Kim S H, Quigley G, Suddath F L, McPherson A, Sneden D, Kim J J, Weinzierl J, Blattmann P, Rich A
Proc Natl Acad Sci U S A. 1972 Dec;69(12):3746-50. doi: 10.1073/pnas.69.12.3746.
Three isomorphous heavy-atom derivatives have been obtained of orthorhombic crystals of phenylalanine transfer RNA from yeast. These derivatives contain osmium, samarium, and platinum. The positions of the heavy atoms have been determined; these have been used to calculate a three-dimensional electron-density map of transfer RNA at a resolution of 5.5 A. The map shows a high contrast between the molecular boundaries and the solvent areas, so that most of the external shape of the molecule can be determined. The molecule appears to be 92 A long and to have a width varying from 16 A to 34 A. There are some narrow regions in the molecule that connect more globular regions. The electron density map shows chains of dense objects approximately 6 A apart that are probably due to adjacent phosphate groups on the polynucleotide chain. At the present stage of the analysis it is not possible to trace the entire backbone unambiguously; however, the data at this resolution suggest no apparent similarity between the folding of the molecule and any of the tertiary structure models proposed for transfer RNA.
已获得来自酵母的苯丙氨酸转移核糖核酸正交晶体的三种同晶型重原子衍生物。这些衍生物含有锇、钐和铂。已确定重原子的位置；利用这些位置计算出了分辨率为5.5埃的转移核糖核酸三维电子密度图。该图显示分子边界与溶剂区域之间有高对比度，因此可以确定分子的大部分外形。该分子似乎长92埃，宽度在16埃至34埃之间变化。分子中有一些狭窄区域连接着更多的球状区域。电子密度图显示了间距约为6埃的密集物体链，这可能是由于多核苷酸链上相邻的磷酸基团所致。在分析的现阶段，无法明确追踪整个主链；然而，此分辨率下的数据表明该分子的折叠与为转移核糖核酸提出的任何三级结构模型之间没有明显相似性。
