Zwitterion genetic

The above concept is based on the fact that in organic chemistry the reaction between a nucleophile and an electrophile proceeds without any catalyst. The new copolymerization consists of the combination between a monomer (MN) having nucleophilic reactivity and a monomer (ME) having electrophilic reactivity. The interaction between these two monomers generates a zwitterion 27 called genetic zwitterion . 

A typical and illustrative example is the copolymerization of 2-oxazoline 30 with P-propiolactone 31 which yields a 1 1 alternating copolymer 32 at room temperature. A genetic zwitterion 33 is produced by ring opening of 31 upon attack of the nucleophile 30 (Eq. (23)). 

Zwitterions are the propagating species in a number of spontaneous polymerizations that occur upon mixing electron donor and acceptor monomers. Several reviews of spontaneous polymerizations via zwitterion intermediates are available [317-323]. In this novel type of polymerization reaction there is no need to add an initiator or catalyst. Alternating copolymers have been obtained in some cases when at least one of the monomers contains a heterocycle. In these polymerizations a nucleophilic monomer (Mn) and an electrophilic monomer (Me) react to form a zwitterion [Eq. (89)]. This zwitterion is referred to as a genetic zwitterion. ... 

Polymer chain growth is initiated by the dimerization reaction of two molecules of zwitterion 487 to form oligomeric zwitterion 488 [Eq. (89)]. Polymer chain growth continues by the addition of other zwitterions. These zwitterions can be the genetic zwitterion 487, oligomeric zwitter-... 

A variety of monomer pairs have been used in spontaneous zwitterion polymerizations. Examples of nucleophilic and electrophilic monomer pairs, genetic zwitterions, and polymer structures are shown in Table 2. 

The initial zwitterion that forms upon combination of a nucleophilic with an electrophilic monomer is called a genetic zwitterion Intramolecular reactions can produce macrocycles ... 

In this reaction the number of copolymer molecules increases at first, then reaches a maximum, and finally decreases as the conversion becomes high. " " When the concentration of both monomers is high, then the formation of genetic zwitterions is favored. As the concentration of macrozwit-terions becomes high and the monomer concentration decreases, the macrozwitterions react preferentially with each other. When stoichiometry is not observed and )5-propiolactone molecules predominate in the reaction mixture, the carboxylate end groups can react in various ways. They can react not only with the cyclic onium sites of the zwitterions, but also with free j -propiolactones, and incorporate more than 50% of the propiolactone units. ... 

The two moles of the "genetic zwitterion" 1 react with each other to produce its dimer 2 which is the smallest species of propagation (Eq 2). Then, the propagation species grows by its reaction with 1 (Eq 3). Zwltterlons 2 and 3 (nil) are called "macro zwitterion", which are dlfferenciated from genetic zwitterion 1. The Intermolecular reaction between two moles of macrozwltterlon and the Intramolecular cycllzatlon of macro zwitterion are also possible, although the contribution of each process depends upon the natures of monomers, reaction conditions and the extent of monomers conversion. 

Alternating copolymerization between 2-oxazollne and yi -proplolactlone 5 (BPL) occurs at room temperature through the genetic zwitterion 6, where 4 acts as Mu and 5 behaves as Mg (2,... 

The Interaction between two zwltterions (genetic zwitterion or macro zwitterion) occurs via the opening of the oxazolinium ring of the cationic site (Eq 6). 

Fig. 3 a Molecular structure of L-glutamic acid in the zwitterion form, b Structural fragment used in the genetic algorithm structure solution calculations for L-glutamic acid, showing the variable torsion angles °... 

Carboxylesterases include cholinesterase (pseudocholinesterase), arylcarboxyesterases, liver microsomal carboxylesterases, and other unclassified liver carboxylesterases. Cholinesterase hydrolyzes oholihe-like esters (succinylcholine) and procaine as well as acetylsalicylic acid. Genetic variant forms of cholinesterase have beeh idehtified in human serum (e.g., succinylcholine toxicity when administered as ganglionic blocker for muscle relaxation). Meperidine is hydrolyzed only by liver microsomal carboxylesterases (Fig. 10.19). Diphenoxylate is hydrolyzed to its active metabolite, diphenoxylic acid, within 1 hour (Fig. 10.19). Presumably, the peripheral pharmacological action of diphenoxylate is attributed to zwitterionic diphenoxylic acid, which is readily eliminated in the urine. 

Amino acids, the monomeric units of peptides and proteins. From analysis of the vast number of proteins, it follows that 20 proteinogenic or standard amino acids are the building blocks of aU proteins. These amino acids are specified by the genetic code. With selenocysteine and pyrrolysine two additional members have been identified. Besides the imino acid proline, all other building blocks are known as a-amino acids, H2N-CHR-COOH, but the zwitterion form, H3N+-CHR-C00, occurs at physiological pH values. The amino acids can therefore act as either acids or bases. Depending on the side-chain residue R, amino acids can be classified into those with (a) non polar side chains [Gly/G Ala/A Val/V Leu/L Ile/I Met/M Pro/P Phe/F Trp/W] ... 

Proteins and peptides are composed of amino acids. They are zwitterions carrying both positive and negative charges. The peptides and polypeptides are similar to proteins in structure but smaller in size. While DNA carries the genetic information, proteins perform catalytic, hormonal, and structural functions. In many of the proteins of clinical interest, such as the urinary protein uromodulin, their functions are not well imderstood nevertheless, they remain to be important and vital. Proteins are important for their function as well as for their diagnostic significance. CE is useful for quantitation, pmity... 

Proteins are complex natural macromolecules made up of successive amino acids that are covalently bonded together in a head-to-tail arrangement through amide bonds. Each protein molecule is composed of an exact sequence of amino acids determined by the genetic code and arranged in a linear fashion. Proteins are zwitterions because they contain both positive and negative charges in a proportion that depends on the amino-acid composition. Hence, proteins are weak... 

In addition, free monomers sometimes take part in propagation, i.e., Mn and Mg may react respectively with the cationic and anionic sites of zwitterion (genetic or macro)(Eqs A and 5). 

D. J. Abraham and A. J. Leo, Proteins Struct., Punct., Genet., 2,130 (1987). Extension of the Fragment Method to Calculate Amino Acid Zwitterion and Side Chain Partition Coefficients. 

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