Thermal Phase Transitions in Phospholipid as Studied by High Frequency Epr

Smirnov, Alex I.

Abstract

EPR spin-probe studies of thermal phase transitions in liposomes are usually carried out at X-band (9.5 GHz). X-band studies suffer from low spectral resolution; for non-deuterated nitroxides, only the high-field component is split. Better resolution, as well as measurement of rotational correlation times, can be obtained only with specially designed nitroxides. In this project, we demonstrate and discuss the prospects of high-frequency (95 GHz) EPR for obtaining rotational and partitioning information about spin probes in lipid systems. We monitored the thermal phase transition for aqueous dispersions of the phospholipid DPPC (1,2-2,2,6,6-tetramethylpiperdine-1-oxyl) partitioned between both membrane (hydrocarbon) and aqueous phases. W-band completely resolves the entire TEMPO EPR spectrum in both aqueous and hydrocarbon environments. Therefore the TEMPO partition coefficients can be determined with better accuracy at W-band. The more informative high-frequency EPR data were analyzed using a fast rotational model to derive the rotational correlation times during the thermal phase changes in the DPPC membrane.

Funding Agency

• Agency: National Institute of Health (NIH)
• Institute: National Center for Research Resources (NCRR)
• Type: Biotechnology Resource Grants (P41)
• Project #: 2P41RR001811-11
• Application #: 5223685
• Support Year: 11
• Fiscal Year: 1996

Publications

Hurth, Kyle M; Nilges, Mark J; Carlson, Kathryn E et al. (2004) Ligand-induced changes in estrogen receptor conformation as measured by site-directed spin labeling. Biochemistry 43:1891-907

Woodmansee, Anh N; Imlay, James A (2002) Reduced flavins promote oxidative DNA damage in non-respiring Escherichia coli by delivering electrons to intracellular free iron. J Biol Chem 277:34055-66

Denisov, Ilia G; Makris, Thomas M; Sligar, Stephen G (2002) Formation and decay of hydroperoxo-ferric heme complex in horseradish peroxidase studied by cryoradiolysis. J Biol Chem 277:42706-10

Atsarkin, V A; Demidov, V V; Vasneva, G A et al. (2001) Mechanism of oxygen response in carbon-based sensors. J Magn Reson 149:85-9

Mangels, M L; Harper, A C; Smirnov, A I et al. (2001) Investigating magnetically aligned phospholipid bilayers with EPR spectroscopy at 94 GHz. J Magn Reson 151:253-9

Breitzer, J G; Smirnov, A I; Szczepura, L F et al. (2001) Redox properties of C6S8(n-) and C3S5(n-) (n = 0, 1, 2): stable radicals and unusual structural properties for C-S-S-C bonds. Inorg Chem 40:1421-9

Denisov, I G; Hung, S C; Weiss, K E et al. (2001) Characterization of the oxygenated intermediate of the thermophilic cytochrome P450 CYP119. J Inorg Biochem 87:215-26

Kirkor, E S; Scheeline, A (2000) Nicotinamide adenine dinucleotide species in the horseradish peroxidase-oxidase oscillator. Eur J Biochem 267:5014-22

Rapoport, N; Smirnov, A I; Pitt, W G et al. (1999) Bioreduction of Tempone and spin-labeled gentamicin by gram-negative bacteria: kinetics and effect of ultrasound. Arch Biochem Biophys 362:233-41

Maringanti, S; Imlay, J A (1999) An intracellular iron chelator pleiotropically suppresses enzymatic and growth defects of superoxide dismutase-deficient Escherichia coli. J Bacteriol 181:3792-802