Elongational flow studies on type IV collagen: Comparison with type I

Elongational flow techniques have been used to investigate the birefringent response of monodisperse type IV collagen in dilute solution and the results compared with type I. collagen. A four‐roll mill apparatus was used to characterize the solutions at low strain rates, $\dot{\varepsilon}$ ⩾ 300 s⁻¹. The birefringence is nonlocalized and rises gradually to a plateau value, in accordance with rigid‐rod behavior. The gradients of the tangent to the curves at zero strain rate are estimated for types IV and I collagen. The concentrations of the solutions used were in the dilute to semidilute regimes. Using a value of 300 nm for the length of type I collagen, values of 364–408 nm were calculated for the length of the type IV collagen molecule, depending on the concentration regime chosen, which is consistent with biochemical predictions based on a rigid molecule. The results imply that the behavior of type IV collagen molecules in solution is similar to type I collagen, despite the presence of several sequence interruptions in the type IV helix. © 1993 John Wiley & Sons, Inc.