Spatial charge distribution effects in the conductance of syringomycin E ion channels formed in lipid bilayersстатья
Информация о цитировании статьи получена из
Web of Science
Статья опубликована в журнале из перечня ВАК
Статья опубликована в журнале из списка Web of Science и/или Scopus
Дата последнего поиска статьи во внешних источниках: 7 сентября 2017 г.
Аннотация:Channel-forming activity of syringomycin E produced by phytopathogenic bacterium Pseudomonas syringae pv. syringae was studied. By using planar lipid bilayers modified with syringomycin E, the conductance of single channels formed by antibiotic as a function of the transmembrane potential difference (V), the ionic composition, and pH of the bathing solution was measured for different membranes (charged DOPS/DOPE, and uncharged DPhPC) was measured. For all cases indicated, the current-voltage curves of single channels were superlinear in V and asymmetrical in its sign, the degree of their asymmetry being dependent on variations in the ionic concentration, pH, and the surface membrane charge. The channel conductance did not change when 1 M NaCl was replaced by 1 M RbCl within the range of -250...+250 mV. It suggests the absence of voltage-dependent expanding of channel lumen as a possible reason for the observed superlinearity of current-voltage curves. The equivalent conductance of channels (the ratio of conductance and the electrolyte concentration) in the zero current conditions was practically independent of the NaCl concentration for pH 6 for DOPS/DOPE, pH6. However, the above value was a linear function of the square root concentration of electrolyte for DPhPC. At the same time, the channel conductance for charged bilayers increased monotonically, when pH decreased from 6 to 2, which shows the influence of the surface charge titration. A similar effect was observed when a charge titration was performed with Ca+2-ions. It is shown that the spatially distributed charges stemming from the membrane lipids and the channel-forming molecules are responsible for the observed features of the channels. The estimates based on this model are in agreement with experimental results.