Dr. S P Gupta, was a professor of Chemistry at the Birla Institute of Technology and Science, Pilani. The present monograph combines his expertise in quantum chemistry and biophysics which he has taught for years at the postgraduate level and in which he has made notable contributions at research front. The author is a noted theoretical chemist who applies quantum chemical and other theoretical methods to deal with the problems of chemistry, pharmaceutical chemistry and biophysics. He has published hundreds of papers in national and international journals in these areas and has several reviews to his credit in ChemicalReviews: For his significant contributions in pharmaceutical chemistry, he was made fellow of the National Academy of Sciences, India, in 1985 and awarded the Ranbaxy Research Foundation award for the year 1989.