polyanion

[pŏl′ē-ănī′ən]
n.
  1. Any of multiple anionic sites on proteoglycans in the renal glomeruli that restrict filtration of anionic molecules and facilitate filtration of cationic proteins.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.