Heme-independent Redox Sensing by the Heme-Nitric Oxide/Oxygen-binding Protein (H-NOX) from Vibrio cholerae.

Heme nitric oxide/oxygen (H-NOX)-binding proteins act as nitric oxide (NO) sensors among various bacterial species. In several cases, they act to mediate communal behavior such as biofilm formation, quorum sensing, and motility by influencing the activity of downstream signaling proteins such as histidine kinases (HisKa) in a NO-dependent manner. An H-NOX/HisKa regulatory circuit was recently identified in Vibrio cholerae, and the H-NOX protein has been spectroscopically characterized. However, the influence of the H-NOX protein on HisKa autophosphorylation has not been evaluated. This process may be important for persistence and pathogenicity in this organism. Here, we have expressed and purified the V. cholerae HisKa (HnoK) and H-NOX in its heme-bound (holo) and heme-free (apo) forms. Autophosphorylation assays of HnoK in the presence of H-NOX show that the holoprotein in the Fe(II)-NO and Fe(III) forms is a potent inhibitor of HnoK. Activity of the Fe(III) form and aerobic instability of the Fe(II) form suggested that Vibrio cholerae H-NOX may act as a sensor of the redox state as well as NO. Remarkably, the apoprotein also showed robust HnoK inhibition that was dependent on the oxidation of cysteine residues to form disulfide bonds at a highly conserved zinc site. The importance of cysteine in this process was confirmed by mutagenesis, which also showed that holo Fe(III), but not Fe(II)-NO, H-NOX relied heavily upon cysteine for activation. These results highlight a heme-independent mechanism for activation of V. cholerae H-NOX that implicates this protein as a dual redox/NO sensor.

Quantitative and qualitative evaluation of kernel anthocyanins from southwestern United States blue corn.

BACKGROUND: Anthocyanin-rich blue corn is an emerging specialty crop in the USA. The antioxidant properties of blue corn offer health benefits in the human diet. The objectives of this study were to identify, characterize and quantify the anthocyanins from blue corn. Hypotheses tested were that total anthocyanin content was similar among southwestern US accessions and that it would vary across locations. It was also examined whether different anthocyanin components were unique to certain genotypes. RESULTS: Across all locations and accessions, an average of 0.43 g kg(-1) total anthocyanin content (TAC) was observed. Accessions Santa Clara Blue and Ohio Blue displayed the highest TAC. The TAC of accession Flor del Rio was lower by nearly a factor of six. A total of five anthocyanin components were identified. Cyanidin 3-glucoside was the most abundant, followed by pelargonidin and peonidin 3-glucoside. Succinyl and disuccinyl glycosidic forms of cyanidin were also identified. Cyanidin 3-disuccinylglucoside was newly identified as a novel form of anthocyanin. CONCLUSION: Quantitative and qualitative anthocyanin expression was determined to be relatively stable across multiple southwestern environments. Increased expression of red and purple pigmentation in accession Flor del Rio appeared to be associated more with reduced TAC and cyanidin 3-glucoside than with elevated pelargonidin per se. A previously unreported anthocyanin component in blue corn, cyanidin 3-disuccinylglucoside, is present in southwestern landraces. © 2016 Society of Chemical Industry.

Co-liquefaction of mixed culture microalgal strains under sub-critical water conditions.

We report the co-liquefaction performance of unicellular, red alga Cyanidioschyzon merolae and Galdieria sulphuraria under sub-critical water conditions within a stainless-steel batch reactor under different temperatures (150-300°C), residence time (15-60min), and Cyanidioschyzon merolae to Galdieria sulphuraria mass loading (0-100%). Individual liquefaction of C. merolae and G. sulphuraria at 300°C achieved maximum biocrude oil yield of 18.9 and 14.0%, respectively. The yield of biocrude oil increased to 25.5%, suggesting a positive synergistic effect during the co-liquefaction of 80-20mass loading of C. merolae to G. sulphuraria. The biocrude oils were analyzed by FT-ICR MS which showed that co-liquefaction did not significantly affect the distribution of product compounds compared to individual oils. The co-liquefied biocrude and biochar have a higher-heating-value of 35.28 and 7.96MJ/kg. Ultimate and proximate analysis were performed on algae biomass, biocrude and biochar.

Stabilization and prolonged reactivity of aqueous-phase ozone with cyclodextrin.

Recalcitrant organic groundwater contaminants, such as 1,4-dioxane, may require strong oxidants for complete mineralization. However, their efficacy for in-situ chemical oxidation (ISCO) is limited by oxidant decay and reactivity. Hydroxypropyl-ß-cyclodextrin (HPßCD) was examined for its ability to stabilize aqueous-phase ozone (O3) and prolong oxidation potential through inclusion complex formation. Partial transformation of HPßCD by O3 was observed. However, HPßCD proved to be sufficiently recalcitrant, because it was only partially degraded in the presence of O3. The formation of a HPßCD:O3 clathrate complex was observed, which stabilized decay of O3. The presence of HPßCD increased the O3 half-life linearly with increasing HPßCD:O3 molar ratio. The O3 half-life in solutions increased by as much as 40-fold relative to HPßCD-free O3 solutions. Observed O3 release from HPßCD and indigo oxidation confirmed that the formation of the inclusion complex is reversible. This proof-of-concept study demonstrates that HPßCD can complex O3 while preserving its reactivity. These results suggest that the use of clathrate stabilizers, such as HPßCD, can support the development of a facilitated-transport enabled ISCO for the O3 treatment of groundwater contaminated with recalcitrant compounds.