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61.
Isothermal titration calorimetry (ITC) is a fast and robust method to determine the energetics of association reactions in solution. The changes in enthalpy, entropy and heat capacity that accompany binding provide unique insights into the balance of forces driving association of molecular entities. ITC is used nowadays on a day-to-day basis in hundreds of laboratories. The method aids projects both in basic and practice-oriented research ranging from medicine and biochemistry to physical chemistry and material sciences. Not surprisingly, the range of studies utilizing ITC data is steadily expanding. In this review, we discuss selected results and ideas that have accumulated in the course of the year 2006, the focus being on biologically relevant systems. Theoretical developments, novel applications and studies that provide a deeper level of understanding of the energetic principles of biological function are primarily considered. Following the appearance of a new generation of titration calorimeters, recent papers provide instructive examples of the synergy between energetic and structural approaches in biomedical and biotechnological research. 相似文献
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Mariia Yu. Rybak Oksana P. Kovalenko Michael A. Tukalo 《Journal of molecular biology》2018,430(17):2670-2676
Aminoacyl-tRNA-synthetases are crucial enzymes for initiation step of translation. Possessing editing activity, they protect living cells from misincorporation of non-cognate and non-proteinogenic amino acids into proteins. Tyrosyl-tRNA synthetase (TyrRS) does not have such editing properties, but it shares weak stereospecificity in recognition of d-/l-tyrosine (Tyr). Nevertheless, an additional enzyme, d-aminoacyl-tRNA-deacylase (DTD), exists to overcome these deficiencies. The precise catalytic role of hydroxyl groups of the tRNATyr A76 in the catalysis by TyrRS and DTD remained unknown. To address this issue, [32P]-labeled tRNATyr substrates have been tested in aminoacylation and deacylation assays. TyrRS demonstrates similar activity in charging the 2′ and 3′-OH groups of A76 with l-Tyr. This synthetase can effectively use both OH groups as primary sites for aminoacylation with l-Tyr, but demonstrates severe preference toward 2′-OH, in charging with d-Tyr. In both cases, the catalysis is not substrate-assisted: neither the 2′-OH nor the 3′-OH group assists catalysis. In contrast, DTD catalyzes deacylation of d-Tyr-tRNATyr specifically from the 3′-OH group, while the 2′-OH assists in this hydrolysis. 相似文献
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A new class of antenna chromophores so called ‘tetrazolates’ have not been explored much for lanthanide luminescencent complexes. However, we have already published several articles considering pyridineoxide tetrazolates as sensitizer with lanthanide ions. Although this class of antenna attracted much less attention because of its poor photoluminescence quantum yields (tris‐pyridineoxide tetrazolate europium complex = 13% in solution) we tried and successfully achieved to improve the photoluminescence quantum yields for this particular antenna molecule by replacing coordinated water from the inner coordination sphere of europium ion by introducing phosphine oxides as additional chromophore. In the present article the two bis‐phosphine oxides attach two molecules of tris‐pyridineoxide tetrazolate europium(III) complex which leads to the improvement of the overall molar absorption coefficients as well as photo‐physical properties of the complexes. We found more than two‐fold increase (31% in solution) in photoluminescence quantum yield with one of the coordinated phosphine oxides comparing with that of tris‐pyridineoxide tetrazolate europium(III) complex. 相似文献
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Ruben Girsowicz Oksana Koryachenko Chen Sherman Einav Mayzlish-Gati Tirza Doniger 《Soil & Sediment Contamination》2018,27(3):175-185
The present study evaluated the effect of crude oil contamination on a microbial community in hyper-arid soils. The Evrona Nature Reserve of Israel, situated in the Arava, was exposed twice in the last 40 years to petroleum-hydrocarbon-spill pollution. The first pollution event took place 40 years ago and was never treated, presenting a unique future time-point perspective to the second (2014) contamination event. Soil samples were collected after the second spill, and abiotic properties and bacterial diversity in the sampled soil were analyzed. The results showed that there is a significant decrease over time in the number of observed bacterial species in the contaminated samples, coupled together with bacterial species replacement toward species capable of using source oil as the sole carbon and energy source. The presence of petroleum in soil significantly changed the composition and functional diversity of a microbial community, and the Evrona Nature Reserve is still in the middle of a bioremediation process even 40 years after the crude oil contamination. 相似文献
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This study described a pH-gradient dissolution method combined with flux measurements as an in vitro tool for assessing the risk of bioavailability reduction due to drug-drug interactions (DDI) caused by acid reducing agents (ARAs). The device incorporates absorption chambers into USP II dissolution vessels, with fiber optic UV-probes monitoring concentration in situ. Dosage forms of Genentech BCS class II drugs, GDC-0810, GDC-0941, and compound A, were tested by starting the dissolution in either pH 1.6 or pH 4.0 media then converting to FaSSIF after 30 min. GDC-0810 showed no significant difference in flux between the two conversion experiments. A supersaturation phase was observed for GDC-0941 in the pH 1.6 experiments after media conversion to FaSSIF; however, it did not appear to occur in the pH 4.0 experiment due to low drug solubility at pH 4.0, resulting in a 95% decrease in flux compared to pH 1.6 experiment. The extent of flux reduction and the total accumulated API mass in the absorption chamber agreed well with the 89% reduction in mean Cmax and the 82% reduction in mean AUC from dog PK study between animals treated with pentagastrin and famotidine. Testing of the compound A optimized formulation tablets showed a 25% reduction in flux and in vitro absorbed amount by changing pH 1.6 to 4.0, correlating well with the AUC decrease in clinical studies. Good correlation between in vitro data and in vivo PK data demonstrated the applicability of the method for formulators to develop drug products mitigating DDI from ARAs. 相似文献
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