GEOMETRIC CONSTRAINTS IN POLYMER-CHAINS - ANALYSIS ON THE PEARL-NECKLACE MODEL BY MONTE-CARLO SIMULATION

A linear chain with hard sphere interaction among its monomers is investigated using a nondynamic Monte Carlo method. The spheres of radius R touch their two first neighbors along the chain, resembling the pearl-necklace model with bond length equal to 2R; the number N of pearls covers the range 10-300. Hard sphere constraint, fixed angle theta between the segments connecting each two of three consecutive pearls, and azimuthal angles taken at random in the 0-2 pi range, define our model. The average end-to-end chain distance and average gyration radius are determined for several angles B in the 60-150 degrees range, and several values of N. We present a finite size analysis of the model and discuss the efficiency of nondynamic methods, as the ensemble grow method (EGM), to simulate chains in the presence of constraints. The results reveal that, as in the freely rotating chain case, the leading constraint in the model is the angle theta. We also comment on the EGM general ideas applied to the protein folding problem.