The vibrational wavenumbers of kyotorphin [L-Tyr(1)-D-Arg(2)] analogue (D-KTP) was determined by using theoretical and experimental methods. The optimised structure of kyotorphin was obtained on the basis of parameter set determined for L-tyrosine and D-arginine molecules. After then the vibrational wavenumbers of kyotorphin were calculated by density functional theory (DFT) approximation, using the B3LYP function with 6-3 1 G(d,p) basis set. The vibrational assignment was given by the help of total energy distribution (TED) of the vibrational modes of the D-KTP. The characteristic Fermi doubled of tyrosine was observed at 853 and 828 cm(-1) in the Raman spectrum of D-KTP and the intensity ratio (I-853/I-828) was found to be 1.6, indicating that both phenoxyl proton and oxygen are involved in H-bonding interaction in D-KTP. (c) 2004 Elsevier B.V. All rights reserved.