EFFECTS OF SPERMINE ON THE RIBONUCLEOPROTEIN PARTICLES 249 



within one particle. There is no reason to disbeHeve that the same does not 

 also hold for the pancreatic particles. For example, when spermine is 

 added to a suspension of these particles, they immediately begin to 

 aggregate, as if the spermine is providing more groups, in this case the 

 positively charged amine groups, for attachment to any negatively charged 

 groups in the vicinity, be they the phosphate groups in the RNA of a 

 single particle or the phosphate groups in the RNA of adjacent particles, 

 the latter explaining the aggregation. 



The experiments mentioned in this paper, while clarifying some 

 aspects of the RNP particle structure, also add some complexities to the 

 picture, for which no adequate answer is available at present. It is clear, 

 for example, that in replacing the Mg + + of the particle, spermine dis- 

 charges only some of the proteins from the particles. A theory based on 

 this finding is as follows. The Mg + + is complexed to the phosphate groups 

 of adjacent RNA chains ; but it is possible that the amino groups of adenine 

 and guanine also contribute to the binding energy of the complex [i8]. 

 When spermine is added, Mg + + is removed, and the salt linkages formed 

 by the spermine amine groups and the RNA phosphate groups are strong 

 enough to stabilize the particle in the absence of Mg + +, by also preserving 

 any hydrogen and ionic bindings between the RNA and protein. However, 

 some of the proteins, namely, the secretory enzymes, presumably the newly 

 synthesized proteins [6], are discharged from the particle. It is our con- 

 tention that these particular proteins are held on to the RNA {" template " .'') 

 by the bridging, by some of the Mg + +, between the phosphate groups of 

 the RNA and the amino groups of the peptide bond or the free amine 

 groups of the basic amino acids. The amine groups of spermine cannot 

 replace the co-ordination bonds of Mg + + in such a situation and the 

 enzymes are discharged from the particles. Since there is only one Mg + + 

 for every ten phosphates of the RNA, it is conceivable that all of the Mg + + 

 is involved in holding these newly synthesized proteins on to the particle. 

 For, since Mg ^ ^ has a co-ordination number of four and possibly six 

 [19], it is possible that some of these co-ordination bonds are involved in 

 only phosphate complexing, while others are involved in complex formation 

 between the phosphate groups and the carbonyl groups of the structural 

 protein or the amino groups of the synthesized proteins. 



However, it appears that the binding of the RNA molecules to each 

 other or to the proteins is not as secure as might be assumed for a stable 

 configuration. It had been previously found that when all the Mg + + and 

 most of the RNA of the particles are removed, the remainder of the 

 particle has a diameter almost twice that of the original particle [7]. 

 Even when the RNA is not removed, as in the present experiments with 

 spermine, the particle diameter becomes twice that of the original particle, 

 as found in electron micrographs by G. E. Palade. This could be explained 



