Specific molar radioactivities

With respect to the point mentioned last, special interest has been focused by several authors on the possible insertion of olefins. Of special relevance are results reported by Schulz and Achtsnit (77). These authors studied the FT catalysis on a cobalt catalyst and added ethylene marked with to the feed. The product was analyzed the specific molar radioactivities of the various fractions are shown in Fig. 3. It is seen that for higher carbon numbers the specific molar radioactivity increases linearly with the carbon number. Upon considering that, if ethylene can be inserted, the chance of this to happen increases linearly with the number of insertion steps that a chain undergoes during its life, this linear dependence is interpreted by the authors as proving ethylene insertion. 

Fig. 2. Specific molar radioactivities in the components of feed and product when reacting a mixture of [ C]-n-hexane (65%) plus inactive 1-hexene (35%) and [ C -n-hexane (62%) plus inactive cyclohexane (38%). Pulse system, catalyst Pt black, carrier gas helium.

This technique has been developed for studying sequential reactions by Gal and co-workers. Theory and earlier results were summarised in a book, describing it as a dynamic method that utihsed the temporal changes of specific (or molar) radioactivities of assumed intermediates. 

Currently, there are several assays for the measurement of PSA. All of them contain monoclonal or polyclonal antibodies labeled with enzymatic, fluorometric, or radioactive markers. These assays have shown significant variations within the same patient specimens. These variations may result from differences in antibody specificity, reaction kinetics, calibration, or the system s sensitivity. Studies have shown that only free PSA and PSA-ACT show immunological reactivity in these assays. Also, reaction kinetics can influence the molar ratio. Some of these assays with shorter incubation times may specifically bind the free PSA molecule (which is a lower weight form of PSA). In the equimolar assays, changing the incubation... 

Radionuclides occur in the environment in such minute physical quantities that they are commonly referred to as being present at sub- or ultra-trace quantities. As an illustration of this Livens and Rimmer (1988) presented values relating the masses and specific activities of several artificial radionuclides and their typical concentrations in surface soils of the UK (see Table 7-1). This indicates the very small mass usually associated with one Becquerel of radioactivity, although as the half life of a radionuclide increases so does the mass per unit of radioactivity. The molarity concept is... 

Strand-specific DNA probes of high specific radioactivity are prepared by first annealing a primer to the single-stranded M13 DNA and then extending it with DNA polymerase (34). Annealing is accomplished in the presence of 100-fold molar excess of primer to DNA template (0.02-2 pg) in a reaction mixmre containing 50 mM NaCl, lOmMTris HCl, pH 7.5,and 7 mM MgCl2. The mixture is... 

Synthesis of Maduramicin-Protein Conjugates. The mixed anhydride method (16) with some modifications (Tsou, H. personal communication) was used to prepare the BSA or OA conjugates to maduramicin (M-BSA, M-OA). A small amount of tritiated maduramicin was added to 100 mg of non-radioactive maduramicin resulting in a specific activity of 23 xCi/gm. Fifty microliters of triethylamine was added to the dried maduramicin followed by the addition of ethyl chloroformate. The mixture was allowed to react for 30 minutes at 4 C with stirring. The conjugating protein BSA or OA was dissolved in water followed by the addition of dimethylformamide to a final concentration of 50%. The final concentration of the protein was about 2 mg/mL. The maduramicin anhydride was added to the cold protein solution dropwise with stirring. The molar ratio of maduramicin to protein was 40 1. The reaction was carried out at 4 C for 3 1/2 hours. The product was dialyzed against 0.01 M sodium phosphate buffer pH 7.4 at 4°C until the radioactivity of the dialysate was below 50 dpm/mL. Estimation of the extent of... 

Synthesis of Maduramicin Monoamide with 1.6-Hexanediamine (M-C NH-A One gram of tritium-labeled maduramicin (specific activity 23 iCi/gm) was dissolved in 10 mL of toluene with 100 xL of triethylamine. Ethyl chloroformate (100 pL) was diluted in 15 mL of toluene and was added dropwise to the cold maduramicin solution and allowed to stir at 4 C for 30 minutes. A 10 fold molar excess of 1,6-hexanediamine (1.2 gm) was dissolved in 10 mL of toluene and added. After 11/2 hours of reaction at 4 C, ice cold water (4 C) was added to remove salts and clarify the toluene solution. The reaction product was monitored by silica gel thin-layer chromatography and radioactivity. Maduramicin monoamide with 1,6-hexanediamine (M-CgN ) was purified by silica gel column chromatography using a gradient of methanol in ethyl acetate with or without triethylamine as the mobile phase. The product was stored in toluene at 4 C. 

Precursor Cmpd Molar Specific Activity (mCi/mMole) Incorporation (%) Radioactivity (%)... 

Intensive quantities related to the activity. In most samples, the radionuclides are not carrier free but inactive isotopes carry them and/or an inactive substance called matrix contains them. (The term no-carrier-added or n.c.a. only means that the production process of a radionuclide sample does not involve adding carrier to it. However, it may not be carrier free.) The specific activity of a radioactive sample is defined as the (absolute) activity of the radioactive sample divided by its mass (unit Bq/kg). Similar quantities are the molar activity (unit Bq/mol) and the activity concentration (unit Bq/dm ), defined as the activity of the sample divided by its molar amount and volume, respectively. 

Note that the term specific activity is also used in the sense of the activity caused by a radioisotope of an element in a sample per the total mass of the element (or a compound of it) contained by the sample. Some authors use the term specific radioactivity in the sense of molar activity, although according to International Union of Pure and Applied Physics (lUPAP) and International Union of Pure and Applied Chemistry (lUPAC) recommendations the adjective specific should be reserved for naming quantities that are divided by mass. So the use of the term in the latter sense should be avoided. 

It was not certain from the above observations whether the synthetis of flavin adenine dinucleotide in animal tissues proceeded by the same mechanism as that demonstrated with the purified enzyme from yeast. The demonstration by Watarai et al. 140) that flavin adenine dinucleotide synthesized from riboflavin 5 -phosphate-P and ATP in rabbit liver homogenates had the same molar specific radioactivity as added riboflavin 5 -phosphate-P would be in accord with a flavin adenine dinucleotide-pyrophosphorylase reaction, but suffered from the lack of demonstration of net synthesis of the coenzyme in the system. 

There are two ways in which specific activity is expressed, radioactivity per unit mass (e.g., mCi/mg) and radioactivity per molar unit (e.g., Ci/mmole or mCi/mmole). 

The latter expression of specific activity is used almost always for high specific activity tritiated compounds, and often for carbon-14-labeled compounds. Measures of radioactivity per molar unit can be calculated from mass spectrometry data ". In this analysis, the distribution of isotopic species (e.g., Hq, Hj,. ..) is determined by measuring the relevant peak intensities in the molecular ion envelope and correcting them for naturally occurring isotopes (e.g., C, present in the molecule this can be done manually or by use of readily available computer algorithms. The contribution of each isotopic species to the total can be used to calculate the average number of isotopic atoms per molecule and thence, from the molar specific activity of the pure isotope, the molar specific activity of the compound. 

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