Effects of oxygen on the metabolism of nitroxide spin labels in cells.
AuthorsChen K, Glockner JF, Morse PD, Swartz HM
JournalBiochemistry
PubMed ID2543442
'The products of the reduction of nitroxides in cells are the corresponding hydroxylamines, which cells can oxidize back to the nitroxides in the presence of oxygen. Both the reduction of nitroxides and the oxidation of hydroxylamines are enzyme-mediated processes. For lipid-soluble nitroxides, the rates of reduction are strongly dependent on ... More
Involvement of histidine-91 of the beta subunit in proton translocation by the pyridine nucleotide transhydrogenase of Escherichia coli.
AuthorsGlavas NA, Hou C, Bragg PD
JournalBiochemistry
PubMed ID7779816
'The pyridine nucleotide transhydrogenase (EC 1.6.1.1) carries out transmembrane proton translocation coupled to transfer of a hydride equivalent between NAD+ and NADP+. Mutations were made in histidine-91 of the beta subunit of the pyridine nucleotide transhydrogenase of Escherichia coli. This amino acid is the only conserved charged residue in the ... More
Cellular metabolism of water-soluble nitroxides: effect on rate of reduction of cell/nitroxide ratio, oxygen concentrations and permeability of nitroxides.
AuthorsSwartz HM, Sentjurc M, Morse PD
JournalBiochim Biophys Acta
PubMed ID3741890
'In order to interpret more accurately studies that have used nitroxides and to improve the efficacy of the use of nitroxides in both basic studies of cells and as contrast agents for in vivo NMR, we have initiated a systematic study of the distribution and metabolism of nitroxides in biological ... More
Oxidation of hydroxylamines to nitroxide spin labels in living cells.
AuthorsChen K, Swartz HM
JournalBiochim Biophys Acta
PubMed ID2840969
'In the presence of oxygen, cells can oxidize hydroxylamines, which are the products of the reduction of nitroxides in cells, back to nitroxides. Lipid-soluble hydroxylamines are oxidized much more rapidly than water-soluble ones, and most of this oxidation is inactivated by heat or trichloroacetic acid, indicating that the principal mechanism ... More
Orientation of substrate and two conformations of lactose permease.
AuthorsDornmair K, Jähnig F
JournalBiochemistry
PubMed ID2844247
'The accessibility of substrate bound to lactose permease of Escherichia coli was investigated by using the fluorescent substrate dansyl galactoside and a membrane-impermeable fluorescence quencher. To determine the orientation of bound substrate, both cells and inside-out vesicles were used. The substrate is oriented with the dansyl group toward the cytoplasm ... More
Oxygen gradients in CHO cells: measurement and characterization by electron spin resonance.
AuthorsGlockner JF, Swartz HM, Pals MA
JournalJ Cell Physiol
PubMed ID2550474
'The concentration of oxygen within cells is important in many physiological and pathological processes, but such oxygen-dependent processes are generally studied as a function of the concentration of extracellular oxygen, due to a lack of suitable methods. Using a newly developed technique based on ESR spectroscopy, we show that respiration ... More
Estimation of transmembrane pH gradients from phase equilibria of spin-labeled amines.
AuthorsCafiso DS, Hubbell WL
JournalBiochemistry
PubMed ID29663
'Spin-labeled secondary amines have been used to measure transmembrane proton gradients in sonicated liposomes. The electron paramagnetic resonance spectra of these probes show changes in the ratio of membrane associated to free aqueous probe as a function of transmembrane pH gradient. As the pH gradient is increased, inside acidic, the ... More
Spin-labeled TMA analogs as probes to study the anionic site of acetylcholinesterase.
AuthorsRosen GM, Rauckman EJ, Hord WW
JournalGen Pharmacol
PubMed ID604161
Amine and carboxylate spin probe permeability in red cells.
AuthorsTodd AP, Mehlhorn RJ, Macey RI
JournalJ Membr Biol
PubMed ID2549250
Permeabilities for a homologous series of amine and carboxylate nitroxide spin probes were measured in human red blood cells by an electron paramagnetic resonance (EPR) method. Permeabilities determined in this study are much lower than would be predicted for a sheet of bulk hydrocarbon and the polarity of the rate-limiting ... More
Factors restricting diffusion of water-soluble spin labels.
