19 Matching Results

Search Results

Advanced search parameters have been applied.

The Path of Carbon in Photosynthesis

Description: The dark fixation of carbon dioxide by green algae has been investigated and found to be closely related to photosynthesis fixation. By illumination in the absence of carbon dioxide followed by treatment with radioactive carbon dioxide in the dark, the amount fixed has been increased ten to twenty fold. This rate of maximum fixation approaches photosynthesis maximum rates. The majority of the radioactive products formed under these conditions have been identified and isolated and the distribution of labeled carbon determined. From these results a tentative scheme for the mechanism of photosynthesis is set forth.
Date: March 8, 1948
Creator: Calvin, M. & Benson, A.A.
Partner: UNT Libraries Government Documents Department

Path of Carbon in Photosynthesis III

Description: Although the overall reaction of photosynthesis can be specified with some degree of certainty (CO{sub 2} + H{sub 2}O + light {yields} sugars + possibly other reduced substances), the intermediates through which the carbon passes during the course of this reduction have, until now, been largely a matter of conjecture. The availability of isotopic carbon, that is, a method of labeling the carbon dioxide, provides the possibility of some very direct experiments designed to recognize these intermediates and, perhaps, help to understand the complex sequence and interplay of reactions which must constitute the photochemical process itself. The general design of such experiments is an obvious one, namely the exposure of the green plant to radioactive carbon dioxide and light under a variety of conditions and for continually decreasing lengths of time, followed by the identification of the compounds into which the radioactive carbon is incorporated under each condition and time period. From such data it is clear that in principle, at least, it should be possible to establish the sequence of compounds in time through which the carbon passes on its path from carbon dioxide to the final products. In the course of shortening the photosynthetic times, one times, one ultimately arrives at the condition of exposing the plants to the radioactive carbon dioxide with a zero illumination time, that is, in the dark. Actually, in the work the systematic order of events was reversed, and they have begun by studying first the dark fixation and then the shorter photosynthetic times. The results of the beginnings of this sort of a systematic investigation are given in Table I which includes three sets of experiments, namely a dark fixation experiment and two photosynthetic experiments, one of 30 seconds duration and the other of 60 seconds duration.
Date: June 1, 1948
Creator: Benson, A.A. & Calvin, M.
Partner: UNT Libraries Government Documents Department

The Path of Carbon in Photosynthesis VII Respiration andPhotosynthesis

Description: The relationship of respiration to photosynthesis in barley seedling leaves and the algae, Chlorella and Scenedesmus, has been investigated using radioactive carbon dioxide and the techniques of paper chromatography and radioautography. The plants are allowed to photosynthesize normally for thirty seconds in c{sup 14}O{sub 2} after which they are allowed to respire in air or helium in the light or dark. Respiration of photosynthetic intermediates as evidenced by the appearance of labeled glutomic, isocitric, fumaric and succinic acids is slower in the light than in the dark. Labeled glycolic acid is observed in barley and algae. It disappears rapidly in the dark and is maintained and increased in quantity in the light in C0{sub 2}-free air.
Date: July 21, 1949
Creator: Benson, A.A. & Calvin, M.
Partner: UNT Libraries Government Documents Department

Carbon Dioxide Fixation by Green Plants

Description: Since the end of the war when the long-lived isotope of carbon, C{sup 14} became available a new tool has been applied in the study of photosynthesis. Because of the interest evoked by the tracer method, research in all areas of photosynthesis has expanded. There have been reviews on various aspects of photosynthesis such as the primary photochemical reaction, quantum efficiency products, and comparative biochemistry, many discussions of which were included in the monograph of The American Society of Plant Physiologists, ''Photosynthesis in Plants''.
Date: January 3, 1950
Creator: Benson, A.A. & Calvin, M.
Partner: UNT Libraries Government Documents Department

The Path of Carbon in Photosynthesis II. Amino Acids

Description: The radioactive amino acid's synthesized from C{sup 14}O{sub 2} by green algae both in the light and in the dark after CO{sub 2}-free preillumination have been separated and identified using paper chromatography and radioautography. The radioactive amino acids identified were aspartic acid, alanine and smaller amounts of 3- and 4-carbon amino acids. This finding as well as the total absence of radioactive glutamic acid substantiates the mechanism for reduction of CO{sub 2} previously postulated by members of this laboratory.
Date: May 25, 1948
Creator: Stepka, W.; Benson, A.A. & Calvin, M.
Partner: UNT Libraries Government Documents Department


Description: The metabolism of C{sup 14} labeled glycolic acid by Scenedesmus has been studied using radiochromatographic techniques for the separation and identification of products. When the pH of the medium was 2.8, appreciable assimilation occurred. The products were identical to those observed in C{sup 14}O{sub 2} photosynthesis. A major reaction anaerobically in the dark resulted in incorporation of C{sup 14} in almost equal amounts in the glycine and serine reservoirs. When the algae were illuminated, a diminution in the amount of glycine was observed.
Date: September 11, 1950
Creator: Schou, L.; Benson, A.A.; Bassham, J.A. & Calvin, M.
Partner: UNT Libraries Government Documents Department

