Theoretical studies of the kinetics of mechanical unfolding of cross-linked polymer chains and their implications for single-molecule pulling experiments.
We have used kinetic Monte Carlo simulations to study the kinetics of unfolding of cross-linked polymer chains under mechanical loading. As the ends of a chain are pulled apart, the force transmitted by each cross-link increases until it ruptures. The stochastic cross-link rupture process is assumed to be governed by first order kinetics with a rate that depends exponentially on the transmitted force. We have performed random searches to identify optimal cross-link configurations whose unfolding requires a large applied force (measure of strength) and/or large dissipated energy (measure of toughness). We found that such optimal chains always involve cross-links arranged to form parallel strands. The location of those optimal strands generally depends on the loading rate. Optimal chains with a small number of cross-links were found to be almost as strong and tough as optimal chains with a large number of cross-links. Furthermore, optimality of chains with a small number of cross-links can be easily destroyed by adding cross-links at random. The present findings are relevant for the interpretation of single molecule force probe spectroscopy studies of the mechanical unfolding of "load-bearing" proteins, whose native topology often involves parallel strand arrangements similar to the optimal configurations identified in the study.
Eom
Kilho
K
Department of Aerospace Engineering & Engineering Mechanics, The University of Texas at Austin, Austin, Texas 78712, USA.
Makarov
Dmitrii E
DE
Rodin
Gregory J
GJ
D001696:Biomechanical Phenomena / Q000379:methods; D003198:Computer Simulation; D003432:Cross-Linking Reagents / Q000032:analysis / Q000737:chemistry; D004548:Elasticity; D007700:Kinetics; D008422:Materials Testing / Q000379:methods*; D008846:Micromanipulation / Q000379:methods*; D018625:Microscopy, Atomic Force / Q000379:methods*; D008956:Models, Chemical; D011108:Polymers / Q000032:analysis / Q000737:chemistry; D011487:Protein Conformation; D011489:Protein Denaturation; D017510:Protein Folding; D011506:Proteins / Q000032:analysis* / Q000737:chemistry*; D013314:Stress, Mechanical
D003432:Cross-Linking Reagents; D011108:Polymers; D011506:Proteins