- Email: [email protected]
The biochemical origins of molecular biology
TIBS - August 1984
334 mentioned above. Ames and his colleagues also discuss possible roles for tRNA ser in the production of enterobactin (which contains three serine moieties), for tRNA cys in the biosynthesis of cysteine, and for tRNA Leu in the production of menaquinone (which requires isopentenyl pyrophosphate that might be made from an intermediate in leucine biosynthesis in E. coli) s. As a final note, tRNA modifying enzymes and tRNA-like structures could be involved in additional mechanisms of regulation. Ames and his colleagues have found a strong resemblance between the leader mRNA of the attenuator region in the h/s operon of S. typhimuriurn and tRNA HiS (Ref. 12). In reviewing their own findings and observations from other laboratories, they suggest that proteins which recognize tRNA His may also bind this leader sequence to influence attenuation.
Good candidates are the tRNA modification enzymes whose recognition sites follow certain rules of sequence and secondary structure 13. In higher organisms specific interactions between modification enzymes and mRNAs could effect transcriptional regulation without the transcriptional-translational coupfing seen in prokaryotes. Additional possible levels of regulation include mRNA processing and translation initiation.
References 1 Nashimura, S. (1979) in Transfer RNA." Structure, Properties and Recognition (Schimmel, P. R., Soil, D. and Abelson, J. N., eds), pp. 59-79, Cold Spring Harbor Laboratories 2 Yanofsky, C. (1981) Nature 289, 751-758 3 Johnston, H. M., Barnes, W. M., Chumley, F. G., Bossi, L. and Roth, J. R. (1980) Proc. Natl Acad. Sci. USA 77, 508-512
The biochemical origins of molecular biology
Introduction Seymour S. Cohen In beginning this series of brief histories the nucleic acids and on DNA particuof biochemical discovery contributing to larly as the genetic material, and on RNA the present state of molecular biology, it and ribosomes as the intermediates in seems appropriate to quote the reflective the synthesis of specific proteins. A few discoveries of the 1940s and aged scientist in McCormmach's Night Thoughts of a Classical Physicist 1. 'It 1950s have usually been selected as the saddened Jakob to see the current major events in the emergent genetic scholastic tendency to judge the past chemistry on which modern biochemfrom a superior present. How rare it was istry and molecular biology have been to come across sensible historical writing based. Most of the 'histories' have stresthat placed the present in perspective sed the work of Avery and his collaborand showed how the parts of physics had ators on DNA as the main substance of the pneumococcal transforming agent in evolved together.' In this series we hope to enlarge the 1944, the Hershey-Chase experiment limited historiography that has essen- pointing to DNA as the major comtially excluded biochemical discovery ponent of a bacteriophage chromosome from the stories of the founding of in 1952, and the Watson--Crick structure molecular biology. We shall draw on of DNA in 1953. Reading these abbreseveral of the biochemists who have viated tales, one might wonder if anything participated in the development of at all had happened between 1944 and thought fundamental to the creation of 1952-53, why Hershey, the immunolthe new specialization in genetic ogist and geneticist, elected to become a chemistry. Their recollections of the biochemist pursuing viral components historical past should help to fill out the containing 32TP and 35S, or if Watson, the record, to provide a more complete student of genetics, had thought at all sense of the common knowledge within about DNA before going off to Europe, which it became reasonable to focus on and before encountering Wilkins and Crick. Nevertheless the participants in Seymour S. Cohen is at the Department of Pharma- the early biochemical experiments know cological Sciences, State University of New York at that by 1951, numerous studies on viral Stony Brook, N Y 11794, USA. nucleic acids had compelled Hershey (~) 1984,ElsevierSciencePublishersB.V.. Amsterdam 0376- 5(k57/84/$1~.00
