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J S Huebner

Publications and source records attributed to J S Huebner.

9 recordsLinked to original sources
PubMed1989

Acrylamide quenching of tryptophan photochemistry and photophysics.

Studies of acrylamide quenching of tryptophan (Trp) fluorescence, photochemistry, and photoionization have been conducted. Quenching of Trp fluorescence in aqueous solution by addition of acrylamide in the concentration range 0.0-0.5 M was measured and resulted in a Stern-Volmer quenching constant of KSV = 21 +/- 3 M-1. Photolysis experiments were performed in which Trp was photolyzed at 295 nm in the presence of varying concentrations of acrylamide. The loss of Trp was monitored using reverse-phase high performance liquid chromatography (RP-HPLC) and was observed to follow first order kinetics. Production of N-formylkynurenine (NFK) was observed by RP-HPLC in irradiated Trp samples both in the presence and absence of added acrylamide. In addition, no new photochemical product was detected. This was taken as evidence that acrylamide did not alter the photochemical pathway but just reduced the reaction rate as expected for a physical quenching mechanism. Plotting the reciprocal of photolysis rate constant versus acrylamide concentration produced a Stern-Volmer constant for quenching of Trp photochemistry of KSV = 6 +/- 2 M-1. The KSV values for both fluorescence quenching and photolysis quenching were thus large, implying efficient quenching of both processes by acrylamide. Assuming an excited singlet state lifetime of 2.8 ns, the calculated second-order quenching rate constants for fluorescence and photolysis were kq = 7.5 x 10(9) and 2.1 x 10(9) M-1 s-1 respectively. The possible involvement of photoionization in the photolysis mechanism was investigated by studies of acrylamide quenching of voltage transients produced by xenon flash lamp excitation of Trp at aqueous/teflon or aqueous/mica interfaces.(ABSTRACT TRUNCATED AT 250 WORDS)

Acrylamides↗
PubMed1982

Erythrosin and pH gradient induced photo-voltages in bilayer membranes.

Erythrosin and light flashes induce voltage transients across bilayer membranes in the presence of transmembrane pH gradients. Fast voltage transients, which rise in less than 50 nsec and fall in approximately 500 nsec, are attributed to photo-deprotonation of dye sorbed in the glycerol region of phospholipid membranes. Six other halogenated xanthene dyes induce similar effects, which apparently resulted from triplet states of monoanionic dye. No photo-effects were observed with fluorescein.

Erythrosine↗
PubMed1979

Lipid and salt effects on carbocyanine dye-induced photo-voltages in bilayer membranes.

Voltage transients induced by flash illumination of bilayer membranes with sorbed dye, 3,3' -dimethyl-2,2' -oxacarbocyanine chloride (diO-C1-3-CI), vary with membrane lipid composition and aqueous solution salt concentration. The voltage transients are probably induced by physical movements of sorbed dye molecules following photo-isomerization. Increased salt (NaCl and NaBr) concentrations in the aqueous solutions reduced the photo-voltage amplitudes by reducing the amount of dye sorbed to the membranes, and by decreasing the effective membrane thickness. The photo-voltage risetimes and falltimes varied systematically with salt concentration and membrane lipid composition, reflecting structural changes in the membrane's surface layer.

Carbocyanines↗
PubMed1979

Voltage transients from photo-isomerizing azo dye in bilayer membranes.

Voltage transients are induced by brief light flashed on bilayer membranes with absorbed 3,3'-bis(alpha-(trimethylammonium)methyl)azobenzene (Bis-Q). The voltages are positive for trans-to-cis photo-isomerization, and negative for cis-to-trans photo-isomerization. The risetimes in phosphatidylethanolamine-decane bilayer membranes indicate that absorbed trans-Bis-Q is photo-isomerized to cis within 2 microseconds, and that cis is photo-isomerized to trans within 15 microseconds.

Azo Compounds↗
PubMed1978

Cyanine dye structural and voltage-induced variations in photo-voltages of bilayer membranes.

Flash illumination alters the voltage across bilayer lipid membranes in the presence of certain cyanine dyes. The waveforms of the photo-voltage vary systematically with dye structure and imposed transmembrane voltage. Experimental results are reported for 27 positively charged cyanine dyes, primarily oxazole derivatives, using lecithin/oxidized cholesterol bilayer membranes and 10-mM sodium chloride solutions. Several dyes do not induce any photo-voltages. Examples are 3,3' diethyl 9 ethyl 2,2' oxacarbocyanine iodide, 3,3' diethyl 2 oxa 2" thiacyanine iodide, and 3,3' dimethyl 2,2' indocarbocyanine iodide. Several dyes, when added to one side of the membranes, induce monophasic waveforms. Examples are 3,3' dimethyl 2,2' oxacarbocyanine chloride, and 3,4,3',4' tetramethyl 2,2' oxazalinocarbocyanine iodide. Other dyes induce a photo-voltage only if transmembrane voltages are imposed. These waveforms are biphasic with some dyes (3,3' diethyl 2,2' oxacarbocyanine iodide, for example) and monophasic with other dyes (3,3' dibutyl 2,2' oxacarbocyanine iodide, for example). The photo-voltage waveforms are explained by models that consider the movement of charged dye molecules within the membrane, following optical excitation. The dye movements are probably induced through charge rearrangements in the dye associated with long-lived triplet states, isomerization, or through excimer formation. These results provide information on the location and orientation of the dye molecules within bilayer membranes. The variations which occur in the waveforms with applied voltage indicate that these membranes are fluid in the direction perpendicular to the membrane plane.

Fluorescent Dyes↗
PubMed1975

Photo-voltages of bilayer lipid membranes in the presence of cyanine dyes.

The transmembrane photo-voltage waveforms induced by 10 different cyanine dyes absorbed to one side of bilayer lipid membranes are described. The membranes were prepared from lecithin, oxidized cholesterol, and mixed lecithin and oxidized cholesterol. An 8-mus flash illumination was used. Three dyes induced a photo-voltage which developed in a few milliseconds, then discharged in less than the membranes' resistance-capacitance time. Five dyes induced a photo-voltage which increased for much longer than the membranes' resistance-capacitance time. Two dyes did not induce any photo-electric effects. Models are presented which correlate the dye structure with the type of photo-voltage waveform induced.

Benzoxazoles↗