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
✍ Scribed by Hirokazu Matsunaga; Takayuki Iida; Takeshi Fukushima; Tomofumi Santa; Hiroshi Homma; Kazuhiro Imai
- Publisher
- John Wiley and Sons
- Year
- 1996
- Tongue
- English
- Weight
- 193 KB
- Volume
- 10
- Category
- Article
- ISSN
- 0269-3879
No coin nor oath required. For personal study only.
✦ Synopsis
Boron trifluoride-etherate (BF,), 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 o-ku-Gly and L-Pro-L-ku are described, utilizing 7-N~-dimethylaminosuIphonyl-4-(2,l,~benzoxadiazolyl) isothiocyanate (DBD-NCS) as a fluorogenic Edman reagent. The peptide labelled with DBD-NCS was cyclized/cleaved with I Yo BF3 in dichloroethane containing 0.02% ethanethiol at 50 "C for 5 min. The resultant DBD-thiazolinone (TZbamino 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 a-carbon atoms of amino acids (DBD-TZ-L-Leu; 370, +Pro; 6%). Even after 30 min of the cyclizationlcleavage reaction at SOT, DBD-TZ-amino acids retained their configuration to the same degree. On the other hand, DBD-TZ-amino acid obtained by cyclizationlcleavage reaction with TFA at 50°C for 5 min was racemized to a great extent (DBD-TZ-L -~u ; 31%, -0-Pr0; 48%). BF3 should be the most recommendable acid at the cyclizationlcleavage reaction for amino acid sequence and configuration determination of peptides containing o-amino acid residues.