Specific incorporation rate

The incorporation rate can be calculated from radioactivity whose units are the becquerel (1 Bq = 1 disintegration/s) or the curie (1 Ci = 3.7 10 disintegrations/s) or from the increase in the natural isotopic concentrations, given in atoms % excess, in the precursor and the product. Both absolute and specific incorporation rates can be calculated and usually are expressed as a percentage ... 

The absolute incorporation rate in which the amount of administered precursor is correlated with the amount incorporated into the product is usually less reliable than the specific incorporation rate or the dilution of the precursor. It depends, to a great extent, on how much product is synthesized during the experiment and is therefore, usually subject to wide variation. In addition, its calculation requires an exact determination of the total amount of product formed, a condition which usually cannot be satisfied. 

The specific incorporation rate (or the dilution of the precursor) gives the amount of product formed from the labeled precursor relative to that formed from the pool of endogenous precursor. Thus, for a specific incorporation rate of 0.1 % (or a dilution of 1 1,000), one product molecule in a thousand is formed from the isotopically labeled precursor. The specific incorporation rate is therefore dependent on the ratio of incorporation of endogenous to administered precursor molecules. It is influenced by the absolute rate of synthesis during the experiment only when this ratio is altered. It is easier to determine the specific activity of the product than its absolute amount since only a small portion of the product has to be isolated. 

The specific incorporation rate permits conclusions regarding the closeness of relationship between the product and the precursor since it is usually higher if the precursor is transformed to the end product in one or a few steps. This corre-... 

The specific incorporation rates in this type of experiments are usually low. In higher plants they are frequently in the range of O.OI %. The low rates are mainly due to loss of precursors to competing reactions during transport to the sites of biosynthesis and to dilution of labeled precursors by large pools of unlabeled precursors and end products. 

In microorganisms the specific incorporation rates may be much higher because precursor transport plays an insignificant role and the experimental conditions can be controlled so that the product present at the end of the experiment was synthesized only during the experiment, i.e., the measured incorporation rates are not reduced by unlabeled product already present at the beginning of the experiment. 

Further information about possible intermediates can be obtained by so-called competition experiments. Here the specific incorporation rate of a labeled precursor is determined in the presence and absence of greater amounts of an unlabeled suspected intermediate. Incorporation of the unlabeled compound into the product reduces the specific incorporation rate of the labeled precursor. If the unlabeled compound is not an intermediate, the specific incorporation rate... 

Since there are various specific growth rates and different values of rate constants while substrate concentration varies, therefore mix inhibition exists. Andrew26 incorporated a substrate inhibition model27 in the Monod equation the modified Monod equations with second-order substrate inhibition are presented in (3.14.5.1) and (3.14.5.2).16,17... 

Table 9.2 Incorporation rate of [2-14C]-pyruvate into monoterpenes of isolated peppermint oil gland secretory cells in the presence of fosmidomycin, a specific inhibitor of 1-deoxy-D-xylulose 5-phosphate reductoisomerase, an enzyme of the mevalonate-independent pathway of isoprenoid biosynthesis.

A number of studies with widely diverse species have established that the major site of cuticular hydrocarbon synthesis is within the cells associated with the epidermal layer or the peripheral fat body, particularly the oenocytes. In Schistocerca gregaria, Diehl (1973, 1975) separated the oenocyte-rich peripheral fat body from the central fat body tissue and observed the highest rate of hydrocarbon synthesis in the oenocyte-rich peripheral fat body. In Tenebrio molitor, Romer (1980) demonstrated that isolated oenocytes efficiently and specifically incorporated [14C]acetate into hydrocarbon. Similar studies in Periplaneta americana (Nelson, 1969), Sarcophaga bullata (Arnold and Regnier, 1975), and Musca domestica (Dillwith et al., 1981) demonstrated that hydrocarbon synthesis occurs primarily in the epidermal tissue. 

