Translational and Rotational Dynamics of Collagen in Dilute Solution

The translational and rotational dynamics, including the translational−rotational coupling, of collagen in an aqueous 0.25 mg/mL solution of 0.1 N HCl were studied by polarized dynamic light scattering. An autocorrelator with variably spaced delayed times allowed computation of dynamic light-scattering intensity autocorrelation functions over a wide dynamic range. Methods of data analysis included the method of cumulants and the inverse Laplace transform−regularization method as embodied in Provencher's CONTIN program. The value determined for the translational diffusion coefficient using the method of cumulants is 8.4 × 10 -12 m 2 /s. This value is smaller than the value of 9.5 × 10 -12 m 2 /s found using CONTIN. The method of cumulants appears to result in an erroneous value of D due to the presence of dust or aggregates. The D value found from CONTIN analysis corresponds to a hydrodynamic length of 2390 Å using Broersma's relations and assuming the diameter d = 13.6 Å. The rotational diffusion coefficient was determined to be 1110 s -1 . The Hagerman−Zimm and Yoshizaki−Yamakawa theories for the ratio of the value of ϑ expected for a rigid rod to that for a semirigid rod of the same contour length were used to determine values of 1600 and 1650 Å for the persistence length of collagen.