Some chemical and analytical aspects of polysaccharide modifications. IV. Electron spin resonance studies of nitroxide-labelled chitin and chitosan derivatives

1984 ◽  
Vol 62 (5) ◽  
pp. 975-980 ◽  
Author(s):  
Manssur Yalpani ◽  
Laurance D. Hall
Keyword(s):  
Spin Label ◽  
Water Soluble ◽  
Spin Labels ◽  
Chitosan Derivatives ◽  
Terminal Galactose ◽  
Spin Resonance ◽  
Nitroxide Spin Labels ◽  
Covalently Linked ◽  
Chitin And Chitosan ◽  
Probe Spin

Nitroxide spin labels have been attached to chitin, chitosan, and their derivatives in order to investigate the solution and gel characteristics of these polymers. Thus, chitin was nonselectively acylated using the chloroacetamide label 3 to afford. the corresponding nitroxide derivative 4. Selective and nonselective labelling of chitosan was accomplished either via reductive alkylation using the keto label 5 and sodium cyanoborohydride or via a chitosan sulfate intermediate using labels 3 or 5. Two branched water soluble chitosan derivatives, carrying C-6 oxidized, terminal galactose side chains were selectively labelled by reductive animation using the amine label 13 to yield derivatives 14 and 15. Motional correlation values of the covalently-linked nitroxide moieties were shown to reflect the nature of the linkage between spin label and polymer, as well as structural differences between the branch residues of derivatives 14 and 15. The spin-probe – spin-label method was employed to demonstrate structural heterogeneities for the chitosan derivatives 7 and 15.

scholarly journals Binding of two spin-labelled derivatives of chlorpromazine to human erythrocytes

1989 ◽  
Vol 264 (3) ◽  
pp. 633-641 ◽  
Author(s):  
J L Olivier ◽  
C Chachaty ◽  
C Wolf ◽  
D Daveloose ◽  
G Bereziat
Keyword(s):  
Spin Label ◽  
Binding Sites ◽  
Spin Probe ◽  
Slow Motion ◽  
Water Soluble ◽  
Spin Labels ◽  
Exponential Dependence ◽  
Exchange Frequency ◽  
Derivatives Of ◽  
Positively Charged

The binding to human intact erythrocytes of two different spin-labelled derivatives of chlorpromazine has been studied. The influence of the positively charged side chain of the drug has been the focus of our attention. The positively charged amphiphilic compound (spin derivative I) is water-soluble up to 80 microM at pH values below 5.9. The apolar analogue (spin derivative II) aggregates in aqueous buffer from the lowest concentration tested. Both spin derivatives undergo a slow reduction inside the erythrocyte. The reduced nitroxides are readily reoxidized by adding a low, non-quenching, concentration of potassium ferricyanide to the intact erythrocytes. The fractions of spin label I and II bound to the erythrocyte membrane or to the erythrocyte-extracted lipids remain constant as a function of the temperature (3-42 degrees C) and as a function of the concentration of the spin label up to 150 microM. E.s.r. spectra of both spin labels show a two-component lineshape when they are bound to intact erythrocytes. Below 35 degrees C for the positively charged spin probe, and below 32 degrees C for the apolar spin probe, the simulation of the lineshape shows that more than 50% of the spectrum originates from a slow-motion component. This slow-motion component is also found in erythrocyte-extracted lipids probed by the positively charged spin label below 25 degrees C. In contrast, no slow-motion component is detected in the range 4-40 degrees C for the apolar spin label in erythrocyte-extracted lipids. In this environment the apolar probe experiences a single fast anisotropic motion with an exponential dependence on 1/temperature. Detailed lineshape simulations take into account the exchange frequency between binding sites where the probe experiences a fast motion and binding sites where it experiences a slow motion. The exchange frequency is strongly temperature-dependent. Characterization of the different motions experienced inside the different locations has been achieved and compared for whole erythrocytes and for the extracted lipids. The biochemical nature of the binding sites (membrane protein/acidic phospholipid) giving rise to the slow-motion component is discussed as a function of the polarity of the spin-labelled drug and as a function of the temperature controlling the fluidity of the lipid bulk and influencing the distribution of the drug inside the membrane.

