The Phase Transition Of D-/L-amino Acid Crystals

There are20kinds of amino acid. Except glycine having no chirality, the othersare L-amino acids. However, all the DNA and RNA are right-handed chirality. Thiscase is called chiral symmetry breaking in biological phenomena. Why biomassselects left-handed chiral chemical substances is still a mystery.1991, A.Salampredicted that D-amino acids can transform into L-amino acids, which had beenproved impossible by many researchers. During a research of Alzheimer s disease,particularly worth mentioning is that there is a mass of D-amino acid in patientsbrains, especially D-aspartate. In this case, we believed that L-amino acid maytransform into D-amino acid in typical condition, and this change can do bad effect onthe normal functions of human body.In order to find the mechanism of second-order phase transition of amino acid,we did some comparing research of D-/L-valine in X-ray scattering, nuclear magneticresonance, specific heat, Raman and Gaussian software.We found that there do exist second-order phase transition between D-andL-valine. The heat enthalpy difference between D-and L-valine is6.7385J/mol, andthe peak of phase change is around270K. The data of the polarization Raman alsoshows that the shear vibration of amidogen in amino acids. What s more, we provedthis phenomenon theoretically by Gaussian.The data of NMR proved more in-depth at the amino acids that-H nuclear hasmuch more impaction for the spin relaxation time of molecular in quantum physics. It proves the occurrence of phase transitions of amino acids directly related the spinningproperties of particle in the nuclear.