. Principles of modern biology. Biology. 164 - The Cell many teams of workers, in many laboratories. But it is fair to say Melvin Calvin and col- laborators at the Radiation Laboratory of the University of California have been outstand- ing leaders in this field—as was duly recog- nized by the Nobel Prize award in 1961. Techniques. Two important technical devel- opments contributed greatly to the prosecu- tion of the carbon-tracing work. The dis- covery and preparation of radioactive car- bon (C14), by Samuel Ruben and Martin Kamen in 1940, provided an excellent tracer, because radiocarbon is
. Principles of modern biology. Biology. 164 - The Cell many teams of workers, in many laboratories. But it is fair to say Melvin Calvin and col- laborators at the Radiation Laboratory of the University of California have been outstand- ing leaders in this field—as was duly recog- nized by the Nobel Prize award in 1961. Techniques. Two important technical devel- opments contributed greatly to the prosecu- tion of the carbon-tracing work. The dis- covery and preparation of radioactive car- bon (C14), by Samuel Ruben and Martin Kamen in 1940, provided an excellent tracer, because radiocarbon is very stable (its half- life is more than 5000 years) and because the radioactivity provides a means of localizing compounds in which C14 is a constituent. But almost equally important was the develop- ment of paper chromatography, initiated by two English workers, A. J. P. Martin and R. L. M. Synge. Paper chromatography provides a method for achieving the separation and identifica- tion of unknown compounds, when these are dissolved in small amounts in an aqueous extract of cellular material. The separation results from small differentials in the solubil- ities of the compounds, as is indicated in Fig. 9-5. A drop of the aqueous solution of un- known compounds (X, Y, and Z) is placed on the filter paper, near the bottom, where the paper is in contact with a suitable organic solvent, saturated with water. As the organic solvent creeps by capillarity upward in the paper, it first will pick up compound X—if this displays the greatest degree of solubility in the particular organic solvent—and com- pound X will be carried the greatest distances from the locus of the original spot (Fig. 9-5). Likewise Y and Z, if this is the sequence of decreasing solubility, will not be picked up as quickly or carried as far by the upward- flowing solvent (Fig. 9-5). A further two- dimensional separation of the components can also be achieved by a second-stage treat- ment in which the position
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