Maintaining nitric oxide (NO) homeostasis is essential for normal plant physiological processes. However, very little is known about the mechanisms of NO modulation in plants. Here, we report a unique mechanism for the catabolism of NO based on the reaction with the plant hormone cytokinin. We screened for NO-insensitive mutants in Arabidopsis and isolated two allelic lines, cnu1-1 and 1-2 (continuous NO-unstressed 1), that were identified as the previously reported altered meristem program 1 (amp1) and as having elevated levels of cytokinins. A double mutant of cnu1-2 and nitric oxide overexpression 1 (nox1) reduced the severity of the phenotypes ascribed to excess NO levels as did treating the nox1 line with trans-zeatin, the predominant form of cytokinin in Arabidopsis. We further showed that peroxinitrite, an active NO derivative, can react with zeatin in vitro, which together with the results in vivo suggests that cytokinins suppress the action of NO most likely through direct interaction between them, leading to the reduction of endogenous NO levels. These results provide insights into NO signaling and regulation of its bioactivity in plants.is one of the most widespread signaling molecules in living organisms (1, 2). In plants, NO is involved in the regulation of numerous physiological processes during growth and development and is also an important modulator of disease resistance (2-4). Several laboratories discovered that NO is produced not only from nitrate/nitrite but also from L-arginine (L-Arg), which is the main substrate for NO synthesis in animals (4-6). NO is also a widespread atmospheric pollutant. Therefore, this gas not only is a pivotal player in signal transduction but also has the potential to exert significant deleterious effects by being a pollutant. As an inevitable result, increased NO levels in the atmosphere can influence multiple NO-regulated processes in organisms. Despite the wealth of information gathered from analyses of NO functioning in plants, the molecular processes underlying NO effects in plants are still largely unknown.NO differs from other signaling molecules by being reactive, lipophilic, and volatile. In fact, chemically, NO is a free radical, and such a reactive molecule is unlikely to interact specifically with a single specific receptor (3). In animals, NO appears to act through the chemical modification of targets. NO can bind to transition metals of metalloproteins (metal nitrosylation). It also can bind covalently to cysteine (S-nitrosylation) and tyrosine (tyrosine nitration) residues (3,7,8). Such specific protein modifications are emerging as key mechanistic intermediates for NO signal transduction. In plant cells, NO has also been found to regulate the activity of various target proteins through S-or metal-nitrosylation and probably through tyrosine nitration as well (9-13).Furthermore, it has been shown that NO takes part in different phytohormone signaling pathways, frequently under the control of hormonal stimuli. For instance, NO functions in auxin-induc...

Mesenchymal stem cells (MSCs) can differentiate into different types of cells and thus have tremendous potential for cell therapy and tissue engineering. 5-Azacytidine (5-aza), a DNA demethylation reagent, has been reported to induce MSCs to differentiate into cardiomyocytes in vitro. To determine a global effect of 5-aza on MSCs, we investigated the protein expressions of rat MSCs with two-dimensional gel electrophoresis (2-DE). We have generated a proteome reference map of rat MSCs, and have successfully identified 34 proteins with MALDI-TOF-MS analysis. Nine proteins showed distinct regulation in MSCs after 5-aza treatment. The proteins regulated by 5-aza included cytoskeletal proteins, cadmium-binding proteins, and metabolic proteins, etc. These proteins have been reported to be involved in cell proliferation and differentiation through different signaling pathways, and the molecular mechanism of MSCs differentiation is discussed at the proteome level.

In the field of analytical chemistry, sample preparation and chromatographic separation are two core procedures. The means by which to improve the sensitivity, selectivity and detection limit of a method have become a topic of great interest. Recently, porous organic frameworks, such as metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), have been widely used in this research area because of their special features, and different methods have been developed. This review summarizes the applications of MOFs and COFs in sample preparation and chromatographic stationary phases. The MOF- or COF-based solid-phase extraction (SPE), solid-phase microextraction (SPME), gas chromatography (GC), high-performance liquid chromatography (HPLC) and capillary electrochromatography (CEC) methods are described. The excellent properties of MOFs and COFs have resulted in intense interest in exploring their performance and mechanisms for sample preparation and chromatographic separation.

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In this work, a [Cu(mal)(bpy)]⋅H2O (mal, L-(-)-malic acid; bpy, 4,4'-bipyridyl) homochiral metal-organic frameworks (MOFs) was synthesized and used for modifying the inner walls of capillary columns by utilizing amido bonds to form covalent links between the MOFs particles and capillary inner wall. The synthesized [Cu(mal)(bpy)]⋅H2 O and MOFs-modified capillary column were characterized by X-ray diffraction, thermogravimetric analysis, particle size distribution analysis, nitrogen absorption characterization, FTIR spectroscopy, SEM, and energy-dispersive X-ray spectroscopy (EDX). The MOFs-modified capillary column was used for the stereoisomer separation of some drugs. The LODs and LOQs of six analytes were 0.1 and 0.25 μg/mL, respectively. The linear range was 0.25-250 μg/mL for ephedrine, 0.25-250 μg/mL for pseudoephedrine, 0.25-180 μg/mL for D-penicillamine, 0.25-120 μg/mL for L-penicillamine, 0.25-180 μg/mL for D-phenylalanine, and 0.25-160 μg/mL for L-phenylalanine, all with R(2) > 0.999. Finally, the MOFs-modified capillary column was applied for the analysis of active ingredients in a real sample of the traditional Chinese medicine ephedra.

This article describes a new application of graphene oxide (GO) in CE based on the coating of fused silica capillary for chiral separation. The coated capillary was characterized by SEM, energy dispersive X-ray spectroscopy, and Raman spectra. The results indicated that the capillary was coated with GO. Chiral separations were carried out in the GO-coated capillary for the ephedrine-pseudoephedrine (E-PE) isomers and β-methylphenethylamine (β-Me-PEA) isomers at the optimal buffer conditions without any chiral selector by CE. The precision and reproducibility of GO-coated capillary were investigated, and the RSDs of migration time (n = 6) for the E-PE isomers were 1.35-1.41%, and 0.97-3.50% for β-Me-PEA isomers, respectively. The LOD for E-PE isomers and β-Me-PEA isomers was 3 μM and 18 μM, respectively.