are becoming increasingly important. Among the first types to be synthesized were chiral amino acids ionically or covalently bound to amino-propyl silica and named Pirkle phases after their originator. The ionic form is susceptable to hydrolysis and can be used only in normal phase HPLC whereas the more stable covalent type can be used in reverse phase separations but is less stereoselective. Polymeric phases based on chiral peptides such as bovine serum albumin or a -acid glycoproteins bonded to... 

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