Dynamic light scattering apparatus

我们都收到同样的电子邮件。 上面写着，“尺寸很重要”。 但这个信息没有告诉你的是，形状也很重要。 两个互补的技术，分析超离心和动态光散射（DLS）允许一个量化的大小和形状的生物大分子和视图，对于一个恒定的分子量，大小和形状如何变化的分子去做他们做的事情。 我们有一种分析超灵敏度仪，并且在使用它方面有相当的经验。我们没有DLS仪器。动态光散射对于生物化学家在三种不同的情况下是重要的：（1）它允许人们确定在一个均匀的分子集合中的单个分子看起来有多大。它产生一个扩散系数，它可以与等效球体的大小有关。 (2)如果集合中的分子不均匀，而是由多个种类组成，则最大的种类在数据分析中提供最强的信号;当评估样品的结晶时，该信息是必不可少的。 (3)如果溶液含有快速相互转化的单体多聚体，则数据产生颗粒尺寸的平均值，其是单体和多聚体之间的平衡位置的函数。 如果我们联合收割机现在将这些数据与来自分析超离心和分子量（来自质谱或序列分析）的数据相结合，则来自这些独立确定的实验参数的全局分析允许我们精确地确定分子在我们使其经受变化的环境条件时如何改变形状、大小和水合作用。 情况（1）对所有申请人来说都是至关重要的，情况（2）与Peter Pawelek的工作相关，情况（3）与MJ Kornblatt、Pawelek和Turnbull相关。

We all receive the same email message.  It says, "size matters".  What the message does not tell you is that shape also matters.  Two complementary techniques, analytical ultracentrifugation and dynamic light scattering (DLS) allow one to quantify the size and shape of biological macromolecules and view, for a constant molecular weight, how size and shape change as molecules go about doing the things they do.  We have an analytical ultracentrifuge and are reasonably experienced at using it.  We do not have a DLS apparatus. Dynamic light scattering for biochemists is important in three different situations: (1) It allows one to determine how big the individual molecules in a uniform collection of molecules appear to be. It yields a diffusion coefficient, which can be related to the size of an equivalent sphere.  (2) If the molecules in the collection are not uniform but consist of multiple species, the largest of the species contributes the strongest signal in the data analysis; this information is essential when evaluating samples for crystallization.  (3) If a solution contains rapidly interconverting multimers of monomers, the data yield an average value of the size of the particles that is a function of the equilibrium position between the monomers and multimers.   If we now combine this data with that from the analytical ultracentrifuge and the molecular weight (from mass spectroscopy or sequence analysis), the global analysis from these independently determined experimental parameters  permits us to pinpoint how the molecules change shape, size and hydration as we subject them to changing environmental conditions.  Situation (1) is central to all the applicants, situation (2) is relevant to Peter Pawelek's work and situation (3) is relevant MJ Kornblatt, Pawelek and Turnbull.