Effects of osmolytes on the refolding of recombinant Pelodiscus sinensis brain-type creatine kinase
PROCESS BIOCHEMISTRY
Authors: Sun, Xiao-Bao; Lim, Gyu Tae; Lee, Jinhyuk; Wan, Jia-Xin; Lin, Hai-Zhen; Yang, Jun-Mo; Wang, Qian; Park, Yong-Doo
Abstract
The protective effects of osmolytes on the renaturation of Pelodiscus sinensis brain-type creatine kinase (P-CKB) were determined in this study. The P-CKB gene was cloned and was heterologously expressed in Escherichia coli BL21 (DE3). The purified recombinant protein was subjected to 6 M urea denaturation and further applied with six different osmolytes (glycine, proline, sorbitol, DMSO, betaine, and trehalose). Our results demonstrated that the addition of glycine or DMSO could contribute toward the reactivation of unfolded P-CKB and prevent aggregation. Interestingly, 25 mM glycine was found to be the best concentration to reactivate denatured P-CKB, while high-concentration glycine led to the opposite effect as monitored by a red shift in the intrinsic fluorescence spectra and the aggregation of protein, which probably could be attributed to an additional inactive protein complex that formed during the fast refolding reaction. Docking simulation results showed the osmolyte docking energies to be relatively low and clustering groups were spread on the surface of P-CKB, indicating that osmolytes directly protected the surface of P-CKB. The results in this study could provide a better understanding of structural and functional changes in P-CKB during refolding in addition to the role of osmolytes in heterothermic animals.
On the quantification of seismic performance factors of Chevron Knee Bracings, in steel structures
ENGINEERING STRUCTURES
Authors: Farahi, Mojtaba; Mofid, Massood
Abstract
As a matter of fact, it is necessary to have the values of Response Modification Factor Omega(0), Over-strength Factor 120, and Deflection Amplification Factor C-d in order to design seismic-force-resisting systems according to design and loading codes. This study is intended to evaluate these factors for a structural lateral bracing system called Chevron Knee Bracing (CKB). In this type of bracing, the knee elements assist the system to dissipate energy through the formation of plastic flexural and/or shear hinges within the presented bracing system. The approach utilized in this study is according to FEMA P695 based on low probability of structural collapse and involves nonlinear static and dynamic analyses. Over-strength and ductility of this type of bracing is investigated through performing nonlinear static analyses. Conducting Incremental Dynamic Analyses (IDA), Collapse Margin Ratios (CMRs) of the defined archetypes model are achieved and modified to obtain an Adjusted Collapse Margin Ratio, ACMR for each archetype. The values of calculated ACMRs are compared with the accepted values proposed by FEMA P695 in which the total system collapse uncertainty is considered to prove the validity of presumed seismic performance factors of CKB systems. (c) 2012 Elsevier Ltd. All rights reserved.