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1.
Phys Chem Chem Phys ; 22(21): 12267-12272, 2020 Jun 04.
Artigo em Inglês | MEDLINE | ID: mdl-32432245

RESUMO

A PEG-Tyr block copolymer forms a kinetically stable colloidal solution in water at room temperature which undergoes an irreversible conversion to a gel phase upon heating. A micellar solution and a gel can therefore be studied under identical experimental conditions. This made it possible to compare physical properties and chemical reactivity of micelles and gels in identical chemical environments and under identical conditions. EPR spectra of the spin-labelled copolymer showed that tyrosine mobility in gels was slightly reduced compared to micelles. Chemical reactivity was studied using photochemical degradation of tyrosine and tyrosine dimerization, in the absence and in the presence of an Fe(iii) salt. The reactivity trends were explained by reduced tyrosine mobility in the gel environment. The largest reactivity difference in gels and micelles was observed for bimolecular dityrosine formation which was also attributed to the reduction in molecular mobility.


Assuntos
Peptídeos/química , Polietilenoglicóis/química , Óxidos N-Cíclicos/química , Géis/química , Géis/efeitos da radiação , Micelas , Peptídeos/efeitos da radiação , Polietilenoglicóis/efeitos da radiação , Marcadores de Spin , Raios Ultravioleta
2.
Free Radic Biol Med ; 121: 20-25, 2018 06.
Artigo em Inglês | MEDLINE | ID: mdl-29660404

RESUMO

EPR spectroscopy was used to monitor formation of free radicals in human hair upon UV irradiation. While the EPR spectra of brown hair were dominated by melanin signal, those of white hair were keratin-derived. The decay of UV induced keratin radicals was enhanced at increased ambient humidity. We argue that at higher humidity the swollen hair provides a more liquid-like environment, and higher molecular mobility in this environment leads to faster radical reactions. This interpretation is consistent with the increased UV-triggered protein damage in hair at high humidity as demonstrated by the protein loss, MALDI-TOF and FT-IR data.


Assuntos
Radicais Livres/metabolismo , Cabelo/metabolismo , Umidade , Proteínas/metabolismo , Proteólise/efeitos da radiação , Raios Ultravioleta/efeitos adversos , Espectroscopia de Ressonância de Spin Eletrônica , Radicais Livres/efeitos da radiação , Cabelo/efeitos da radiação , Humanos , Queratinas/metabolismo , Queratinas/efeitos da radiação , Melaninas/metabolismo , Melaninas/efeitos da radiação , Proteínas/efeitos da radiação
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