[18] Lipid coumarin dye as a probe of interfacial electrical potential in biomembranes

摘要: The coumarin method has been applied for the determination of surface potentials in a few biological membranes, such as thylakoids,25 electroplax,26 vesicular stomatitis virus,27 and mycoplasms.28 Furthermore, it used reconstituted system ATP/ADP transport protein mitochondria.17 As shown last example provides best values potential relation to Gouy-Chapman model. With respect general application biomembranes, there are two basic obstacles: (1) location probe inhomogeneous membrane made lipids proteins is unknown. (2) insight with an actual effect average on transport, pore gating, contact [Eq. (1)] limited at present time. The practical problems hardly more involved than other techniques: In some systems blue fluorescence may be superimposed background. pKmw negative membranes rather high. Up now impossible design lipid pH indicators (carbonylcoumarin,29 dansyl,30,31 acridine,31 chinin,31 naphthoic acid32) pKi = 6–7 red fluorescence, conserving crucial feature its insensitivity details surface. The main success up field pure colloidal systems. Surface charge density have characterized insoluble monolayers,4,5 micelles,6,21 vesicles,8,15,18 foam films.7,33 These results basis studies native biomembranes formation junctions. Some remain solved: validity thermodynamic cycle checked experimentally by relating probed macroscopically determined electrical monolayers solvent-free bilayers. interaction matrix studied detail NMR techniques theoretical simulation. (3) polarization mixed investigated. (4) neutral interfaces pK that every charged appropriate chosen. The interfacial polarity emphasized previously4,6 illustrated recently glycosurfactant.34 Finally, should noted not only analytical tool probing but synthetic sensors effects induced agonists, enzymes, or cells, direct transduction signal semiconductor.35