ABSTRACT
Organic radicals are fascinating materials because of their unique properties, which make them suitable for a variety of applications. Their synthesis may be challenging, and big efforts have focused on chemical stability. However, introducing a new material in electronics not only requires chemically stable molecules but also stable monolayers and thin films in view of their use in devices. In this work, we have investigated the thin films of a derivative of the Blatter radical that was synthesized bearing in mind the thermodynamic factors that govern thin film stability. We have proved our concept by investigating the electronic structure, the paramagnetic character, and stability of the obtained films under UHV and ambient conditions by in situ X-ray photoelectron spectroscopy, ex situ atomic force microscopy, and electron paramagnetic resonance spectroscopy.
ABSTRACT
We describe preparation and magnetic properties of an organic pi-conjugated polymer with very large magnetic moment and magnetic order at low temperatures. The polymer is designed with a large density of cross-links and alternating connectivity of radical modules with unequal spin quantum numbers (S), macrocyclic S = 2 and, cross-linking S = (1/2) modules, which permits large net S values for either ferromagnetic or antiferromagnetic exchange couplings between the modules. In the highly cross-linked polymer, an effective magnetic moment corresponding to an average S of about 5000 and slow reorientation of the magnetization by a small magnetic field (less than or equal to 1 oersted) below a temperature of about 10 kelvin are found. Qualitatively, this magnetic behavior is comparable to that of insulating spin glasses and blocked superparamagnets.
ABSTRACT
We developed a new cationic lipid suitable for use as a DNA carrier in the presence of 10% sera. The novel compound (abbreviated as Arg-Chol) contains cholesterol and a dipeptide consisting of glycine and sterically protected arginine. The efficiency of reporter gene transfection using liposomes based on this new reagent was compared with that of liposomes made with other cationic derivatives of cholesterol. Lipoplexes formulated with the newly synthesized lipid mediate in vitro transfection of B16(F10) murine melanoma cells in the presence of 10% sera more efficiently than in other cell lines and compared with other cholesterol derivatives studied.
Subject(s)
Cholesterol/analogs & derivatives , Luciferases/genetics , Transfection/methods , Animals , Blood , Cell Line , Cholesterol/chemical synthesis , Culture Media , Drug Carriers , Endothelium, Vascular , Genes, Reporter , Humans , Liposomes , Melanoma, Experimental , Mice , Phosphatidylethanolamines , Plasmids , Tumor Cells, CulturedABSTRACT
Disulfiram (CAS 97-77-8, DSF), a potent anticarcinogenic compound, is known to form mixed disulfides with sulfhydryl group containing amino acids or proteins in vivo. In the present study the stabilities of two mixed disulfides which may arise in the metabolism of disulfiram, i.e. S-(N,N-diethyldithiocarbamoyl)-N-acetyl-L-cysteine (AC-DDTC) and S-(N,N-diethyldithiocarbamoyl)-L-glutathione (GS-DDTC) in phosphate buffer (pH 7.2) and in rat liver subcellular fractions were investigated as well as their influences on the glutathione (GSH)-related detoxifying system, on the metabolism of [14C] N-nitrosodiethylamine (NDEA) and on the genotoxic activity of NDEA in rats. Both substances were stable in buffer and in microsomes but were degraded in cytosol showing a half life of 4.7 h (AC-DDTC) and 3.2 h (GS-DDTC). Addition of GSH to the incubation media accelerated the degradation of mixed disulfides in cytosol. In vivo administration of AC-DDTC and GS-DDTC (1.7 mmol/kg i.p.) led to an increase in hepatic GSH content and to an inhibition of the activity of NDEA deethylase. Both mixed disulfides inhibited the metabolism of NDEA. After a 28 mg/kg i.p. dose of [14C] NDEA only 0.4% was excreted unchanged in the urine. Pretreatment with AC-DDTC and GS-DDTC caused a 10 to 20 fold increase in the amount of NDEA excreted in the urine. The occurrence of DNA single strand breaks in rat liver cells induced by NDEA was completely neutralized by the pretreatment with AC-DDTC.
Subject(s)
Antimutagenic Agents/pharmacology , Diethylnitrosamine/metabolism , Diethylnitrosamine/toxicity , Disulfides/pharmacology , Disulfiram/pharmacology , Mutagens/metabolism , Mutagens/toxicity , Animals , DNA Damage , DNA, Single-Stranded/drug effects , Diethylnitrosamine/antagonists & inhibitors , Disulfides/chemistry , Disulfiram/chemistry , Glutathione/metabolism , Glutathione Reductase/metabolism , Glutathione Transferase/metabolism , Liver/drug effects , Liver/enzymology , Liver/metabolism , Male , Rats , Rats, Sprague-Dawley , Subcellular Fractions/drug effects , Subcellular Fractions/enzymology , Subcellular Fractions/metabolismABSTRACT
It is generally assumed that thiol anticarcinogens like disulfiram (DSF) or sodium 2-mercaptoethane-sulfonate (mesna) after in vivo administration react rapidly with serum protein sulfhydryl groups forming mixed disulfides. Different methods have been established for the synthesis of mixed disulfides between cysteine or glutathione and diethyldithiocarbamate (DDTC) or mesna in order to elucidate their chemical and biological effects. A short summary is given of pilot biochemical experiments carried out with two mixed disulfides.
