What experiment demonstrated the function of proteins that allow diffusion facilitated?

The experiment by Peter Agre who discovered the protein Aquaporin demonstrated the function of proteins that allow facilitated diffusion of water.

Explanation:

Aquaporins are water channel proteins that facilitated diffusion of water. Agre was able to prove its function when a frog's oocytes showed increased water permeability when an unknown protein (membranous) from the RBCs was introduced into them. The oocytes without proteins did not facilitate water diffusion.

Aquaporins are membranous proteins that belong to larger intrinsic proteins but act as pores on the cellular membranes to facilitate water diffusion.