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Lead toxicity has been proved to be related with inducing oxidative stress of organisms and causing inactivation of antioxidant enzymes, the mechanism of which remains unknown. This study investigated and compared superoxide dismutase (Cu/Zn SOD) activity inhibited in lead-treated zebrafish livers and explored the mechanism of SOD inactivation by lead at the molecular level using multiple spectroscopic techniques, isothermal titration calorimetric (ITC) measurement, molecular docking study and ICP-AES detection. Results showed lead exposure decreased SOD activities in zebrafish livers due to direct interactions between lead and SOD, resulting in conformational and functional changes of the enzyme. To be specific, Studies at the molecular level indicated that lead bound into the active site channel of SOD, hindered the path of the catalytic substrate (O(2)(-•)), damaged its skeleton conformation and secondary structure, and interacted with the enzymatically related residue (Arg 141) through electrostatic forces (ΔH < 0, ΔS > 0), and caused the release of Cu(2+) and Zn(2+) from the catalytic pocket of SOD. This work shows a correlation between results on organismal and molecular levels, and obtains a possible model hypothesizing mechanisms of lead toxicity using in vitro experiments instead of in vivo ones.

BackgroundCareer maturity is an important parameter as nursing undergraduates prepare for their future careers. However, little is known regarding the relationships between attributions, future time perspective and career maturity among nursing undergraduates. The purpose of this study was to investigate the degree of career maturity and its relationship with attributions and future time perspective.MethodsA cross-sectional survey was designed. This survey was administered to 431 Chinese nursing undergraduates. Independent-sample t-tests and one-way ANOVA were performed to examine the mean differences between categories of binary and categorical demographic characteristics, respectively. Pearson correlations and multiple linear regressions were used to test the relationships between attributions, future time perspective and career maturity.ResultsThe degree of career maturity was moderate among nursing undergraduates and that internal attributions of academic achievement, future efficacy and future purpose consciousness were positively associated with career maturity (all p < 0.01). These three factors accounted for 37.6 % of the variance in career maturity (adjusted R2 = 0.376).ConclusionsThese findings might assist nursing educators and career counselors to improve nursing undergraduate career maturity by elucidating the imperative roles of internal attributions and future time perspective and to facilitate their transition from school to clinical practice.

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