Methionine, labelled with

It is not entirely clear, however, which alkaloid is the first to be synthesized, but Imaseki (349) and Shibata (259) concluded that it was hyoscyamine. Similarly Marion and co-workers (350, 351) using ornithine labeled with in the a-position noted that the hyoscyamine in Datura stramonium was radioactive but that the hyoscine was not and that only the hyoscyamine was radioactive after feeding mature plants of the same species with methionine labeled with in the methyl group. 

TABLE 1. Chemical oxidation of methionine in HL-60 cell proteins previously uniformly labeled with [35S]methionine ... 

FIGURE 28-3 Two-dimensional fluorographs showing the 35S methionine-labeled polypeptides in the three major anterograde rate components of axonal transport SCa, slow component a SCb, slow component b FC, fast component. Note that rate component not only has a characteristic rate but a characteristic polypeptide composition. The discovery that each rate component has a different polypeptide composition led to the structural hypothesis. (With permission from Tytell, M. etal. SciencellA 179-181, 1981 [6] illustration provided by Dr. Michael Tytell.)... 

The main radiopharmaceuticals labelled with fluorine-18, routinely prepared ([2-i F] fluorodeoxyglucose [ F]FDG [26-28], [i F]fluoro-L-DOPA [29], [i F]altanserin [30, 31], [ F]setoperone [32]) are presented with their uses in Table 2. For comparison, the most common tracers labelled with carbon-11 (methionine [33], palmitic acid [34], flumazenil (RO 15.1788) [35], PK 11195 [36], raclopride [37], deprenyl [38], Way-100635 [39], McN-5652Z [40], CGP 12177 [41]) are shown in Table 3. By far, [ F]FDG is the most widely studied, particularly in oncology for the diagnosis of tumours, detection of sub-clinical diseases, assessment of therapy responses, and detection of recurrence. F-Steroids [42], F-proteins or peptides, or F-labelled tissue specific agents have also been synthesized for the detection and monitoring of various malignancies [43]. 

M. L. Sinnot and P. J. Smith, Affinity labelling with deaminatively generated carbonium ion. Kinetics and stoicheiometry of die alkylation of methionine-500 of die lacZ p-galactosidase of Escherichia coli by p-D-galactopyranosylmethyl-p-nitrophenyltriazene, Biochem. J., 175 (1978) 525—538. 

A more extensive study of mobilities of 3H- and 14C-labeled amino acids again found that amino acids labeled with 14C at Cl or C2 are retained on the column, relative to the unlabeled forms.135 Lysine is an exception. Tritiation at C3 also increases the retention time, but tritiation at C2 of glycine or at C4, C5, or C6 of lysine decreases it, and large decreases are seen with methionine tritium-labeled in the methyl and with tyrosine tritium-labeled at C3, 5. The 14C IEs can be attributed to a decrease of acidity, but the IEs of distant 3H may be due to hydrophobic interactions with the resin. A remarkable result is that intramolecular isotopic isomers (isotopomers) can be distinguished on the basis of their chromatographic mobilities. 

KinaseX samples that are residue type-specifically labeled with II Thr, [ H]Lys and I111 Met have been also produced and NOEs between these residues and inhibitors have been observed (data not shown). Since there is one threonine, one lysine and one methionine in the ADP binding pocket of kinaseX, sequence-specific assignments for these residues can be obtained directly by the observation of protein-inhibitor NOEs. 

Methionine Sulfoxide Adsorption Check. S35-labeled methionine sulfoxide was prepared by oxidizing methionine-S35 with peroxide (6). Five microliters (ca. 20,000 counts per minute per microliter) of an aqueous solution of the sulfoxide was injected into each of 20 cockroaches. The first 10 were immediately immersed in hot 80% ethanol, and the remainder in hot 5% trichloroacetic acid to be homogenized and extracted. The extraction procedures were similar to those described above, except that precautions to prevent oxidation were not taken and the supernatant liquids, except for the acidified ethanol and ether washes, were not combined but were collected separately in 100-ml. volumetric flasks. The protein residues were hydrolyzed in 6N HC1 and, like the other fractions, were then diluted to 100 ml. with water for radiometric analysis. 

Fig. 1. Export kinetics of MBP anti MBP16-1 in SecB and SecB" cells. Wild-type cells (top) or cells devoid of SecB (bottom) synthesizing either wild-type preMBP (left-hand column) or export-defective preMBP16-l (right-hand column) were pulse labeled with [ S]methionine for 15 sec followed by addition of excess unlabeled methionine. Samples were removed at the indicated chase points, processed for immunoprecipitation with anti-MBP antiserum, and analyzed by SDS-PAGE. The positions of precursor (p) and mature (m) MBP are indicated by arrows. From Collier and Bassford (1989).

Selective photosensitized oxidation of some amino acids present in proteins can be also utilized for specific labeling with a chosen sensitizer (methylene blue and hematoporphyrin for methionine, crystal violet or cresol red for cysteine, proflavine for tryptophan, etc.). This topic is described by Scoffone et al. 

Recombinant human leptin was recently cloned (8) and expressed in E. coli, and demonstrated to effectively regulate adiposity in mice through modulation of appetite and metabolism (9, 10). The molecule contains four methionine residues at positions 1, 54, 68, and 136. In this paper, we report the separation and characterization of three norleucine-incorporated recombinant human leptins which were uniformly labeled with 15n isotope or double labeled with and isotopes. The extent of incorporation at each methionine residue can be determined by reverse-phase HPLC and amino acid analysis methods. The norleucine incorporation was observed preferentially occurring at the internal Met residues. 

BSs protected cereal leaf cells from heat shock or saline stress. Leaf pre treatment with BSs decreased cell ultrastructure degradation from heat shock and high salt conditions. BSs increased HSG formation which is supposed to protect preformed mRNA in plant cells during heating. BSs enhanced heat shook resistance of the leaf protein-synthesizing system. The effect of BSs on RNA and protein synthesis was shown earlier (14). We observed protein synthesis activation in wheat leaves by BSs in normal and under stress conditions. Two-dimensional SDS-FAAGE of dS-methionine labeled proteins demonstrated BS-induced changes in the set of polypeptides synthesized in leaves and in the rate of their synthesis. 

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