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Blondes in Venetian Paintings, the Nine-Banded Armadillo, and Other Essays in Biochemistry . By Konrad Bloch. New Haven: Yale Univ. Press. Pp. 288. $32.50. As one who is quite familiar with author Konrad Bloch's scientific research, where experimental evidence reigns supreme and speculation is shunned, I enjoyed die philosophical approach adhered to in this book. In the preface Bloch tells us that rather than write his personal memoirs he preferred to offer this series of essays drawing "on material tucked away in my mind, incidents, episodes, encounters, chance observations during travels." He succeeds brilliantly in entertaining the reader, evoking the reader's own memories and, perhaps more importantly, stimulating the reader's thoughts on the broader aspects of the topics touched on in this book. An astute chemical observer, Bloch starts out with the cogent observation that many women in Venetian Renaissance paintings are portrayed as exquisite blondes, while the men appearing in the same paintings usually have dark hair color. Following his suspicion that these ladies were artificial blondes, he learns from the literature of the time that noble ladies indeed rinsed their hair with a tincture called "aqua bionda" and then exposed it to the sun. Perhaps not surprisingly, similar practices were known all over Italy and even in ancient Rome. The author's inquiries into the chemistry of aqua bionda led to the conclusion that the ancient bleaching agent was very probably none other than hydrogen peroxide, generated from plant materials under the influence of sunlight. The essays that follow deal with less esoteric topics and are usually selected from among the author's own research or that of others closely familiar to him. As a rule, the emphasis is not on minute detail, but rather on the broader significance of the work. In other cases, however, the essence is in the detail. This is so in an important chapter describing several examples where unsuspected reagent contamination played a significant role in the discovery of major new biomolecules and biochemical processes. In the essay "The Evolutionary Perfection of a Molecule," Bloch points out the stunning coincidence that the sequence of late intermediates on the biosynthetic padi to cholesterol parallels the appearance of these same intermediates as membrane constituents in ascending forms of life. The thoughts expressed in this chapter add a new dimension to the author's life work, which won him die Nobel Prize in Physiology and Medicine. Particularly enlightening is the essay on "Oxygen and Evolution," which reminds the reader of the fact that the large majority of synthetic reactions producing the essential building stones necessary for life on earth, such as proteins, nucleic acids and lipids, were perfected by nature before the appearance of oxygen on earth. Remarkably, the author emphasizes that this basic chemistry has remained unchanged after oxygen appeared in the atmosphere. With the appearance of oxygen, a new lifestyle was made possible and became the main driving force for evolution. New reactions utilizing oxygen were added, expanding the biochemical repertoire. The author illustrates this point with the case of the two independent routes leading to unsaturated fatty acids required by all organisms to alter the "liquidity" of their membranes. The more complex process invented by the prokaryotes in the oxygenfree world was replaced by the more efficient oxygen-requiring desaturation process of the eukariotes. The author lists many of the new biosynthetic reactions made possible by the introduction of oxygen into the atmosphere, such as the synthesis •ectives in Biology and Medicine, 39, 3 ¦ Spring 1996 461 of cholesterol, the steroid hormones, the prostaglandins and leukotrienes, and vitamin A. All this, of course, in addition to the greater economy achieved by the more efficient utilization of common nutrients, made possible by replacing fermentation by respiration. A particularly beautiful example of this type of evolutionary approach to biochemistry is described in another essay dealing with the discovery of a hitherto unknown anaerobic pathway to the vitamin nicotinamide, the precursor of the coenzyme NAD. Only an oxygen-requiring pathway from tryptophan was known by 1960. Hayaishi, the pioneer in the field of oxygenases, reasoned that an early anaerobic process leading to nicotinamide was likely to exist, and indeed demonstrated such a...

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Additional Information

ISSN
1529-8795
Print ISSN
0031-5982
Pages
pp. 461-462
Launched on MUSE
2015-01-07
Open Access
No
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