The Path of Carbon in Photosynthesis. XVI. Kinetic Relationshipsof the Intermediates in Steady State Photosynthesis

Description: A kinetic study of the accumulation of C{sup 14} in the intermediates of steady state photosynthesis in C{sup 14}O{sub 2} provides information regarding the sequence of reactions involved. The work described applied the radio-chromatographic technique for analysis of the labeled early products. The simultaneous carboxylation reaction resulting in malic acid as well as phosphoglycerate is demonstrated in experiments at high light intensity. A comparison of radioactivities in a number of phosphorylated sugars as a function of time reveals concurrent synthesis of fructose and sedoheptulose phosphates followed by that of ribulose phosphates and later by that of glucose phosphates. The possibility that the cleavage of C{sub 4} compounds to C{sub 2} carbon dioxide acceptors may involve C{sub 7} and C{sub 5} sugars and evidence for this mechanism is presented.
Date: June 5, 1952
Creator: Benson, A.A.; Kawaguchi, S.; Hayes, P. & Calvin, M.
Partner: UNT Libraries Government Documents Department


Description: Although there has been considerable progress toward an understanding of the processes of photosyntehsis in recent years, the advances have been followed rather lcosely by symposia, monographs and reviews of the subject matter, particularly during the last three years. In view of the comprehensive coverage it would appear that the present review might very well be limited to a discussion of certain subjects of special interest to the authors and some with which they are especially familiar. These are (1) the extensive discussion by Warburg and his co-workers of their proposal for the existence of a light induced oxygen absorption (and corresponding carbon dioxide evolution) which can amount to three or four times the net oxygen evolution by the same light; and (2) the discovery of the early participation of 7 and 5 carbon sugars in carbon dioxide reduction in photosyntehsis together with some observations on the kinetics of the metabolic transformations. While it is true that a considerable number of significant publications have appears in other aspects of photosynthesis (the Hill reaction and its coupling with carbon dioxide reduction; photochemistry of chlorophyll and related synthetic materials as model reactions in relatively simple defined physical systems; transfer of light energy within the pigment systems) it is felt that they represent confirmation and extension of ideas which have already been discussed in a variety of earlier reviews and that a re-evaluation of them might very well be postponed until a later time.
Date: March 1, 1952
Creator: Calvin, M.; Bassham, J.A.; Benson, A.A. & Massini, P.
Partner: UNT Libraries Government Documents Department

The Path of Carbon in Photosynthesis. XVIII The Identification ofNucleotide Coenzymes

Description: The radioactive compounds to be observed when algae or green leaves are allowed to photosynthesize in C{sup 14}O{sub 2} for short periods are almost all phosphorylated derivatives of sugars. Of these, phosphate esters of trioses, sedoheptulose and fructose are the first to incorporate C{sup 14} followed closely by ribulose diphosphate, glucose-6-phosphate and a phosphate of mannose. It has been noted, in earlier papers of this series, that on radiograms of the products of photosynthesis, a dark area appeared in a position occupied by no known sugar phosphate and which gave glucose on acid hydrolysis or on treatment with a phosphatase preparation. This has hitherto been referred to as an 'unknown glucose phosphate'. It was found that this substance was more labile to acid than glucose-l-phosphate, itself a readily hydrolysable phosphate, and furthermore that other labile glucose derivatives were formed as intermediates during the acid hydrolysis. Accumulation of labeled glucose in this area precedes that in sucrose and suggests its synthetic relationship to sucrose phosphate synthesis.
Date: January 19, 1953
Creator: Buchanan, J.G.; Lynch, V.H.; Benson, A.A.; Calvin, M. & Bradley,D.F.
Partner: UNT Libraries Government Documents Department

Reduction of Carbon Dioxide inAqueous Solutions by IonizingRadiation

Description: The question of the conditions under which living matter originated on the surface of the earth is still a subject limited largely to speculation. The speculation has a greater chance of approaching the truth insofar as it includes and is based upon the ever wider variety of established scientific fact. One of the purposes of the herein reported observation was to add another fact to the ever increasing information which might have any bearing upon this most interesting question. It is not our purpose in the present communication to discuss the various proposals or the arguments which have been adduced for and against them. One of the most popular current conceptions is that life originated in an organic milieu on the surface of the earth, (1,2,3,4,5). The problem to which we are addressed is the origin of that organic milieu in the absence of any life. It appeared to us that one source, if not the only source, of reduced carbon compounds in complex arrangements might be the interaction of various high energy radiations with aqueous solutions of inorganic materials, particularly carbon dioxide, and nitrogenous compounds such as ammonia and nitrogen, since it appears that these compounds were the commoner forms in which the essential elements found themselves on the primordial earth. While it has long been known that high energy radiations can cause organic decomposition and oxidation, it seemed useful to us to demonstrate that conditions could be found in which high energy radiations could induce the reduction with water of carbon dioxide and the ultimate creation of polyatomic molecules (other than simple polymerization of monomers) of carbon, oxygen, hydrogen and nitrogen.
Date: March 13, 1951
Creator: Garrison, W.M.; Morrison, D.C.; Hamilton, J.G.; Benson, A.A. & Calvin, M.
Partner: UNT Libraries Government Documents Department


