Amino Acid Crystal Temperature Polarized Raman Spectra And Valine Molecules To Change The Temperature Sers Spectra

Lots of scientists work hard for many years to uncover the secret of life which is the most complex phenomenon in the world. Among the twenty amino acids in protein of life, except glycine, the nineteen amino acids are L form; whereas, RNA and DNA which to make up ribose are all D form, which is called parity violating. In 1991, A. Salam suggested that a phase transition of D- to L-amino acid beneath a certain critical temperature Tc may have taken place. Based on this theory, Professor Wang Wenqing has done a series work of amino acids and found that D-amino acids have quite different behavior when the temperature was lowered and all D and L-enantiomers have a phase transition at about 270K, but not found D forms changed into L forms. It was supposed that the transition was about amido.In this paper, the temperature dependent Raman spectra of DL-Alaine crystals have been discussed in details and the peaks were given a tentative assignment. Also, a comparison of Raman spectra between D-Alaine and DL-Alaine was carried out.Furthermore, the temperature dependent Raman spectra of D and L-Valine crystals were obtained. Through the comparison of Raman spectra between L-Valine and D-Valine, it is found that the influence of temperature on the crystals is remarkable and the three hydrogen bonds of amido are different; while, the vibration of amido-cyanogen in D and L-Valine crystals changing with temperature are distinctive.It is well known that temperature is an important factor of Surface Enhanced Raman Scattering spectrum, so an in-situ temperature dependent SERS spectrum of Valine which can gain strong signal of SERS on gold nano-particles was measured. The SERS spectrum changed distinctly with temperature which was supposed that the adsorbate existed mainly in a physical-sorption state at 273K and changed into chemical-sorption state at 173K.