Macromolecular dimensions obtained by an efficient Monte Carlo method without sample attrition

The statistical dimensions of macromolecular chains of fixed contour length can be rapidly calculated by Monte Carlo methods applied to a model consisting of dynamic self-avoiding random chains on a lattice. This ’’slithering snake’’ model involves moving the head of a chain one space in a lattice with all other elements of the chain moving forward along the old contour. Possible moves of the head are selected at random, but if such a move is precluded by double occupancy, the old configuration is retained, with head and tail interchanged, and then counted as if a move were made. This technique gives unbiased statistical results except for the effect of double cul-de-sacs. The method can also be applied to interacting chains, either free or confined to a box. Calculations have been made for 10-link chains on a square planar lattice for two different concentrations in infinite space and for two concentrations in a small box.