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Flexibility of collagen determined from dilute solution viscoelastic measurements

The frequency dependences of the storage and loss shear moduli, G′ and G″, of pronase‐treated collagen dissolved in acetate buffer at pH 4.0 were measured at 17.0°C by use of the Birnboim‐Schrag multiple lumped resonator apparatus. Some of the solutions contained 70% glycerol. The infinite‐dilution moduli were determined and compared with theoretical models for a rigid cylinder and a semiflexible rod. Only the latter could fit the data. A rotational time of 144 μs and a slowest flexural relaxation time of 21 μs, both reduced to water at 20°C, were determined from the fit. The intrinsic viscosity and rotational relaxation time correspond to a semiflexible rod with persistence length of about 170 nm and a Young's modulus of 4 × 1010 dyn/cm2.