AQPs (aquaporins), the rapid water channels of cells, play a key role in maintaining osmotic equilibrium of cells. In this paper, we reported the dynamic mechanism of AQP osmosis at the molecular level. A theoretical model based on molecular dynamics was carried out and verified by the published experimental data. The reflection coefficients ( \sigma%DIFDELCMD < }%%% ) of neutral molecules are mainly decided by their relative size with AQPs, and increase with a third power up to a constant value 1. This model also indicated that the reflection coefficient of a complete impermeable solute can be smaller than 1. The H+ concentration of solution can influence the driving force of the AQPs by changing the equivalent diameters of vestibules surrounded by loops with abundant polar amino acids. In this way, pH of solution can regulate water permeability of AQPs. Therefore, an AQP may not only work as a switch to open or close, but as a rapid response molecular valve to control its water flow. The vestibules can prevent the channel blockage of AQPs by a primary screening before their constriction region. This model also provides a prediction tool to the structure of AQPs by the \sigma%DIFDELCMD < }%%% s of special solutes. The puzzling variance between \sigma%DIFDELCMD < } %%% to erythrocytes AQP1 and \sigma%DIFDELCMD < } %%% to oocytes-expressing AQP1 was also explained .
 %DIFDELCMD < }%%% This work presents a modified Kedem-Katchalsky equations for osmosis through nano-pore. osmotic reflection coefficient of a %DIFDELCMD < }%%% %DIFDELCMD < } %%% %DIFDELCMD < } %%% 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 .
D
AQPs (aquaporins), the rapid water channels of cells, play a key role in maintaining osmotic equilibrium of cells. In this paper, we reported the dynamic mechanism of AQP osmosis at the molecular level. A theoretical model based on molecular dynamics was carried out and verified by the published experimental data. The reflection coefficients (
D
\sigma
R
) of neutral molecules are mainly decided by their relative size with AQPs, and increase with a third power up to a constant value 1. This model also indicated that the reflection
This work presents a modified Kedem-Katchalsky equations for osmosis through nano-pore. osmotic reflection
D
complete impermeable solute can be smaller than 1. The H+ concentration of solution can influence the driving force of the AQPs by changing the equivalent diameters of vestibules surrounded by loops with abundant polar amino acids. In this way, pH of solution can regulate water permeability of AQPs. Therefore, an AQP may not only work as a switch to open or close, but as a rapid response molecular valve to control its water flow. The vestibules can prevent the channel blockage of AQPs by a primary screening before their constriction region. This model also provides a prediction tool to the structure of AQPs by the
D
\sigma
D
s of special solutes. The puzzling variance between
D
\sigma
D
to erythrocytes AQP1 and
D
\sigma
R
to oocytes-expressing AQP1 was also explained
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