4 Yarus, M. (1982) Science 218, 646~52 5 Cortese, R., Kammen, H. O., Spengler, S. J. and Ames, B. N. (1976) J. BioL Chem. 249, 1103-1108 6 Turnbough, C. L., Neiil, R. J., Landsberg, R. and Ames, B. N. (1979) J. Biol. Chem. 254, 5111-5119 7 Buck, M. and Griffiths, E. (1982) Nucl. Acids Res. 10, 2609-2624 8 Buck, M. and Ames, B. N. (1984) Cell 36, 523-531 9 Eisenberg, S. P., Soil, L. and Yams, M. (1979) J. Mol. BioL 135, 111-176 10 McCray, J. W. and Herrmann, K. M. (1976) J. Bacteriol. 125, 608~15 11 Bossi, L. and Roth, J. R. (1980) Nature 286, 123-127 12 Ames, B. N., Tsang, T. H., Buck, M. and Christman, M. (1983) Proc. Natl Acad. Sci. USA 80, 5249-5242 13 Tsang, T. H., Buck, M. and Ames, B. N. (1983) Biochim. Biophys. Acta 741, 180--196 RUTH STARZYK Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
and Watson to weigh the possible significance of these polymers, and had helped to draw these workers to their own fruitful studies. Based on the methodological contributions of Delbrtick and Luria and the startling pictures of the electron microscopists on phage systems, a biochemistry of virus multiplication had in fact begun in 1945. Some of the earliest experiments had demonstrated extraordinary rates of synthesis of phage DNA, and methods of labeling virus and bacterial DNA had been developed in a search for precursors of viral substance2'3. Before the important Hershey--Chase experiments, the very image of a bacteriophage as a syringe transferring viral DNA to its host had been evoked as a result of electron microscopy and biochemical studies of phage ghosts 4'5. Nevertheless, the probable functionality of the phage DNA and an outline of its mode of duplication and expression were first established by the several alert geneticists who exploited biochemical and physical methodologies. The late 1940s and early 1950s saw an explosion of knowledge of intermediary metabolism in which studies of microbial nutrition, genetics and physiology had provided valuable test systems, enzymes and substrates. However, knowledge of the biosynthesis of the nucleic acids and their components had tended to lag behind, in part at least because of the impenetrability of bacteria to nucleotides. Recognition of the genetic role of phage nucleic acids hastened the development of the enzymology necessary to clarify the origins of their building
TIBS - August 1984 blocks, as well as creating a lively interest in the structure and biological relations of the nucleic acids generally. Indeed this same problem of the roles of the phage DNA had led G. R. Wyatt and the author to determine the base compositions of mutant pairs of T-even phages, Supplementing the fundamental study of Chargaff who some years earlier had found T = A and G = C in many DNAs, our analyses detected a new base, which completely replaced cytosine5. The study of the origins of this new pyrimidine revealed not only the enzymatic mechanism of its formation but also that the phages, and most other viruses, determine the synthesis of new enzymes that enlarge and redirect the metabolic capabilities of infected cells5. It may be mentioned that many of these viral functions and enzymes were identified by biochemical methods in the period 1957 to 1959, some years before their viral determinants were detected by genetic techniques. Much cellular RNA was found in ribosomes and their subunits. A very few years later, a new biochemical technique, the ion exchange separation of specific nucleotides, revealed the existence of unusual metabolically active RNA species in phage infection6, setting the stage for the discovery of classes of DNA-like R N A which shuttled from chromosome to ribosome. And the genetic role of phage nucleic acid was extended to the nucleic acids of plant and animal viruses by 1956 and 1957 respectively. The clarification of the biosynthesis of nucleotides and their different stages of phosphorylation permitted the detection of enzymes synthesizing polynucleotides, approaching the structures of natural DNA and RNA. Numerous enzymes, DNA and RNA polymerases, were discovered, as well as many new degradative systems for these polymers. The mechanism of duplication of DNA postulated by Watson and Crick was tested and confirmed to a first approximation, using an ingenious biological and biochemical system. The role and specificity of templates in DNA and RNA synthesis became important subjects of study, and the phenomena of complementarity and coding were defined as crucial to the newly recognized phenomena of transcription and translation. The discovery by Nirenberg of the interaction of a ribosomal system with poly (U) to form polyphenylalanine placed the previously detected synthesis of amides and of peptide bonds in a new experimental context.
