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961.
The effect of Ficoll 70 on the thermal stability and structure of creatine kinase (CK) was studied using far-UV CD spectra
and intrinsic fluorescence spectra. The thermal transition curves monitored by CD spectra were fitted to a two-state model
using a modified form of the van’t Hoff equation to obtain the transition temperature (T
m) and enthalpy change (ΔH
u) of thermally induced denaturation of CK in the absence and presence of Ficoll 70. An increase in T
m with constant ΔH
u was observed with increasing Ficoll 70 concentration, suggesting that Ficoll 70 enhances the thermal stability of CK. Fluorescence
spectral measurements confirmed this protective effect of Ficoll 70 on CK structure. In addition, we observed a crowding-induced
compaction effect on the structure of both native state and thermally denatured state of CK in the presence of Ficoll 70,
which is more obvious on the structure of the denatured ensemble compared to that of the native ensemble. Our observations
qualitatively accord with the predictions of previously proposed crowding theory for the effect of intermolecular excluded
volume on protein stability and structure. These findings imply that the effects of macromolecular crowding are essential
to our understanding of protein folding and unfolding occurring in vivo. 相似文献
962.
Zinc metalloproteins are involved in many biological processes and play crucial biochemical roles across all domains of life. Local structure around the zinc ion, especially the coordination geometry (CG), is dictated by the protein sequence and is often directly related to the function of the protein. Current methodologies in characterizing zinc metalloproteins' CG consider only previously reported CG models based mainly on nonbiological chemical context. Exceptions to these canonical CG models are either misclassified or discarded as “outliers.” Thus, we developed a less‐biased method that directly handles potential exceptions without pre‐assuming any CG model. Our study shows that numerous exceptions could actually be further classified and that new CG models are needed to characterize them. Also, these new CG models are cross‐validated by strong correlation between independent structural and functional annotation distance metrics, which is partially lost if these new CGs models are ignored. Furthermore, these new CG models exhibit functional propensities distinct from the canonical CG models. Proteins 2015; 83:1470–1487. © 2015 The Authors. Proteins: Structure, Function, and Bioinformatics Published by Wiley Periodicals, Inc. 相似文献
963.
In this study, the effects of electric field on the activity of anammox biomass were investigated. In batch mode, experimental results demonstrated that the nitrogen removal rate enhanced by 25.6 % compared with the control experiment at the electric field of 2 V/cm with application time of 20 min. However, continuous application (24 h) of electric field impacted a mal-effect on anammox biomass during the intensity between 1 and 4 V/cm. After the electric field was removed, the activity of anammox biomass could recover within 2 weeks. This implied that the mal-effect of electric field on anammox biomass was reversible. The decrease of heme c contents and crude enzyme activity demonstrated to be the main reason for the depress of the anammox biomass activity. Transmission electron microscope observation also proved the morphological change of anammox biomass under electric field. 相似文献
964.
Bioprocess and Biosystems Engineering - pH excursions exist due to frequent base addition and environmental heterogeneity in large-scale bioreactors. Such excursions could lead to suboptimal... 相似文献
965.
Zhen Kang Sen Yang Guocheng Du Jian Chen 《Journal of industrial microbiology & biotechnology》2014,41(11):1599-1607
Secretory expression of valuable enzymes by Bacillus subtilis and its related species has attracted intensive work over the past three decades. Although many proteins have been expressed and secreted, the titers of some recombinant enzymes are still low to meet the needs of practical applications. Signal peptides that located at the N-terminal of nascent peptide chains play crucial roles in the secretion process. In this mini-review, we summarize recent progress in secretory expression of recombinant proteins in Bacillus species. In particular, we highlighted and discussed the advances in molecular engineering of secretory machinery components, construction of signal sequence libraries and identification of functional signal peptides with high-throughput screening strategy. The prospects of future research are also proposed. 相似文献
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The activity of NAD+-dependent PGDH was measured in the cytosolic fractions (100,000 x g) of uterine tissues obtained from transsexual, pregnant and non-pregnant women. The specific activity (mean +/- SD) of the enzyme at maximum velocity of the enzyme reaction in these three groups of women was 5.5 +/- 2.30, 0.53 +/- 0.27 and 0.54 +/- 0.25 mU/mg protein respectively using PGE2 as substrate, and with PGF2 alpha as substrate the respective values were 5.48 +/- 2.80, 0.49 +/- 0.41 and 0.51 +/- 0.30 mU/mg protein. These data suggest that, with either substrate, the uterine enzyme activity in the transsexuals was about 10-fold greater than in pregnant and non-pregnant women (p less than 0.001). However, the Km values of the enzyme for both PGE2 and PGF2 alpha were similar in all three groups, indicating the presence of same enzyme in the uterus of transsexual, pregnant and non-pregnant women. We speculate that PGDH activity was raised in the uterus of transsexual women because of the prolonged androgen therapy they received for the management of female-to-male transsexualism. 相似文献