The mathematical has provided very useful tools for relationships between the structures and molecular properties. Topological indices are numerical parameters of a graph which characterize its topology and are usually graph invariant. In this study the relationship between the Randic' (1X), Balaban (J), Szeged (Sz), Harary (H), Wiener (W), Hyper-Wiener (WW) and Wiener Polarity (Wp)to the thermal energy (Eth kJ/mol), heat capacity (CV J/mol K) and entropy (SJ/mol K) of 19 natural amino acids is represented. Physicochemical properties are taken from the quantum mechanics methodology with HF level using the ab initio 6-31G basis sets. The multiple linear regressions (MLR) and Back ward methods (with significant at the 0.05 level) were employed to give the QSPR models. After MLR analysis, we studied the validation of linearity between the molecular descriptors in the best models for used properties. The predictive powers of the models were discussed by using the method of cross-validation. The results have shown that one descriptor (W) could be efficiently used for estimating the entropy (S), heat capacity (Cv) and Wiener Polarity index could be used for modeling and predicting the thermal energy of respect compounds.

Afsaneh Safari and Fatemah. Shafiei