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EOOJC REVIEWS Horizons in Biochemistry. Albert Szent-Györgyi Dedicatory Volume. Edited by Michael Kasha and Bernard Pullman. New York & London: Academic Press, 1962. Pp. xiv+604. $16.00. This superb Festschriftopens with a tribute byRené Wurmser to the unique influence of Albert Szent-Györgyi on the development ofmolecular biology. Everyone interested in the history ofdynamic biochemistry will welcome this admirable summary not only of Szent-Györgyi's great experimental discoveries—vitamin C, the catalytic role of dicarboxylic acids in cell respiration, elucidation of the complex nature of the actomyosin system and its contractile response to ATP, and so on—but also ofhis profoundly courageous and imaginative contributions to biochemical theory. Inparticular, Wurmserstresses the fruitful consequences ofSzent-Györgyi's insistence that many biologicalproblems will remain intractable until they are approached at a submolecular level by quantum mechanical methods. The other twenty-seven essays in this fine book cover such diverse topics as enzymeaction, chemical aspects ofevolution and genetics, the molecular organization of subcellular particles, quantum chemistry, cancerous and molecular diseases, semiconduction by macromolecules, and even the physical basis ofmental events. And they bear witness to the widespread inspiration which the ideas and experiments of Szent-Györgyi have given to contemporary biological research. The first group ofessays deals with biochemical evolution. With great lucidity, Bernal discusses mechanisms which mayhave operated intheevolution ofbiochemical molecules. Such a process is implied by the remarkable unity ofstructural and metabolic devices found in all forms ofearthly life, and must have occurred largely prior to the biological evolution of various species. Recent model experiments have shown that the building blocks ofproteins and nucleic acids can be formed fromsimple inorganicsubstances without any intervention of biological catalysts, and under environmental conditions which probably existed in the course ofthe earth's history. Bernal suggests that vegetable acids, sugars, lipids, and porphyrins may have been formed in a similar abiotic manner. How these molecules sorted themselves out is one ofthe major problems ofbiochemical evolution . Bernal considers novel evidence that certain biological molecules may have originated from other planets, suggesting that life as we know it may have had more than a single origin. Calvin's article concerns evolutionary aspects ofphotosynthetic processes. It includes some intriguing speculations on the evolution of various types of metalloporphyrin catalysts, and on the mechanism of pyrophosphate formation coupled with biological oxidations. Gaffron writes on dating stages in photochemical evolution. 264 Book Reviews Perspectives in Biology and Medicine · Winter 1963 The origin and evolution ofbioluminescent systems constitute the subject ofan important essay by McElroy and Seliger. AU known bioluminescent reactions are oxidative ones in which oxygen is employed as the ultimate electron acceptor. The light-emitting substances (luciferins) are generally nitrogen heterocyclicswhose ?—>t* tripletlevels are well separated from their vibrational ground states, and are therefore phosphorescent. Flavin mononucleotide is the luciferin in some luminous bacteria, and McElroy and Seliger conjecture that the nature ofthe singlet and triplet excited states ofpyridine and flavin nucleotides, and ofthe cytochromes, played a role in the evolutionary selection of these substances as intermediates in cell respiration (as Szent-Györgyi has often pointed out). Intheevolutionofaerobesfromoriginalanaerobicforms oflife, there was astruggle for anaerobic conditions. Because oxygen is toxic to anaerobes, this conflict for anaerobic existence led to the selection oforganisms possessing enzymes which catalyzed a rapid removal of oxygen. Such enzymes may have been oxidases promoting luminescent reactions , i.e., potential luciferases. However, further evolution resulted in the present electron transport systems in which oxygen is reduced to form water. With the development ofsuchrespiratorymachinery, the originalluminescent oxidativereactions were no longer an aid to survival. In this vein, McElroy and Seliger argue that bioluminescent reactions are essentially vestigial, although through secondary evolutionary processes they may continue to serve useful adaptive functions. There follows a discussion by Rich ofthe evolution ofmechanisms for the transfer of biochemical information. He proposes that nucleic acids rather than proteins were developed as the primary biological macromolecules, and that "Ufe" really began with the coupling ofnucleic acid polymerization with amino acid polymerization. Rich considers the possible evolutionary advantage ofthe presence in living things oftwo types ofnucleic acids—DNA serving as a primary repository ofgenetic instructions, while RNA is more involved in the translation ofthis information into the...


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