Ion distribution profiles between polar and charged membranes as observed by anomalous X-ray diffraction

The distribution profiles of rubidium ions near polar, zwitterionic 1,2-di stearoyl-sn-glycero-3-phospho choline (DSPC) and charged, anionic 1,2-di stearoyl-sn-glycero-3-phospho glycerol (DSPG-) membranes were determined by means of anomalous X-ray diffraction close to the K-absorption edge of $\rm Rb ^+$, which was measured to be 15.225 keV. The samples were kept in the L$_\beta'$-phase at 30$\;\rm{}^\circ C$. The DSPC suspensions in 2 M RbCl were examined at 15.125 keV, 15.196 keV, 15.210 keV, the $\rm DSPG ^-$ suspensions in 0 M RbCl and 2 M RbCl at 14.667 keV and 15.196 keV. This gave up to seven peaks in the powder-like diffraction pattern and revealed, for the first time directly, different rubidium ion distributions in either of the investigated systems: rubodium ions are enriched by 100% in the proximity of the charged $\rm DSPG ^-$ headgroups and depleted by 25% from the vicinity of the zwitterionic DSPC headgroups. The latter phenomenon results in rubidium ion concentration maximum in the aqueous compartment between polar, but uncharged bilayers

Electronic data capture and use of internet technologies in a double-blind randomised intervention trial

SCOPUS: cp.kinfo:eu-repo/semantics/publishe