Units of activity

NOTE One unit of activity is equivalent to 1 mole of PCP. Mean SEM of at... 

FIGURE 2. Panel A Elution pattern of endogenous PCP-like material from fractionated porcine brain. Activity is expressed in terms of equivalents of PCP required to inhibit 3H-PCP bindina to rat brain membranes. One unit of activity is eqivalent to 1 mole of PCP. 

Becquerel (Bq)—International System of Units unit of activity and equals that quantity of radioactive material in which one transformation (disintegration) occurs per second (see Units). 

The activity is a measure of the quantity of radioactive material. For these radioactive materials it is customary to describe the activity as the number of disintegrations (transformations) per unit time. The unit of activity is the curie (Ci), which was originally related to the activity of one gram of radium, but is now defined as that quantity of radioactive material in which there are ... 

The SI unit of activity is the becquerel (Bq) 1 Bq = that quantity of radioactive material in which there is 1 transformation/second. Since activity is proportional to the number of atoms of the radioactive material, the quantity of any radioactive material is usually expressed in curies, regardless of its purity or concentration. The transformation of radioactive nuclei is a random process, and the number of transformations is directly proportional to the number of radioactive atoms present. For any pure radioactive substance, the rate of decay is usually described by its radiological half-life, TR, i.e., the time it... 

Current collector Maximum discharge capacity on the unit of active material mass, mA-h/g Maximum discharge capacity on the unit of electrode square, UkA-h/cm2 Maximum discharge capacity on the unit of electrode mass, mA-h/g... 

This very long half-life (1.25x1(r years) isotope comprises 0.0117 percent of all potassium. Thus, this isotope is present in all of us and has always been so. In addition, the materials around us, including the soil and the building materials, contain both potassium and the heavy naturally occurring radioactive elements thorium and uranium that contribute to a level of radiation to which we are all continuously exposed. Thus, there is always radiation exposure to the general public and we must understand the exposure due to radon in this context. The amount of radioactivity is described in units of activity. The activity is the number of decay events per unit time and is calculated as follows... 

Any biopharmaceutical must obviously conform to final product potency specifications. Such specifications are usually expressed in terms of units of activity per vial of product (or per thera-... 

The substrate commonly employed is 0.5-1.0% of pectin in 50-200 mM sodium chloride (20-60 ml) at a suitable pH and 30°. The pectinesterase activity is mostly expressed in micro-equivalents of ester hydrolyzed per minute at the given pH and temperature. The use of a variety of units of activity, which was complicated and prevented ready comparison of the results of various authors, has now been discontinued. 

Activity The activity of a radioactive material is the number of nuclear disintegrations per unit time. Up to 1977, the accepted unit of activity was the curie (Ci), equivalent to 37 billion disintegrations/s, a number that approximated the activity of 1 g radium-226. The present unit of activity is the becquerel (Bq), equivalent to 1 disintegration/s. 

Becquerel (Bq) The presently accepted unit of activity is the becquerel, equivalent to 1 disintegration/s. About 0.037 Bq = 1 picocurie. 

The International Reference Standard for neomycin is defined as containing 680 units of activity per mg or alternatively 1 unit of activity is contained in 0.00147mg of standard material. 

Heparin is an anticoagulant that prevents the formation of blood clots. Like insulin, it is also measured in units of activity. IV heparin may be administered by standard gravity flow or electronic infusion devices. The normal adult heparinizing dosage is 20,000-40,000 units per 24 hours. In general, IV heparin is ordered in units per hour. Heparin may also be ordered by the physician to infuse at a predetermined flow rate in mL per hour. 

Bessey-Lowry Activity One unit of activity may be defined as the amount of enzyme present in 1 millilitre of serum that liberates lp mol of / -nitrophenol (0.1391 mg) per horn at pH 10.5 after 30 minutes at 38°C. 

Temperature Correction Factor The rate of the above reaction is temperature dependent. Hence, if the temperature (experimental) is higher or lower than that used to define a unit of activity, a definite correction factor should be applied as per Table 2.10. 

The curie unit (Ci) is based on the activity of 1 g of pure radium-226, which undergoes 3.7 X 1010 transformations per second. It is therefore defined as the quantity of a radioactive isotope which gives 3.7 X 1010 disintegrations per second. The SI unit of activity is the becquerel (Bq), which is equal to one nuclear transformation per second. Hence ... 

Because of the difficulties in measuring the amount of enzyme in the conventional units of mass or molar concentration, the accepted unit of enzyme activity is defined in terms of reaction rate. The International Unit (IU) is defined as that amount of enzyme which will result in the conversion of 1 /nmol of substrate to product in 1 minute under specified conditions. The SI unit of activity, which is becoming more acceptable, is the katal and is defined as that amount of enzyme which will result in the conversion of 1 mol of substrate to product in 1 second. A convenient sub-unit is the nanokatal, which is equal to 0.06 International Units. 

Assays for endo-l,4- -glucanase [EC 3.2.1.4] (i.e., CMCase) and saccharifying cellulase (i.e., international filter paper U, IFPU) activities partially followed the methods recommended in the 1987 lUPAC report (65). When even undiluted enzyme samples fail to give the required glucose yield under prescribed assay conditions, the lUPAC committee recommends a less precise method. In the current study, cellulase activities in digester extracts were so low that the CMCU could only be defined as follows one CMC unit of activity was that amount of enzyme required to liberate one Hg glucose from CMC in 60 min. 

General protease, a-amylase, and exoglucanase activities were estimated using hide powder-, amylose-, and celliilose-azure substrates, respectively, as described earlier (49). Here, standard curves were developed for the hydrolysis of each azure-linked substrate by standard enzymes of known activity. By this method, one cellulose-azure hydrolysis unit corresponds to one filter paper unit, one unit of hide powder-azure activity corresponds to the hydrolysis of 1.0 nmole of iV-benzoyl-L-tyrosine ethyl ester (BTEE) per min, and one amylose-azure unit of activity corresponds to the hydrolysis of 1.0 nmole of maltose from starch per 30 min. 

With the above design each run is an experiment performed at the settings noted in columns Xj, X2, and X3, with each run having a response (yl - y8). For example, if one were looking for enzymatic activity, the responses yl to y8 would be in units of activity per mg of protein. Notice that for factor A at the low levels (0), the levels for B and C are the same as the levels when A is at its high level (1), i.e. the design... 

Protein concentrations are often reported in terms of mass per unit volume (eg., mg/ml) or in units of activity per volume. Care should be exercised when using these forms of concentrations. To have valid steady-state kinetics, the total enzyme concentration must be much less than the substrate concentration. Hence, one should always be cognizant of the true concentration of active enzyme in terms of molarity. 

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