  This work presents a modified Kedem-Katchalsky equations for osmosis through
nano-pore. osmotic reflection coefficient of a solute was found to be chiefly
affected by the entrance of the pore while filtration reflection coefficient
can be affected by both the entrance and the internal structure of the pore.
Using an analytical method, we get the quantitative relationship between
osmotic reflection coefficient and the molecule size. The model is verified by
comparing the theoretical results with the reported experimental data of
aquaporin osmosis. Our work is expected to pave the way for a better
understanding of osmosis in bio-system and to give us new ideas in designing
new membranes with better performance.
