Comparison of the binding interactions of 4-hydroxyphenylpyruvate dioxygenase inhibitor herbicides with humic acid: Insights from multispectroscopic techniques, DFT and 2D-COS-FTIR.

4-Hydroxyphenylpyruvate dioxygenase (HPPD) inhibitor is one of the important herbicides to solve the problem of weed control. With the widespread and continued use of HPPD inhibitor (HPPDi) herbicides, it may inevitably put pressure on the environment. Humic acid (HA) can effectively interact with pesticides through sorption or covalent bond formation and promote the degradation of pesticides, which can reduce the risk of pesticides in the environment. In the present study, the interactions of four HPPDi herbicides (sulcotrione, tembotrione, topramezone and mesotrione) with HA were reported and comparative assessment of the binding using multispectral technology, density functional theory (DFT) calculation and two-dimensional correlation spectroscopy (2D-COS). Time-resolved measurements and the Stern-Volmer constant at different temperature verified that HPPDi can bind with HA through the static quenching mechanism. From the thermodynamic parameters, the interaction force between HA and sulcotrione, tembotrione, topramezone and mesotrione was provided by electrostatic force. DFT, binding constant and three-dimensional (3D) fluorescence peak variation all indicated that the order of the binding ability of the four HPPDi and HA was mesotrione > tembotrione > sulcotrione > topramezone. According to dynamic light scattering (DLS), pH 7 is most conducive to the formation of HA-HPPDi complexes. Fourier transform infrared spectroscopy (FTIR) and 2D-COS showed that HA combined with HPPDi through aromatic C-H, CO and C-X, and the first binding group to HA was almost all CO. Sulcotrione, tembotrione, topramezone and mesotrione quench the endogenous fluorescence of HA by a static quenching mechanism and bind to HA through electrostatic interaction to form a complex. These results provide important insights into the combination of environmental pollutants with HA.

Drivers and mediators of healthcare workers' anxiety in one of the most affected hospitals by COVID-19: a qualitative analysis.

OBJECTIVE: To report the driving and mediating factors of healthcare workers' anxiety during the COVID-19 pandemic. DESIGN: Qualitative indepth interview study. SETTING: The Central Hospital of Wuhan, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China. PARTICIPANTS: 53 healthcare workers who were or were not diagnosed with COVID-19. RESULTS: During the COVID-19 pandemic, healthcare workers were initially not sufficiently psychologically prepared. Then they suffered from severe anxiety and apprehension during the peak stage, regardless of whether they were infected with SARS-CoV-2 or not. These negative emotions were exacerbated by four drivers, namely infection risk, supplies, isolation and media. As the epidemic gradually came under control, healthcare workers experienced less anxiety from these factors, but became concerned about their low financial status. To reduce anxiety, healthcare workers diverted their attention from the risk of infection through personal entertainment and religious beliefs and focused on treating their patients. Furthermore, assistance from other people, including colleagues, families, friends, patients and society, helped protect healthcare workers from anxiety. CONCLUSIONS: Personal and social support can relieve healthcare workers' anxiety to some extent during the different stages of an epidemic. Both protective equipment and financial allowance motivate healthcare workers to focus on patient care, although the latter matters more as the epidemic comes under control.