Thermomechanics of a heterogeneous fluctuating chain

In this paper we present a theory to efficiently calculate the thermo-mechanical properties of fluctuating heterogeneous rods and chains. The central problem is to evaluate the partition function and free energy of a general heterogeneous chain under the assumption that its energy can be expressed as a quadratic function in the kinematic variables that characterize the configurations of the chain. We analyze the effects of various types of boundary conditions on the fluctuations of the rods and chains and show that our results are in agreement with recent work on homogeneous rods. The results for the heterogeneous chains are verified through Monte Carlo simulations. Finally, we consider a special heterogeneous chain with only two bending moduli and use it as a model to interpret experiments on partially unfolded protein oligomers. (C) 2009 Elsevier Ltd. All rights reserved.