Radicals among sugars, radiation chemistry of carbohydrates

Inrwmrional Journal of Applied Radiation & Isotopes, Vol. 31. pp. 389 10 391 Pergamon Press Ltd 1980. Printed in Great Britain

FOOK REVIEWS Rdicals

mwg

!hgars, Radiation Chemistry of Carbohydrates by N. K. KOCHETKOV,

O+~LENOV. Published

L. I. Ku~~llrsrov and M. A. by Pergamon Press, Headington Hill Hall, Oxford OX3 OBW, England 247 pp. Price U.S. $43.00

MANY reviews and monographs dealing with radiation processes in inorganic and simple organic materials have been published in recent years. The more difficult field of radiation-induced reaction sequences in organic substances of biological significance has been less extensively covered. The present monograph reviews the literature on radiation chemistrv of carbohydrates from 1961 (the time at which an earlier review was published by G. -0. Phillips) up to 1978. In the meantime, a smaller review (55 pp.) entitled “Radiation Chemistry of Carbohydrates”, emphasizing the irradiation of foodstuffs containing sugars, has been prepared also by J. F. Dauphin and L. R. Saint-L&e and published in Radiation Chemistry of Major Food Corn ponents (Elsevier, 1977)..Most of the text of the present monograph has been prepared by Professor N. K. Kochetkov and two co-authors, all from the N. D. Zelinsky Institute of Organic Chemistry of the U.S.S.R. Academy of Sciences in Moscow, who have covered the field up to 1974 and less completely up to 1977. Their text is complemented by an appendix written by Professor G. 0. Phillips which fills in the gaps from 1975 up to the time of going to press in 1978. The book starts off with a brief introduction to the subject, followed by a chapter on “Radiation Chemistry of Water and Aqueous Solutions”. Inevitably the latter contains much general theory which can also .be found in other reviews of radiation chemistry. However, it is fairly brief (8 pages with 43 references) and can serve as a useful summary of the basic facts upon which all the rest of the book is based, avoiding the need of too frequent referral to other texts. The third chapter, dealing with “General Approaches and Methods of Investigation of the Radiolysis of Carbohydrates”, provides information on experimental methodology: kinetic methods, using intermediates and scavengers to elucidate reaction pathways; electron spin resonance measurements on monocrystals or frozen aqueous sugar solutions; pulse radiolysis which has proved so important in the study of primary processes; chromatographic separation methods such as column-, paper-, gel- and gas-liquid chromatography; spectroscopy; polarography; spectropolarimetry; potentiometry; chemical, radiochemical and enzymatic methods are dealt with at varying length. A special section of the chapter deals with structural analysis of carbohydrate radiolysis products: it includes subsections on applications of nuclear magnetic resonance and of mass spectrometry in addition to those on conventional chemical techniques. The largest and the most impprtant part of the book consists of Chapters 4 and 5, “Radiolysis of Various Classes of Carbohydrates” and “The Major Transformations of Carbohvdrates Induced bv Irradiation”. The first of these deals with the different radiation sensitivity of various types of carbohydrates, the formation of transient products of radiolysis and, particularly, the structure of the major final products. The second deals with the predominant pathways of carbohydrate transformations following y-irradiation and the possible mechanisms of these reactions. It is in this latter chapter particularly in which the experience of the authors, who have worked for considerably more than a decade on the radiation chemistry of carbohydrates, enables them to evaluate the likelihood of proposed mechanisms, many of which have been explored

at their own laboratory. Inevitably, however, a certain bias is also introduced here towards those schemes which result from organic chemical investigations, in which the authors excel. Based upon the data accumulated in the literature which is reviewed in the previous chapters, the reader is taken through the various stages in the radiolysis of carbohydrates. The radiation-induced transformation of the solute in dilute aqueous solution occurs mainly as a result of interaction with reaction intermediates of water radiolysis (OH’, e, and H’) and shows a yield of 3-6 molecules per 100 eV, unless chain processes are operative. The early processes are accessible to direct investigation by pulse radiolysis. Primary carbohydrate radicals formed in an early stage of the reaction sequence may undergo disproportionation, unimolecular decomposition, isomerixation or combination reactions: they may also react with the solvent, with radiolytic products of it, with gases dissolved in it, or with the solute. Of the major processes induced by y-irradiation of carbohydrates, oxidation is of particular importance. It may occur without shortening of the carbon chain in which case it will give rise to aldoses or alduloses from alditols and to uranic or aldonic acids, dialdoses and hexosuloses from hexoses. In irradiated glycosides or polysaccharides additional aldehydo, carbonyl or carboxyl groups are formed. In the presence of oxygen, oxidation occurs by addition of an oxygen molecule to the primary radicals, forming intermediate peroxy radicals, which can be observed by ESR measurements. In the absence of oxygen the mechanism is less well established and may either proceed by reactions with OH radicals or by disproportionation reactions of the primary carbohydrate radicals involving direct hydrogen abstraction, electron transfer or an enol intermediate. Oxidative degradation also is frequently found to occur. Compounds with a carbon chain shorter than that of the original sugar result from the scission of C-C bonds, usually with subsequent oxidation. In the presence of oxygen the process is again channelled through peroxy radicals while the route in the absence of oxygen is more complicated, less certain and leading to different products. Other processes which have been investigated include the formation of deoxysugars and of deoxyketosugars as well as the radiation-induced mission of the glycosidic bonds in oligo- and polysaccharides and that of the sugar-phosphate bond in sugar phosphates. These processes are discussed in the monograph with the aid of structural formulae. The Appendix which has been prepared by G. 0. Phillips lists a total of 98 publications which have been issued between 1975 and 1978, giving a very brief summary of the subject matter of each which rarely exceeds two or three lines. Following this are two tables of G-values and 21 reaction schemes takeh from a review “Free radical reactions of carbohydrates as studied by radiation techniques”, which has been prepared by the leader of another imnortant group working in this-field, Professor C. v. So&tag, for Aduances in Carbohydrate Chemisrrv. This appendix is a very useful contribution to the monograph: without it, it would be somewhat dated already. Even as it is, the mere listing of neatly a hundred publications cannot make up for the omission of their treatment in the main text, and the schemes taken from v. Sonntag’s review, interesting and well-produced as they ate, lack the support of textual interpretation and discussion in relation to other proposed 389

