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Studies on Amino Acid Incorporation in 

 Bacteria Using Ionizing Radiation 



ELLIS KEMPNER ERNEST POLLARD 



Biophysics Department, Yale University a 



In recent years a growing body of evidence supports the idea that ribonucleo- 

 protein particles form at least one of the sites of protein synthesis [1]. Evidence 

 regarding this highly interesting system can be obtained by working with cell- 

 free systems of purified particles, and undoubtedly such evidence is valuable and 

 convincing. The drastic destruction of cell organization which is involved, how- 

 ever, leaves the question that perhaps the whole nature of amino acid incor- 

 poration is not being observed, but only the part that can survive the disrup- 

 tion of order in the cell. A method of study having the great advantage that 

 the cell is intact, or very nearly so, throughout the whole process is the use of 

 ionizing radiation as a powerful local disruptive agent. Such radiation is able 

 to penetrate all parts of the cell; it acts only at single, nearly isolated points, and 

 is wholly without action elsewhere. Such high-energy spot probes, or line 

 probes, can be employed against the organization of the cell, and, from the 

 effect on any particular part of the synthetic process, deductions can be made 

 regarding the process itself. Under good conditions, information can be ob- 

 tained on the following points: (a) the approximate size (within a factor of 

 2 in volume) of the region concerned with synthesis and sensitive to radiation; 

 (b) the approximate thickness (within a factor of 2 or 3), and hence the ap- 

 proximate length; and (c) the sensitivity of the synthetic region to radiation 

 (within a factor of 2) . These data can be compared with the sizes, thicknesses, 

 and lengths of cellular elements that could take part in the synthetic process. 

 This comparison can then be used as one more piece of evidence regarding the 

 nature of the process. A start along this line of investigation was made by 



1 Aided by a grant from the John A. Hartford Foundation. 



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