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1.
Ignatenko OV Gazaryan IG Mareeva EA Chubar TA Fechina VA Savitsky PA Rojkova AM Tishkov VI 《Biochemistry. Biokhimii?a》2000,65(5):583-587
Heme-containing plant peroxidases (EC 1.11.1.7) contain a highly conserved single tryptophan residue. Its replacement with Phe in recombinant horseradish peroxidase (rHRP) increased the stability of the mutant enzyme in acid media. The kinetic properties of native, wild-type, and W117F mutant recombinant horseradish peroxidase in the reactions of ammonium 2, 2;-azino-bis(3-ethylbenzthiazoline-6-sulfonate) (ABTS), guaiacol, and o-phenylenediamine oxidation are very similar. However, significant changes in the reaction rate constant characteristic for the monomolecular rate-limiting step ascribed either to product dissociation from its complex with the enzyme or electron transfer from the substrate to the active site within the Michaelis complex were observed. The data indirectly indicate the participation of the single Trp residue in oxidation of ABTS and guaiacol and possible differences in kinetic mechanisms for oxidation of ABTS, guaiacol, and o-phenylenediamine. 相似文献
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I Iu Mikha?lova T Iu Mareeva I N Tsygannik I I Mikhaleva L V Onoprienko A A Vikhrov E A Markvicheva W Panghorn W Duax V A Nesmiianov V Z Pletnev 《Bioorganicheskaia khimiia》1999,25(4):247-252
Antigen-binding fragments (Fab) of mouse monoclonal antibodies to human interleukin-2 were obtained in preparative quantities by a modified procedure. These Fab-fragments were shown to be homogeneous according to the isoelectric focusing method. Various monocrystals of these free Fab-fragments and their complexes with the antigenic peptide corresponding to the 59-72 sequence of interleukin-2 were obtained. These were shown to be suitable for X-ray and were preliminarily studied by X-ray. 相似文献
3.
M. G. BETTS D. MITCHELL A. W. DIAMOND J. BÉTY 《The Journal of wildlife management》2007,71(7):2266-2273
ABSTRACT Roadside survey data have been used frequently to assess species occurrence and population trends and to establish conservation priorities. However, most studies using such data assume that samples are representative of either the amount of habitat or its rate of change at larger spatial scales. We tested both of these assumptions for the Breeding Bird Survey (BBS) from 1974 to 2001 in New Brunswick, Canada. Our study focused on mature forest—a cover type that we predicted would be characterized by rapid change due to human activities and that is of high ecological importance. We also sought to determine whether land cover changes adjacent to BBS routes were related to bird population trends detected in BBS data. Within all 3 time periods examined (1970s, 1980s, and 1990s), the amount of mature forest adjacent to BBS routes was significantly lower than in surrounding 1° blocks of latitude and longitude. This could be problematic for studies that use roadside data to compare the relative abundance of species. On average, mature forest declined at a rate of-1.5% per year over the 28-year study period. We detected no significant difference in the rate of change between degree blocks and BBS routes over this time span. However, in the 1970s and 1980s, mature forest declined more rapidly in degree blocks (-2.7%/yr) than adjacent to BBS routes (-0.5/yr). We also found that the BBS trend for a mature forest-associated species, blackburnian warbler (Dendroica fusca), was correlated with the trend in mature forest along BBS routes. This, combined with slower rates of mature forest change along routes in the 1970s and 1980s, suggests that BBS data may have underestimated population declines during this period. It is important that research be conducted to test for potential biases in roadside surveys caused by uneven rates of landscape change, particularly in regions characterized by rapid habitat alteration. 相似文献
4.
Glucagon signalling in the dorsal vagal complex is sufficient and necessary for high‐protein feeding to regulate glucose homeostasis in vivo
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Mary P LaPierre Mona A Abraham Jessica TY Yue Beatrice M Filippi Tony KT Lam 《EMBO reports》2015,16(10):1299-1307
High‐protein feeding acutely lowers postprandial glucose concentration compared to low‐protein feeding, despite a dichotomous rise of circulating glucagon levels. The physiological role of this glucagon rise has been largely overlooked. We here first report that glucagon signalling in the dorsal vagal complex (DVC) of the brain is sufficient to lower glucose production by activating a Gcgr–PKA–ERK–KATP channel signalling cascade in the DVC of rats in vivo. We further demonstrate that direct blockade of DVC Gcgr signalling negates the acute ability of high‐ vs. low‐protein feeding to reduce plasma glucose concentration, indicating that the elevated circulating glucagon during high‐protein feeding acts in the brain to lower plasma glucose levels. These data revise the physiological role of glucagon and argue that brain glucagon signalling contributes to glucose homeostasis during dietary protein intake. 相似文献
5.
