thiohydantoins and thiocyanic-acid

A novel and efficient method to prepare amino acid thiohydantoins, which are required as reference standards for development of C-terminal protein sequencing, is reported. Amino acid thiohydantoins were prepared using a straightforward method involving reaction of 20 free amino acids with acetyl chloride as activating reagent and trimethylsilyl isothiocyanate (TMS-ITC) as derivatizing reagent. The products were characterized by HPLC, uv spectra, amino acid analysis, MS, and NMR. Different reaction conditions were investigated and the chemical mechanism of the formation of amino acid thiohydantoins was illustrated.

Topics: Acetates; Amino Acids; Aminoacylation; Chlorides; Chromatography, High Pressure Liquid; Isothiocyanates; Magnetic Resonance Spectroscopy; Mass Spectrometry; Proteins; Sequence Analysis; Spectrophotometry, Ultraviolet; Thiocyanates; Thiohydantoins; Trimethylsilyl Compounds

Pure amino acid thiohydantoins are required as reference standards for development of C-terminal-sequencing procedures based on thiohydantoin formation of the C-terminal amino acids of peptides and proteins. Proline thiohydantoin was prepared using a straightforward method involving reaction of acetylproline with ammonium thiocyanate. It was characterized by UV spectrophotometry, mass spectrometry and back-hydrolysis to the free amino acid. These data establish unequivocally that the thiocyanate procedure is applicable to proline as well as to the other common amino acids. This work also validates earlier claims that proline thiohydantoin can be prepared by reaction with thiocyanic acid.

Topics: Amino Acid Sequence; Chromatography, High Pressure Liquid; Mass Spectrometry; Proline; Spectrophotometry, Ultraviolet; Thiocyanates; Thiohydantoins