Buffer solution phosphate-type

A novel ring-opening reaction of oxirans, catalysed by copper and pyridine, generates c/s-diols under mild conditions. The bicyclic epoxides (186 = 1 or 2) yield (187 n = 1) (95%) and (187 = 2) (85%) in neutral, phosphate-buffered, solution. This type of reaction may have some relevance to the metabolic pathways for fused aromatic compounds, which are thought to proceed via arene oxides and diol epoxides. The catalyst system may be used to add OH", Cr, or MeO regiospecifically to the benzylic centre of indene oxide, with proton addition to the oxygen atom of oxiran. 

Each buffer system is generally applicable over a limited range, viz., about 2 units of pH, but by making suitable mixtures of acids and acid salts, whose pfca values differ from one another by 2 units or less, it is possible to prepare a universal buffer mixture by adding a pre-deter-mined amount of alkali, a buffer solution of any desired pll from 2 to 12 can be obtained. An example of this type of mixture is a system of citric acid, diethylbarbituric acid (veronal), boric acid and potassium dihydrogen phosphate this is virtually a system of seven acids whose exponents are given below. 

However, at zero buffer concentration the maximum stability was shifted to a pH of 5.85. Ampicillin was stable in solutions at pH 3 - 9 when stored for 24 hours at 5°C and 25°C. Ampicillin was unstable in solutions at pH 10 when stored at above conditions. Bundgaard demonstrated a metastable intermediate in iso-meration of penicillin to penicillenic acid in aqueous solutions. The degradation of ampicillin trihydrate in solution is greatly influenced not only by pH, but also by the types of buffer salts used j. 2-Amino-2 (hydroxymethyl)-1,3-propanediol (Tris) buffer of pH 7 is highly deleterious to the stability of ampicillin, but not at pH 5.0. Citrate presents a converse pattern in that ampicillin is relatively stable at pH 7 but not so at pH 5. Phosphate is intermediate in action but tends to resemble the Tris pattern. Jacobson and Russo-Alesi prepared ampicillin trihydrate solutions at a concentration of 5 mg/ml by dissolving it in buffer solutions of pH 5.0 or pH 7.0 prepared from O.lM sodium acetate and acetic acid and in buffers of pH 8.0 or pH 8.8 prepared from O.lM 2-amino-2 (hydroxy methyl)- ,... 

Nature of the Suppression Effect of Caraway Seed. Since analytical data demonstrated that the addition of caraway seeds depleted volatile sulfur compounds in sauerkraut, this effect was studied using aqueous extracts of caraway seeds and authentic volatile sulfur compounds in model systems. Cell-free crude caraway seed extracts were prepared by blending the unheated spice seeds with chilled (ice water) potassium phosphate solutions (50 mM, pH 7) containing 0.1 M potassium chloride (1 5, w/w) in a cold room (4°C). Homogenates were then clarified by filtration and centrifugation as described by Chin (21). Data in Figure 7 shows that unheated and heat-treated crude caraway seed extracts (1 mL in a 3 mL buffered solution, pH 8) removed methanethiol (10 pg) from the headsapce in closed serum-type vials (120 mL) at 37 which indicated that both heat-stable and heat-labile entities in caraway seed were involved in the depletion of methanethiol. 

The diagnostic features of this analysis have been used by Chao et al. [1982] in their investigation of the growth of passive films on nickel and Type 304 stainless steel in borate and phosphate buffer solutions. Typical complex plane and... 

ATP formation on creatine and MgCl2 concentrations was also examined and the results are summarized in Fig. 6 and Fig. 7. Without creatine, ATP formation occurred later and more slowly but at the same high conversion level. The addition of excess creatine caused acceleration of ATP formation. Without creatine, the induction period took two times longer. As shown in the time conversion curve with heptakis-(2,6-dimethyl)-g-CD (DM-g-CD) without creatine, ATP formation occurred later and more slowly at the same conversion level. Besides these examinations, the effect of O2, buffer solution and temperature were observed. Without O2, the reaction did not proceed. Ionic strength and pH of the phosphate buffer and reaction temperature were optimum under the present conditions. The results obtained here showed the same kind of catalytic activity of the CD in the equilibrium between ADP and ATP in this scheme 1. This new type of transphosphorylation seems to be a... 

Hydrolysis is not only dependent on the pH (catalysis by H or OH ions), but may also be catalysed by certain ions, such as phosphate and acetate. In general, higher ion concentrations promote hydrolysis reactions [12]. In a buffered solution, hydrolysis thus depends on the pH, the type of buffer and the concentration of that buffer. 

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