A Spin Label Study of the Influence of Cholesterol on Egg Lecithin Multibilayers

1972 ◽  
Vol 50 (9) ◽  
pp. 969-981 ◽  
Author(s):  
Roy D. Lapper ◽  
Sabina J. Paterson ◽  
Ian C. P. Smith
Keyword(s):  
Electron Spin Resonance ◽  
Random Walk ◽  
Electron Spin ◽  
Spin Label ◽  
Theoretical Models ◽  
Cholesterol Content ◽  
Electron Spin Resonance Study ◽  
Spin Labels ◽  
Spin Resonance ◽  
Egg Lecithin

A detailed electron spin resonance study of a cholestane spin label in hydrated egg lecithin multibilayers of variable cholesterol content is presented. Several theoretical models are proposed in an attempt to explain the observed electron spin resonance spectra for the egg lecithin–cholesterol multibilayer system; we conclude that the most probable model is that of restricted random walk of individual spin labels where the amplitude of the random walk decreases from about 46° at 0 mol% cholesterol content to a minimum of 17° at 55 mol% cholesterol. Also, as the cholesterol content of the multibilayers increases, so the rate of random walk decreases from rapid to intermediate on the electron spin resonance time scale. The results clearly indicate that cholesterol is able to order egg lecithin films, orientating all molecules towards a normal to the surface of the film and decreasing their mobility. The condensing and stiffening influence of cholesterol in phospholipids is undoubtedly one of its major roles in biological membranes.

Preparation and characterization of water-soluble chitin and chitosan derivatives

1998 ◽  
Vol 36 (1) ◽  
pp. 49-59 ◽  
Author(s):  
Masatoshi Sugimoto ◽  
Minoru Morimoto ◽  
Hitoshi Sashiwa ◽  
Hiroyuki Saimoto ◽  
Yoshihiro Shigemasa
Keyword(s):  
Water Soluble ◽  
Chitosan Derivatives ◽  
Chitin And Chitosan

New mono- and difunctionalized 2,2,5,5-tetramethylpyrrolidine- and Δ3-pyrroline-1-oxyl nitroxide spin labels

1982 ◽  
Vol 60 (12) ◽  
pp. 1439-1447 ◽  
Author(s):  
John F. W. Keana ◽  
Kálmán Hideg ◽  
G. Bruce Birrell ◽  
Olga H. Hankovszky ◽  
George Ferguson ◽  
...  
Keyword(s):  
Alkylating Agent ◽  
Conjugate Addition ◽  
Crystallographic Analysis ◽  
Water Soluble ◽  
Covalent Attachment ◽  
Spin Labels ◽  
Phenacyl Bromide ◽  
Trans Isomers ◽  
Nitroxide Spin Labels ◽  
Mobile Component

Several new nitroxide spin labels have been prepared. Nitroxide mesylate 5 and p-hydroxyacetophenone gave 6 which was selectively brominated with cupric bromide to give the alkylating agent 7. The more water soluble phenacyl bromide analogue 17 was prepared either via the route 8 → 11 → 17 or else via the route 15 → 16 → 11 → 17. Preliminary results indicate that toward aconitase, nitroxide alkylating agent 17 behaves similarly to phenacyl bromide. Several new difunctional nitroxides were prepared with an eye toward application as saturation transfer esr spin labels. Conjugate addition of HCN to 11 gave 18, condensation of which with p-azidobenzaldehyde gave photolabile 19. Azide 20 could similarly be prepared directly from 11. Aldehyde 15 underwent condensation with p-azidoacetophenone to give azide 21. This substance was allowed to react with hemoglobin. Upon photolysis the esr spectral mobile component was substantially reduced, suggesting covalent attachment at more than one site. Conjugate addition of HCN to 23 gave a mixture of cis, trans isomers 24 and 25; the structure of 25 was established by X-ray crystallographic analysis to be the trans isomer. Conjugate addition of ethyl thioglycolate to 15 led to heterocycles 29–34.

