THE FORM BIREFRINGENCE OF MACROMOLECULES
THE FORM BIREFRINGENCE OF MACROMOLECULES
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DOI：
10.1107/s0365110x53002519
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发表时间：
1953-01-01
期刊：
影响因子：
--
通讯作者：
PIPPARD, AB
中科院分区：
文献类型：
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作者：
BRAGG, WL;PIPPARD, AB
Perutz已经证明，当血红蛋白晶体中的水被盐溶液取代时，双折射会发生变化。计算了这种取代在双折射体中的作用，并与Perutz的观察结果进行了比较。关于这种效应的数量级是一致的，但光学数据表明分子（a/b,- 1.45）比x射线数据推断的分子（a/b,- 1.45）更长。~ 1.3)。这种差异不需要强调，因为分子的形式还不确定，双折射变化的测量是非常近似的。对这种效应的进一步探索可能会产生一种估计其他蛋白质分子形态的有用方法在前面的论文中，Perutz（1953）测量了当盐溶液取代血红蛋白晶体分子之间的水时双折射的变化。观察到的双折射被认为部分是由于分子本身的固有双折射，部分是由于浸没在低折射率液体中的高折射率大分子的拉长形式。双折射形式的计算，以及当液体折射率变化时双折射形式的变化，在本笔记中进行了计算，并与Perutz的观察结果进行了比较。将介电常数为~ 9的长、短轴为a和b的平行球体按规则排列在介电常数稍低的液体中，电场平行于长轴时比电场平行于短轴时极化程度更大。本文第2节推导了相应的方程，其中表明f (e~-ex) e= ezJr 1+(1-~~ z)/sz} L'
Perutz has shown that the birefringence changes when the water in a haemoglobin crystal is re-placed by salt solution. The effect of this substitution in the birefringenee is calculated and com-pared with Perutz's observations. There is agreement as to the order of magnitude of the effect, but the optical data indicated a more elongated molecule (a/b,-~ 1.45) than that deduced from the X-ray data (a/b,.~ 1.3). This discrepancy is not to be stressed, since the form of the molecule is not yet certain and the measurements of change in birefringence are very approximate. A further exploration of the effect may yield a useful method of estimating the form of other protein mole-cules.1 In the preceding paper Perutz (1953) has measured the change in birefringence which occurs when a salt solution replaces water between the molecules of the haemoglobin crystal. The observed birefringence is considered to be due partly to an intrinsic birefringence of the molecule itself, and partly to the elongated form of large molecules of high refractive index which are immersed in a liquid of lower refractive index. Calculations of the form birefringence, and of its variation when the refractive index of the liquid is varied, are made in this note and compared with Perutz's observations. If parallel spheroids with major and minor axes a and b and dielectric constant~ 9 are arranged in a regular way in a liquid of somewhat lower dielectric constant el, they are polarized to a greater extent when the electric field is parallel to the long axis than when it is parallel to a short axis. The appropriate equations are derived in § 2 of this note, where it is shown that f (e~-ex) e= ezJr 1+(1-~~ z)/sz} L'