title: The elasticity of spectrin-actin gels at high protein concentration.
abstract: Human erythrocyte spectrin of high purity was studied alone and mixed with rabbit skeletal actin by dynamic rheometry as a function of protein concentration at pH 7.4 and 24 degrees C. Pure spectrin had a very low storage modulus, G', increasing slightly with increase in protein concentration (approximately 3 dynes/cm at 25 mg/ml). In contrast, unpurified cytoskeletal extracts containing spectrin, actin, and band 4.1 showed a marked concentration dependence for G', increasing to 150 dynes/cm at 20 mg/ml. Mixtures of purified spectrin and skeletal actin at a weight ratio of 4:1 also showed G' markedly dependent on concentration (approximately 150-200 dynes/cm at 20 mg/ml). Maximum elasticity of spectrin-actin gels occurred at a molar ratio of actin monomers to spectrin tetramers of 14:1. We conclude that the reconstituted in vitro spectrin-actin network consists of actin fibers cross-linked by spectrin tetramers at regular intervals. The gel is rapidly reformed after mechanical disruption or thermal collapse, indicating that the polymer fibers are in equilibrium with the constituent monomers.
mesh_terms: D000096:Acetone; D000199:Actins; D002850:Chromatography, Gel; D004910:Erythrocyte Membrane / Q000032:analysis; D005782:Gels; D006801:Humans; D008433:Mathematics; D008958:Models, Molecular; D011108:Polymers; D012212:Rheology; D013049:Spectrin
chemical_list: D000199:Actins; D005782:Gels; D011108:Polymers; D013049:Spectrin; D000096:Acetone