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Electron-energy-rich coenzymes in cells, NADH and NADPH, are re-energized repeatedly through the Embden-Meyerhof and pentose-phosphate glycolytic pathways, respectively. This study demonstrates extraction of their electron energies in red blood cells (RBCs) for in vivo extracellular chemical reactions using an electron mediator shuttling across the biomembrane. Hemoglobin-vesicles (HbVs) are an artificial oxygen carrier encapsulating purified and concentrated Hb solution in liposomes. Because of the absence of a metHb-reducing enzymatic system in HbV, HbO2 gradually autoxidizes to form metHb. Wistar rats received HbV suspension (10 mL/kg body weight) intravenously. At the metHb level of around 50%, methylene blue [MB(+); 3,7-bis(dimethylamino)phenothiazinium chloride] was injected. The level of metHb quickly decreased to around 16% in 40 min, remaining for more than 5 h. In vitro mixing of HbV/MB(+) with RBCs recreated the in vivo metHb reduction, but not with plasma. NAD(P)H levels in RBCs decreased after metHb reduction. The addition of glucose facilitated metHb reduction. Liposome-encapsulated NAD(P)H, a model of RBC, reduced metHb in HbV in the presence of MB(+). These results indicate that (i) NAD(P)H in RBCs reacts with MB(+) to convert it to leukomethylene blue (MBH); (ii) MB(+) and MBH shuttle freely between RBC and HbV across the hydrophobic lipid membranes; and (iii) MBH is transferred into HbV and reduces metHb in HbV. Four other electron mediators with appropriate redox potentials appeared to be as effective as MB(+) was, indicating the possibility for further optimization of electron mediators. We established an indirect enzymatic metHb reducing system for HbV using unlimited endogenous electrons created in RBCs in combination with an effective electron mediator that prolongs the functional lifespan of HbV in blood circulation.

Purpose This study aims to delineate opportunity recognition as a competency from opportunity recognition as an outcome in the form of ideas and opportunities. In addition, a model was developed to examine the antecedents that lead to opportunity recognition competency, the intention to be an entrepreneur and finally, the actual number of ideas and opportunities discovered. Design/methodology/approach This study adopted cross-sectional design and collected quantitative data from a total of 247 randomly selected final year students from two private universities in Malaysia. Partial least squares structural equation modelling was applied to test the associations. Findings Study revealed that opportunity recognition competency and ability to develop ideas or exploitable opportunities are distinct constructs. Students with high competency in recognising opportunities are interested to be an entrepreneur but are not necessarily prepared with tangible ideas or exploitable opportunities. Absorptive capacity, entrepreneurial alertness and entrepreneurial knowledge were found to be significant predictors of opportunity recognition competency. Practical implications Firstly, in managing outputs of entrepreneurship education and trainings, opportunity recognition competency and number of ideas and opportunities should be separately and explicitly measured. Secondly, entrepreneurial alertness and entrepreneurial knowledge must be emphasised in entrepreneurial education or training on guiding students to be alert to information and honing their opportunity recognition competency skills through active search techniques. Originality/value This study is one of the few studies that clarify and empirically distinguish the concept of opportunity recognition as competency from opportunity recognition as an outcome in the forms of ideas and exploitable opportunities.