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Persistence Length of Titin from Rabbit Skeletal Muscles Measured with Scattering and Microrheology Techniques

Emanuela Di Cola ^*, Thomas A. Waigh ^*, John Trinick , Larissa Tskhovrebova , Ahmed Houmeida , Wim Pyckhout-Hintzen  and Charles Dewhurst 

^* Polymers and Complex Fluids, Department of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, United Kingdom; School of Biomedical Sciences, University of Leeds, Leeds, LS2 9JT, United Kingdom; Institut für Festkörperforschung, Forschungszentrum Jülich, D-52425 Jülich, Germany; and Institut Laue-Langevin, BP 156-38042, Grenoble Cedex 9, France

Correspondence: Address reprint requests to Thomas A. Waigh, E-mail: t.a.waigh{at}leeds.ac.uk.

The persistence length of titin from rabbit skeletal muscles was measured using a combination of static and dynamic light scattering, and neutron small angle scattering. Values of persistence length in the range 9–16 nm were found for titin-II, which corresponds to mainly physiologically inelastic A-band part of the protein, and for a proteolytic fragment with 100-nm contour length from the physiologically elastic I-band part. The ratio of the hydrodynamic radius to the static radius of gyration indicates that the proteins obey Gaussian statistics typical of a flexible polymer in a -solvent. Furthermore, measurements of the flexibility as a function of temperature demonstrate that titin-II and the I-band titin fragment experience a similar denaturation process; unfolding begins at 318 K and proceeds in two stages: an initial gradual 50% change in persistence length is followed by a sharp unwinding transition at 338 K. Complementary microrheology (video particle tracking) measurements indicate that the viscoelasticity in dilute solution behaves according to the Flory/Fox model, providing a value of the radius of gyration for titin-II (63 ± 1 nm) in agreement with static light scattering and small angle neutron scattering results.

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