335 History and the historiography of molecular biology It may be instructive to indicate how a foreshortened history of molecular biology, stressing the triple play of Avery to Hershey to Watson-Crick, came to be written. Certainly the alltoo-brief description presented above of the interdependence of biology, biochemistry and chemistry in the evolution of the early experiments and theory appears somewhat richer in texture than the usual account. Robert Olby has described early efforts at Cambridge University to develop an institutional framework for the study of the molecular basis of biological function. The term 'molecular biology' had first been coined in 1938 by W. Weaver of the Rockefeller Foundation who was attempting to develop a plan of support for the application of physical science to selected areas of biology, i.e. biochemistry, cell biology and genetics7. The Foundation's program of support was spectacularly successful in aiding workers such as Rudolf Schoenheimer, Linus Pauling, Robert Robinson, George Beadle and many other important investigators. However the term 'molecular biology' itself did not catch on, perhaps initially because it seemed presumptuous and more practically because World War II interrupted studies of macromolecular structure and prevented the formation of a specialized journal. Olby suggests that the term 'molecular biology' first became fashionable in 1959 with the introduction of the
Journal of Molecular Biology. The Journal was founded in England with an editorial board composed of English and American scientists studying the structure of biological macromolecules and the relation of such structure to their biological functions. Directions to prospective authors in the first issue in 1959 begin with 'The Journal of Molecular Biology will publish papers on the nature, production and replication of biological structure at the molecular level, and its relation to function. Suitable subjects are sub-cellular organization: molecular genetics: structure of proteins, nucleic acids, carbohydrates, lipids, etc. and their synthetic analogs, as investigated by X-rays, light absorption and other methods: problems of inter- and intra-molecular energy transfer. ,8 This list of topics suitable for the journal is essentially unchanged today. It seems hardly different from a subset of the eleven topics listed in a discussion
of the scope of biochemistry in a typical text of the time. It was not claimed at the time of the appearance of the journal that 'molecular biology' described a new discipline rather than a new specialization. However the growth of phage biology did lead to such a claim. In 1963, G. Stent had prepared a text entitled 'Molecular Biology of the Bacterial Viruses', in which 'molecular biology' is not defined; nor is the term used explicitly in his preface or text. The term does not appear in the Subject Index but it is stated that the book is an account of how the hereditary unit 'viral DNA achieves its autocatalytic and heterocatalytic functions'. Stent has written in his Preface that his book follows the general plan of a syllabus on phage prepared in 1949 in Delbriick's laboratory by a group of phage workers; these did not include the biochemists working in the field. It is of interest that this didactic volume on phage is essentially ahistoric; for example, it presents the biochemical complexities of the Hershey-Chase experiment of 1952, before the far earlier metabolic experiments on the effects of a virus on the biosynthetic pattern of an infected bacterium, or on the earlier use of isotopic techniques in phage systems. In 1966 J. Cairns, G. Stent and J. Watson edited a Festschrift for M. Delbriick, namely Phage and the Origins of Molecular Biology. The editors did not undertake to define 'molecular biology' in a preface or in their own essays. The editors had either assumed that the term was understood by the entire possible readership, or had intended to subsume molecular biology under the relatively few topics covered by the essayists. In a later review of this book, Kendrew objected to the apparent exclusion of the structural chemistry of most biological macromolecules and other structures from this exclusively 'informationist' view of molecular biology9. Although the components of metabolic biochemistry and enzymology were largely omitted from the Festschrift, biochemists never explicitly objected to their exclusion from the definition, as had Kendrew. In the late 1940s both Delbriick and Luria, the earliest leaders of the phage group, believed that biochemistry would not contribute to problems of phage multiplication. This perception has been recorded by their students and colleagues in the Delbriick Festschrift. It is evident from these and other accounts that the language, approaches and tech-
TIBS - August 1984
336 niques of biochemistry presented difficulties for many of the phage biologists. They continued their own approaches and methods, and minimized those of another discipline. The 'Club', as it was dubbed by Brenner, attempted to 'do things in such a w a y . . . that it doesn't need all the bloody tubes and counters and so on. And I think that the cult got founded around these ideas of how to solve the code without ever opening the black box. '1° Nevertheless, Doermann, a phage geneticist, had been compelled to open the black box, i.e. a virus-infected cell, by 1949, and told us that infecting viruses lost their intactness within the cell. A. D. Hershey used 'the bloody tubes and counters' to perform his crucial experiments on the phage chromosome and on protein synthesis, as welt as devising hydrolytic and chromatographic procedures to study phage D N A synthesis. Using disrupted 'black boxes' and 'bloody tubes and counters', the biochemists nevertheless solved the complex mechanisms of protein synthesis, detected the synthesis of phagespecific R N A , later proven to be messenger R N A , solved the coding problem directly, and isolated the R N A hypothesized by Crick to serve as an adaptor in protein synthesis. The biochemists also provided the methodology and techniques used by both Meselson and Stahl to demonstrate semiconservative replication of D N A and by Brenner, Jacob and Meselson in showing that a phage-specific R N A became associated