390

Book Reviews

reaction sequences shown in the book. This is all the more regrettable since, in Professor Phillips’ own words, “The rapid growth of the subject in the last 5 years particularly has necessitated considerable modification of previous ideas about mechanisms of radiation-induced reactions in carbohydrates, with the result that the general reader is unable to readily assess the current position”: he should consult v. Sonntag’s schemes for information on that position, reading them in association with the discussion within the body of the text (where, however, no reference to them is made). The production of the book obviously took place in great haste by reproducing the authors’ typescripts in their original form including numerous stylistic, grammatical and orthographic shortcomings. This reviewer has always admired the quick eye of those who could prove their thorough study of a book by detecting and reporting linguistic errors. It needs no great perspicacity to detect such errors in this book and the following examples have

Quantitative

been picked up from it almost at random: “compensate . . . to the drawbacks (p. 2), “the study of. are important” (p. 2), “interaction of y-irradiation with water” (p. 6), “beheaviour” (p. 82). What is meant by “The conformation of non-irradiated and ESR spectra of y-irradiated at 77°K polycrystalline pentoses” (p. 85)? Such relaxation of linguistic standards may be condoned in the interest of the rapid publication of a very up-to-date text; it is less acceptable in a review which gives (essentially) full treatment of literature only up to 1974, while many important publications which appeared between 1975 and 1978 are rather cursorily treated in the Appendix. In spite of these shortcomings, the book can be recommended to the reader interested in the radiation chemistry of carbohydrates for its detailed and careful treatment of some fifteen years of research in this field. 0. SU~~HNK IAEA, Vienna

Concepts and Dosimetry in Radiobiology, ICRU Report 30. International

ICRU Report 30, entitled “Quantitative Concepts and Dosimetrv in Radiobioloav” is a valuable review and serves to-provide useful descriptions of many aspects of radiobiological research. As with many other ICRU Reports, this one will no doubt serve as a handbook which will be on the desk of many practitioners. At the same time it also serves to educate, and the appendices contain many photographs and diagrams that are very valuable, since they show how other investigators have solved difficult problems in the mounting of samples (some of which are alive and kicking) and dosimeters. The treatment of dose-effect relationships is adequate, if somewhat superficial, yet it must be remembered that many books have been devoted to this one topic. This Report does an excellent job of making clear many complex concepts, and the list of definitions is particularly helpful. The discussion of the specification of radiation quality is somewhat uneven, and I think a bit less emphasis should have been placed on the limited concept of LET. More recent work on particle track structure analysis and measurements of event size distributions in lineal energy are more useful to the attempts at interpreting radiobiological data. Although there is much controversy in the field of microdosimetry, I think that many of the researchers working on these problems would agree that LET is a misleading concept in the specification of radiation quality. The section dealing with the determination of absorbed dose is useful to the person who is not an expert, and it does refer to more complete works. Perhaps it is the result of time and space constraints, but it is unfortunate that the

Commision on Radiological Units.

authors of this Report chose to describe calorimetric dosimetry in such a brief and cursory manner. It must be remembered that many ‘of the corrections applied to ionimetric and chemical dosimeters were determined by calibration with respect to calorimeters, which are the fundamental instruments for the measurement of absorbed dose. In addition, calorimeters have been used for practical dose measurements, such as those mentioned in the report, by Epp and co-workers. For the sake of completeness, it is necessary to point out that there are a number of typographical errors in this Report. I suppose that it is a fundamental law of the universe that relates entropy to typos. On p. 24, although Antje Rubach’s name may be phonetically correct, it should not be spelled with a “k”. In this same section the notation w is used, and unfortunately this is inconsistent with the notation of ICRU Reoort 31. which uses onlv W to denote the energy expended-in gas per ion pair formed. Table 4.5 contains an obvious misprint for the value of W for 6oCo photons in CO2 which should be 32.9, according to the report of Smith et al. These criticisms are not meant to detract from the worth of this report which, on balance, is a very good work. I found the appendices to be particularly interesting since they contained photographs of some familiar faces and apparatus, and the drawing of the mouse in Fig. A.18 provided a welcome bit of whimsy. JOSEPHC. MCDONALD

Memorial Sloan-Kettering Cancer Center, New York, N.Y.

Operational Radiation Safety Program, NCRP Report No. 59. National Council on Radiation Protection

and Measure-

ments THIS Report contains information that will permit management personnel with minimal training in this area but who are committed to establishing and maintaining an adequate ionizing-radiation safety program to evaluate a proposed program or a proposed program change. The detail is sufficient to allow such personnel to construct checklists or similar evaluation guides and to compare proposals to acceptable standards and guidance such as as-low-as-

reasonably-achievable publications. Of particular benefit are the references at the end of each section, even though the listings, of necessity given publishing demands, are not as timely as could be wished. Two minor flaws were noted: there is no mention of warning or information signs or posters except in the section on orientation and training. whereas it should be covered in the warning-systems section; and, indicating