Investigating conformation changes and network formation of mucin in joints functioning in human locomotion

Abstract

Many different processes take place to facilitate lubrication of the joints functioning in human locomotion system. The main purpose of this is to avoid destroying the articular cartilage. Viscoelastic properties of the joints system are very sensitive on both temperature and concentration changes because of the change in conformation presented in the system proteins and protein network formation. We are searching for an answer to the question on how changes in temperature and concentration influence the conformational entropy of mucin protein which is a part of one of the key components, lubricin, which is believed to be responsible for gel formation inside synovial fluid. We are using molecular dynamic technique to obtain the information about dihedral (phi, psi) angles of the mucin during protein self - assembly by means of the computer simulation with a time duration up to 50 ns, parameterized by six temperatures ranged between 300 - 315 K, and six concentrations 10.68 - 267.1 g/L. The results show that between c3 and c4 (160 g/L and 214 g/L) a transition exists where crowding begins affecting the dynamics of protein network formation. In such a concentration ranges mucin has a chance to change the frictional properties of the system. Simultaneously there were no significant changes in conformations of the mucins molecules even after they created networks. The temperature changes also did not affect much of mucins conformations but it introduced slightly modifications in dihedral angles and after some critical value T=306 K it changed conformational entropy trend from decreasing to raising.