The goals of the science of photobiology can be divided into four categories: to develop (I) ways to optimize the beneficial effects of light on man and his environment, (2) methods to protect organisms, including man, from the detrimental effects of light, (3) phohemical tools for use in studies of life processes, and (4) phohemical therapies in medicine. To achieve these goals will require the knowledgeable collaboration of biologists, chemists, engineers, mathematicians, physicians, and physicists; because photobiology is a truly multidisciplinary science. While a multi­ disciplinary science is more intellectually demanding, it also has a greater potential for unexpected breakthroughs that can occur when data from several areas of science are integrated into new concepts for theoretical or practical use. Phohemical and Photobiological Reviews continues to provide in­ depth coverage of the many specialty areas of photobiology. It is hoped that these reviews will provide an important service to the younger scientists in the field and to senior scientists in related fields, because they provide a ready access to the recent literature in the field, and more importantly, they frequently offer a critical evaluation of the direction that the field is taking, or suggest a redirection when appropriate. Kendric C. Smith Editor vii Contents v Contents of Earlier Volumes ...................................... . Preface ............................................... . vii Chapter 1. The Activation of Enzymes with Light ................... .