Bacterial production was estimated by incorporation of 3H-thymidine (Fuhrman and Azam 1982). Duplicate 10 ml subsamples were incubated for 1 h in the dark at 2°C in the presence of 20 nM of 3H-thymidine (Amersham 40-50 Ci mol ), filtered on 0.2-pm cellulose acetate membrane filters (Sarto-rius) and extracted with ice-cold 5% Trichloroacetic acid (TCA) (Becquevort and Smith 2001). Thymidine incorporation was converted into bacterial production using conversion factors of Ducklow et al. (1999) established for the Ross Sea bacterial communities (i.e., 8.6 X 1017 bacteria produced per mole of thymidine incorporated in the cold TCA insoluble material). For bacterial production, the relative standard deviation was 9.3% (n = 20). The specific growth rate was estimated from bacterial production and bacterial biomass. 

Proctor DJ, Ma H, Kierzek E, Kierzek R, Gruebele M, Bevilac-qua PC. Folding thermodynamics and kinetics of YNMG RNA hairpins specific incorporation of 8-bromoguanosine leads to stabilization by enhancement of the folding rate. Biochemistry 2004 43 14004-14014. 

P4-9 Sargent Nigel Ambercromby. Scoundrels Incorporated, a small R D company has developed a laboratory scale process for the elementary, solid-cata-lyzed-gas-phase reaction A + B C -F D (names coded for proprietary reasons). The feed is equal molar in A and B with the entering molar flow r e of A is 25 mol/min and the volumetric feed is 50 dm /min. Engineers at Scoundrels calculated that an industrial scale packed bed reactor with 500 kg of a very rare and expensive metal catalyst will yield a 66% conversion when run at 32 C and a feed pressure of 25 atm. At these conditions the specific reaction rate is 0.4 dm /mol-min-kg catalyst. Scoundrels sells this process and catalyst to Queless Chemicals who then manufactured fee packed bed. When Oueless put the process onstream at the specifications provided by Scoundrels, they could only achieve 60% conversion with 500 kg catalyst. Unfortunately the reaction was carried out at 3U°C rather than 32°C. The... 

The two parameters in Eq. (7-92) are the maximum specific growth rate pmax (h-1) and the saturation constant K, (g substrate/L). The value of K. is obtained as the substrate concentration at which p = 1h pm (see Fig. 7-6). The form of Eq. (7-92) is entirely empirical, but it incorporates two important features (1) At high substrate concentration the whole cell machinery is involved in cell synthesis, and the specific growth rate reaches a maximum pmax (2) at low substrate concentration formation of biomass is a first-order rate process (as in any other chemical reaction) and p -> (pmax/Ks)Cs. Note that for many commonly used microorganisms Ks is much... 

This critical review describes an experimental method and mathematical model to quanfily in vivo incorporation rates, half-lives, and turnover rates of FAs into brain phospholipids. FA incorporation is independent of cerebral blood flow and is thus a direct measure of brain phospholipid metabolism. Because specific FAs enter specific phospholipids at stereospecific positions, a combination of saturated and polyunsaturated FA labels can he used to investigate the active participation of phospholipids in brain signal transduction, membrane remodeling, and neuroplasticity. 

Interestingly, both PCS and OKS accepted acetyl-CoA, resulting from decarboxylation of malonyl-CoA, as a starter substrate (7), but not so efficiently as in the case of R. palmatum ALS (4c). This was confirmed by the C incorporation rate from [l- C]acetyl-CoA in the presence of cold malonyl-CoA, while the yield from [2- C]malonyl-CoA was almost at the same level either in the presence or absence of cold acetyl-CoA. In contrast, the yield of the heptaketide by R palmatum ALS was two- to three-fold higher in the presence of acetyl-CoA. Theoretical C specific incorporation from [l- C]acetyl-CoA should be 20% (1/5) in PCS and 12.5% (1/8) in OKS if acetyl-CoA serves as a starter of the polyketide forming reactions, which was largely consistent with the experimental results (7). 

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