Glycine, enriched

Despite our earlier failure in formate feeding experiments, [3- C]serine, [1,2- CJglycine, and [Me- C]methionine were found to enrich C-13 in neosaxitoxin effectively (7). The best incorporation was observed with methionine, indicating it is the direct precursor via S-adenosylmethionine. Glycine C-2 and serine C-3 must have been incorporated through tetrahydrofolate system as methyl donors in methionine biosynthesis. 

As for the GABAa receptor, positive modulators that enhance glycine receptor activity have been identified. These include alcohols, neurosteroids, tropeines and the divalent metal ion Zn2+, which is highly enriched in some types of excitatory neuron [27], Zn2+ release from such neurons may potentiate glycine receptors at neighboring inhibitory synapses and thus facilitate inhibition following strong excitation. 

I-Solenoid repeats usually have several x or x x sequence patterns that correspond to the /1-strands (here, denotes an apolar residue, and x is mostly polar but can be any residue except pro line). The middle -position in x x usually has a bulky apolar residue, while -residues in positions close to turns are often alanine, glycine, serine, or threonine. These positions are also occupied by asparagine residues that stack to form H-bonded ladders inside the /1-solenoid. The strand-associated x and x x patterns are interrupted by regions enriched in polar residues and glycine (Hennetin et al., 2006). These are regions of turns and loops. The long loops frequently contain proline residues. In several /1-solenoids, the alternation of apolar and polar residues that is typical for /1-strands is not well observed and outside positions are occupied by apolar residues. 

Scheme 4). This unexpected enrichment of two neighboring carbons from a single-labeled precursor can be explained by assuming that labeled glycine was introduced into TCA cycle via malate. In the cycle, the molecular asymmetricity will be lost at the succinate step, and the labeling will appear on both C-2 and C-3 of succinate. The result seems to support Scheme Ic, since C-4 and C-3 of glutamate correspond to C-11 and C-12 of the toxin molecule in such a scheme. 

Bradley and coworkers used the 3D pharmacophore ensemble model to filter a virtual combinatorial library of 3924 N-substituted glycine peptoids (30) containing three known a, actives down to a set of 639 products. Using a cut-down technique, a 160 compound combinatorial library was designed in which the number of compounds that passed the ensemble model filter was maximized. This library contained two of the three known actives present in the original 3924 compound virtual library. This represents a substantial enrichment [(2 actives/160 products) X 100 = 1.25% vs (3 actives/3924 products) x 100 = 0.076%]. 

Diastereoselective Alkylation of Glycine Schiff Base with Optically Enriched Alkyl Halides... 

One may envisage that such conglomerates of crusts of glycine crystals might be spread to yield enantio-enriched environments, as in the mechanism proposed by Welch [68]. 

Combined operation of the hydrophobic and kinetic effects using nonmixtures of L/D-leu of 53 47 (6% ee) in a total concentration of 2.4% wt/wt of glycine resulted in the formation of a crust of floating glycine crystals containing only D-leu, thus enriching the initial L-leu ee of the solution, Fig. 13 [133-135],... 

Fig. 7. Sub-mitochondrial compartmentation of the one-carbon unit metabolism in a mutant of Saccharomyces cerevisiae unable to produce C -tetrahydrofolate (CrTHF) by other pathways than the mitochondrial cleavage of glycine to C l -THF, carbon dioxide, and ammonia. 13C-NMR analysis of choline and serine indicated the existence of two mitochondrial pools of glycine, serine, and Cj -THF. Values in italics refer to the fractional enrichment of the carbon atoms. Values in bold refer to the relative contributions of endogenous (unlabeled) and exogenous (labeled) glycine [47]...

Several enantiomerically-enriched templates have also been employed in the preparation of chiral, non-racemic piperidines. The RCM of N, O- and O, O-acetals have been developed by Rutjes and co-workers into a powerful method for the preparation of a wide-variety of heterocycles <02MI736> (Scheme 17). Here the reaction of an enantiopure Ts-protected allyl glycine is employed to prepare a chiral, non-racemic, cyclic amino acid derivative. These N,0-acetals can be readily transformed into synthetically useful iV-sulfonyliminium ions by treatment with BF3 OEt2 <00CC699>. 

Protein comprises about 10% by weight of the organic matrix. The proteins are phosphorylated, and are enriched in aspartic acid, glutamic acid and glycine. Some of the proteins and the chitin are intimately associated. The carbonated apatite layer contains much more protein than the magnetite layer [22]. To date, nothing is known about the individual proteins within the framework. 

---