[Spectral characteristics of muscle aspartyl- and valyl-tRNA- synthetases in normal animals and in an experimental model of prolonged starvation].

Conformational differences between asparagyl- and valyl-tRNA synthetases from normal (ARSn) and long-fasting (ARSf) rabbit's muscle were revealed by means of UV fluorescence and differential spectroscopy. The fluorescence spectra indicate more hydrophobic environment of tryptophan residues in the ARSf's at similar quantum yields. The differential absorption spectra reveal the distinctions between tryptophanyl microenvironments for ARS's of different amino acid specificity and for ARSn's and ARSf's of the same specificity. Lower accessibility of tryptophan residues in ARSn's in comparison with ARSf's was shown by selective fluorescence quenching with Cs+ and I- ions. The effect of long-wave shift of fluorescence spectra at the edge excitation was used for studies on microenvironment of chromophors and the rate of the dipole-orientational relaxation of this microenvironment.