Interactions of carboxyl groups

For polycaproamide, the formation of cross-linked structures occurs more slowly at 280°C the polymer is converted to an infusible, insoluble product after 12 days. The authors explain the cross-linking of polyamides by the presence of secondary amino groups, formed in the interaction of the terminal amino groups, as was indicated above, as well as ketone groups, formed according to the following reaction (interaction of carboxyl groups) ... 

Later, many research groups demonstrated the ability of nucleation of HA crystals onto collagen through a chemical interaction of carboxylate groups of collagen macromolecules [138-140]. All the reports suggested that the nucleation process... 

Hayama et al.132 discussed the catalytic effects of silver ion-polyacrylic add systems toward the hydrolyses of 2,4-dinitrophenylvinylacetate 84 (DNPVA) by using the weak nudeophilicity of carboxylic groups and the change-transfer interactions between olefinie esters and silver ions133Metal complexes of basic polyelectrolytes are also stimulating as esterase models. Hatano etal. 34, 13S) reported that some copper(II)-poly-L-lysine complexes were active for the hydrolyses of amino acid esters, such as D- and L-phenylalanine methyl ester 85 (PAM). They... 

The interaction of Ca2+ with pectins is discussed. The role of carboxylic acid salt formation and the degree of polymerization are first considered in terms of electrostatic and/or cooperative specific interactions. Then the effect of the degree of esterification and that of the pattern of carboxylic group distribution are discussed pectin esterase forms blocks which behave as fully hydrolyzed polymers and favor aggregation. Finally, the role of the calcium addition on the degree of aggregation was established. All the data show the important role of molecular structure of the pectins on calcium interactions. 

Characteristics of toxicity for a number of metals are presented in Table 7.5. While the exact tissue and molecular site of the toxic action of each metal is different, toxicity generally results from interaction of the metal with specific functional groups on macromolecules in the cell. These groups include sulfhydryl, carboxyl, amino, phosphoryl, and phenolic moieties. Interactions of such groups with metals can lead to disruption of enzyme activities and transport processes and eventually... 

DFT calculations were used to quantify the different interactions. All interactions were found to be repulsive. The most repulsive interactions were along the copper rows (in the [lIO] direction), due to a through-surface interaction between carboxylate groups of different tartaric acid molecules binding next to each other. In addition to these interactions we have proposed the existence of an adsorbate-induced surface stress which reduces the binding energy when more than three tartaric acid molecules bind to the same copper row. This surface stress causes the empty troughs in the (9 0,1 2) ordered structure. ... 

It appears from the evolution of the adhesion index that a distinction has to be made between the interactions carbon blacks are able to have with unsaturated or with saturated (or near-to-saturated) elastomers. Thus, the adhesion index of butyl rubber is enhanced upon oxidation of the black, while the reverse is observed with polybutadiene 38). The improvement of the reinforcing ability of carbon black upon oxidation, in the former case, has been interpreted by Gessler 401 as due to chemical interactions of butyl rubber with active functional groups on the solid surface. Gessler, relating the reinforcing characteristics of the oxidized carbon black for butyl rubber to the presence of carboxyl groups on the surface of the filler, postulated a cationic... 

Substituted-4-oxo-4//-pyrido[l,2-a]pyrimidines of type 74 (6-R H) are transformed to l,4-dihydro-4-oxo-l,8-naphthyridines on the action of heat.bl)-71-7l, 1 29 1 33 323 325 Ring transformation is facilitated by the nearly coplanar disposition of the 4-CO group and the 6-substituent of the pyrido-[l,2-u]pyrimidines. The steric interaction of these groups is shown by the relatively long C-4—N-5 bond (e.g., 147 pm for ethyl 6-methyl-4-oxo-4/f-pyrido[l,2-u]pyrimidine-3-carboxylate, as determined by X-ray study326). The strain caused by this interaction is relieved when the C-4—N-5 bond cleaves. Ring transformation probably takes place via the reactive imino-ketene intermediate (75).130... 

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