# 【2.5.1】蛋白质链柔性预测（Karplus Schulz Flexibility ）

In this method, flexibility scale based on mobility of protein segments on the basis of the known temperature B factors of the a-carbons of 31 proteins of known structure was constructed. The calculation based on a flexibility scale is similar to classical calculation, except that the center is the first amino acid of the six amino acids window length, and there are three scales for describing flexibility instead of a single one.

## 二、方法解读

Bnorm= (B + Dp)/( Bp+ Dp),

• Bp是蛋白P所有Cα原子B值的平均值（除去N端和C端各3个残基）
• 蛋白质 Bnorm的均值应该为1
• 当Bnorm值的均方根偏差为0.3时，Dp才会被给出来。在使用Dp进行调节之前，大多数31种蛋白质的均方根偏差在0.2到0.4之间。

## 讨论

1. 这个方法本质是用B-factor来预测链的柔性，但B-factor为啥可以反映柔性呢？

## 参考资料

• Karplus & Schulz Flexibility Prediction: Karplus PA, Schulz GE. 1985. Prediction of chain flexibility in proteins. Naturwissenschaften 72:212-213.