L-Glutamate

Synthesis. Using hexamethyl amine as initiator, we have copolymerized, in DNF solution, the N-carboxy-anhydride [NCA] of benzyl -L-glutamate with the NCAs of the following amino acids cinnamyl-L-glutamate, carbobenzoxy-L-lysine, L-leucine, dL-phenyl alanin, L-phenyl alanin. 

To obtain block copolymers, we copolymerize successively the NCAs of the two a amino acids. At the end of the polymerization of the first block we protect the NHp terminus by an D-nitrophenyl-sulphenyl group to allow its fractionation and its characterization. After elimination of the protecting group we polymerize the NCA of the second amino acid. 

To obtain random copolymers, we polymerize simultaneously the NCAs of the two amino acids and we follow the copolymer composition during polymerization to be sure that it remains nearly constant and that there is no formation of blocks. 

Structure. All the random and block copolymers we have synthesized exhibit liquid crystalline structures in dioxane. 

We have not studied the cholesteric phases found between about 50 % and 80 % of solvent for some copolymers, because X-Ray diffraction patterns of this phase are very poor [one observes only a band at low angles) and do not allow a detailed analysis of the cholesteric structure. 

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MSG, C8H8NNa04,H20. Flavouring agent extensively used as a food additive. Prepared from natural or synthetic L-glutamic acid. 

A search for derivatives of L-glutamate can be performed by a substructure search (SSS) (sec Section 6.3). figure 10,3-24b shows the query of the SSS observe that here, too, the stereochemistry can be specified and this is then considered in the SSS. The query provides 25 hits, including L-glutamatc, N-acctylghjtamate, etc. but also compounds such as tctrahydrofolatc, folate, etc. which would never be found by a name search,... 

Ammonia reacts with the ketone carbonyl group to give an mine (C=NH) which is then reduced to the amine function of the a ammo acid Both mine formation and reduc tion are enzyme catalyzed The reduced form of nicotinamide adenine diphosphonu cleotide (NADPH) is a coenzyme and acts as a reducing agent The step m which the mine is reduced is the one m which the chirality center is introduced and gives only L glutamic acid... 

L Glutamic acid is not an essential ammo acid It need not be present m the diet because animals can biosynthesize it from sources of a ketoglutaric acid It is however a key intermediate m the biosynthesis of other ammo acids by a process known as transamination L Alanine for example is formed from pyruvic acid by transamination from L glutamic acid... 

In transamination an amine group is transferred from L glutamic acid to pyruvic acid An outline of the mechanism of transamination is presented m Figure 27 4... 

Step 1 The amine function of l glutamate reacts with the ketone carbonyl of pyruvate to form an mine... 

The intrinsic viscosity of poly(7-benzyl-L-glutamate) (Mq = 219) shows such a strong molecular weight dependence in dimethyl formamide that the polymer was suspected to exist as a helix which approximates a prolate ellipsoid of revolution in its hydrodynamic behaviorf ... 

Poly(7-benzyl-L-glutamate) is known to possess a helical structure in certain solvents. As part of an investigationf of this molecule, a fractionated sample was examined in chloroform (CHCI3) and chloroform saturated ( 0.5%) with dimethyl formamide (DMF). The following results were obtained ... 

Flavor Enhancers. Flavor enhancers have the abihty to enhance flavors at a level below which they contribute any flavor of their own. Worldwide, the most popular flavor enhancers are monosodium L-glutamate [142-47-2] (MSG), NaC HgNO, and the 5 -ribonucleotides disodium 5 -inosinate [131-99-7] (IMP), and disodium S -guanjIate [85-75-5] (GMP), C QH 2-N50gP -2Na. 

Polymer Solutions. Perhaps the most extensively studied macromolecular Hquid crystals are the synthetic polypeptides, such as poly( y-benzyl L-glutamate) [25513-40-0] (PBLG). PBLG is a homopolymer of the L-enantiomorph of a single amino acid with the foUowiag repeat unit. 

Hydroxylated amino acids (eg, 4-hydroxyproline, 5-hydroxylysine) and A/-methylated amino acids (eg, /V-methylhistidine) are obtained by the acid hydrolysis of proteins. y-Carboxyglutamic acid occurs as a component of some sections of protein molecules it decarboxylates spontaneously to L-glutamate at low pH. These examples are formed upon the nontranslational modification of protein and are often called secondary protein amino acids... 

In the food industries a number of amino acids have been widely used as flavor enhancers and flavor modifiers (see Flavors and spices). For example, monosodium L-glutamate is well-known as a meat flavor-enhancer and an enormous quantity of it is now used in various food appHcations (see Amino acids, L-MONOSODIUM glutamate (MSG)). Protein, hydroly2ed by acid or en2yme to be palatable, has been used for a long time in flavoring agents. 

Amino acid polymers like poly(y-methyl-L-glutamate) [29967-97-3] h.a.ve been developed as raw materials for artificial leathers (see Leatherlike materials). Derivatives of amino acids are now finding new appHcations in industry and agriculture. 

Crystalline Structures. Crystal shape of amino acids varies widely, for example, monoclinic prisms in glycine and orthorhombic needles in L-alanine. X-ray crystallographic analyses of 23 amino acids have been described (31). L-Glutamic acid crystallizes in two polymorphic forms (a and P) (32), and the a-form is mote facdely handled in industrial processes. The crystal stmeture has been determined (33) and is shown in Figure 1. 

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