AuthorsKeith AD, Snipes W, Mehlhorn RJ, Gunter T
JournalBiophys J
PubMed ID890035
Line broadening of spin label signals is treated in terms of concentration, viscosity, charge and temperature dependencies. Line broadening of spin label signals may be caused either by spin label interactions or by the interaction between a spin label and a second paramagnetic species. Line broadening has been related to ... More
Lipid vesicle adsorption versus formation of planar bilayers on solid surfaces.
AuthorsNollert P, Kiefer H, Jähnig F
JournalBiophys J
PubMed ID8534815
The absorption and spreading behavior of lipid vesicles composed of either palmitoyloleoylphosphatidylcholine (POPC) or Escherichia coli lipid upon contact with a glass surface was examined by fluorescence measurements. Fluorescently labeled lipids were used to determine 1) the amount of lipid adsorbed at the surface, 2) the extent of fusion of ... More
Rapid measurement of drug release from temperature-sensitive liposomes by electron paramagnetic resonance and radioisotope techniques.
AuthorsMagin RL, Morse PD
JournalBiochim Biophys Acta
PubMed ID6313067
We have developed two new methods for quantifying drug release from temperature-sensitive liposomes. Large unilamellar vesicles were made by the reverse phase evaporation process. They contained a water-soluble electron paramagnetic resonance probe, trimethyl-4-amino-2,2,6,6-tetramethyl piperidine N-oxyl and the radioisotope cytosine-[3H]1-beta-D-arabinofuranoside in their aqueous compartment. Release of the electron paramagnetic resonance probe ... More
Pharmacokinetics of nitroxide NMR contrast agents.
AuthorsGriffeth LK, Rosen GM, Rauckman EJ, Drayer BP
JournalInvest Radiol
PubMed ID6511263
Pharmacokinetics of the nitroxide stable free radical functionality of compounds containing this moiety were evaluated in the rat. The agents were injected i.v. at either high (1.75 mmoles/kg) or low (10 mumoles/kg) dose, and timed blood samples were drawn and assayed for nitroxide concentration by EPR spectrometry. Similarly, various organs ... More
Human erythrocyte membrane permeability and nitroxyl spin-label reduction.
Nitroxyl spin labels are paramagnetic compounds that have demonstrated utility as contrast enhancing agents in proton magnetic resonance imaging. The time-course of contrast enhancement depends on distribution and elimination of these agents. Reduction, resulting in formation of the diamagnetic hydroxylamine, is the major metabolic pathway observed in vivo. This bioreduction ... More
Topographical organization of the N-terminal segment of lung pulmonary surfactant protein B (SP-B(1-25)) in phospholipid bilayers.
AuthorsWang Y, Rao KM, Demchuk E
JournalBiochemistry
PubMed ID12680754
The location and depth of each residue of lung pulmonary surfactant protein B (SP-B(1-25)) in a phospholipid bilayer (PB) was determined by fluorescence quenching using synthesized single-residue-substituted peptides that were reconstituted into 1,2-dipalmitoyl phosphatidylcholine (DPPC)-enriched liposomes. The single-residue substitutions in peptides were either aspartate or tryptophan. The aspartate was subsequently ... More
Topographical organization of cytochrome b6 in the thylakoid membrane of spinach chloroplasts determined by fluorescence studies with N-cyclohexyl-N'-[4-(dimethylamino)naphthyl]carbodiimide.
AuthorsWang Y, Beattie DS
JournalBiochemistry
PubMed ID8373766
In a recent study [Wang & Beattie (1992) Biochemistry 31, 8445-8459], we reported that dicyclohexylcarbodiimide (DCCD) was bound to either aspartate-155 or glutamate-166 localized in an amphiphilic, non-membrane-spanning, helix of cytochrome. Moreover, DCCD inhibits proton translocation in a cytochrome bf complex reconstituted into proteoliposomes without significant inhibition of electron transfer, ... More
Utilizing ESEEM spectroscopy to locate the position of specific regions of membrane-active peptides within model membranes.
AuthorsCarmieli R, Papo N, Zimmermann H, Potapov A, Shai Y, Goldfarb D
JournalBiophys J
PubMed ID16258052
Membrane-active peptides participate in many cellular processes, and therefore knowledge of their mode of interaction with phospholipids is essential for understanding their biological function. Here we present a new methodology based on electron spin-echo envelope modulation to probe, at a relatively high resolution, the location of membrane-bound lytic peptides and ... More