Mobility of water in a confined proteinaceous environment
Sprache des Vortragstitels:
Water mobility adjacent to proteinaceous surfaces is commonly assessed by spectroscopic means. For example, neutron scattering studies found the surface water molecules on fully deuterated GFP molecules less mobile than bulk water molecules. Measuring the water flux through proteinaceous pores represents an alternative way of obtaining the mobility of interfacial water molecules. The most interesting insight comes from studies of pores that are too narrow to let two water molecules overtake each other. A variety of biological important membrane channels belong to this class: water channel proteins (aquaporins, AQPs), excitatory sodium and potassium channels and their bacterial ancestors (KcsA and KvAP), and some antibiotics like gramicidin-A channels. We have exploited scanning electrochemical microscopy, electrophysiological recordings, fluorescence correlation spectroscopy and measurements of light scattering intensity to determine the unitary water permeability pf of these proteins. We found that an increase in the total number of hydrogen bonds that any of the single file water molecules may form with pore lining residues while traversing the channel decreases their pf . The corresponding water diffusion coefficients of the single file water molecules cover more than two orders of magnitude, i.e. the mobility of the water molecules drops from bulk water mobility to values more than hundred times smaller.
 Horner A, et al. (2015) The mobility of single-file water molecules is governed by the number of H-bonds they may form with channel-lining residues. Science Advances 1(2):e1400083.