with the protein-synthesizing structures of the cell, presumably to direct the synthesis of phage-specific proteins. It is obvious then that a sound definition of molecular biology should include biochemistry, as well as other disciplines. Olby has recently presented such a definition, which includes Weaver's program, as well as the past and modern reality. He defines molecular biology as 'an interdisciplinary study utilizing biochemistry, genetics and structural chemistry in pursuit of the molecular basis to the form, function and evolutionary descent of living things. ' u If it has taken so long to understand that molecular biology is a hybrid discipline encompassing biochemistry it is because the history of the definition itself has been both obscured and ignored. Various volumes of the past decade on the history of molecular biology have neglected or distorted important aspects of the evolution of the discipline. At the least it is desirable for the biochemists to clarify their own part in the work, and the initial essays in this journal will discuss three aspects of this participation. Max Lauffer will discuss the characterization of the molecular properties of the plant viruses, as seen by a leader of the Princeton group headed by W. M. Stanley. Early experiments in phage biochemistry will be described by Lloyd Kozloff, a major contributor of the Chicago group of E. A. Evans, and the initial clarification of in vitro protein synthesis will be presented by Paul Zamecnik, whose laboratory in Boston
Biosensors Michael Gronow Biosensors are a synergistic combination o f biochemistry and micro-electronics, which simplify biochemical and chemical analysis on a micro and macro scale. E n z y m e metabolism, molecular recognition and whole-cell metabolism can be utilized in biosensors. Practically, they can take four forms - hand-held devices, laboratory instruments, flow type sensors (for large volumes) and implanted sensors (for whole body monitoring). Biosensors will be widely used in clinical analysis, health care, veterinary and agricultural applications, industrial processing and monitoring and environmental and pollution control.
The original biosensors were known as 'biocatalytic membrane electrodes' or 'bioelectrochemical sensors'. In biochemical terms these technologies have evolved from the use of immobilized Michael Gronow is at Cambridge Life Sciences plc, Cambridge Science Park, Milton Road, Cambridge CB4 4BH, UK. 1984, Elsevier Science Publishers B.V., Amsterdam
enzymes in conjunction with pH electrodes, amperometric devices and oxygen electrodes. These combinations have, in some people's minds, become synonymous with the term biosensor. In a biochemical reaction a number of variables are involved and the reaction often takes place in a complex environ-
0376 - 5667/84/$(E.00
made many of the initial discoveries. The fact that these men are drawn entirely from the US is obviously related to the disruption of international science by World War II and its aftermath, which gave American biochemistry a temporary lead in several specializations. We might also suppose that the war, by bringing Delbriick and Luria together and by compelling them to work in relative isolation, also cc,rltributed to the origins of phage biology.
References
1 McCormmach,R. (1982) Night Thoughts of a Classical Physicist, p. 104, Harvard University Press 2 Cohen, S. (1947) Cold Spring Harbor Syrup. Quant. Biol. 12, 35-49 3 Kozloff, L. M. and Putnam, F. W. (1950) J. Biol. Chem. 182, 229-241 4 Hershey, A. D. (1966) in Phage and the Origins of MolecularBiology (Cairns. J., Stent, G. and Watson, J. D., eds), pp. 100-108, Cold Spring Harbor Laboratory of Quantitative Biology 5 Cohen, S. S. (1968) Virus-Induced Enzymes, Columbia UniversityPress 6 Volkin, E. and Astrachan, L. (1956) Virology 2, 149-161 70lby, R. (1974) The Path to The Double Helix, Universityof Washington Press 8 Journal of Molecular Biology (1959), VoL 1 9 Kendrew, J. (1967) Sci. Amer. CCXVI, pp. 149-144 10 Judson, H. F. (1979) The Eighth Day of Creation: The Makers of the Revolution in Biology, pp. 448, Simon and Schuster 11 Olby, R. (1981) in Dictionary of the History of Science (Bynum, W. F., Browne, E. J. and Porter, R., eds), p. 276, Princeton University Press ment. Changes in concentrations of substrate, analyte or ligand usually occur rapidly and, in measuring these changes, the biochemist attempts to keep the other variables to a minimum. However, recent advances in microelectronics, particularly microprocessor design, enable us to not only deal rapidly with data generated but also to adjust for other 'noise' in the system. Thus, the new breed of biosensors will present a unique marriage of immobilized biochemical, transducer and microelectronic components to allow almost instantaneous calculation of substrate, analyte or ligand concentration. No common concensus of opinion exists as yet for the definition of a biosensor. Some definitions incorporate those devices which do not contain an immobilized biological material, for example non-specific or gas sensing electrodes, but I prefer to be more specific:
334 mentioned above. Ames and his colleagues also discuss possible roles for tRNA ser in the production of enterobactin (which contains three serine moieties), for tRNA cys in the biosynthesis of cysteine, and for tRNA Leu in the production of menaquinone (which requires isopentenyl pyrophosphate that might be made from an intermediate in leucine biosynthesis in E. coli) s. As a final note, tRNA modifying enzymes and tRNA-like structures could be involved in additional mechanisms of regulation. Ames and his colleagues have found a strong resemblance between the leader mRNA of the attenuator region in the h/s operon of S. typhimuriurn and tRNA HiS (Ref. 12). In reviewing their own findings and observations from other laboratories, they suggest that proteins which recognize tRNA His may also bind this leader sequence to influence attenuation.
