Imidazole buffer

Figure 8 Swelling of hybrid hydrogels in response to competing metal-chelating ligand. The hydrogels were prepared from HPMA-DAMA copolymers, Ni(II), and TEK42 coiled coil. The gels were swollen in PBS (pH 7.4) at 25°C. The arrow indicates the addition of 100 mM buffered imidazole.

The buffered, imidazole-catalyzed hydrolysis of trifluoroacetanilides appears to be a result of the complexaUon of the carbonyl group by the imidazole nucleus (however, see reference 61) Evidence for such a complex was obtained spectro... 

On examination of a scope of buffers, imidazole-HN03 buffer gave the best result and the effect of different concentrations of imidazole were examined and the largest signal-to-noise ratio (S/N) was obtained at 20 mmol/L. The effect of the buffer pH was also examined, both peak height and S/N ratio increased with increasing pH up to 8.0, but taking the durability of the ODS colunrn into consideration, pH value of... 

Although thermal stability is less likely to be an issue with inorganic buffers, imidazole is known to be unstable at high temperatures, and little work has been done on the high temperature stability of the commonly used Good buffers. 

The bimodal profile observed at low catalyst concentration has been explained by a combination of two light generating reactive intermediates in equihbrium with a third dark reaction intermediate which serves as a way station or delay in the chemiexcitation processes. Possible candidates for the three intermediates include those shown as "pooled intermediates". At high catalyst concentration or in imidazole-buffered aqueous-based solvent, the series of intermediates rapidly attain equihbrium and behave kineticaHy as a single kinetic entity, ie, as pooled intermediates (71). Under these latter conditions, the time—intensity profile (Fig. 2) displays the single maximum as a biexponential rise and fall of the intensity which is readily modeled as a typical irreversible, consecutive, unimolecular process ... 

Finally, students can be critics of published work, and perhaps have already encountered papers in the literature with questionable features. I invite reference to the paper, On the Mechanism of Catalysis by Ribonuclease Cleavage and Isomerization of the Dinucleotide UpU Catalyzed by Imidazole Buffers [Anslyn, E. Breslow, R. J. Am. Chem. Soc. 1989, III, 4473 1482]. A useful exercise is to list any flaws. Any such criticisms can then be compared with those raised in the article, Imidazole Buffer-Catalyzed Cleavage and Isomerization Reactions of Dinucleotides The Proposed Mechanism Is Incompatible with the Kinetic Measurements [Haim, A. J. Am. Chem. Soc. 1992,114, 8383-8388]. 

The P-alanyl dipeptides carnosine and anserine (A -methylcarnosine) (Figure 31-2) activate myosin ATPase, chelate copper, and enhance copper uptake. P-Alanyl-imidazole buffers the pH of anaerobically contracting skeletal muscle. Biosynthesis of carnosine is catalyzed by carnosine synthetase in a two-stage reaction that involves initial formation of an enzyme-bound acyl-adenylate of P-alanine and subsequent transfer of the P-alanyl moiety to L-histidine. 

Fig. 3. QAE-Sephadex gradient separation of the B fruit extract. An 18 mg (uronic acid equivalents) sample of extract was dissolved in 20 ml of 125 mM imidazole-HCl buffer (pH 7.0) and applied to the column. The column was then eluted with 50 ml 125 mM buffer followed by a 125 mM to 1.5 M buffer gradient (500ml), and, finally, 50 ml of 1.5 M buffer. Fractions of 5 ml were collected and assayed for uronic acids. Groups of fractions (26-41, 45-50, 53-75 and 84-100) were pooled, concentrated by ultrafiltration and analyzed by HPLC.

Imidazole-HCl soluble polysaccharides Most of the polysaccharides of this group didn t elute from the Q-Sepharose column with 10 mM buffer (Table 3). The glycosyl composition (Table 4) shows that these polysaccharides are homogalacturonans and ramnogalacturonans with... 

Amino acids such as glycine, alanine, or phenylalanine have been reacted to polypeptides by means of CDI in aqueous imidazole buffer.[49]... 

Amino acids containing nucleobases like uracil and adenine, as well as imidazole, such as / -(uraciM-yl)-a-alanine, j5-(adenin-9-yl)-a-alanine, and j8-(imidazol-l-yl)-a-alanine, can also be polycondensed by CDI in aqueous imidazole buffer solution at pH 6.8 at 0 °C. The polycondensation leads to low conversion (yields of polymer 1% after four days), but pure polypeptides resulted from the reaction. Thus, compared to other alternative procedures for polycondensation, that using CDI proved to be the most effective 503... 

Resuspend the resin in 50 /A of elution buffer E (20 mM Tris-HCl [pH 7.5], 100 mM KC1, 5 mM MgCl2, 0.5 mM /J-mercaptoethanol, 1 mM phenylmethylsulfonyl fluoride, 250 mM imidazole, 10% (v/v) glycerol, 1X Complete Protease Inhibitor Mix tablets [Roche]), briefly vortex, and elute the bound proteins by mixing on a rotator at 4° for 20 min. Please note that a concentration of imidazole and the kind of Roche tablets differs from BB buffer. 

Typically, 15 [A of Ni-NTA beads are washed twice with His-pull down buffer supplement with 20 mM imidazole. Total cell lysates are added to the beads and the contents/tube is rotated for 1 to 1.5 h at 4°. The beads are washed twice with the buffer and once with TKD the rest of the procedure is the same as previously described. 

Electrophoretic band-shift The reaction mixtures contain 20 pi of 50 mM imidazole-HCl (pH 7.5) buffer, 50 mM NH4C1, 10 mM Mg acetate, and 1 pM each IF2 and f[35S]Met-tRNAmetf. After 10 min incubation at 37°,... 

Add an additional 20 pi of 0.1M imidazole, pH 6.0. Mix and react for at least 2 hours at room temperature. The additional buffer prevents pH drift during the carbodiimide reaction. 

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