Objective:To develop a camelid single-domain antibody (SdAb) recognizing linear B-cell epitopes in glutamate dehydrogenase of Clostridium difficile(CD-GDH), and to apply it in Western blot and ELISA. Methods:Purified recombinant CD-GDH was used as bait to screen phage-displayed camelid SdAb library and obtain positive clones. Then those clones were confirmed by Western blot, and their variable domain of heavy chain of heavy chain antibody(VHH) nucleotide sequence were determined. The VHH sequence was synthesized after codon optimization and cloned into the expression vector pET28a. The SdAb was then expressed and purified, and its ability to detect CD-GDH protein in multiple assays was further explored.Results:Six positive clones were obtained, among which clone GA4 was chosen for recombinant expression in Escherichia coli and further purification. The purified GA4 binded well with CD-GDH with a Kd value of 3 nmol/L. In Western blot and ELISA, GA4 was proven to be able to selectively detect both recombinant and endogenous CD-GDH. Conclusions:A camelid SdAb targeting a linear B-cell epitope in CD-GDH is successfully developed, which provides a very useful tool for detecting CD-GDH.

Objective:To develop a camelid single-domain antibody (SdAb) recognizing linear B-cell epitopes in glutamate dehydrogenase of Clostridium difficile(CD-GDH), and to apply it in Western blot and ELISA. Methods:Purified recombinant CD-GDH was used as bait to screen phage-displayed camelid SdAb library and obtain positive clones. Then those clones were confirmed by Western blot, and their variable domain of heavy chain of heavy chain antibody(VHH) nucleotide sequence were determined. The VHH sequence was synthesized after codon optimization and cloned into the expression vector pET28a. The SdAb was then expressed and purified, and its ability to detect CD-GDH protein in multiple assays was further explored.Results:Six positive clones were obtained, among which clone GA4 was chosen for recombinant expression in Escherichia coli and further purification. The purified GA4 binded well with CD-GDH with a Kd value of 3 nmol/L. In Western blot and ELISA, GA4 was proven to be able to selectively detect both recombinant and endogenous CD-GDH. Conclusions:A camelid SdAb targeting a linear B-cell epitope in CD-GDH is successfully developed, which provides a very useful tool for detecting CD-GDH.

Objective: To investigate the association between daily sedentary time and frailty among people aged 50 years and over. Methods: Cross-sectional data was collected from the first wave of World Health Organization Study on global AGEing and adult health in China. A two-level (individual level and community level) logistic model was performed to identify the association between daily sedentary time and frailty. The dose-response relationship between them was analyzed by restrictive cubic spline curve. Results: A total of 13 175 individuals aged 50 years and over were included for analysis. A positive association between daily sedentary time and frailty was noticed, both in urban (OR=1.22, 95%CI: 1.17-1.27) or rural areas (OR=1.11, 95%CI: 1.05-1.18) under study. The dose-response curve showed that daily sedentary time and frailty might present an approximate linear relationship. Conclusion Results from this study showed significant association exsited between daily sedentary time and frailty, approximately with a linear dose-response relationship.