A 2ND-ORDER ASYMMETRIC TRANSFORMATION OF RACEMIC 2-HYDROXYMETHYL[5]THIAHETEROHELICENE INTO A SINGLE ENANTIOMER UPON UPTAKE BY BOVINE SERUM-ALBUMIN

Racemic droxymethylthieno[3,2-e:4,5-e']di[1]benzothiophene (2-HT) with a labile helical structure was converted into a P enantiomer upon upt ake by bovine serum albumin (BSA) in 1% ethanol-water. The effect of t he alteration of the molar ratio [2-HT]:[BSA] on UV and CD spectra of the 2-HT-BSA complex solution revealed that BSA possesses two differen t substrate-binding sites with a distinct ability to recognize chirali ty of enantiomers of 2-HT. The stability of the 2-HT-BSA complex and t he chirality recognition at the two sites of BSA were evaluated by the equilibrium constants and the thermodynamic parameters which were obt ained from the temperature-dependence of CD-absorptional intensities. BSA pretreated at 50 similar to 70 degrees C in an aqueous solution ex hibited a great depression of ability in discriminating chirality betw een enantiomers of 2-HT, though it possessed slightly altered ability for uptake of 2-HT, in comparison with untreated BSA. (C) 1996 Elsevie r Science Ltd