Protein first order release

From this figure it appears that for gels with a high initial water content a first order release of the protein is observed (diffusion controlled release), whereas for gels with a lower initial water content an almost zero order release is observed for 35 days (degradation controlled release). 

While the above discussion centered on the rate of disruption, the objective is usually to attain at least 90 percent release of the valuable protein from the cells. Cell disruption with protein solubilization is considered to be first order in amount of protein remaining [Currie et al., Biotechnol. Bioeng., 14, 725 (1972)] ... 

In a simple model of homogenization in a French press, the process of the disruption of the cell wall is modeled by a first-order law. Then, the amount of protein released, R, varies with the number of passes of broth through the homogenizer, N [Eq. (8.58)], where Rm3X is the maximum amount of protein obtainable through homogenization and k is a constant. 

When C was introduced into the methyl group of S-adenosylmethionine and its rate of reaction with catechol 0-methyltransfer-ase was compared with that of the normal C-containing substrate, the expected effect on Tinax expressed as a first-order rate constant, was seen k- 2 / 13 = 1.09 + 0.05. This effect is small but it can be measured reliably and establishes that the methyl transfer step rather than substrate binding, product release, or a conformational change in the protein is rate limiting. ... 

Proteins in the body undergo continual breakdown and synthesis. Insulin is a polypeptide hormone that stimulates fat and muscle to take up glucose. Once released from the pancreas, it has a first-order half-life in the blood of 8.0 min. To maintain an adequate blood concentration of insulin, it must be replenished in a time interval equal to 1 /k. How long is this interval ... 

In principle, any extraction method can be optimized accordingly as long as suitable and validated expressions for protein release and enzyme inactivation rates are available. In practice Eqs. 2.5 and 2.6 can be complex and depend on many operational variables (Currie et al. 1972). If both protein release and enzyme inactivation are assumed to proceed according to first order kinetics ... 

Homogenizer first order process In (Rmax/( f max - R) oc p where = maximum amount of released protein/unit mass R = amount of protein released/ unit mass at time t p = pressure. 

ADP-ribose-protein conjugate proved stable for at least 12 hr at pH 4.0 and 4°C, as well as in the presence of 1 M ammoniiun chloride at neutral pH and 37°C (the latter condition henceforth will be referred to as "in the absence of hydroxylamine"). The linkage is moderately labile to 1 M and 3 M neutral hydroxylamine at 37°C, with a half-life in 3 M hydroxylamine of 6.0 hr. In 4 M hydroxylamine the half-life of the linkage is 4.0 hr. At basic pH, radioactivity is released very fast from the protein, with a half-life at pH 9.3 of 50 min, and of 20 min in 1 M sodium hydroxide. This is in agreement with and extends our previous findings (4). The release of protein-boimd radioactivity follows single first-order kinetics under aU conditions. This indicates that only one class of mono(ADP-ribosylated) proteins has been formed by incubation of SMP with NAD+. 

First and second-order processes are often coupled together through common chemical intermediates to form more complex mechanisms. There are numerous examples, e.g. the coupling between second-order complex formation, or electron-transfer reactions, and first-order protein conformational changes. The analysis of some of these is given elsewhere (see Chapter 9). Here we consider a mechanism common to many proteases in which the enzyme and its substrate come together in a second-order process which leads to acylation of the enzyme and release of a product. Pi. The atyl enzyme is now hydrolysed to yield a second product, P2, and the original enzyme that enters a second cycle. This may be written as follows ... 

In addition to reacting with enzymes, as described below, both 3 -and 5 -FSBA have been observed to react with certain commonly used buffers, with the concomitant release of fluoride ion in accordance with first-order kinetics. In the case of 3 -FSBA in buffers at pH 8 and 25°, the half-life is about 37 min for 0.01 M potassium phosphate and 0.01 M Tris acetate, whereas triethanolamine chloride at the same pH reacted more vigorously. In 0.01 M sodium barbital at pH 8, the half-life for 3 -FSBA was about 63 min this buffer has proved to be satisfactory for reaction with proteins. The 5 -FSBA does not react as readily with buffers, and at 30° in 0.01 M sodium barbital at pH 7.6, containing 0.2 M KCl and 15% dimethylformamide, its half-life was found to be about 8.4 hr. The reaction with the 3 - and 5 -FSBA might be expected to involve the unprotonated form of susceptible amino acids, and therefore the rate of reaction in many cases may proceed more rapidly at pH values that are on the alkaline side of neutrality. However, it must be kept in mind that the ester linkage of both 3 - and 5 -FSBA has limited stability below pH 6 and above pH 9. 

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