scholarly journals DEER and RIDME Measurements of the Nitroxide-Spin Labelled Copper-Bound Amine Oxidase Homodimer from Arthrobacter Globiformis

2021 ◽  
Author(s):  
Hannah Russell ◽  
Rachel Stewart ◽  
Christopher Prior ◽  
Vasily S. Oganesyan ◽  
Thembaninkosi G. Gaule ◽  
...  
Keyword(s):  
Dipolar Coupling ◽  
Amine Oxidase ◽  
Spin Labels ◽  
Arthrobacter Globiformis ◽  
Copper Amine Oxidase ◽  
Dipole Interactions ◽  
Nitroxide Spin Labels ◽  
Double Electron Electron Resonance ◽  
Dipolar Modulation ◽  
Paramagnetic Centres

AbstractIn the study of biological structures, pulse dipolar spectroscopy (PDS) is used to elucidate spin–spin distances at nanometre-scale by measuring dipole–dipole interactions between paramagnetic centres. The PDS methods of Double Electron Electron Resonance (DEER) and Relaxation Induced Dipolar Modulation Enhancement (RIDME) are employed, and their results compared, for the measurement of the dipolar coupling between nitroxide spin labels and copper-II (Cu(II)) paramagnetic centres within the copper amine oxidase from Arthrobacter globiformis (AGAO). The distance distribution results obtained indicate that two distinct distances can be measured, with the longer of these at c.a. 5 nm. Conditions for optimising the RIDME experiment such that it may outperform DEER for these long distances are discussed. Modelling methods are used to show that the distances obtained after data analysis are consistent with the structure of AGAO.

Thermotropic lipid and protein transitions in Chinese hamster lung cell membranes: relationship to hyperthermic cell killing

1983 ◽  
Vol 61 (6) ◽  
pp. 421-427 ◽  
Author(s):  
James R. Lepock ◽  
Kwan-Hon Cheng ◽  
Hisham Al-Qysi ◽  
Jack Kruuv
Keyword(s):  
Mammalian Cells ◽  
Plasma Membranes ◽  
Chinese Hamster ◽  
Cell Killing ◽  
Water Soluble ◽  
Growth Data ◽  
Protein Fluorescence ◽  
Polar Groups ◽  
Spin Resonance ◽  
Intrinsic Protein Fluorescence

Exposure of mammalian cells to hyperthermic temperatures (ca. 41–45 °C) appears to act as a direct or triggering effect to produce some later response such as cell death, thermotolerance, or heat-shock protein synthesis. The high activation energy of cell killing indicates that the direct effect of hyperthermia might be a thermotropic transition in some cellular component, for this particular response. Both hyperthermic survival and growth data imply that the temperature for the onset of hyperthermic cell killing is 40–41.5 °C for Chinese hamster lung V79 cells. Studies using the electron spin resonance label 2,2-dimethyl-5-dodecyl-5-methyloxazolidine-N-oxide and the fluorescent probe 1,6-diphenyl-1,3,5-hexatriene show the existence of lipid transitions at approximately 7–8 and 23–36 °C (or a broad transition between these temperatures) in mitochondria and whole cell homogenates, that correlate well with changes in growth and hypothermic killing. No lipid transition was detected near 40–41.5 °C that could correlate with hyperthermic killing in either mitochondrial or plasma membranes, but measurements of intrinsic protein fluorescence and protein fluorophore to trans-paranaric acid energy transfer demonstrate the existence of an irreversible transition in protein structure or arrangement above ca. 40 °C in both mitochondrial and plasma membranes. This transition is due to protein rearrangement and (or) unfolding such that there is increased exposure of protein tryptophan and tyrosine residues to polar groups and to paranaric acid. The strength of the transition implies that a significant fraction of total membrane protein is involved in this transition, which may be analogous to the heat-induced denaturation of water-soluble proteins. This alteration in membrane structure above ca. 40 °C could cause many of the observed changes in plasma membrane and mitochondrial function, which may further be involved in cellular responses to hyperthermia.

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