Dense gels of E. coli 70 S ribosomes, their 50 S subunits, CM-like particles, RNP strands and their fragments, 38 S particles obtained from RNP strand folding upon addition of Mg2+ ions, and of unoriented salt-free and free rRNA sodium and magnesium salts were studied by X-ray diffraction. It was shown that under dense gel conditions RNA molecules contained in ribosomes unfolded by desalting, like all other particles considered here, have helical regions. Under these conditions free desalted RNA has no helical regions. Experimental data on X-ray scattering at medium angles were compared with the diffraction curves calculated for homogeneous prolate and oblate ellipsoids, for various ellipsoids containing a dense region or an internal cavity, and for ellipsoids containing internal periodic regions. The results indicate that the internal structure of the 50 S ribosome is periodic, i. e., its components form a periodic lattice. The lattice spacings are approximately 42 and 28 A with a 0.8g/g dry weight sample water content. When the 50 S particle water content drops below 0.2 g/g dry weight the periodic structure is disrupted. This disruption is reversible. It was shown that CM-like particles at high ionic strenght (2 M LiCl) have approximately the same internal periodicity as the 50 S particles, but in contrast they lose this periodicity at low ionic strength (10-2M tris-HCl and 5-10-3 M MgCl2).

中文翻译：

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核糖体结构的X射线衍射研究。

大肠杆菌70 S核糖体，其50 S亚基，CM样颗粒，RNP链及其片段，从RNP链中添加Mg2 +离子折叠获得的38 S颗粒，未定向的无盐和游离rRNA钠的致密凝胶通过X射线衍射研究了镁盐和镁盐。结果表明，在稠密的凝胶条件下，核糖体中包含的通过脱盐而展开的RNA分子与此处考虑的所有其他颗粒一样，具有螺旋区域。在这些条件下，游离的脱盐RNA没有螺旋区域。将有关中等角度X射线散射的实验数据与为均匀的扁长形和扁长的椭球体，包含密集区域或内部空腔的各种椭球体以及包含内部周期性区域的椭球体计算的衍射曲线进行了比较。结果表明50 S核糖体的内部结构是周期性的，即其成分形成周期性的晶格。晶格间距约为42和28 A，干重为0.8 g / g。当50 S颗粒的水含量降至0.2 g / g干重以下时，周期性结构被破坏。这种破坏是可逆的。结果表明，高离子强度（2 M LiCl）下的类CM颗粒具有与50 S颗粒大致相同的内部周期性，但相反，在低离子强度（10-2M tris-HCl和5- 10-3 M MgCl2）。2 g / g干重，周期性结构被破坏。这种破坏是可逆的。结果表明，高离子强度（2 M LiCl）下的类CM颗粒具有与50 S颗粒大致相同的内部周期性，但相反，在低离子强度（10-2M tris-HCl和5- 10-3 M MgCl2）。2 g / g干重，周期性结构被破坏。这种破坏是可逆的。结果表明，高离子强度（2 M LiCl）下的类CM颗粒具有与50 S颗粒大致相同的内部周期性，但相反，在低离子强度（10-2M tris-HCl和5- 10-3 M MgCl2）。