Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0220723 (PCA)
 4,687 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The literature on the toxicity of aminoxyl radicals was critically reviewed. It was concluded that, in general, the aminoxyl radicals possess a very low toxicity and are not mutagenic. In support of this contention, several aminoxyl radicals were evaluated in vitro. Thus, aminoxyl radicals 3-carboxy-2,2,5,5-tetramethylpyrroline-1-oxyl (1), 3-carboxy-2,2,5,5-tetramethylpyrrolidine-1-oxyl (PCA; 2), 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (Tempol;3), and N-(1-hydroxymethyl-2,3-dihydroxypropyl)-3-carboxyamino-2,2,5,5- tetramethylpyrrolidine-1-oxyl (NAT; 4) were evaluated using Salmonella typhimurium tester strains TA 102 and TA 104, with a supplement of xanthine oxidase enzyme. 1, 2, and 4 were found to be nonmutagenic, while 3 elicited in TA 104 only about a twofold increase in the number of revertants above the control. This response is considered to be, at best, marginal in view of wide fluctuations of experimental scores. The results of the present study are in agreement with those of other studies confirming the nonmutagenicity of aminoxyl radicals investigated to date. However, these conclusions are different from those of a study where 3 was tested in the presence of a generated toxic oxygen species that can cause mutagenic changes of the environment.
 ...
PMID:A critical evaluation of the present status of toxicity of aminoxyl radicals. 152 84

Reactive free radicals and reactive oxygen species (ROS) induced by ultraviolet irradiation in human skin are strongly involved in the occurrence of skin damages like aging and cancer. In the present work an ex vivo method for the detection of free radicals/ROS in human skin biopsies during UV irradiation is presented. This method is based on the Electron Spin Resonance (ESR) spectroscopy and imaging and uses the radical trapping properties of nitroxides. The nitroxides 2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO), 3-Carbamoyl-2,2,5,5-tetramethylpyrrolidine-1-oxyl (PCM), and 3-Carboxy-2,2,5,5-tetramethylpyrrolidine-1-oxyl (PCA), were investigated for their applicability of trapping reactive free radicals and reactive oxygen species in skin during UV irradiation. As a result of the trapping process the nitroxides were reduced to the EPR silent hydroxylamins. The reduction rate of TEMPO was due to both the UV radiation and the enzymatic activity of the skin. The nitroxides PCM and PCA are sufficiently stable in the skin and are solely reduced by UV-generated free radicals/ROS. The nitroxide PCA was used for imaging the spatial distribution of UV-generated free radicals/ROS. As a result of the homogeneous distribution of PCA in the skin, it was possible to estimate the penetration of UVA and UVB irradiation: The UV irradiation decreased the PCA intensity corresponding to its irradiance and penetration into the skin. This reduction was shown to be caused mainly by UVA radiation (320-400 nm).
 ...
PMID:UV-induced free radicals in the skin detected by ESR spectroscopy and imaging using nitroxides. 1282 56

Spin-label electron paramagnetic resonance (SL-EPR) spectroscopy has become a powerful and useful tool for studying structure and dynamics of biomacromolecules. However, utilizing these methods at physiological temperatures for in-cell studies is hampered by reduction of the nitroxide spin labels and thus short half-lives in the cellular environment. Consequently, reduction kinetics of two structurally different nitroxides was investigated in cell extracts of Xenopus laevis oocytes using rapid-scan cw-experiments at X-band. The five member heterocyclic ring nitroxide PCA (3-carboxy-2,2,5,5-tetramethylpyrrolidinyl-1-oxy) under investigation features much higher stability against intracellular reduction than the six member ring analog TOAC (2,2,6,6-tetramethylpiperidine-N-oxyl-4-amino-4-carboxilic acid) and is therefore a suitable spin label type for in-cell EPR. The kinetic data can be described according to the Michaelis-Menten model and thus suggest an enzymatic or enzyme-mediated reduction process.
 ...
PMID:Evaluation of spin labels for in-cell EPR by analysis of nitroxide reduction in cell extract of Xenopus laevis oocytes. 2186 65