Discussing endogenous NO(•)/HNO interconversion aided by phenolic drugs and vitamins.

The reduction of NO(•) to HNO/NO(-) under biologically compatible conditions has always been thought as unlikely, mostly because of the negative reduction potential: E°(NO(•),H(+)/HNO) = -0.55 V vs NHE at physiological pH. Nonetheless, during the past decade, several works hinted at the possible NO-to-HNO conversion mediated by moderate biological reductants. Very recently, we have shown that the reaction of NO(•) with ascorbate and aromatic alcohols occurs through a proton-coupled nucleophilic attack (PCNA) of the alcohol to NO(•), yielding an intermediate RO-N(H)O(•) species, which further decomposes to release HNO. For the present work, we decided to inspect whether other common biological aromatic alcohols obtained from foods, such as Vitamin E, or used as over-the-counter drugs, like aspirin, are able to undergo the reaction. The positive results suggest that the conversion of NO to HNO could occur far more commonly than previously expected. Taking these as the starting point, we set to review our and other groups' previous reports on the possible NO-to-HNO conversion mediated by biological compounds including phenolic drugs and vitamins, as well as several thiol-bearing compounds. Analysis of revised data prompted us to ask ourselves the following key questions: What are the most likely physio/pathological conditions for NO(•)-to-HNO conversion to take place? Which effects usually attributed to NO(•) are indeed mediated by HNO? These inquiries are discussed in the context of 2 decades of NO and HNO research.

Gold nanoparticle-coated capillaries for protein and peptide analysis on open-tubular capillary electrochromatography.

We report a new method of immobilization of gold nanoparticles (AuNPs) on a fused-silica capillary through covalent binding. The resulting modified capillary was applied to electrophoretic systems to improve the efficiency of separation and the selectivity of selected solutes. The immobilization of AuNPs on the capillary wall was performed in a very simple and fast way without requiring heating. The surface features of an AuNP-coated capillary column were determined using the scanning electron microscopy. The chromatographic properties of AuNP-coated capillaries were investigated through variation of the buffer pH and separation voltage. Effective separations of synthetic peptides mixture were obtained on the AuNP-coated capillaries. The method shows a remarkable stability since it was reused about 900 times. The capacity factor was duplicated. Therefore, this modification is stable and can be applied to different separation purposes. A complex mixture of tryptic peptide fragments of HSA was analyzed in both the bare- and the AuNP-coated capillaries. Better electrophoretic peptide profile was observed when using the AuNP-coated capillary.