Human spectrin. VI. A viscometric study.

Employing viscometry, human spectrin heterodimers and heterotetramers were analyzed in aqueous solution containing different amounts of salt. (1) In aqueous 0.1 M NaCl, pH 7.5, at 4 degrees C, the intrinsic viscosity of isolated human spectrin heterodimers and heterotetramers was found to be 40 +/- 6 and 79 +/- 7 ml/g, respectively. (2) The intrinsic viscosity of isolated human spectrin heterodimers and heterotetramers increased to 78 +/- 8 and 180 +/- 10 ml/g, respectively, as the ionic strength of the solution was reduced to about 2 mM. (3) This viscometric study indicates that isolated human spectrin heterodimers and heterotetramers are flexible molecules with a contour length of at least 110 and 200 nm, respectively.