Time course of label

Under these conditions, the time-course of label entry into both the TCA-soluble pool and the TCA-insoluble protein was linear for each organ for at least 40 and 50 min, respectively. 

Figure 4. Time course of labeling of POM (particulate organic matter, primarily phytoplankton) with tracer additions of15N in the fertilized and control sides of Lake N2. The solid line represents the predicted labeling, given the turnover time of phytoplankton. Terrestrial detritus remained unlabeled throughout the...

Turnover of Ascorbic Acid. The time course of labeled ascorbic acid in organs is represented by the diflFerential equation ... 

A 10 min period of electrical stimulation in the presence of Pi led to increased labelling of synaptosomal phosphatidate (Bleasdale Hawthorne, 1975) but no consistent, increase in phosphatidylinositol specific radioactivity. The labelling of ATP was unaffected. When sub-synaptosomal membrane fractions were prepared, the increased phosphatidate labelling was seen to be associated with the synaptic vesicle fraction, as in the acetylcholine experiments. Further work (Hawthorne Bleasdale, 1975) showed that electrical stimulation only increased the labelling of phosphatidate in the vesicle fraction when the medium contained calcium ions. This and the time course of labelling (changes seen 2 min after the onset of stimulation) suggest that the metabolism of phosphatidate is closely associated with the process of transmitter release. 

When the time course of labeling was compared to the time course of inhibition for all of the PPIs, labeling of the cysteines in the TM5/TM6 region (either cysteine 813 or 822) correlated with inhibition. Definition of which of these two cysteines was labeled was done by using labeled omeprazole under transport... 

Fig. 2 Time courses of labelings by NEM and EMA of the four cysteine residue of the ADP/ATP carrier in bovine heart submitochondrial particles at 0 °C. Submitochondrial particles (20 mg protein/ml) were treated with EMA (20 nmols/mg protein) or NEM (100 nmols/mg protein) for various periods...

Fig. 8. Time course of labeling of the average cell protein and of cytochrome oxidase. [ C]leucine was added 200 min before the addition of pH]leucine. ...

The half lives and the pool sizes of the precursor polypeptides were derived from the time courses of labeling shown in Fig. 9. They are summarized in Table II. As can be seen, the precursor pool of the 20,000 Mr subunit of cytochrome oxidase is relatively small compared to the precursor pools of the other cytochrome oxidase subunits. This 20,000 Mr subunit was shown to be produced by the chloramphenicol-sensitive mitochondrial protein synthesis (Fig. 7B). Consequently, soon after the addition of chloramphenicol, the precursor pool of this subunit is exhausted, making a further assembly of the holoenzyme impossible. This explains why, after... 

Figure 20 Time course of, 3C DDMAS (left panel) and CPMAS (right panel) of [1-13C] Phe22, [3-BC] Ala-label led hCT dissolved in 0.015M acetic acid solution at the concentration of 80 mg/mL pH of the solution was 33. Acquisition was started after 6 h from dissolution by accumulating 1000 scans for DDMAS and 2000 scans for CPMAS experiments (A) 12 h, (B) 26.4 h, and (C) 179.2 h after dissolution. From Ref. 163 with permission.

In suberizing potato tuber disks, labeled oleic acid was incorporated into co-hy-droxyoleic acid and the corresponding dicarboxylic acid, the two major aliphatic components of potato suberin [73]. Exogenous labeled acetate was also incorporated into all of the aliphatic components of suberin, including the very long chain acids and alcohols in the wound-healing potato slices. The time-course of incorporation of the labeled precursors into the suberin components was consistent with the time-course of suberization. The biosynthetic pathway for the major aliphatic components of suberin is shown in Fig. 8a. 

A few studies have been conducted on cannabis and its derivatives. Alozie et al. (3) measured the radioactivity accumulated in various brain areas following the intravenous injection of 3H-THC, 3H-cannabinol, and 3H-cannabidiol to adult male rats. Five minutes after injection, these three labeled compounds exhibited a homogeneous distribution in brain, suggesting that no specific binding occurred. Such studies must be completed by examining the time course of the evolution of 3H-cannabis derivatives in various brain areas before any firm conclusion can be drawn. 

Note that bonds which are invariant with time are represented in the usual way. The dotted lines represent bonds which change over the time course of the reaction event. Each changed-bond is labeled to indicate its bond order before and after the reaction. Obviously, the unchanging bonds can also be labeled in an identical fashion. (For example, "1 1 would represent an unchanged single bond.) A second example of this representation is illustrated in Figure 1. 

Recently, this method was adapted to label two commercially available liposomal formulations doxorubicin encapsulated in polyethylene glycol (PEG)-coated liposomes (Caelyx /Doxil ) (14) and daunorubicin encapsulated in small distearoyl-phosphatidyl-choline/cholesterol liposomes (Daunoxome ) (15). Although no DTPA was encapsulated in these liposomes, the labeling efficiency was typically between 70% and 80% and the radiolabeled preparations were stable in vivo during the time course of the experiment (four hours). Most likely, the lipophilic In-oxine avidly associates with the lipid bilayer and encapsulation of DTPA might not be necessary when the experimental observation period does not exceed four to six hours. 

N]-, [ C]-, pHjleucine or p Sjmethionine in the case of proteins) for various periods, after which the cells are lysed and the protein of interest is purified (often by immunoprecipitation with specific antibodies). The time course of isotope incorporation gives information about the rate (slope of curve) and extent (amplitude of curve) of the proteins synthesis. To measure degradation, cells are first pulse-labeled (i.e., exposed to radiolabeled precursor for a fixed period, after which sufficient nonla-beled precursor is added to reduce the radiospecific activity of the precursor). Then, the cells are further incubated, and the radiospecific activity of a particular protein of interest is determined (again usually after immunoprecipitation or some other means for achieving its isolation from other cellular proteins). The key point is that the chase allows one to stop radiolabel uptake almost instantaneously, thereby permitting the kinetic... 

Figure 1. Time course of of ligninolytic activity (conversion of ring-labelled 14C-DHP to 14C02), biomass concentration, VAO activity and laccase activity during growth of Pleuroius sajor-caju in agitated mycological broth cultures. (Reproduced with permission from Ref. 25, 1988, Biochemical Society).

Fig. 4.4.3. Covalent labeling of nuclear targeted wl60hAGT-NLS3 in AGT-deficient CHO cells. Confocal micrographs A-C show overlays of transmission and fluorescence channels (exc 488 nm). The size bar in A-C corresponds to 10 pm. Confocal micrographs (A-C) illustrate the time course of the labeling of transiently expressed wl60hAGT-NLS3 with BGAF in AGT-deficient CHO cells. (A) AGT-deficient CHO...

Fig. 14.1. Time course of SV40 infection. Monkey cells in monolayer culture, infected with SV40 at 1-10 p.f.u. per cell. T antigen may be detected by immunofluorescence, viral DNA synthesis by labelling with [yH]thymidine followed by separation of viral DNA (by Hirt extraction, SDS gradient centrifugation or agarose gel electrophoresis) and mature virions by infectivity using a plaque assay. (Data from Tooze, 1973 Girard et al., 1975 and Basilico and Zouzias, 1976.)...

Mundt el al.n9 have adapted the above scheme for the maltose-glycine system (pH 5.5, 70 °C). Multiresponse modelling gave excellent fits for the time course of the concentrations of glucose, melanoidins (A470, number of maltose molecules incorporated from U-14C-labelled maltose), 3-DH (as quinoxaline derivative), maltose, and SIV (in maltose-glycine-SIV systems). 

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