The protein cysteine residue is one of the amino acids most susceptible to oxidative modifications, frequently caused by oxidative stress. Several applications have enabled cysteine-targeted proteomics analysis with simultaneous detection and quantitation. In this study, we employed a quantitative approach using a set of iodoacetyl-based cysteine reactive isobaric tags (iodoTMT) and evaluated the transient cellular oxidation ratio of free and reversibly modified cysteine thiols under DTT and hydrogen peroxide (H2O2) treatments. DTT treatment (1 mM for 5 min) reduced most cysteine thiols, irrespective of their cellular localizations. It also caused some unique oxidative shifts, including for peroxiredoxin 2 (PRDX2), uroporphyrinogen decarboxylase (UROD), and thioredoxin (TXN), proteins reportedly affected by cellular reactive oxygen species production. Modest H2O2 treatment (50 μM for 5 min) did not cause global oxidations but instead had apparently reductive effects. Moreover, with H2O2, significant oxidative shifts were observed only in redox active proteins, like PRDX2, peroxiredoxin 1 (PRDX1), TXN, and glyceraldehyde 3-phosphate dehydrogenase (GAPDH). Overall, our quantitative data illustrated both H2O2- and reduction-mediated cellular responses, whereby while redox homeostasis is maintained, highly reactive thiols can potentiate the specific, rapid cellular signaling to counteract acute redox stress.
The high-spin?low-spin transitions in iron (III) compounds are studied on the basis of the ligand field theory using the model in which the coupling between the iron ion and the intramolecular distortion is the driving force for the spin state transitions. The intermolecular coupling between the molecular distortions is taken into account and the distortions are treated dynamically. Two kinds of the molecular distortions, the uniform dilation and the uniaxial distortion, are considered. The discontinuous high-spin?low-spin transitions may be induced by the coupling with the uniaxial distortion, while the continuous spin state transitions arise from the coupling with the uniform dilation. Temperature dependences of equilibrium cooperative displacement of the ligands, high-spin and low-spin fractions of iron (III) ions, effective magnetic moment, quadrupole splitting in Mössbauer spectra, and internal magnetic field in NMR spectra are calculated based on the model as functions of the coupling strength between iron and the molecular distortion. It is shown that the essential features of the observed temperature dependences may be reproduced consistently in the various quantities by the present model.
Electroless deposition of Ag on atomically flat H-terminated Si(111) surfaces in aqueous alkaline solutions containing Ag ions produced two different sizes of Ag nanowires along atomic step edges: (1) a narrow nanowire of 10 nm in width and 0.5 nm in height and (2) a wide nanowire of 35 nm in width and 11 nm in height. The narrow and wide nanowires were formed by immersion in the solutions containing less than 1 ppb and 8 ppm dissolved-oxygen concentrations, respectively. This result indicates that the dissolved oxygen initiates the formation of Ag nucleation sites and that the fabrication method has a possibility of controlling the size of Ag nanowires.
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