Description: The conclusions which have been drawn from the results of C{sup 14}O{sub 2} fixation experiments with a variety of plants are developed in this paper. The evidence for thermochemical reduction of carbon dioxide fixation intermediates is presented and the results are interpreted from such a viewpoint.
Date: April 1, 1950
Creator: Calvin, M.; Bassham, J .A.; Benson, A.A.; Lynch, V.; Ouellet, C.; Schou, L. et al.
Partner: UNT Libraries Government Documents Department

The Path of Carbon in Photosynthesis. XIV.

Description: It seems hardly necessary to repeat to an audience of this kind the importance of the process known as photosynthesis in the interaction and the interdependence of organisms and in the very existence of life as we know it. This process by which green plants are able to capture electromagnetic energy in the form of sunlight and transform it into stored chemical energy in the form of a wide variety of reduced (relative to carbon dioxide) carbon compounds provides the only major source of energy for the maintenance and propagation of all life.
Date: June 30, 1951
Creator: Calvin, Melvin; Bassham, J.A.; Benson, A.A.; Kawaguchi, S.; Lynch, V.H.; Stepka, W. et al.
Partner: UNT Libraries Government Documents Department

The Path of Carbon in Photosynthesis, XV. Ribulose andSedoheptulose

Description: The intermediates of carbon dioxide reduction by plants include phosphorylated derivatives of hydroxy acids and sugars. Their identification becane possible when the use of labeled carbon dioxide permitted discrimination between the earliest products and the many other components of photosynthetic tissues. A number of compounds were identified by virtue of the chemical and physical properties of the radioactive compounds in tracer amounts and by direct comparison of these properties with those of suspected known metabolic intermediates. It became apparent that several labeled compounds found in short exposures to radioactive carbon dioxide were not substances previously identified as metabolic intermediates. Two phosphate esters in particular were observed in the products of the first few seconds of steady-state photosynthesis by all the photosynthetic microorganisms and higher plants examined in this laboratory. These esters have been isolated by paper chromatography in tracer quantities and enzymatically hydrolyzed to give two sugars, ribulose and sedoheptulose. This paper contains a description of the chemical identification of these sugars and some observations and suggestions regarding the function of their esters. The general importance of these compounds in photosynthesis was surmized before their identification. The products of photosynthesis with C{sup 14}O{sub 2} by each plant included phosphate esters of the same two then unknown compounds in addition to those of the expected glucose, fructose, dihydroxyacetone and glyceric acid. As the time of steady-state photosynthesis in C{sup 14}O{sub 2} decreased, the fractions of total fixed radiocarbon in the esters of the two unidentified compounds increased.
Date: January 1, 1952
Creator: Benson, A.A.; Bassham, J.A.; Calvin, M.; Hall, A.G.; Hirsch, H.; Kawaguchi, S. et al.
Partner: UNT Libraries Government Documents Department

The Path of Carbon in Photosynthesis. XXI. The Cyclic Regenerationof Carbon Dioxide Acceptor

Description: Photosynthesizing plants have been exposed to C{sup 14}O{sub 2} for short periods of time (0.4 to 15 sec.) and the products of carbon dioxide reduction analyzed by paper chromatography and radio autography. Methods have been developed for the degradation of ribulose and sedoheptulose. These sugars, obtained as their phosphate esters from the above C{sup 14}O{sub 2} exposures and from other experiments, have been degraded and their distribution of radiocarbon determined. The distribution of radiocarbon in these sugars, and other data, indicate that sedoheptulose phosphate and ribulose diphosphates are formed during photosynthesis from triose and hexose phosphates, the latter being synthesized, in turn, by the reduction of 3-phosphoglyceric acid.
Date: October 1, 1953
Creator: Bassham, J.A.; Benson, A.A.; Kay, Lorel D.; Harris, Anne Z.; Wilson, A.T. & Calvin, M.
Partner: UNT Libraries Government Documents Department

The Path of Carbon in Photosynthesis. XVII. Phosphorus Compoundsas Intermediates in Photosynthesis

Description: Studies of carbon dioxide fixation in green plants using the C{sup 14} isotope have shown that in very short times phosphoglyceric acid contains most of the radioactivity. The tracer is present almost entirely in the carboxyl group. The importance of organic phosphates in the subsequent metabolism of phosphoglyceric acid can be seen from the accompanying photographs.
Date: July 8, 1952
Creator: Buchanan, J.G.; Bassham, J.A.; Benson, A.A.; Bradley, D.F.; Calvin, M.; Daus, L.L. et al.
Partner: UNT Libraries Government Documents Department