This book compiles a collection of original scientific articles written by Professor Sir Alan Fersht over 40 years of his scientific career. A long-standing icon in the fields of enzymology, protein folding, and protein engineering, Sir Alan Fersht is also one of the world's greatest protein chemists, whose work has been extensively recognized by countless international awards in both chemistry and molecular biology. He has produced a number of classic papers that are cited regularly because of the originality of his work and his insightful analysis. The study of his work on the fusion of physical chemistry and molecular biology provides a course on how to approach the analysis of complex systems in a simple logical manner. His papers are models of clarity, benefitting students of protein chemistry in their understanding of the subject. The beginning of Sir Alan Fersht's career coincided with the birth of modern protein science based on structural biology, which started in earnest momentum in the 1960s. He worked in the then Mecca of molecular biology, the MRC Laboratory of Molecular Biology, and was one of the first protein chemists to exploit the new area of structural biology. The papers are interlaced with personal comments on how each article was important in his career and how he was influenced by the galaxy of legendary scientists in the MRC.