Good candidates are the tRNA modification enzymes whose recognition sites follow certain rules of sequence and secondary structure 13. In higher organisms specific interactions between modification enzymes and mRNAs could effect transcriptional regulation without the transcriptional-translational coupfing seen in prokaryotes. Additional possible levels of regulation include mRNA processing and translation initiation.
References 1 Nashimura, S. (1979) in Transfer RNA." Structure, Properties and Recognition (Schimmel, P. R., Soil, D. and Abelson, J. N., eds), pp. 59-79, Cold Spring Harbor Laboratories 2 Yanofsky, C. (1981) Nature 289, 751-758 3 Johnston, H. M., Barnes, W. M., Chumley, F. G., Bossi, L. and Roth, J. R. (1980) Proc. Natl Acad. Sci. USA 77, 508-512
The biochemical origins of molecular biology
Introduction Seymour S. Cohen In beginning this series of brief histories the nucleic acids and on DNA particuof biochemical discovery contributing to larly as the genetic material, and on RNA the present state of molecular biology, it and ribosomes as the intermediates in seems appropriate to quote the reflective the synthesis of specific proteins. A few discoveries of the 1940s and aged scientist in McCormmach's Night Thoughts of a Classical Physicist 1. 'It 1950s have usually been selected as the saddened Jakob to see the current major events in the emergent genetic scholastic tendency to judge the past chemistry on which modern biochemfrom a superior present. How rare it was istry and molecular biology have been to come across sensible historical writing based. Most of the 'histories' have stresthat placed the present in perspective sed the work of Avery and his collaborand showed how the parts of physics had ators on DNA as the main substance of the pneumococcal transforming agent in evolved together.' In this series we hope to enlarge the 1944, the Hershey-Chase experiment limited historiography that has essen- pointing to DNA as the major comtially excluded biochemical discovery ponent of a bacteriophage chromosome from the stories of the founding of in 1952, and the Watson--Crick structure molecular biology. We shall draw on of DNA in 1953. Reading these abbreseveral of the biochemists who have viated tales, one might wonder if anything participated in the development of at all had happened between 1944 and thought fundamental to the creation of 1952-53, why Hershey, the immunolthe new specialization in genetic ogist and geneticist, elected to become a chemistry. Their recollections of the biochemist pursuing viral components historical past should help to fill out the containing 32TP and 35S, or if Watson, the record, to provide a more complete student of genetics, had thought at all sense of the common knowledge within about DNA before going off to Europe, which it became reasonable to focus on and before encountering Wilkins and Crick. Nevertheless the participants in Seymour S. Cohen is at the Department of Pharma- the early biochemical experiments know cological Sciences, State University of New York at that by 1951, numerous studies on viral Stony Brook, N Y 11794, USA. nucleic acids had compelled Hershey (~) 1984,ElsevierSciencePublishersB.V.. Amsterdam 0376- 5(k57/84/$1~.00
4 Yarus, M. (1982) Science 218, 646~52 5 Cortese, R., Kammen, H. O., Spengler, S. J. and Ames, B. N. (1976) J. BioL Chem. 249, 1103-1108 6 Turnbough, C. L., Neiil, R. J., Landsberg, R. and Ames, B. N. (1979) J. Biol. Chem. 254, 5111-5119 7 Buck, M. and Griffiths, E. (1982) Nucl. Acids Res. 10, 2609-2624 8 Buck, M. and Ames, B. N. (1984) Cell 36, 523-531 9 Eisenberg, S. P., Soil, L. and Yams, M. (1979) J. Mol. BioL 135, 111-176 10 McCray, J. W. and Herrmann, K. M. (1976) J. Bacteriol. 125, 608~15 11 Bossi, L. and Roth, J. R. (1980) Nature 286, 123-127 12 Ames, B. N., Tsang, T. H., Buck, M. and Christman, M. (1983) Proc. Natl Acad. Sci. USA 80, 5249-5242 13 Tsang, T. H., Buck, M. and Ames, B. N. (1983) Biochim. Biophys. Acta 741, 180--196 RUTH STARZYK Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
