Cysteine racemization in peptide synthesis: a new and easy detection method.
A new method has been developed for the rapid determination of D-cysteine contents in synthetic peptides. It is based on the reduction of cystine residues, when present, with tris-alkylphosphines, selective derivatization of the cysteine residues with 4-vinylpyridine, followed by acid hydrolysis of the (4-pyridylethyl)cysteine-peptides. Baseline enantiomeric resolution of the D,L-S-beta-(4-pyridylethyl)cysteine, and thus quantification of D-enantiomer contents at levels < or = 1%, is easily achieved by capillary zone electrophoresis exploiting the host-guest complexation principle with crown ethers or by gas chromatography on chiral glass capillary columns upon conventional derivatization of the hydrolysate. The acid-stability of the (4-pyridylethyl)cysteine derivative prevents racemization via thiazoline intermediates and allows for standardization of the acid hydrolysis-dependent racemization.
Siedler
F
F
Max-Planck-Institut für Biochemie, Martinsried, Germany.
Weyher
E
E
Moroder
L
L
D000595:Amino Acid Sequence; D003545:Cysteine / Q000737:chemistry*; D006868:Hydrolysis; D008969:Molecular Sequence Data; D010455:Peptides / Q000138:chemical synthesis*; D011487:Protein Conformation; D013237:Stereoisomerism
D010455:Peptides; D003545:Cysteine