Abstract: The first unifying principle in biochemistry is that the key molecules have the same handedness or chirality.The parity violating of electroweak neutral current (mediated by the Z0 boson) is suggested as the main force inducing the observed homochirality.After exposing D-/L-alanine and valine crystals to temperatures ranging from 300 K to 100 K,we observed a second order phase transition by differential scanning calorimetry and DC magnetic susceptibilities measurement.No configuration change was found by chirasil-Val capillary column gas chromatography thus failing to validate Salam′s predicted parity-violating energy difference (PVED) induced DL phase transition.The present studies show the experimental evidence provided by quantitative and apparently reliable estimates of PVED in phase transition of D- / L-alanine and valine crystals.

Key words: Second order phase transition, Alanine, Valine, Parity-violating energy difference