and Watson to weigh the possible significance of these polymers, and had helped to draw these workers to their own fruitful studies. Based on the methodological contributions of Delbrtick and Luria and the startling pictures of the electron microscopists on phage systems, a biochemistry of virus multiplication had in fact begun in 1945. Some of the earliest experiments had demonstrated extraordinary rates of synthesis of phage DNA, and methods of labeling virus and bacterial DNA had been developed in a search for precursors of viral substance2'3. Before the important Hershey--Chase experiments, the very image of a bacteriophage as a syringe transferring viral DNA to its host had been evoked as a result of electron microscopy and biochemical studies of phage ghosts 4'5. Nevertheless, the probable functionality of the phage DNA and an outline of its mode of duplication and expression were first established by the several alert geneticists who exploited biochemical and physical methodologies. The late 1940s and early 1950s saw an explosion of knowledge of intermediary metabolism in which studies of microbial nutrition, genetics and physiology had provided valuable test systems, enzymes and substrates. However, knowledge of the biosynthesis of the nucleic acids and their components had tended to lag behind, in part at least because of the impenetrability of bacteria to nucleotides. Recognition of the genetic role of phage nucleic acids hastened the development of the enzymology necessary to clarify the origins of their building
TIBS - August 1984 blocks, as well as creating a lively interest in the structure and biological relations of the nucleic acids generally. Indeed this same problem of the roles of the phage DNA had led G. R. Wyatt and the author to determine the base compositions of mutant pairs of T-even phages, Supplementing the fundamental study of Chargaff who some years earlier had found T = A and G = C in many DNAs, our analyses detected a new base, which completely replaced cytosine5. The study of the origins of this new pyrimidine revealed not only the enzymatic mechanism of its formation but also that the phages, and most other viruses, determine the synthesis of new enzymes that enlarge and redirect the metabolic capabilities of infected cells5. It may be mentioned that many of these viral functions and enzymes were identified by biochemical methods in the period 1957 to 1959, some years before their viral determinants were detected by genetic techniques. Much cellular RNA was found in ribosomes and their subunits. A very few years later, a new biochemical technique, the ion exchange separation of specific nucleotides, revealed the existence of unusual metabolically active RNA species in phage infection6, setting the stage for the discovery of classes of DNA-like R N A which shuttled from chromosome to ribosome. And the genetic role of phage nucleic acid was extended to the nucleic acids of plant and animal viruses by 1956 and 1957 respectively. The clarification of the biosynthesis of nucleotides and their different stages of phosphorylation permitted the detection of enzymes synthesizing polynucleotides, approaching the structures of natural DNA and RNA. Numerous enzymes, DNA and RNA polymerases, were discovered, as well as many new degradative systems for these polymers. The mechanism of duplication of DNA postulated by Watson and Crick was tested and confirmed to a first approximation, using an ingenious biological and biochemical system. The role and specificity of templates in DNA and RNA synthesis became important subjects of study, and the phenomena of complementarity and coding were defined as crucial to the newly recognized phenomena of transcription and translation. The discovery by Nirenberg of the interaction of a ribosomal system with poly (U) to form polyphenylalanine placed the previously detected synthesis of amides and of peptide bonds in a new experimental context.
