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these can be hydrolysed but the reaction with acetate anion is more efficient than that with hydroxide and so the acetate esters are usually the initial products in commercial syntheses.
اینها را می توان هیدرولیز کرد اما واکنش با آنیون استات کارآمدتر از واکنش با هیدروکسید است و بنابراین استرهای استات معمو
最后更新： 2022-09-10
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the most frequently used methods for estimating orotic acid in milk have been variations of a colorimetric procedure. assay here involves the isolation of orotic acid by dialysis and anion exchange and silicic acid chromatography.
متداولترین روشها برای تخمین اسید اروتیک در شیر ، تغییرات روش رنگ سنجی بوده است. سنجش در اینجا شامل جداسازی اسید اروتیک توسط دیالیز و تبادل آنیون و کروماتوگرافی اسید سیلیسیک است.
最后更新： 2021-06-10
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) shows the conventional helical screw model [35], [36]. although there are variations on this model, the general 42 ieee transactions on nanobioscience, vol. 4, no. 1, march 2005 idea is that upon depolarization the s4 segment rotates along its axis and at the same time translates as a unit perpendicular to the membrane, thus changing the exposure of the charges from the intracellular to the extracellular solution, effectively translocating 4 per subunit [see fig. 7(a)]. in the original version of the model, the change of exposure required a large 16- translocation of the s4 segment, and the positively charged arginines were making saline bridges with aspartate or gluta- mates residues that had to be broken to initiate the movement. in more recent versions [37]–[39], the charges are in water crevices in both the closed and open position, decreasing the amount of translation required of the s4 segment. fig. 7(b) shows the transporter model [40]–[42]. in the closed position, the charges are in a water crevice connected to the intracellular solution, and in the open position they are in an- other water crevice connected to the extracellular solution. the translocation of the charges is achieved by a tilt and rotation of the s4 segment with little or no translation. in this case, the field is concentrated in a very small region that changes from around the first charge in the closed state to the fourth charge in the open state. fig. 7(c) shows the paddle model introduced by the mackinnon group [33] where the s4 segment is located in the periphery of the channel and the charges are embedded in the bilayer. the s4 segment makes a large translation such that the most extracellular charge goes from exposed to the extracellular medium in the open state to completely buried in the bilayer in the closed state. the helical screw and transporter models are similar but they differ dramatically from the paddle model in that the gating charges in the paddle model are embedded in the bilayer, while in the helical screw and transporter models, the charges are surrounded by water, anions, or making salt bridges. in con- trast with the transporter model, the helical screw model has in common with paddle models the large translation of the s4 segment. in sections vi-c–vi-e, we will review biophysical experi- ments that were designed to test the topology of the channel and the extent of the conformational changes of the gating charge. in the absence of a native crystal structure, these experiments are the only data that we can use to support or reject the available models of voltage sensor operation.
مدل های مارپیچ و پیچ های حمل و نقل مشابه هستند اما تفاوت های چشمگیری با مدل دست و پا زدن دارند به این دلیل که بارهای دروازه در مدل پارو در لایه دو لایه تعبیه شده است ، در حالی که در مدل های مارپیچ و مارپیچ ، بارها توسط آب ، آنیون ها یا ساختن پل های نمکی. در تطابق با مدل حمل و نقل ، مدل پیچ مارپیچ با مدل های پارویی ترجمه بزرگ قطعه s4 مشترک است. در بخشهای vi c – vi e ، ما تجربه بیوفیزیکی را مرور خواهیم کرد
最后更新： 2021-05-11
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