Edmund S. Copeland

LIGHT‐INDUCED LEAKAGE OF SPIN LABEL MARKER FROM LIPOSOMES IN THE PRESENCE OF PHOTOTOXIC PHENOTHIAZINES

Abstract— Liposomes prepared from dipalmitoyl lecithin, cholesterol and dicetyl phosphate and containing a trapped spin label marker were exposed to long wavelength UV light in the presence of a series of phenothiazine tranquilizers. EPR spectroscopy was used to detect spin label marker released from liposomes, taking advantage of the disappearance of line broadening from electron spin exchange which occurred on spin label release. The minimum effective phototoxic dose in mice of these phenothiazines was also determined. Kinetic studies of light‐induced spin label release from phenothiazine‐sensitized liposomes showed that membrane damage was rapidly induced and that the damaging species were short‐lived. The damage process was oxygen dependent and could be temporarily prevented by cysteamine or α‐tocopherol added immediately before irradiation. Only those phenothiazines which mediated light‐dependent liposomal membrane damage had phototoxic activity in mice and the degree of photosensitization was parallel in the two systems. In both photosensitization phenomena, the nature of the substituent at the phenothiazine 2‐position was more important than the phenothiazine side chain.

Liposome spin immunoassay: A new sensitive method for detecting lipid substances in aqueous media

A new sensitive immunoassay procedure is described for quantitative detection of glycolipids and other lipids in aqueous media. As with other immunoassays specific antiserum is first reacted with the free lipid hapten. The amount of antibody activity remaining is measured by assaying the release, in the presence of complement, of spin label marker from liposomes containing the same lipid hapten. Using this method, 2.6 pmol of aqueous Forssman hapten was detected, and the sensitivity could be increased further.

STRUCTURE-FUNCTION STUDIES OF THE AMINOTHIOL RADIOPROTECTANTS. THE EFFECT OF CARBON CHAIN LENGTH IN MERCAPTOETHYLAMINE HOMOLOGS.

The relation between chemical structure and physical-chemical radiation protection in E. coli has been studied in a series of aminothiols. The aminothiols utilized in this study were β-mercaptoethy...

The organosulfur peroxy radical in biological systems: An ESR study using an aminothiol model system

Abstract The organosulfur peroxy radical has been induced in a model frozen aqueous aminothiol system using gamma-irradiation and has been characterized using electron spin resonance spectroscopy. Attention is directed to the similarity of a composite ESR spectrum consisting of the organosulfur peroxy radical and an alkyl peroxy radical to spectra previously reported for sulfur-containing biological materials exposed to oxygen under various experimental conditions. Aqueous solutions of mercaptopentylamine (MPA, 1.0 M ) were equilibrated with nitrogen or oxygen and gamma-irradiated at 77 K. The free radicals observed after annealing at 193 K have been identified as the neutral organosulfur radical (with both gases) and the organosulfur peroxy radical (with oxygen). The neutral organosulfur radical spectrum was subtracted from the composite (oxygen) to obtain the organosulfur peroxy radical spectrum. When this ESR spectrum was added to that of a bacteria alkyl peroxy radical induced in oxygen-equilibrated E. coli B/r irradiated at 77 K and similarly annealed, the composite spectrum obtained is essentially identical to that observed when 0.1 M MPA is present in the frozen bacterial suspension during irradiation. The composite ESR spectrum is also similar to previously reported spectra for sulfur-containing biological materials exposed to physical stress in the presence of oxygen.

Structure-Function Studies of the Aminothiol Radioprotectants. Effect of Carbon Chain Length in Mercaptoethylamine Homologs: Mammalian Radioprotection

The relation between chemical structure and radiation protection in mice has been studied for a series of aminothiols. The aminothiols used in this study were β-mercaptoethylamine (MEA) and its pro...

A Simple Method for Estimating H1 in ESR Experiments—The Microwave Power Saturation of γ‐Irradiation Induced Glycylglycine Radicals

A technique is described whereby the shape of the first derivative electron spin resonance (ESR) spectra observed for γ‐irradiated glycylglycine can be used in ESR experiments to estimate the microwave magnetic field H1 in the 40–1000 mG range. The ratio of the minor to major derivative peak heights of the glycylglycine doublet is found to vary with H1. Slow passage progressive saturation studies are included in an attempt to explain the phenomenon. The technique provides a means of measuring H1, without knowing effective cavity Q, incident power, or the field concentrating effects of quartz inserts and is proposed as an interlaboratory ESR microwave power comparison standard.

Characterization of Secondary Radical Reactions in Irradiated Ribonuclease

Solid ribonuclease (RNase) has been irradiated in vacuum at 196°K and subsequently heated. The kinetics of formation of secondary radicals have been studied by following the growth of these radicals at different temperatures. Progressive power saturation studies have been applied to determine

[7] Spin immunoassay

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Production of Free Radicals in Reduced Glutathione and Penicillamine by Thermal Hydrogen Atoms and X-radiation

for primary and secondary radicals. It is shown that the carbon radicals formed during irradiation at 196°K have

An ESR study of secondary radical reactions in an irradiated sulfur-containing glycoprotein.

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