335 History and the historiography of molecular biology It may be instructive to indicate how a foreshortened history of molecular biology, stressing the triple play of Avery to Hershey to Watson-Crick, came to be written. Certainly the alltoo-brief description presented above of the interdependence of biology, biochemistry and chemistry in the evolution of the early experiments and theory appears somewhat richer in texture than the usual account. Robert Olby has described early efforts at Cambridge University to develop an institutional framework for the study of the molecular basis of biological function. The term 'molecular biology' had first been coined in 1938 by W. Weaver of the Rockefeller Foundation who was attempting to develop a plan of support for the application of physical science to selected areas of biology, i.e. biochemistry, cell biology and genetics7. The Foundation's program of support was spectacularly successful in aiding workers such as Rudolf Schoenheimer, Linus Pauling, Robert Robinson, George Beadle and many other important investigators. However the term 'molecular biology' itself did not catch on, perhaps initially because it seemed presumptuous and more practically because World War II interrupted studies of macromolecular structure and prevented the formation of a specialized journal. Olby suggests that the term 'molecular biology' first became fashionable in 1959 with the introduction of the
Journal of Molecular Biology. The Journal was founded in England with an editorial board composed of English and American scientists studying the structure of biological macromolecules and the relation of such structure to their biological functions. Directions to prospective authors in the first issue in 1959 begin with 'The Journal of Molecular Biology will publish papers on the nature, production and replication of biological structure at the molecular level, and its relation to function. Suitable subjects are sub-cellular organization: molecular genetics: structure of proteins, nucleic acids, carbohydrates, lipids, etc. and their synthetic analogs, as investigated by X-rays, light absorption and other methods: problems of inter- and intra-molecular energy transfer. ,8 This list of topics suitable for the journal is essentially unchanged today. It seems hardly different from a subset of the eleven topics listed in a discussion
of the scope of biochemistry in a typical text of the time. It was not claimed at the time of the appearance of the journal that 'molecular biology' described a new discipline rather than a new specialization. However the growth of phage biology did lead to such a claim. In 1963, G. Stent had prepared a text entitled 'Molecular Biology of the Bacterial Viruses', in which 'molecular biology' is not defined; nor is the term used explicitly in his preface or text. The term does not appear in the Subject Index but it is stated that the book is an account of how the hereditary unit 'viral DNA achieves its autocatalytic and heterocatalytic functions'. Stent has written in his Preface that his book follows the general plan of a syllabus on phage prepared in 1949 in Delbriick's laboratory by a group of phage workers; these did not include the biochemists working in the field. It is of interest that this didactic volume on phage is essentially ahistoric; for example, it presents the biochemical complexities of the Hershey-Chase experiment of 1952, before the far earlier metabolic experiments on the effects of a virus on the biosynthetic pattern of an infected bacterium, or on the earlier use of isotopic techniques in phage systems. In 1966 J. Cairns, G. Stent and J. Watson edited a Festschrift for M. Delbriick, namely Phage and the Origins of Molecular Biology. The editors did not undertake to define 'molecular biology' in a preface or in their own essays. The editors had either assumed that the term was understood by the entire possible readership, or had intended to subsume molecular biology under the relatively few topics covered by the essayists. In a later review of this book, Kendrew objected to the apparent exclusion of the structural chemistry of most biological macromolecules and other structures from this exclusively 'informationist' view of molecular biology9. Although the components of metabolic biochemistry and enzymology were largely omitted from the Festschrift, biochemists never explicitly objected to their exclusion from the definition, as had Kendrew. In the late 1940s both Delbriick and Luria, the earliest leaders of the phage group, believed that biochemistry would not contribute to problems of phage multiplication. This perception has been recorded by their students and colleagues in the Delbriick Festschrift. It is evident from these and other accounts that the language, approaches and tech-
TIBS - August 1984
336 niques of biochemistry presented difficulties for many of the phage biologists. They continued their own approaches and methods, and minimized those of another discipline. The 'Club', as it was dubbed by Brenner, attempted to 'do things in such a w a y . . . that it doesn't need all the bloody tubes and counters and so on. And I think that the cult got founded around these ideas of how to solve the code without ever opening the black box. '1° Nevertheless, Doermann, a phage geneticist, had been compelled to open the black box, i.e. a virus-infected cell, by 1949, and told us that infecting viruses lost their intactness within the cell. A. D. Hershey used 'the bloody tubes and counters' to perform his crucial experiments on the phage chromosome and on protein synthesis, as welt as devising hydrolytic and chromatographic procedures to study phage D N A synthesis. Using disrupted 'black boxes' and 'bloody tubes and counters', the biochemists nevertheless solved the complex mechanisms of protein synthesis, detected the synthesis of phagespecific R N A , later proven to be messenger R N A , solved the coding problem directly, and isolated the R N A hypothesized by Crick to serve as an adaptor in protein synthesis. The biochemists also provided the methodology and techniques used by both Meselson and Stahl to demonstrate semiconservative replication of D N A and by Brenner, Jacob and Meselson in showing that a phage-specific R N A became associated
