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We have examined the competitive binding of oxygen and carbon monoxide to the multisubunit hemocyanin of the tarantula Eurypelma californicum. Employment of high-precision thin-layer methods has enabled detailed characterization of the pure oxygen and pure carbon monoxide binding curves, as well as binding curves performed under mixed-gas conditions. The pure oxygen binding curve and the displacement of oxygen by carbon monoxide at full ligand saturation are highly cooperative, but in the absence of oxygen, carbon monoxide binds noncooperatively. The results were analyzed globally within the framework of a nested allosteric model [Robert, C.H., Decker, H., Richey, B., Gill, S.J., & Wyman, J. (1987) Proc. Natl. Acad. Sci. U.S.A. 84, 1891-1895] which takes into account the hierarchy of subunit structure present in the macromolecule. The use of two ligands enables one to recognize two distinct levels of allosteric interaction functioning in the protein assembly. The binding characteristics of the allosteric states demonstrated for Eurypelma follow a similar pattern as those found earlier for Homarus americanus. 相似文献
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Bini Mathew Timothy S. Snowden Michele C. Connelly R. Kiplin Guy Robert C. Reynolds 《Bioorganic & medicinal chemistry letters》2018,28(12):2136-2142
Non-steroidal anti-inflammatory drugs (NSAIDs) have a variety of potential indications that include management of pain and inflammation as well as chemoprevention and/or treatment of cancer. Furthermore, a specific form of ibuprofen, dexibuprofen or the S-(+) form, shows interesting neurological activities and has been proposed for the treatment of Alzheimer’s disease. In a continuation of our work probing the anticancer activity of small sulindac libraries, we have prepared and screened a small diversity library of α-methyl substituted sulindac amides in the profen class. Several compounds of this series displayed promising activity compared with a lead sulindac analog. 相似文献
65.
Evaluation of the use of malic acid decarboxylase‐deficient starter culture in NaCl‐free cucumber fermentations to reduce bloater incidence 下载免费PDF全文
Y. Zhai I.M. Pérez‐Díaz J.T. Diaz R.L. Lombardi L.E. Connelly 《Journal of applied microbiology》2018,124(1):197-208
Aims
Accumulation of carbon dioxide (CO2) in cucumber fermentations is known to cause hollow cavities inside whole fruits or bloaters, conducive to economic losses for the pickling industry. This study focused on evaluating the use of a malic acid decarboxylase (MDC)‐deficient starter culture to minimize CO2 production and the resulting bloater index in sodium chloride‐free cucumber fermentations brined with CaCl2.Methods and Results
Attempts to isolate autochthonous MDC‐deficient starter cultures from commercial fermentations, using the MD medium for screening, were unsuccessful. The utilization of allochthonous MDC‐deficient starter cultures resulted in incomplete utilization of sugars and delayed fermentations. Acidified fermentations were considered, to suppress the indigenous microbiota and favour proliferation of the allochthonous MDC‐deficient Lactobacillus plantarum starter cultures. Inoculation of acidified fermentations with L. plantarum alone or in combination with Lactobacillus brevis minimally improved the conversion of sugars. However, inoculation of the pure allochthonous MDC‐deficient starter culture to 107 CFU per ml in acidified fermentations resulted in a reduced bloater index as compared to wild fermentations and those inoculated with the mixed starter culture.Conclusions
Although use of an allochthonous MDC‐deficient starter culture reduces bloater index in acidified cucumber fermentations brined with CaCl2, an incomplete conversion of sugars is observed.Significance and Impact of the Study
Economical losses due to the incidence of bloaters in commercial cucumber fermentations brined with CaCl2 may be reduced utilizing a starter culture to high cell density. 相似文献66.
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Bajaj A Connelly SM Gehret AU Naider F Dumont ME 《Biochimica et biophysica acta》2007,1773(6):707-717
The yeast pheromone receptor, Ste2p, is a G protein coupled receptor that initiates cellular responses to alpha-mating pheromone, a 13 residue peptide that carries a net positive charge at physiological pH. We have examined the role of extracellular charged groups on the receptor in response to the pheromone. Substitutions of Asn or Ala for one extracellular residue, Asp275, affected both pheromone binding and signaling, suggesting that this position interacts directly with ligand. The other seven extracellular acidic residues could be individually replaced by polar residues with no detectable effects on receptor function. However, substitution of Ala for each of these seven residues resulted in impairment of signaling without affecting pheromone binding, implying that the polar nature of these residues promotes receptor activation. In contrast, substitution of Ala for each of the six positively charged residues at the extracellular surface of Ste2p did not affect signaling. 相似文献
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