Effect of ionic strength on the flexibility of Col IV molecules

Collagen IV (Col IV) is the most abundant structural component of the basement membrane underlying epithelial and endothelial cells. In this study, we examined how ionic concentration impacts the flexibility of purified Col IV in-vitro. By using atomic force microscope (AFM) we imaged Col IV molecules and their network formation at two different ionic strengths of phosphate buffer saline (PBS). By analyzing the contour of Col IV via standard and segmented worm-like chain model, we ascertained the persistence length of isolated molecules. Our results demonstrate a significant increase in persistence length and height of Col IV at the higher ionic concentration accompanied by a decrease in contour length. The network morphology was also visibly altered at higher ionic strength. These results can be utilized to understand how the basement membrane architecture and flexibility can be altered in health and disease.