Boron trifluoride-etherate (Lewis acid) as an efficient acid at cyclization/cleavage reaction of D/L-amino acids affording the retention of their original configuration in the Edman sequencing method of peptides.
Boron trifluoride-etherate (BF3), one of the Lewis acids, was found to be an efficient acid in the Edman sequencing method, affording the retention of the N-terminal amino acid configuration at the cyclization/cleavage reaction from peptides. Examples for the sequencing of D-Leu-Gly and L-Pro-L-Leu are described, utilizing 7-N,N-dimethylaminosulphonyl-4-(2,1,3-benzoxadiazolyl) isothiocyanate (DBD-NCS) as a fluorogenic Edman reagent. The peptide labelled with DBD-NCS was cyclized/cleaved with 1% BF3 in dichloroethane containing 0.02% ethanethiol at 50 degrees C for 5 min. The resultant DBD-thiazolinone (TZ)-amino acid was separated on a phenylcarbamoylated cyclodextrin column with fluorometric detection at 524 nm with excitation at 387 nm. DBD-TZ-amino acids thus obtained showed remarkable retention of their configuration of alpha-carbon atoms of amino acids (DBD-TZ-L-Leu; 3%, -D-Pro; 6%). Even after 30 min of the cyclization/cleavage reaction at 50 degrees C, DBD-TZ-amino acids retained their configuration to the same degree. On the other hand, DBD-TZ-amino acid obtained by cyclization/cleavage reaction with TFA at 50 degrees C for 5 min was racemized to a great extent (DBD-TZ-L-Leu; 31%, -D-Pro; 48%). BF3 should be the most recommendable acid at the cyclization/cleavage reaction for amino acid sequence and configuration determination of peptides containing D-amino acid residues.
Matsunaga
H
H
Faculty of Pharmaceutical Science, University of Tokyo, Japan.
Iida
T
T
Fukushima
T
T
Santa
T
T
Homma
H
H
Imai
K
K
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry*; D001880:Boranes / Q000737:chemistry*; D003500:Cyclization; D004151:Dipeptides / Q000737:chemistry; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry*; D017421:Sequence Analysis / Q000379:methods*; D013050:Spectrometry, Fluorescence
D000596:Amino Acids; D001880:Boranes; D004151:Dipeptides; D010455:Peptides; C101707:boron trifluoride etherate