Charge asymmetry of the purple membrane measured by uranyl quenching of dansyl fluorescence. [Halobacterium halobium]

Journal Article · Tue May 01 00:00:00 EDT 1984 · Biophys. J.; (United States)

DOI:https://doi.org/10.1016/S0006-3495(84)84245-9· OSTI ID:5864116

Renthal, R; Cha, C H

Purple membrane was covalently labeled with 5-(dimethylamino) naphthalene-1-sulfonyl hydrazine (dansyl hydrazine) by carbodiimide coupling to the cytoplasmic surface (carboxyl-terminal tail: 0.7 mol/mol bacteriorhodopsin) or by periodate oxidation and dimethylaminoborane reduction at the extracellular surface (glycolipids: 1 mol/mol). In 2 mM acetate buffer, pH 5.6, micromolar concentrations of UO/sub 2//sup 2 +/ were found to quench the dansyl groups on the cytoplasmic surface (maximum = 26%), while little quenching was observed at the extracellular surface (maximum = 4%). Uranyl ion quenched dansyl hydrazine in free solution at much higher concentrations. Uranyl also bound tightly to unmodified purple membrane, (apparent dissociation constant = 0.8 ..mu..M) as measured by a centrifugation assay. The maximum stoichiometry was 10 mol/mol of bacteriorhodopsin, which is close to the amount of phospholipid phosphorus in purple membrane. The results were analyzed on the assumptions that UO/sub 2//sup 2 +/ binds in a 1:1 complex with phospholipid phosphate and that the dansyl distributon and quenching mechanisms are the same at both surfaces. This indicates a 9:1 ratio of phosphate between the cytoplasmic and extracellular surfaces. Thus, the surface change density of the cytoplasmic side of the membrane is more negative than - 0.010 charges/A/sup 2/.

• Research Organization: Univ. of Texas, San Antonio
• OSTI ID: 5864116
• Journal Information: Biophys. J.; (United States), Vol. 45:5
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
FLUORESCENCE
QUENCHING
PHOTOSYNTHETIC MEMBRANES
CHARGE DISTRIBUTION
LABELLING
BIOCHEMICAL REACTION KINETICS
CELL MEMBRANES
HYDRAZINE
PERIODATES
PHOSPHATES
PHOTOSYNTHETIC BACTERIA
RHODOPSIN
URANYL COMPOUNDS
ACTINIDE COMPOUNDS
CELL CONSTITUENTS
HALOGEN COMPOUNDS
IODINE COMPOUNDS
KINETICS
LUMINESCENCE
MEMBRANES
NITROGEN COMPOUNDS
ORGANIC COMPOUNDS
OXYGEN COMPOUNDS
PHOSPHORUS COMPOUNDS
PIGMENTS
PROTEINS
REACTION KINETICS
URANIUM COMPOUNDS
550200* - Biochemistry