Association between circadian rhythm disorder with depressive and anxiety symptoms of college students in Jinzhou City / 中国学校卫生

Objective@#To explore the association between circadian rhythm with depressive and anxiety symptoms of college students in Jinzhou City, to provide a theoretical basis for targeted depression and anxiety prevention among college students.@*Methods@#A total of 1 938 college students were selected by convenient sampling method from November to December 2020 for questionnaire survey. The relationship between circadian rhythm and depression and anxiety symptoms was analyzed by using questionnaire,survey including Self Rating Depression Scale (SDS), Self Rating Anxiety Scale (SAS) and Munich Chronotype Questionnaire (MCTQ).@*Results@#There were significant differences in the distribution of depressive symptoms in different majors, smoking, drinking and physical exercise ( χ 2=46.80, 5.88, 5.76, 12.23, P <0.05). There were significant differences in the distribution of anxiety symptoms in different majors, smoking and drinking ( χ 2=9.41, 5.80, 5.56, P <0.05). Stratified analysis showed that the depressive symptoms of different chronotype were statistically varied by age, gender, professional, grade, registered residence, body mass index, smoking, drinking, and sports( χ 2=8.16, 14.42, 12.25, 6.19, 10.99, 15.29, 17.41, 15.63, 7.47, 9.59, 10.51 , P <0.05). The anxiety symptoms of different chronotype were statistically different in age (21 years) and smoking (no), ( χ 2= 8.34 , 7.16, P <0.05). Spearman rank correlation showed that the corrected Mid sleep on Free Days Corrected for Sleep Debt on Work Days (MSFsc) was positively correlated with the standard scores of depression and anxiety ( r s=0.10, 0.09), and social jet lag was positively correlated with the standard scores of depression and anxiety ( r s=0.09, 0.05)( P <0.05). After controlling for age, major, smoking and drinking, binary Logistic regression showed that mean sleep length was inversely correlated with depressive symptoms ( OR =0.82), and weekly insomnia frequency was positively correlated with depressive symptoms ( OR=1.14 ).Early type and intermediate type of chronotypes were negatively correlated with depression ( OR =0.66,0.57). Intermediate type of chronotype was negatively correlated with anxiety symptoms ( OR =0.65).@*Conclusion@#Circadian rhythm is related to depressive and anxiety symptoms,among which the average sleep length, early rise and intermediate sleep patterns are negatively related to depression symptoms, and intermediate sleep patterns and anxiety symptoms, suggesting that circadian rhythm disorder may affect depression and anxiety symptoms.

2′-O-methyl nucleotide modified DNA substrates influence the cleavage efficiencies of BamHI and BglII.

Induction of endonucleolytic DNA cleavage is an essential event that links the initiating stimuli to the final effects of cells. The cleavage efficiency and thus the final yield could be affected by many factors, including structures of DNA substrates, composite structures of enzymes–substrates or enzymes–nucleic analogs and so on. However, it is not clear whether a nucleotide derivative-substituted in DNA substrates can influence the efficiency of enzymatic cleavage. To investigate the effect of sugar pucker conformation on DNA–protein interactions, we used 2′-O-methyl modified nucleotides (OMeN) to modify DNA substrates of isocaudemers BamHI and BglII in this study, and used FRET assay as an efficient method for analysis of enzyme cleavage. Experimental results demonstrated that OMeN-substituted recognition sequences influenced the cleavage rates significantly in a position-dependent manner. OMeN substitutions can reduce the cleavage as expected. Surprisingly, OMeN substitutions can also enhance the cleavage rates. The kinetics parameters of Vmax and Km have been obtained by fitting the Michaelis-Menten kinetic equation. These 2'- OMe nucleotides could behave as a regulatory element to modulate the enzymatic activity in vitro, and this property could enrich our understanding about the endonuclease cleavage mechanism and enhance our ability to regulate the enzymatic cleavage efficiency for applications in synthetic biology.

Realizing directional cloning using sticky ends produced by 3′-5′ exonuclease of Klenow fragment.

The Klenow fragment (KF) has been used to make the blunt end as a tool enzyme. Its 5′-3′ polymerase activity can extend the 5′ overhanging sticky end to the blunt end, and 3′-5′ exonuclease activity can cleave the 3′ overhanging sticky end to the blunt end. The blunt end is useful for cloning. Here, we for the first time determined that a sticky end can be made by using the 3′-5′ exonuclease activity of KF. We found that KF can cleave the blunt end into certain sticky ends under controlled conditions. We optimized enzyme cleavage conditions, and characterized the cleaved sticky ends to be mainly 2 nt 5′ overhang. By using these sticky ends, we realized ligation reaction in vitro, and accomplished cloning short oligonucleotides directionally with high cloning efficiency. In some cases, this method can provide sticky end fragments in large scale for subsequent convenient cloning at low cost.

Identification of a premature termination of DNA polymerization in vitro by Klenow fragment mutants.

DNA polymerization products by Klenow fragment (KF) are blunt-ended. In the present study, we found that the Klenow fragment mutants with partial deletions of thumb subdomain were unable to extend primers to the 5′ terminal of templates, thus creating 5′ overhanging sticky ends 2 nt long. We termed this phenomenon as PmTP (premature termination of polymerization). The KF mutants produced homogenous sticky-ended products only under mild reaction conditions, whereas under vigorous reaction conditions, the sticky ends were prone to be blunt-ended. It was also identified that deletions of more than four residues of KF thumb subdomain could induce PmTP, and tworesidue deletion of KF thumb subdomain only induced PmTP in a lower-concentration situation. Structure modelling analysis suggested that shortening or destruction of α helix H1 at the tip of the thumb subdomain was crucial to PmTP, while the conserved residues in front of α helix was less important. PmTP might be caused by the reduced DNAbinding affinity of the mutants. The sticky ends made by PmTP have potential applications in gene splicing and molecular cloning techniques.