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101.
H H Jawad D E Watt 《International journal of radiation biology and related studies in physics, chemistry, and medicine》1986,50(4):665-674
Measurements have been made of the inactivation of the metallo-enzyme dihydro-oratic dehydrogenase in solution by characteristic X-rays at energies above and below the K absorption edge of the constituent iron atom. From the dose-survival curves and knowledge of the equilibrium electron spectrum generated by the X-ray 'field', inactivation cross-sections are deduced and expressed in terms of intrinsic efficiencies for the various proposed direct and indirect mechanisms of inactivation. It is concluded that the inactivation is caused by direct X-ray interaction in an area equivalent to about 30 per cent of the mean geometrical cross-section of the molecule, and is independent of whether the target is wet or dry. The contribution from Auger electron cascades, Coulomb charges etc. initiated by the inner-shell vacancy in the metal atom is negligible--possibly due to saturation effects. It seems that the presence of the metal atom simply serves to enhance the overall interaction probability with the molecule in a manner consistent with expectations from the photon absorption coefficients. No anomalously large damage is detected. These conclusions are supported by comparison with published results for other metallo-enzymes and bromine-loaded bacteria. 相似文献
102.
Hilariòn Vàsquez Chayma Ouhibi Marine Forges Yves Lizzi Laurent Urban Jawad Aarrouf 《Journal of Phytopathology》2020,168(9):524-532
Preharvest hormetic doses of UV-C radiation can decrease the susceptibility of tomato leaves to Botrytis cinerea L. infection. UV-C light treatments have been shown to be very effective for reducing disease development in several species, including tomato (Solanum lycopersicum L.). Treating cultivated tomato plants with UV-C light is of interest not only because of the disinfecting effects of UV-C light but also because of its ability to stimulate plant defences (SDP) against diseases, provided that the applied doses are high enough to be effective while low enough to prevent deleterious effects. In the present study, the effects of UV-C light on plants were evaluated by biochemical analyses, including analyses of the activities of antioxidant enzymes and phenylalanine lyase (PAL); the concentration of malondialdehyde (MDA), an indicator of membrane integrity; and chlorophyll fluorescence parameters, such as the maximum quantum efficiency of photosystem II (FV/FM) and the Strasser performance index (PI). In this work, treatments with single doses of 0.85 kJ/m2 of UV-C light were found to significantly increase plant defences against B. cinerea, reducing the affected leaf area by 51% compared to the affected area of control plants. This decrease in susceptibility was associated with increased PAL activity and the amount of bound phenolics compared to levels in control plants (not treated with UV-C). 相似文献
103.
Lipid interference in the radioimmunoassay of steroids can cause an apparent variation in post-prandial serum concentrations of unconjugated estriol. The effects of increased concentrations of dextran-coated charcoal (15--60 g/l) in the radioimmunoassay of estriol standards with and without triglycerides were studied. All concentrations of dextran-coated charcoal used in this study eliminated the previously observed effects of estriol-lipid partitioning. When we used similar concentrations of dextran-coated charcoal, we found that serum cortisol levels in pregnant women declined significantly during the day (P less than 0.001), but no significant variation in estriol concentrations was observed. These results indicate that the previously reported diurnal variation in serum unconjugated estriol concentrations attributed to steroid-lipid partitioning can be eliminated by increasing the concentration of dextran-coated charcoal in assays using this method of separation. 相似文献
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Khan Jawad A. Sohail Azmat Jayaraman Kumaresan Szöllősi Dániel Sandtner Walter Sitte Harald H. Stockner Thomas 《Neurochemical research》2020,45(6):1387-1398
Neurochemical Research - Neurotransmitter:sodium symporters are highly expressed in the human brain and catalyze the uptake of substrate through the plasma membrane by using the electrochemical... 相似文献
106.
Daptomycin is a lipopeptide antibiotic that is used clinically to treat severe infections caused by Gram-positive bacteria. Its bactericidal action involves the calcium-dependent binding to membranes containing phosphatidylglycerol, followed by the formation of membrane-associated oligomers. Bacterial cells exposed to daptomycin undergo membrane depolarization, suggesting the formation of channels or pores in the target membranes. We here used a liposome model to detect and characterize the permeability properties of the daptomycin pores. The pores are selective for cations, with permeabilities being highest for Na+, K+, and other alkali metal ions. The permeability is approximately twice lower for Mg++, and lower again for the organic cations choline and hexamethonium. Anions are excluded, as is the zwitterion cysteine. These observations account for the observed depolarization of bacterial cells by daptomycin and suggest that under typical in vivo conditions depolarization is mainly due to sodium influx. 相似文献
107.
Hatice Karauzum Rajan P. Adhikari Jawad Sarwar V. Sathya Devi Laura Abaandou Christian Haudenschild Mahta Mahmoudieh Atefeh R. Boroun Hong Vu Tam Nguyen Kelly L. Warfield Sergey Shulenin M. Javad Aman 《PloS one》2013,8(6)
Previous efforts towards S. aureus vaccine development have largely focused on cell surface antigens to induce opsonophagocytic killing aimed at providing sterile immunity, a concept successfully applied to other Gram-positive pathogens such as Streptococcus pneumoniae. However, these approaches have largely failed, possibly in part due to the remarkable diversity of the staphylococcal virulence factors such as secreted immunosuppressive and tissue destructive toxins. S. aureus produces several pore-forming toxins including the single subunit alpha hemolysin as well as bicomponent leukotoxins such as Panton-Valentine leukocidin (PVL), gamma hemolysins (Hlg), and LukED. Here we report the generation of highly attenuated mutants of PVL subunits LukS-PV and LukF-PV that were rationally designed, based on an octameric structural model of the toxin, to be deficient in oligomerization. The attenuated subunit vaccines were highly immunogenic and showed significant protection in a mouse model of S. aureus USA300 sepsis. Protection against sepsis was also demonstrated by passive transfer of rabbit immunoglobulin raised against LukS-PV. Antibodies to LukS-PV inhibited the homologous oligomerization of LukS-PV with LukF-PV as well heterologous oligomerization with HlgB. Importantly, immune sera from mice vaccinated with the LukS mutant not only inhibited the PMN lytic activity produced by the PVL-positive USA300 but also blocked PMN lysis induced by supernatants of PVL-negative strains suggesting a broad protective activity towards other bicomponent toxins. These findings strongly support the novel concept of an anti-virulence, toxin-based vaccine intended for prevention of clinical S. aureus invasive disease, rather than achieving sterile immunity. Such a multivalent vaccine may include attenuated leukotoxins, alpha hemolysin, and superantigens. 相似文献
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Ping Shi J. Max Goodson Mor-Li Hartman Hatice Hasturk Tina Yaskell Jorel Vargas Maryann Cugini Roula Barake Osama Alsmadi Sabiha Al-Mutawa Jitendra Ariga Pramod Soparkar Jawad Behbehani Kazem Behbehani Francine Welty 《PloS one》2015,10(9)