Spectral characterization of 15N spin labels

Keith, Alec D.; Horvat, David; Snipes, Wallace

doi:10.1016/0009-3084(74)90041-3

Cited by 27 publications

(15 citation statements)

References 5 publications

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“…The formula includes the (h o /h −1 ) ratio and ∆H o value measured as the width (W o ) of the first derivative of the midfield line ( Fig. 1(a)) [23][24][25]28].…”

Section: Epr Spectroscopymentioning

confidence: 99%

Isolated erythrocyte membranes of transfusion‐dependent and non‐transfused thalassemia patients in Jakarta, investigated by electron paramagnetic resonance spectroscopy

Udyaningsih-Freisleben

Kurniati²,

Prasetyo

et al. 2003

BioFactors

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Erythrocyte membrane structural parameters were studied in transfusion-dependent beta-thalassemia patients, in long-term transfused patients (regularly transfused < 15 years), and in those who had not yet obtained transfusions. Controls were voluntary students up to 30 years of age without diagnosis or clinical signs of thalassemia. Membranes were isolated and investigated by sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE) and electron paramagnetic resonance (EPR) spectroscopy. Data obtained from the thiol-reactive spin label N-ethyl-maleimidoproxyl reveal immobilization of protein environment in erythrocyte membranes from thalassemic patients. SDS-PAGE shows both degradation and aggregation of membrane proteins. Thalassemic erythrocyte membranes exert higher order parameters in the hydrophobic region as determined by 16-doxyl-stearic acid. Rotational correlation times of this spin label increase only in transfused patients. Polarity is higher in membranes of all patients than in controls. In the polar interface, order parameters obtained from 5-doxyl-stearic acid increase in non-transfused and decrease in transfusion-dependent patients as compared with controls. Transfused patients exert increasing membrane order in the hydrophobic region and counter-currently decreasing order in the polar interface indicating loss of membrane integrity along with the loss of fluidity and polarity gradients and the loss the energetic barrier function of the membrane.

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“…The formula includes the (h o /h −1 ) ratio and ∆H o value measured as the width (W o ) of the first derivative of the midfield line ( Fig. 1(a)) [23][24][25]28].…”

Section: Epr Spectroscopymentioning

confidence: 99%

Isolated erythrocyte membranes of transfusion‐dependent and non‐transfused thalassemia patients in Jakarta, investigated by electron paramagnetic resonance spectroscopy

Udyaningsih-Freisleben

Kurniati²,

Prasetyo

et al. 2003

BioFactors

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“…For SP-BY-,, in 100% methanol, or with lip-ids suspended in PBS, pH 7.4, the motion of the probe attached to SP-B,_*, is nearly isotropic. A rotational correlation time ( T~) may be calculated that provides an empirical parameter sensitive to motion in the region probed by the spin label (Keith et al, 1974): 7 R = 6.5 X 10"0.AH,[(h,/h-,)"2 -I ]…”

Section: Evaluation Of the Flexibility And Polarity Of Lipid-incorpormentioning

confidence: 99%

Conformation and molecular topography of the N‐terminal segment of surfactant protein B in structure‐promoting environments

et al. 1996

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Although the effects of surfactant protein B (SP-B) on lipid surface activity in vitro and in vivo are well known, the relationship between molecular structure and function is still not fully understood. To further characterize protein structure-activity correlations, we have used physical techniques to study conformation, orientation, and molecular topography of N-terminal SP-B peptides in lipids and structure-promoting environments. Fourier transform infrared (FTIR) and CD measurements of SP-B1_25 (residues 1-25) in methanol, SDS micelles, egg yolk lecithin (EYL) liposomes, and surfactant lipids indicate the peptide has a dominant helical content, with minor turn and disordered components. Polarized FTIR studies of SP-B,-25 indicate the long molecular axis lies at an oblique angle to the surface of lipid films. Truncated peptides were similarly examined to assign more accurately the discrete conformations within the SP-B,_,, sequence. Residues Cys-8-Gly-25 are largely a-helix in methanol, whereas the N-terminal segment Phe-1-Cys-8 had turn and helical propensities. Addition of SP-Bl-25 spin-labeled at the N-terminal Phe (i.e., SP-BT_25) to SDS, EYL, or surfactant lipids yielded electron spin resonance spectra that reflect peptide bound to lipids, but retaining considerable mobility. The absence of characteristic radical broadening indicates that SP-B1-25 is minimally aggregated when it interacts with these lipids. Further, the high polarity of SP-BI-25 argues that the reporter on Phe-1 resides in the headgroup of the lipid dispersions. The blue-shift in the endogenous fluorescence of Trp-9 near the N-terminus of SP-B1-25 suggests that this residue also lies near the lipid headgroup. A summary model based on the above physical experiments is presented for SP-BI-2S interacting with lipids.

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“…Where the spin-label motion was nearly isotropic and the high field hyperfine extremum could not be resolved, an empirical motion parameter Zo was calculated. This gives an approximation of the rotational correlation time of a spin-label in a given solvent (Keith, Horvat & Snipes, 1974) and is obtained from the relationship…”

Section: Spectral Measurementsmentioning

confidence: 99%

Changes in lipid ordering and state of aggregation in lymphocyte plasma membranes after exposure to mitogens

et al. 1978

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An electron spin probe study was made of the effect of a number of mitogenic agents on the ordering and state of aggregation of the plasma membrane lipids of lymphocytes. These agents, which included phytohemagglutinin, Concanavalin A, the calcium ionophore A23187 and periodate, caused a 20% decrease in lipid ordering in the region of the bilayer probed by 5-nitroxide stearic acid. The corresponding methyl ester probe showed marked probe-probe interaction under the same conditions indicating an aggregation of lipids in the area probed by this label. Studies with mixed lipid vesicles and ganglioside-free cells indicate that these areas are rich in glycolipids capable of hydrogen bonding to the ester probe. The decrease in ordering and the increase in aggregation of the membrane lipids were correlated with the patching and capping of the ligand-receptor complexes. Furthermore, the disappearance of fluorescent ligand from the surface of treated cells corresponded with the return of the spectral parameters of the probes to control cell values. It was concluded that glycolipids might play an important role in ligand-induced cell surface changes either as bearers of receptor groups, as in the case of some gangliosides, or in association by hydrogen-bonding with receptor proteins.

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Spectral characterization of 15N spin labels

Cited by 27 publications

References 5 publications

Isolated erythrocyte membranes of transfusion‐dependent and non‐transfused thalassemia patients in Jakarta, investigated by electron paramagnetic resonance spectroscopy

Isolated erythrocyte membranes of transfusion‐dependent and non‐transfused thalassemia patients in Jakarta, investigated by electron paramagnetic resonance spectroscopy

Conformation and molecular topography of the N‐terminal segment of surfactant protein B in structure‐promoting environments

Changes in lipid ordering and state of aggregation in lymphocyte plasma membranes after exposure to mitogens

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