The laser-induced fluorescence spectrum of jet-cooled L-tyrosine exhibits more than 20 vibronic bands in the 35450-35750 cm-1 region. We attribute these bands to eight conformers by using results of UV-UV hole-burning spectroscopy. These isomers are classified into four groups; each group consists of two rotational isomers that have a similar side-chain conformation but different orientations of the phenolic OH. The splitting of band origins of rotational isomers is 31, 21, 5, and 0 cm-1 for these groups. IR-UV spectra suggest that conformers belonging to two of the four groups have an intramolecular OH・・・N hydrogen bond between the COOH and NH2 groups. By comparing experimental and theoretical results of L-tyrosine with those of L-phenylalanine, we propose probable conformers of L-tyrosine.

This is a preprint of an article published by American Chemical Society in Journal of Physical Chemistry A, 2007, available online: http://pubs.acs.org/doi/abs/10.1021/jp070163a.

This study is supported by the Grant-in-Aids for Scientific Research (18205003 and 18685001) by the Ministry of Education, Science, Sports, and Culture, Japan. T.E. thanks the support of Satake foundation.