with the protein-synthesizing structures of the cell, presumably to direct the synthesis of phage-specific proteins. It is obvious then that a sound definition of molecular biology should include biochemistry, as well as other disciplines. Olby has recently presented such a definition, which includes Weaver's program, as well as the past and modern reality. He defines molecular biology as 'an interdisciplinary study utilizing biochemistry, genetics and structural chemistry in pursuit of the molecular basis to the form, function and evolutionary descent of living things. ' u If it has taken so long to understand that molecular biology is a hybrid discipline encompassing biochemistry it is because the history of the definition itself has been both obscured and ignored. Various volumes of the past decade on the history of molecular biology have neglected or distorted important aspects of the evolution of the discipline. At the least it is desirable for the biochemists to clarify their own part in the work, and the initial essays in this journal will discuss three aspects of this participation. Max Lauffer will discuss the characterization of the molecular properties of the plant viruses, as seen by a leader of the Princeton group headed by W. M. Stanley. Early experiments in phage biochemistry will be described by Lloyd Kozloff, a major contributor of the Chicago group of E. A. Evans, and the initial clarification of in vitro protein synthesis will be presented by Paul Zamecnik, whose laboratory in Boston
Biosensors Michael Gronow Biosensors are a synergistic combination o f biochemistry and micro-electronics, which simplify biochemical and chemical analysis on a micro and macro scale. E n z y m e metabolism, molecular recognition and whole-cell metabolism can be utilized in biosensors. Practically, they can take four forms - hand-held devices, laboratory instruments, flow type sensors (for large volumes) and implanted sensors (for whole body monitoring). Biosensors will be widely used in clinical analysis, health care, veterinary and agricultural applications, industrial processing and monitoring and environmental and pollution control.
The original biosensors were known as 'biocatalytic membrane electrodes' or 'bioelectrochemical sensors'. In biochemical terms these technologies have evolved from the use of immobilized Michael Gronow is at Cambridge Life Sciences plc, Cambridge Science Park, Milton Road, Cambridge CB4 4BH, UK. 1984, Elsevier Science Publishers B.V., Amsterdam
enzymes in conjunction with pH electrodes, amperometric devices and oxygen electrodes. These combinations have, in some people's minds, become synonymous with the term biosensor. In a biochemical reaction a number of variables are involved and the reaction often takes place in a complex environ-
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made many of the initial discoveries. The fact that these men are drawn entirely from the US is obviously related to the disruption of international science by World War II and its aftermath, which gave American biochemistry a temporary lead in several specializations. We might also suppose that the war, by bringing Delbriick and Luria together and by compelling them to work in relative isolation, also cc,rltributed to the origins of phage biology.
References
1 McCormmach,R. (1982) Night Thoughts of a Classical Physicist, p. 104, Harvard University Press 2 Cohen, S. (1947) Cold Spring Harbor Syrup. Quant. Biol. 12, 35-49 3 Kozloff, L. M. and Putnam, F. W. (1950) J. Biol. Chem. 182, 229-241 4 Hershey, A. D. (1966) in Phage and the Origins of MolecularBiology (Cairns. J., Stent, G. and Watson, J. D., eds), pp. 100-108, Cold Spring Harbor Laboratory of Quantitative Biology 5 Cohen, S. S. (1968) Virus-Induced Enzymes, Columbia UniversityPress 6 Volkin, E. and Astrachan, L. (1956) Virology 2, 149-161 70lby, R. (1974) The Path to The Double Helix, Universityof Washington Press 8 Journal of Molecular Biology (1959), VoL 1 9 Kendrew, J. (1967) Sci. Amer. CCXVI, pp. 149-144 10 Judson, H. F. (1979) The Eighth Day of Creation: The Makers of the Revolution in Biology, pp. 448, Simon and Schuster 11 Olby, R. (1981) in Dictionary of the History of Science (Bynum, W. F., Browne, E. J. and Porter, R., eds), p. 276, Princeton University Press ment. Changes in concentrations of substrate, analyte or ligand usually occur rapidly and, in measuring these changes, the biochemist attempts to keep the other variables to a minimum. However, recent advances in microelectronics, particularly microprocessor design, enable us to not only deal rapidly with data generated but also to adjust for other 'noise' in the system. Thus, the new breed of biosensors will present a unique marriage of immobilized biochemical, transducer and microelectronic components to allow almost instantaneous calculation of substrate, analyte or ligand concentration. No common concensus of opinion exists as yet for the definition of a biosensor. Some definitions incorporate those devices which do not contain an immobilized biological material, for example non-specific or gas sensing electrodes, but I prefer to be more specific: