SpyTag/SpyCatcher molecular cyclization confers protein stability and resilience to aggregation.

The capacities for thermal and inhibitor tolerance are critical for industrial enzymes and loss of activity is a major challenge in deploying natural enzymes for commercial applications. Protein engineering approaches, such as site-directed mutagenesis and directed evolution, have been devoted to modifying natural enzymes. Recently, a post-translation protein engineering strategy, the SpyTag/SpyCatcher system, was introduced. Here, we have generated a thermo- and ion-tolerant cyclized xylanase (C-TFX) by fusing the SpyTag and SpyCatcher peptides to its N- and C- terminus respectively. Compared with the linear enzyme, C-TFX retained greater residual activity after heating or metal ion exposure. Intrinsic fluorescence and circular dichroism analysis revealed that the isopeptide bond mediated by SpyTag/SpyCatcher cyclization contributed to enhanced thermo- and ion-stability, probably by stabilizing its secondary and conformational structure. In addition, the heat-challenged C-TFX was observed to degrade natural lignocellulosic substrates efficiently. The cyclized xylanase was more stable and resistent to denaturation and aggregation than the linear enzyme. The "superglue" SpyTag/SpyCatcher cyclization system enables the enzyme to maintain its structural conformation, which will be of particular interest in engineering of enzymes for industrial application such as feed additives and functional oligosaccharides production.

[Effect of Herba Scutellariae Barbatae flavonoids in delaying aging of Caenorhabditis elegans and human umbilical vein endothelial cells in vitro].

OBJECTIVE: To explore the effects of Herba Scutellariae Barbatae flavonoids (HF) in delaying aging of Caenorhabditis elegans and human umbilical vein endothelial cells (HUVECs) in vitro. METHODS: The effects of 30 or 50 mg/L of HF on nematode life span, reproductive capacity, oxidative stress, and antioxidant enzyme activity of C. elegans were assessed, and the effects of HF on the expressions of the genes encoding antioxidant enzymes and the aging-related genes were analyzed using real-time RT-PCR in both C. elegans and cultured HUVECs. Results Compared with the blank control group, C. elegans with HF treatment showed significantly improved mean and maximum lifespan with a prolonged mean lifespan under acute heat stress at 35 degrees celsius;. HF treatment did not impair the reproductive capacity or cause significant changes in the offspring number of C. elegans. In addition, HF enhanced SOD and CAT activity and up-regulated the expression of daf-16 and sir-2.1 (SIRT1) genes in C. elegans and HUVECs. CONCLUSIONS: HF may delay aging of C. elegans and enhance their resistance to acute heat stress without damaging their reproductive capacity possibly by up-regulating the activity of antioxidant enzymes and expressions of antioxidant genes. HF also may protect endothelial cells against oxidative damage.

Efficacy and Safety of Duloxetine on Osteoarthritis Knee Pain: A Meta-Analysis of Randomized Controlled Trials.

OBJECTIVES: The aim of this meta-analysis was to evaluate the efficacy and safety of duloxetine for management of osteoarthritis knee (OAK) pain. METHODS: A systematic literature search of articles for management of OAK using duloxetine were performed in PubMed, EBSCO, EMBASE, ScienceDirect, MEDLINE, ClinicalTrials.gov, Google Scholar, and Cochrane Central Register of Controlled Trials from the available date of inception until the latest issue (October 2013). Potentially relevant randomized controlled trials (RCTs) regarding to comparison of efficacy and safety of duloxetine with placebo for managing OAK pain were included. Also, studies with specific data regarding to pain reductions and response rate, Patient Global Impression of Improvement (PGI-I), functional improvement, Western Ontario and McMaster Osteoarthritis Index (WOMAC), adverse events (AEs), treatment-emergent AEs (TEAEs), mortality were included and analyzed, and those with confounding conditions were excluded. Studies were assessed for quality using the Jadad five-point score for RCTs. Finally, a meta-analysis of all RCTs eligible for inclusion criteria was performed using Review Manager 5.1 meta-analysis software. RESULTS: Three RCTs that enrolled 1,011 patients were included in our meta-analysis. There were statistically significant differences between patients taking duloxetine and those taking placebo with regard to the reductions in pain intensity (992 patients, mean difference [MD] = -0.88, 95% confidence interval [CI] -1.11--0.65, P < 0.0001), a moderate improvement in pain intensity (>= 30% response rate; 989 patients, risk ratio [RR] = 1.49, 95% CI 1.31-1.70, P < 0.0001), a substantial improvement in pain intensity (>=50% response rate; 989 patients, RR = 1.69, 95% CI 1.27-2.25, P = 0.0004). Statistically significant differences in PGI-I (976 patients, MD = -0.47, 95% CI -0.63 to -0.30, P < 0.0001) and WOMAC-physical function subscale (977 patients, MD = -4.25, 95% CI -5.82 to -2.68, P < 0.0001) were observed. Similarly, more AEs, TEAEs, and discontinuations for any reason were associated with the use of duloxetine than with placebo (1,011 patients, RR = 2.15, 95% CI 1.48-3.11, P < 0.0001; 1,011 patients, RR = 1.32, 95% CI 1.16-1.49, P < 0.0001; 1,011 patients, RR = 1.43, 95% CI 1.14-1.78, P = 0.002, respectively). However, differences in serious AEs were not significantly statistically different. Moreover, no deaths occurred during these three studies. CONCLUSION: This analysis suggests duloxetine (60/120 mg quaque die (QD)), compared with placebo control, resulted in a greater reduction in pain, improved function and patient-rated impression of improvement, and acceptable adverse effects for the treatment of OAK pain after approximately 10-13 weeks of treatment.