Maximum specific activity

Urokinase (from human urine) [9039-53-6] Mr 53,000, [EC 3.4.21.31]. Crystn of this enzyme is induced at pH 5.0 to 5.3 (4") by careful addition of NaCl with gentle stirring until the soln becomes turbid (silky sheen). The NaCl concentration is increased gradually (over several days) until 98% of saturation is achieved whereby the urokinase crystallises as colourless thin brittle plates. It can be similarly recrystd to maximum specific activity [104K CTA units/mg of protein (Sherry et al. J Lab Clin Med 64 145 1964)]. [Lesuk et al. Science 147 880 1965 NMR Bogusky et al. Biochemistry 28 6728 1989.] It is a plasminogen activator [Gold et al. Biochem J 262 1989 ]. 

The preparation and use of LiEt3BT and LiAlT4 at maximum specific activity (57.5 Cimmol" ) has also been described. ... 

The maximum specific activities of coelenterazine luciferases appear to be in a range of 1015-1016 photons s 1 mg-1, but much... 

In an ideal pure preparation of Na,K-ATPase from outer renal medulla, the al subunit forms 65 70% of the total protein and the molar ratio of a to is 1 1, corresponding to a mass ratio of about 3 1 [1,5]. Functionally the preparation should be fully active in the sense that each a/ unit binds ATP, Pj, cations and the inhibitors vanadate and ouabain. The molecular activity should be close to a maximum value of 7 000-8 000 Pj/min. The highest reported binding capacities for ATP and phosphate are in the range 5-6 nmol/mg protein and close to one ligand per otjS unit [29], when fractions with maximum specific activities of Na,K-ATPase [40 50 pmo Pj/min mg protein) are selected for assay. 

Radionuclide Half-life Decay Maximum specific activity (GBq mop ) mg GBq mg Ci ... 

Radionuclide Half-life Decay (%) Maximal particle energy (MeV) Theoretical maximum specific activity (Ci/pmole)... 

It is evident from Table 1 that certain limiting factors exist. For example, experiments with bromine-82 are limited to a duration of about one week because of the short half-life. At the other end of the scale, experiments with stable carbon-13 are limited to dilutions of less than x 500. Even with radioactive isotopes the maximum specific activity available may limit dilution though not to the same extent. Thus, chlorine-36 can stand dilutions up to x 107 but tritium can improve on this to a factor of x 1012. 

Another useful quantitative definition of enzyme efficiency is specific activity. The specific activity of an enzyme is the number of enzyme units or katals per milligram of protein. This is a measure of the purity of an enzyme. If a solution contains 20 mg of protein that express 2 units of activity (33 nkatals), the specific activity of the enzyme is 2 units/20 mg = 0.1 units/mg or 33 nkatals/20 mg = 1.65 nkatals/mg. As an enzyme is purified, its specific activity increases. That is, during purification, the enzyme concentration increases relative to the total protein concentration until a limit is reached. The maximum specific activity is attained when the enzyme is homogeneous or in a pure form. 

Consider you want to make 18F for use in PET studies. What would be the maximum specific activity (dpm/g F) of the 18F made by irradiating 1.0 g of KF in a flux of 1010 fast neutrons/cm2-s. You may assume the 18F(n,2n) cross section is 300 millibarns. Consider you want to produce the 18F carrier free (i.e., with no stable fluorine present). Devise a synthetic scheme for producing the carrier-free 18F. Defend your choice of reactions. 

Since the optimal ordinate Ea equals u/2, this permits one from the value of e to judge how far the given catalyst stands from its maximum specific activity. Since the optimal abscissa qbond energy values Qak, Qbk, Qck, and Qi,k, we can expect to obtain the optimum catalyst for a given reaction. 

Bovine plasma albumin and dog serum albumin have been iodinated with di- I-labeled methyl p-hydroxybenzimidate. The authors did not attempt to obtain maximum specific activity, but rather examined the effect of reaction conditions on the rate of amidination and yield of iodinated product. The set of conditions given above is only one of the many tested. It was chosen because it gave the highest incorporation of I. Overall the results showed that the iodination reaction will proceed at pH 7.5-9.5 and... 

Iodide Concentration. The iodide concentration has a major influence on the reaction. This is shown by the data in Table I. Maximum labeling of DNA is obtained when the iodide concentration is 10 M whereas maximum specific activity is obtained when the iodide concentration is 8 X 10- M. 

If C is made from B, the specific activity of C can never rise above S.A. maximum of B. Similarly, the specific activity of D can never be greater than S.A. maximum of C Also, the maximum specific activity of C occurs when the specific activity of C equals the specific activity of B. Similarly, the maximum specific activity of D occurs when the specific activity of D equals the specific activity of C. These observations establish the direct precursor-product relationships between B and C and behveen C and D. 

The term specific activity has several meanings. It may refer to any one of the following radioactivity per unit mass of an element, radioactivity per mass of labeled compound, or radioactivity per unit volume of a solution. The denominator of reference must be specified. In terms of radioactivity per unit mass, the maximum specific activity attainable for each radionuclide is that for the pure radionuclide. For example, pure C has a specific activity of 62Ci/mol or 4400Ci/kg. As usually available, is a tracer for compounds in which it represents only a small fraction of the total carbon, most of which is the natm-aUy occurring mixture of stable and stable C. If there is no stable element present, the radionucfide is said to be carrier free. 

Tab. 10.1 Maximum specific activities of HGL, DGL, HPL and pancreatic extracts (Creon ) on various triglycerides. Specific activities are expressed in international units (1 LJ = lpmol of free fatty acid released per minute) per mg of pure enzyme, except for Creon for which specific activities are expressed in U per mg of pancreatic extract (PE). One Creon 25000 capsule contains 500 mg pancreatic extract and 25000 lipase units measured using olive oil-gum arabic as substrate. This lipolytic activity corresponds to around 8-9 mg of active pancreatic lipase in one capsule of Creon 25000 .

A maximum specific activity of approximately 850 GBq/mg was achieved when irradiation was carried out at a thermal neutron flux of 1 x 10 n-cni -s for 21 d, which corresponds to around 21% of the maximum achievable specific activity. Tlie specific activity of the Lu obtained was significantly higher than the theoretically calculated value under the irradiation conditions employed (7.9 at.%), accounting for only thermal neutron capture. This could perhaps be attributed to the contribution from epithermal neutrons (resonance integral 1087 b), which is not accounted for in theoretical calculations. 

Amax (mmol g-1 min-1) Maximum specific activity of the enzyme... 

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