Persistence length is the maximum length of the uninterrupted polymer chain persisting in a particular direction. It can be used for flexible polymer chains like proteins, DNA and synthetic polymers. We have performed persistence length analysis for a dataset of ~1000 representative globular proteins from PDB database. Frequency analysis of persistence length shows that the values vary from 15Ă to 60Ă within the 95% confidence limits and average around 40Ă(fig). This filter can be employed to evaluate the value of persistence length for a given protein and to find out whether the value is in acceptable limits for globular proteins or not. HOW TO USE TOOL