光散射201403.docVIP

For an exploration of the molecular dimensions of IDPs, coupled with thorough control of their monomeric state, the combination of dynamic light scattering (DLS) and static light scattering (SLS) is a method of choice. IDPs ：intrinsically disordered proteins 静态光散射： 如果将溶液中的聚合物分子看作一个个各向同性的粒子,以一定频率的入射光照射这些粒子,它们不吸收入射光能量,而仅作为二次波源向各个方向发射与入射光频率相同的球面散射光,这种没有频率位移(即无能量变化)的散射称为弹性光散射( elastic light scattering) ,也常称为经典光散射( classical light scattering)、静态光散射( static light scattering) 、time-averaged light scattering 在静态光散射情况下,通常用瑞利比来表征一个体系的散射能力和角度依赖性。 当qRg1 A perceptible angular dependence of the scattering intensity （可见的光强的角度依赖）can only be expected for particles with RG 10 nm. Thus, light scattering is not an appropriate method for monitoring changes of RG during unfolding and refolding of small monomeric proteins. However a substantial angular dependence is observed for large protein aggregates. The optical constant K=4π2n02(dn/dc)2/λ4NA depends only on experimental parameters and the scattering properties of the molecules in the particular solvent, which is reflected by dn/dc. The exact knowledge of dn/dc, the dependence of n on protein concentration in the present case, is very important for absolute measurements of the molecular mass. 在一定温度下，测得不同角度时标准物、溶剂和溶液的散射光强I0（θ）、Is（θ）、I（θ），可得到相应得R（θ），实测或从高分子手册上查知n和dn/dC的数值，于是K成为已知的常数。KC/ R（θ）是θ和C的函数。抽象地看，这是对应于一个空间曲面的函数z=f（x，y），其中x=q2，y=C，z= KC/ R（θ） dn/dc可用微分折光仪测定， Measurements of the refractive index increment dn/dc are much more time-consuming and require the use of differential refractometers,which are also frequently used as concentration detectors in chromatography techniques. Therefore, instruments for measuring dn/dc can be obtained from manufacturers of light scattering devices and chromatography systems as well。However, it is recommended to try to obtain appropriate values of dn/dc from the literature for particular buffer and solvents before starting tedious experiments. The refractive index n and dn/dc were meas