文献归纳 读书笔记 10.30

精读：
1. Kinetics of Protein Adsorption  Ramsden  Biopolymers on interface
2. Structural Changes in Proteins Adsorbed on Polymer Surfaces
M. E. SODERQUIST AND A. G. WALTON, Journal of Colloid and Interface Science 75 pp386

泛读：
3. A kinetic model of partially reversible protein adsorption
Paul R. Van Tassel, Pascal Viot, and Gilles Tarjus， J. Chem. Phys. 106 (2), 8， 761

All of above are talking about the mechanism of protein adsorption on solid-liquid interface. Walton demonstrate that there should be some protein conformation change when it adsorbed on the surface. The most important proof is the circular dichroism. By detecting the difference between the adsorption of alpha-helix and beta-folding, they found that the native and desorbed protein are different in conformation composition. They established a model that protein reformed itself when adsorbed on the surface, and then have different rate and somehow become irreversible adsorption process. That is also the reason for a “kink” in protein isothermal. (However, this is an old article, the data graph they used is too rough. TIRF could provide a better image, which sometimes show this “kink” while sometimes not.) They concluded that the at the latter part of the adsorption, the more important interaction is protein - protein on interface, not the protein - surface interaction.

Tassel’s paper used the idea Walton proposed. So they have the model named “partial irreversible” protein adsorption. They show the simulation result of different “surface correlation” functions. Notice that sometimes there is an “overshoot” phenomenon during the adsorption.

For us, first good news is albumin will have a 2.5mg/m2 adsorption on surface when it takes “side-on”. [2]. And albumin has a easiest tendency to have protein conformation changed, which should be considered in our case. Another thinking is if we could get the desorbed protein, we can use circular dichroism to detect if there is any conformation chance on the surface. Also, if the decrease during the adsorption observed during the protein adsorption process, maybe it’s not because of the baseline drifting. [3]

In conclusion, this process is different. Mass conservation law is only a partial thermodynamically way to describe this process. If you consider PURE kinetical way. 1) when to introduce irreversibility? 2)how to describe the reformed protein’s kinetic constant? 3)”Phase transition” on the surface?

个人感觉：美国真的很不重视理论，现在看下来，polymer brushes，还有这个adsorption kinetics都是法国人搞得有声有色。

Powered by ScribeFire.

Copolymer Sequence Distribution on the Miscibility of PEO/PS-co-PAA blends

Poly(etylene glycol)和Poly(acrylic acid)按照 L.H. Sperling的Polymeric Multicomponent Materials: An Introduction 里面的观点，是全部组成范围内可溶的。Polystyrene和PEO还有PAA都是不可溶的。所以有一种方法改性PS-PEO体系的溶混性就是通过copolymerize一个PAA链段到PS链上。这两篇文章可以和在一起看，前一篇是实验的结果，发现PAA 7mol%以后就出现可溶现象。后面一篇是对这个体系的理论计算，个人比较喜欢这种有实验有理论的paper.这样才是science. 简单的说来，就是仍旧使用Flory-Huggins方程，加上少许修改：

溶度参数可以拆成composition的贡献和monomeric unit distribution的两部分的贡献：（简明起见，AA段就是a, Styrene段b, Etylene oxide段c.

其中 其他几个也同理。sequence distribution带来的贡献， 就在这项中体现。

具体的模拟方法我没有详细去检验，先验证了Force Field，然后用了Docking Method (懂得牛人可以说说这个到底是什么吧，粗粗看看好像就是mean field approximation。)

模拟的结果稍稍有点让人惊讶，结果是aaa段和c的作用力在一定温度范围内居然给copolymer的miscibility带来的是负面的效果。 因为AA和EO之间是有氢键的，很不可理解。作者对于这个的解释是AA在某种情况下倾向于自身形成complex compound,而不是和EO形成complex compound.

这篇文章的simulation让人的感觉还是有些不全的地方，因为稍微推导了一下，如果PAA-PS共聚物中间的PAA比率很高的话几乎就等于，但是这个时候必然是可溶的，但是好像按照文章的说法的话不能解释这种现象。而且现在ms比较流行SCF理论，不知道SCF计算对这个的结果是怎么样的。文章里面的理论解释block的话还有一定的欠缺。而且就Figure2来说，AA比率增大，增大，这个似乎有点问题。

anyway, FYI. 有兴趣地同修可以阅读一下两篇原文。欢迎排砖，探讨~

1. Won Ho Jo and Sang Cheol Lee Macromolecules, 1990, 23. 2261

2. Kyoungsei Choi and Won Ho Jo Macromolecules, 1997, 30, 1509