Prediction Of Equilibrium Constants Research Articles

Calculation and prediction of rate and equilibrium constants for aggregation of porphyrin by molecular dynamics, Docking and QSPR methods

The aggregation of 85 porphyrin derivatives and a report on a kinetic and thermodynamic study of such aggregation behavior on varying the derivatives of porphyrin was carried out using molecular dynamics simulation and Docking. Distance diagrams of simulated compounds were obtained and decrease of curves is a clear evidence of the aggregation. Aggregation rates were studied by origin software. In order to calculate interaction energies of derivatives, compounds were docked and the equilibrium constant of porphyrin-porphyrin interaction were obtained. Quantitative Structure-Property Relationship (QSPR) studies were performed for the sets of 85 Porphyrin derivatives. Multiple Linear Regression method (MLR) and Principal Component Analysis (PCA) were used and resulted in useful models with good prediction ability. This models were able to predict the kinetic and equilibrium constant for all sets of our compounds. The correlation coefficients for prediction of rate and logarithm of equilibrium constants were 0.67 and 0.97 by MLR method respectively and 0.90 for prediction of equilibrium constant by PCA analyses. In order to have a better prediction, compounds were divided into two groups, oxygenated and non-oxygenated group and correlation coefficient for prediction of rate constants of them were obtained 0.89 and 0.94 by MLR model respectively. Results of structure-property relationship showed that, larger, more hydrophobe and more planner derivatives have higher aggregation rate.

A theoretical treatment of cation exchangers - I. The prediction of equilibrium constants from osmotic data

The theories put forward to explain ion-exchange phenomena in natural and synthetic materials are examined. It is suggested that a reasonable interpretation of ion exchange in swelling materials can be made by treating the exchanger phase as a concentrated aqueous electrolyte. It is assumed ( a ) that the free energy of the exchanger is a function of its volume and its composition only and ( b ) that the exchanger phase obeys the laws of concentrated electrolyte solutions so far as they are known. The water uptake at different vapour pressures of polystyrene sulphonates of different degrees of cross-linking has been investigated for various monovalent cations. The data indicate that the anions do not contribute towards the statistical entropy terms of the solutions, but otherwise the osmotic coefficients of the monovalent cations have similar trends as in the case of strong 1:1 electrolytes. An approximate calculation may be made of the distribution constants of the exchangers when in contact with solutions containing two cations. With a few exceptions the values obtained are in reasonable agreement with both the absolute values and the trends observed experimentally for different ions, different cross-linkage and different solution compositions.