Ion selectivity from local configurations of ligands in solutions and ion channels.

Probabilities of numbers of ligands proximal to an ion lead to simple, general formulae for the free energy of ion selectivity between different media. That free energy does not depend on the definition of an inner shell for ligand-counting, but other quantities of mechanistic interest do. If analysis is restricted to a specific coordination number, then two distinct probabilities are required to obtain the free energy in addition. The normalizations of those distributions produce partition function formulae for the free energy. Quasi-chemical theory introduces concepts of chemical equilibrium, then seeks the probability that is simplest to estimate, that of the most probable coordination number. Quasi-chemical theory establishes the utility of distributions of ligand-number, and sharpens our understanding of quasi-chemical calculations based on electronic structure methods. This development identifies contributions with clear physical interpretations, and shows that evaluation of those contributions can establish a mechanistic understanding of the selectivity in ion channels.

Effect of 2-5 years of tobacco smoking on ventilatory function tests.

Smoking is a pernicious scourge of the world today. There is paucity of literature on the effect of acute smoking on ventilatory functions. The present work is undertaken to study the effect of 2-5 years of tobacco smoking on ventilatory functions. The study group consisted of 30 male, young, healthy subjects, free from cardiopulmonary diseases and with history of smoking of 2-5 years duration, on an average of 10 cigarettes per day. The control group consisted of 30 age-and sex-matched healthy individuals who had naver smoked tobacco. The ventilatory function tests were carried out using electronic spriolyser. There was a significant lowering of the following parameters in smokers: Vital capacity (VC), inspiratory reserve volume (IRV), inspiratory capacity (IC), forced vital capacity (FVC), forced expiratory volume at the end of first second (FEV1), maximum midexpiratory flow (MMEF), peak expiratory flow (PEF), midexpiratory flow75 (MEF75), maximum voluntary ventilation (MVV). This study shows that 2-5 years of tobacco smoking leads to a definite tendency to narrowing of both the large and the small airways.