The relationship between mobile phone dependence and academic burden among junior middle school students in Guizhou Province / 中国学校卫生

Objective@#To explore the relationship between mobile phone dependence (MPD) and academic burden among junior middle school students in Guizhou Province, under the "double reduction" policy by using a multi level model, so as to provide a basis for preventing the occurrence of MPD.@*Methods@#From December 2021 to January 2022, 7 868 students from grade 1 to grade 3 in 3 cities (prefecture) of Guizhou Province were selected by multi stage stratification random sampling method, and on site investigation was conducted by self compiled questionnaire and Self rating Questionnaire for Adolescent Problematic Mobile Phone Use(SQAPMPU). Using MLwiN 2.30 to fit a multi level model of the relationship between MPD and academic burden among junior middle school students.@*Results@#The MPD detection rate of junior middle school students in Guizhou Province was 20.9%. The multi level model revealed that MPD of junior middle school students was clustered at the level of school and class ( χ 2= 1 565.32 , P <0.01), and high perceived academic pressure had a positive predictive effect on MPD among junior middle school students ( β =1.96). Homework duration ≥90 min/d at weekends had a negative predictive effect on MPD ( β =-0.55), while participation in off campus training on learning days had a positive predictive effect ( β =1.66)( P <0.05).@*Conclusion@#The MPD occurrence level is higher among junior middle school students in Guizhou Province. Perceived academic pressure, time spent on homework during weekends, off campus training and other academic burdens have an impact on MPD among junior middle school students, which should be a cause of concern for schools, families and social departments.

Crystal Structure and Function of PqqF Protein in the Pyrroloquinoline Quinone Biosynthetic Pathway.

Pyrroloquinoline quinone (PQQ) has received considerable attention due to its numerous important physiological functions. PqqA is a precursor peptide of PQQ with two conserved residues: glutamate and tyrosine. After linkage of the Cγ of glutamate and Cϵ of tyrosine by PqqE, these two residues are hypothesized to be cleaved from PqqA by PqqF. The linked glutamate and tyrosine residues are then used to synthesize PQQ. Here, we demonstrated that the pqqF gene is essential for PQQ biosynthesis as deletion of it eliminated the inhibition of prodigiosin production by glucose. We further determined the crystal structure of PqqF, which has a closed clamshell-like shape. The PqqF consists of two halves composed of an N- and a C-terminal lobe. The PqqF-N and PqqF-C lobes form a chamber with the volume of the cavity of ∼9400 Å(3) The PqqF structure conforms to the general structure of inverzincins. Compared with the most thoroughly characterized inverzincin insulin-degrading enzyme, the size of PqqF chamber is markedly smaller, which may define the specificity for its substrate PqqA. Furthermore, the 14-amino acid-residue-long tag formed by the N-terminal tag from expression vector precisely protrudes into the counterpart active site; this N-terminal tag occupies the active site and stabilizes the closed, inactive conformation. His-48, His-52, Glu-129 and His-14 from the N-terminal tag coordinate with the zinc ion. Glu-51 acts as a base catalyst. The observed histidine residue-mediated inhibition may be applicable for the design of a peptide for the inhibition of M16 metalloproteases.