| We present studies of physical properties of biological materials on the examples of DNA, membranes and shells. We study the effects of excluded volume interactions on the melting transition of homogeneous DNA assuming validity of underlying Poland-Scheraga model. We discuss the effects of external stress on the thermal denaturation of DNA, and find regimes where the applied force can either inhibit or promote the phase transition. We find that in three dimensions the heat capacity acquires a logarithmic dependence on reduced temperature. We also investigate the microrheology of nanoparticle membranes and shells by computing the mechanical response function and thermal fluctuation spectrum of a viscoelastic plane membrane and a spherical shell that are permeable to the surrounding solvent. We identify fundamental length and time scales in the systems, and compute the thermal displacement correlation functions. We apply our studies to the analysis of experimental data on red blood cells and make predictions of their bending and shear moduli. |
