The use of polyethyleneimine for demonstration of anionic sites in basement membranes and collagen fibrils.

Strong cationic polyethyleneimine (PEI) is used to trace anionic sites in lung, choroid plexus, glomeruli, blood vessels and also on collagen fibrils. In the mentioned tissues, PEI is found in the basement membranes with a spacing identical to that found on collagen fibrils. It is assumed that the acid endgroups of tropocollagen molecules are responsible for the binding of PEI.