RESUMO
Spin hyperpolarization can dramatically increase signal intensities in magnetic resonance experiments, providing either improved bulk sensitivity or additional spectroscopic detail through selective enhancements. While typical hyperpolarization approaches have utilized microwave irradiation, one emerging route is the use of optically generated triplet states. We report an investigation into the effects of solution viscosity on radical-triplet pair interactions, propose a new standard for quantification of the hyperpolarization in EPR experiments, and demonstrate a significant increase in the optically generated 1H NMR signal enhancement upon addition of glycerol to aqueous solutions.
RESUMO
Two-dimensional Fourier transform ion cyclotron resonance mass spectrometry (2D FTICR MS or 2D MS) allows direct correlation between precursor and fragment ions without isolation prior to fragmentation. The method has been optimized for the analysis of complex mixtures and used so far for the analysis of small molecules and peptides obtained by tryptic digestion of proteins and entire proteins. In this work, a 2D MS method is developed to characterize complex mixtures of polymers using infrared multiphoton decay (IRMPD) and electron capture dissociation (ECD) as fragmentation techniques, and D-α-tocopheryl polyethylene glycol 1000 succinate (TPGS), Polysorbate 80, and poly(methyl methacrylate) (PMMA) as analytes. The use of 2D MS allowed generation of fragment m/z values for all the compounds in the mixture at once and allowed tandem mass spectrometry of species very close in m/z that would have been difficult to isolate with a quadrupole for standard MS/MS. Furthermore, the use of unique features of 2D MS such as the extraction of neutral-loss lines allowed the successful assignment of peaks from low abundant species that would have been more difficult with standard MS/MS. For all the samples, the amount of information obtained with 2D MS was comparable with what obtained with multiple 1D MS/MS experiments targeted on each individual component within each mixture but required a single experiment of about 20-40 min.
RESUMO
l-Tryptophan (Trp), melatonin (MLT) and the Trp-peptide pentagastrin quenched the formation of azidyl radicals generated on irradiation of the anticancer complex trans,trans,trans-[Pt(pyridine)2(N3)2(OH)2] with visible light, giving rise to C3-centred indole radicals which were characterized for Trp and MLT using an EPR spin-trap; indole, together with azidyl and hydroxyl radicals, have potential roles in a multitargeting mechanism of action against resistant cancers.