Amino Acids in Solid Parahydrogen
Takamasa Momose
Department of Chemistry, The University of British Columbia, Vancouver, CANADA
The existence of amino acids in interstellar space has been discussed for many years, but
it is still under debate. The effect of UV radiation on amino acids may be one of the keys for the
search of interstellar amino acids, since strong UV radiation in interstellar space may change the
chemical form of these amino acids. In this experiment, conformational compositions of a
couple of amino acids and the effect of UV photolysis were investigated via matrix-isolation
FTIR spectroscopy and quantum chemical calculations. Solid parahydrogen was used as the
matrix. In comparison with amino acids isolated in Ar matrices, it was found that more
conformers were detected in as-deposited sample in parahydrogen than in Ar. Furthermore, more
enhanced correlation between conformational ratio and sublimation temperature was found for
some amino acids isolated in parahydrogen. UV photolysis of amino acids in parahydrogen
resulted in not only its conformational changes, but also photodissociation into a CO2 molecule
and fragments. On the other hand, the linewidths of infrared transitions are significantly broader
in parahydrogen than in Ar, in general. Advantages and disadvantages for using parahydrogen
matrices for the host of matrix isolation spectroscopy of amino acids will be discussed.