Buffered systems activities

An important physiological buffering system active in the blood is the bicarbonate system. Bicarbonate (H2CO3) is a weak acid that is involved in maintaining the pH of human blood in the neighborhood of 7.4. The acid-base equilibration for bicarbonate is expressed... 

However, the ability to act as a builder encompasses much more than so far been mentioned. Builders influence the coagulation of solid soil, often form a buffer system, and promote the soil suspending activity of washing liquors. They are further able to reduce the catalytic effect of ferric and manganic ions. Thus they support the stabilization of peroxides in detergents. Similarly, rancidness caused by catalytic processes of soap and fragrances can be avoided. 

Assays. Protein concentrations were measured by the method of Bradford (18) and the various contractile protein ATPase activities by tRe method of Martin and Doty (19). Gel electrophoresis was carried out by the method of Ames (20) on 1.5 ran polyacrylamide slabs using the discontinuous SDS buffer system of Laemnli (21). Dried gels were scanned at 550 nm for densiometry measurements. 

MgCl2 (1 and lOmM) enhanced the glucuronidation activity of HLMs toward estradiol, acetaminophen and morphine [22]. So it is beneficial to include MgCl2 in glucuronidation reactions. However, it may not be feasible to add MgCl2 to a high pH buffer system due to... 

Dissolve the toxin to be conjugated in 0.1M sodium phosphate, 0.15 MNaCl, pH 7.5, at a concentration of lOmg/ml. Some protocols use as an SPDP reaction buffer, 50mM sodium borate, 0.3 M NaCl, 0.5 percent n-butanol, pH 9.0. Both buffer systems work well for the NHS ester modification reaction, although the pH 9 buffer is at the higher end of effective derivatization with active esters, since the hydrolysis rate is dramatically increased at this level of alkalinity. 

Commonly used cells use Pt/C>2 or Pt/air as reference electrodes. At very low partial pressures of oxygen, care must be taken to avoid direct permeation of oxygen through stabilized zirconia from the air (or reference electrode) [74, 75]. The effect may be avoided by applying reference electrodes with activity near that observed at the working electrode. A well-defined buffer system like a metal-metal... 

The pH optimum of an enzyme will often vary from one substrate to another and must be determined for each substrate. The buffer system used will often affect the overall activity of an enzyme and may alter its pH optimum. In general, the amino buffers such as glycylglycine and tricine, etc. (Table 8.2) result in a greater enzyme activity than do the simple inorganic buffers such as phosphate and carbonate. Buffers are most effective over a narrow pH range (approximately two units) which centres on their pK, value. Those buffers with pKa values similar to the known optimum pH of the enzyme should be tested for their effect on the activity of the enzyme over a limited pH range. 

RNA amplification by PCR has been facilitated by the use of a single heat-stable enzyme. Thus, DNA polymerase from Thermus thermophilus, which has enhanced reverse transcriptase (rT) activity in presence of manganese, can be used with one buffer system. The high temperature used for rT (70°C) to produce a complementary DNA copy from RNA, and the subsequent amplification of DNA at 60°C, increases efficiency by destabilizing secondary structures in the RNA template. This procedure has been used for the amplification of hepatitis C viral RNA (Yl). 

The electrical current in an electrophoresis cell is carried largely by the ions supplied by buffer compounds. Proteins constitute only a small proportion of the current-carrying ions in an electrophoresis cell. Buffer systems for electrophoresis are classified as either continuous or discontinuous, depending on whether one or more buffers are used. They are further classified as native or denaturing, depending on whether their compositions maintain or destroy protein structure and activity. 

Vemuri et al.17 looked at the effects of various cryoprotectants, freezing rates, and buffer systems on the shelf-life of lyophilized recombinant alphar antitrypsin (rAAT). Alpharantitrypsin (AAT) is labile in solution therefore, a more stable presentation was required. A competitive ELISA was used to measure total AAT in a sample. The AAT in the sample competed with HRP-labeled AAT for binding to the specific antibody. A stable formulation containing lactose as a cryoprotectant was found that maintained the protein s specific activity. 

Fig. 11. A plot of proton activity pan as a function of electromotive force (mV) for the ethylene glycol-glass electrode at +21°C and — 19°C. The response of the electrode (R ) is given by the slope of the line. The concentration of ethylene glycol is 50% by volume. The points are the experimental results in different buffer systems (a, chloroacetate b, acetate c, cacodylate d, Tris) the straight lines represent ideal behavior.

Enzyme activity measurements are greatly affected by buffer systems used in analysis. In measuring alkaline phosphatase activity under optimal conditions, ethylaminoethanol buffer yielded activity 3.8 times... 

Each point on the activity curve of a test compound represented the average of the results of each concentration tested in triplicate, air-induction was strongly pH dependent (24, our results, data not shown), so the buffer system was used to minimize variation in pH. Standard deviations rarely reached 10%, the average being 4.7% (n = 92) for results of 100 Miller units and above. 

Air oxidation of synthetic fully reduced co-conotoxin GVIA (9) (Scheme 4), a 27-residue peptide, 64 generated a main product that possessed the identical biological activities as the natural product whose cystine framework was determined with the synthetic compound. 65 The choice of buffer system and peptide concentration can, however, dramatically affect the folding efficiency when the DMSO-mediated oxidation method was applied. 661... 

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