The Science Of Photobiology

The first edition of The Science of Photobiology was published in 1977, and was the first textbook to cover all of the major areas of photobiology. The science of photobiology is currently divided into 14 subspecialty areas by the American Society for Photobiology. In this edition, however, the topics of phototechnology and spectroscopy have been com bined in a new chapter entitled "Photophysics." The other subspecialty areas remain the same, i.e., Photochemistry, Photosensitization, UV Radiation Effects, Environmental Photobiology, Photomedicine, Circadian Rhythms, Extraretinal Photoreception, Vision, Photomorphogenesis, Photomovement, Photosynthesis, and Bioluminescence. This book has been written as a textbook to introduce the science of photobiology to advanced undergraduate and graduate students. The chapters are written to provide a broad overview of each topic. They are designed to contain the amount of information that might be presented in a one-to two-hour general lecture. The references are not meant to be exhaustive, but key references are included to give students an entry into the literature. Frequently a more recent reference that reviews the literature will be cited rather than the first paper by the author making the original discovery. The chapters are not meant to be a repository of facts for research workers in the field, but rather are concerned with demon strating the importance of each specialty area of photobiology, and documenting its relevance to current and/or future problems of man.

Photobiology - the science of light and life - begins with basic principles and the physics of light and continues with general photobiological research methods, such as generation of light, measurement of light, and action spectroscopy. In an interdisciplinary way, it then treats how organisms tune their pigments and structures to the wavelength components of light, and how light is registered by organisms. Then follow various examples of photobiological phenomena: the design of the compound eye in relation to the properties of light, phototoxicity, photobiology of the human skin and of vitamin D, photomorphogenesis, photoperiodism, the setting of the biological clock by light, and bioluminescence. A final chapter is devoted to teaching experiments and demonstrations in photobiology. This book encompasses topics from a diverse array of traditional disciplines: physics, biochemistry, medicine, zoology, botany, microbiology, etc., and makes different aspects of photobiology accessible to experts in all these areas as well as to the novice.

It is not always the case that the subject of a scientific book and its relevance to everyday li fe are so timely. Photobiology and its si ster subject Radiobiology are now a must for understanding the environment we live in and the impact light, ultraviolet light, and radiation have on all aspects of our life. Photobiology is a true interdisciplinary field. Photobiology research plays a direct role in diverse fields, and a glance at the topics of the symposia covered in this book by over 100 articles shows the breadth and depth of knowledge acquired in fundamental research and its impact on the major issues and applied problems the world is facing. Half a century of photobiology research brought about an understanding of the importance of light to life, both as a necessary source of energy and growth as weIl as its possible dangers. Research in photochemistry and photobiology led to the discoveries of ceIlular repair mechanisms of UV induced damages to DNA and this led to understanding of the effects of hazardous environmental chemieals and mutagenecity , and to the development of genetic engineering. This topic was given due emphasis in several symposia and chapters in this book.

Molecular Photobiology: Inactivation and Recovery describes the deleterious photochemical reactions occurring in biological systems. This book is composed of 10 chapters that specifically tackle light interactions in the ultraviolet region of the spectrum resulting to damaged proteins and nucleic acids in living systems. This book deals first with the kinds of photochemical reactions that can occur and the possible effects of photochemistry on molecular, cellular, and organismal levels. The succeeding chapters highlight the principle of recovery mechanisms, wherein evidence shows that cells can repair their damaged genetic material, and thus recover from the otherwise inactivating effects of light. The remaining chapters are devoted to the comparison and contrast of some biological effects of ionizing radiation and those of ultraviolet radiation. This book is of value to molecular photobiologists, photochemists, biochemists, and radiation scientists and researchers.

The fIrst edition of the Science 0/ Photobiology edited by Kendric C. Smith (plenum Press, 1977) was a comprehensive textbook of photobiology, devoting a chapter to each of the subdisciplines of the fIeld. At the end of many of these chapters there were brief descriptions of simple experiments that students could perform to demonstrate the principles discussed. In the succeeding years some photobiologists felt that a more complete publica tion of experiments in photobiology would be a useful teaching tool. Thus, in the 1980s the American Society for Photobiology (ASP) attempted to produce a laboratory manual in photobiology. Cognizant of these efforts, Kendric Smith elected to publish the second edition of The Science o/Photobiology (1989) without experiments; anticipating the comple tion of the ASP laboratory manual. Unfortunately, the initial ASP efforts met with limited success, and several years were to pass before a photobiology laboratory manual became a reality. One of the major stumbling blocks to production of an accurate and reliable laboratory manual was the requirement that the experiments be tested, not just by the author who is familiar with the techniques, but by students who may be quite new to photobiology. How could this be accomplished with limited resources? Many ideas were considered and discarded, before a workable solution was found. The catalyst that enabled the careful screening of all experiments in this book was a NATO Advanced Study Institute (ASI) devoted entirely to this purpose.

Although the history of photomedicine dates back thousands of years, with even preliterate cultures appreciating the healing properties of sunlight, for many workers in the discipline photomedicine is associated with the observation about 100 years ago of Niels Finsen, a Danish physician. Finsen recognized that people with tuberculosis who lived in Norway and who had very little exposure to sunlight often developed facial lesions (lupus vulgaris) which would decrease and sometimes disappear during the summer months. This very observant physician reasoned that artificial light ought to produce the same effect as sunlight and began utilizing the radiation from the newly available carbon arc. At first, he used a glass lens to concentrate the radiation, but since this produced considerable burning, he replaced this with a hollow glass lens filled with water. However, while this reduced the heat burns, it did not actually duplicate the effect of direct sunlight. Finally, using a hollow lens filled with water but equipped with quartz windows, Finsen was able to imitate, even improve upon, the effect of sunlight. As a result, lupus vulgaris was practically eliminated from the Scandinavian countries.