Effect of pH on collagen flexibility determined from dilute solution viscoelastic measurements |
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Authors: | Eric J. Amis Craig J. Carriere John D. Ferry Arthur Veis |
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Affiliation: | Department of Chemistry, University of Wisconsin, Madison, WI 53706, USA;Department of Biochemistry and Oral Biology, Northwestern University Medical School, Chicago, IL 60611, USA |
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Abstract: | The frequency dependences of the storage and loss shear moduli, G′ and G″ of dilute solutions of collagen at pH 7.4, ionic strength approximately 0.2, were measured at 15.0°C by the Birnboim—Schrag multiple-lumped resonator apparatus. By use of two solvents, water and 50% glycerol, the effective reduced frequency range was extended to cover 2.5 logarithmic decades. The intrinsic viscosity and longest (rotational) relaxation time were considerably smaller than those determined at pH 4.0 in an earlier study. At pH 4.0, the behaviour could be modelled by a rodlike molecule with partial flexibility along its entire length and a persistence length of 161 nm with no loose joints. The behaviour at pH 7.4 corresponds approximately to the expectation for a semiflexible rod with two loose joints near the ends and a similar persistence length (169nm) for the centre segment. |
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Keywords: | Collagen viscoelastic measurements pH effects coiled-coils |
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