Labeling patterns for

By degradation of 14C-labeled porphyrins formed from labeled acetate and glycine molecules, Shemin and Rittenberg established the labeling pattern for the... 

Fig. 2. Confocal microscopic images of an organotypic hippocampal slice depicting an interneuron displaying both CB1- and mGlula-like immunoreactivity in the stratum radiatum of the CA1 region. High magnification displays a characteristic membrane staining for mGlul a (A) and a typical punctate labeling pattern for CB1 (B). Scale bar 50 fim.

Fig. 11 Theoretical labelling patterns for a C3 metabolite. Unlabelled molecule, mO = m(0,0,0) molecules labelled in one carbon atom, m+1 = m(l,0,0) + m(0,l,0) + m(0,0,l) molecules labelled in two carbon atoms, m(+2) = m(l,l,0) + m(0,l,l) + m(l,0,l) full labelled molecule, m(+3) = m(l,l,l). The symbols represent open circles) 12C atom, (filled circles) 13C atom...

Triketides are relatively rare. Triacetic acid lactone (4.2) has been detected in Penicillium patulum. It is also produced by fatty acid synthase in the absence of the reductant NADPH. Radicinin (4.3) is a major phytotoxin isolated from Ahernaria radicina (Stemphyllium radicinum) which causes a black rot of carrots. It is also formed by other Ahernaria species. Its pyrano[4,3- ]pyran structure, the identification of which had eluded purely chemical degradative studies, was established in one of the earlier applications of NMR spectroscopy to natural product structure elucidation. The biosynthesis of radicinin from acetate units was studied in 1970 by both radio-isotope methods using carbon-14 and by carbon-13 enrichment studies with NMR methods of detection. This was one of the first applications of this NMR technique to biosynthetic problems. These results established the labelling pattern for radicinin shown in 4.3. 

Figure 12.4. The isotopic labeling pattern for a mixed-labeling experiment.

Fig. 26.8. Labeling patterns for biosynthesis of alicyclic rings (Goodwin and Williams, 1965 and Williams et al., 1967a modified and used with permission of the copyright owner, the Biochemical Society, London).

Overall, the results of these in vivo experiments constitute a remarkably clear proof that the manner by which acetate is converted to sucrose in the endosperm tissue is that predicted from the proposed enzymatic sequence, and we can thus be confident that the pathway is that shown in Fig. 4. Any diversionary or recycling reactions would have blurred the labeling patterns for malate and glucose, and yet they remained constant for the whole experimental period of 2 h. 

The FT n.m.r. spectrum at 15.08 MHz of C-enriched methyl palmi-toleate (50), which was isolated from the lipid fraction, was recorded on 1.2 mg in CHCI3 solution. The spectrum showed enhanced signal intensities for the eight alternate carbon atoms (C-2, C-4, C-6, C-8, C-10, C-12, C-14, and C-16). This is the expected labelling pattern for the fatty acid derived from CH3C02Na. Mass spectrometry of the C-enriched ester indicated a 32% enrichment for the eight alternate sites. 

Fig. 2. Proposed labelling pattern for pyocyanine derived from glycerol-1,3- C (Ingram and Blackwood, 1959)...

Figure 1. Transverse section of barley leaf epidermal cells taken perpendicular to the long axis of the cells and anticlinal to the leaf surface. The section has been labeled by the EMSIL technique (see Methods) utilizing purified C. sativus endopolygalacturonase and monoclonal antibody EPG-4, which is specific for this enzyme, in order to localize the substrate of the enzyme at the typical site penetrated by the fungal pathogen. Bar = 1 pm. Inset Comparable cell wall region as in Fig. 1 but labeled with monoclonal antibody JIM 5 to localize non-esterified pectin. Bar = 1 pm. Note the identical labeling patterns obtained with either method.

Figure 20 shows more definitively how the location and orientation of a hyperplane is determined by the projection directions, a and the bias, o- Given a pattern vector x, its projection on the linear discriminant is in the a direction and the distance is calculated as d(x ) / cf The problem is the determination of the weight parameters for the hyper-plane ) that separate different pattern classes. These parameters are typically learned using labeled exemplar patterns for each of the pattern classes. 

Figure 4 shows confocal images of the staining pattern for DDC (Fig. 4A), serotonin (Fig. 4B), and TH (Fig. 4C) in the segmental ventral ganglion of the CNS from third instar larvae. Panels B and C are the same CNS double stained with serotonin and TH. The DDC-expressing cells can be categorized into a set of paired ventral lateral serotonin cells (Fig. 4A,B labeled VL in 4A), and two morphologically distinct types of dopamine cells, the medial dopamine cells (Fig. 4A,C labeled M) and the dorsal-lateral dopamine cells (Fig. 4A,C labeled DL). Figure 4 demonstrates clearly that individual DDC cells synthesize either serotonin or dopamine, but not both. One additional set of cells shows TH immunoreactivity in the ventral ganglion. These six large vacuolated cells are located more laterally than any other DDC cells (Fig. 4C, unlabeled short arrows). It is likely that the immunoreactivity in these cells results from a non-specific cross-reaction, since these cells are not...

The 13C labels allow for use of 13C NMR in which the peaks containing the 13C label enrichment show satellites corresponding to a 1JCc coupling ( 30 Hz). The distribution pattern of 13C labels found was more complicated than one single pathway and pointed toward both pelletierine and cocaine-derived alkaloid pathways, both which incorporate two acetate units Hemscheidt T, Spenser ID (1993) J Am Chem Soc 115 3020... 

Optional when using a fluorescent label, a short treatment (1 3 min) with 4% formaldehyde in PBS before mounting in water-soluble media is recommended for blocking the detachment of the fluorophore from the antibody this preserves the staining pattern for a longer storage. Wash sections in PBS for 2x3 min. 

In reality, the ideal isotope labeling pattern (one component 100% labeled, the other one 0%) is almost never fulfilled first, a 100% isotopic enrichment will be generally very hard to reach (and very costly ) for chemically synthesized as well as for overexpressed compounds. On the other hand, even the nonenriched components will always contain NMR-active isotopes at natural abundance unless they are derived from specially isotope-depleted (and again very expensive) starting material. 

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