Self-Diffusion of a Semiflexible Polypeptide in a Magnetically Aligned Liquid Crystalline Phase

The tracer self-diffusion coefficient of semiflexible poly(-benzyl-,L-glutamate) with a length of approximate to 160nm and a diameter of approximate to 1.6nm is determined by fluorescence photobleaching recovery in the magnetically aligned liquid crystalline phase. The rate of diffusion in the direction of molecular alignment declines with concentration in the liquid crystalline phase, while the rate perpendicular to the direction of molecular alignment remains approximately constant. At concentrations just sufficient to sustain the liquid crystalline phase, the parallel diffusion exceeds the perpendicular diffusion by a factor of almost 5. This ratio declines to as little as 2 at higher concentrations. Comparisons are made with previous studies on other systems ranging from rigid virus particles to small mesogens.