Mareeva T Lebedeva T Anikeeva N Manser T Sykulev Y 《The Journal of biological chemistry》2004,279(43):44243-44249
Antibodies recognizing peptide bound to a major histocompatibility complex (MHC) protein usually have a higher affinity for the composite peptide.MHC (pMHC) ligand than T cell receptors (TCR) with the same specificity. Because the solvent-accessible peptide area constitutes only a small portion of the contacting pMHC surface, we hypothesized that the contribution of the MHC moiety to the TCR-pMHC complex stability is limited, ensuring a small increment of the binding energy delivered by the peptide to be distinguishable by the TCR or the peptide-specific antibody. This suggests that the gain in affinity of the antibody-pMHC interaction can be achieved through an increase in the on-rate without a significant change in the off-rate of the interaction. To test the hypothesis, we have analyzed the binding of an ovalbumin peptide (pOV8) and its variants associated with soluble H-2Kb protein to the 25-D1.16 monoclonal antibody and compared it with the binding of the same pMHC complexes to the OT-1 TCR. This comparison revealed a substantially higher on-rate of the antibody-pMHC interaction compared with the TCR-pMHC interaction. In contrast, both the antibody and the TCR-pMHC complexes exhibited comparably fast off-rates. Sequencing of the 25-D1.16 VH and VL genes showed that they have very few somatic mutations and those occur mainly in framework regions. We propose that the above features constitute a signature of the recognition of MHC-bound peptide antigens by TCR and TCR-like antibodies, which could explain why the latter are rarely produced in vivo. 相似文献
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Laman AG Shepeliakovskaia AO Ulitin AB Markova EV Mareeva TIu Bystrov NS Brovko FA Nesmeianov VA 《Bioorganicheskaia khimiia》2002,28(2):126-134
To develop a phage display of single-chain antibodies (scFv), fractions of total cell DNA and RNA were obtained from splenocytes of naive mice. The DNA fragments encoding variable regions of light and heavy immunoglobulin chains were amplified and isolated using primers specific to the conservative regions of these genes. The construction of the library was based on the principle of stochastic combining of the DNA fragments encoding the light and heavy antibody chains with the DNA linker, whose structure corresponded to the (Gly4Ser)3 sequence. The scFv library was constructed using the E. coli TG1 strain and the phagemid vector pHEN1. The repertoire of the library exceeded 5 x 10(7) independent recombinant clones. The clones producing antibodies to the granulocyte colony-stimulating human factor were isolated. The affinity constants of the resulting scFv were in the range of 2 x 10(4) to 1.8 x 10(7) M-1. 相似文献
8.
Abstract: Dry biofilm on rocks and other substrata forms an important drought refuge for benthic algae in intermittent streams following the cessation of flow. This dry biofilm is potentially susceptible to disturbance from bushfires, including direct burning and/or scorching and damage from radiant heat, particularly when streams are dry. Therefore, damage to dry biofilms by fire has the potential to influence algal recolonization and assemblage structure in intermittent streams following commencement of flow. The influence of fire on benthic algal assemblages and recolonization was examined in intermittent streams of the Grampians National Park, Victoria, Australia, using a field survey and manipulative field experiment. The field survey compared assemblages in two intermittent streams within a recently burnt area (within 5 months of the fire) with two intermittent streams within an unburnt area. The two burnt streams were still flowing during the fire so most biofilms were not likely to be directly exposed to flames. Considerable site‐to‐site and stream‐to‐stream variation was detected during the field survey, which may have obscured potential differences attributable to indirect effects of the fire. The manipulative field experiment occurred in two intermittent streams and consisted of five treatments chosen to replicate various characteristics of bushfires that may influence dry biofilms: dry biofilm exposed directly to fire; dry biofilm exposed to radiant heat; dry biofilm exposed to ash; and two procedural controls. After exposure to the different treatments, rocks were replaced in the streams and algae were sampled 7 days after flow commenced. Differences occurred across treatments, but treatment differences were inconsistent across the two streams. For example, direct exposure to fire reduced the abundance of recolonizing algae and altered assemblage structure in both streams, while radiant heat had an effect on assemblage structure in one stream only. The manipulative field experiment is likely to have represented the intensity of a small bushfire only. Nonetheless, significant differences across treatments were detected, so these experimental results suggest that fire can damage dry biofilms, and hence, influence algal recolonization and assemblage structure in intermittent streams. 相似文献
9.
Fokin AV Afonin PV Mikhaĭlova IIu Tsygannik IN Mareeva TIu Nesmeianov VA Pangborn W Lee N Duax W Siszak E Pletnev VZ 《Bioorganicheskaia khimiia》2000,26(8):571-578
The three-dimensional structure of the antigen-binding fragment of a monoclonal antibody to human interleukin-2 was determined in two crystal forms by the X-ray method of molecular replacement at 2.2 and 2.9 A resolutions. The spatial structure of the protein and the stereochemistry of its antigen-binding site were analyzed. 相似文献
10.
Priscilla TY Law Siaw Shi Boon Chenghua Hu Raymond WM Lung Grace PY Cheung Wendy CS Ho Zigui Chen Paola Massimi Miranda Thomas David Pim Lawrence Banks Paul KS Chan 《Journal of cellular and molecular medicine》2019,23(2):1517-1527
Human papillomavirus 58 (HPV58) ranks the second or third in East Asian cervical cancers. Current studies on HPV58 are scarce and focus on the prototype. Previously, we identified the three most common circulating HPV58 E7 strains contained amino acid alterations: G41R/G63D (51%), T20I/G63S (22%) and T74A/D76E (14%) respectively. Among them, the T20I/G63S variant (V1) had a stronger epidemiological association with cervical cancer. We therefore suggested that V1 possessed stronger oncogenicity than the other two variants. Here, we performed phenotypic assays to characterize and compare their oncogenicities with HPV58 E7 prototype. Our results showed that overexpression of V1 conferred a higher colony‐forming ability to primary murine epithelial cells than prototype (P < 0.05) and other variants, implicating its higher immortalising potential. Further experiments showed that both V1 and prototype enhanced the anchorage‐independent growth of NIH/3T3 cells (P < 0.001), implicating their stronger transforming power than the two other variants. Moreover, they possessed an increased ability to degrade pRb (P < 0.001), which is a major effector pathway of E7‐driven oncogenesis. Our work represents the first study to compare the oncogenicities of HPV58 E7 prototype and variants. These findings deepened our understanding of HPV58 and might inform clinical screening and follow‐up strategy. 相似文献