Correlation amides

Tjandra N and Bax A 1997 Solution NMR measurement of amide proton chemical shift anisotropy in N-15-enriched proteins. Correlation with hydrogen bond length J. Am. Chem. Soc. 119 8076-82... 

As an example, experimental kinetic data on the hydrolysis of amides under basic conditions as well as under acid catalysis were correlated with quantitative data on charge distribution and the resonance effect [13]. Thus, the values on the free energy of activation, AG , for the acid catalyzed hydrolysis of amides could be modeled quite well by Eq. (5)... 

Acid amide herbicides are nonionic and moderately retained by soils. The sorption of several acid amide herbicides has been investigated (369). Acetochlor [34256-82-1] is sorbed more than either alachlor or metolachlor, which are similarly sorbed by a variety of soils. Sorption of all the herbicides is well correlated to soil organic matter content. In a field lysimeter study, metolachlor has been found to be more mobile and persistent than alachlor (370) diphenamid [957-51-7] and napropamide [15299-99-2] have been found to be more readily leached (356). 

Inhibition of Nitrosamine Formation. Nitrites can react with secondary amines and A/-substituted amides under the acidic conditions of the stomach to form /V-nitrosamines and A/-nitrosamides. These compounds are collectively called N-nitroso compounds. There is strong circumstantial evidence that in vivo A/-nitroso compounds production contributes to the etiology of cancer of the stomach (135,136), esophagus (136,137), and nasopharynx (136,138). Ascorbic acid consumption is negatively correlated with the incidence of these cancers, due to ascorbic acid inhibition of in vivo A/-nitroso compound formation (139). The concentration of A/-nitroso compounds formed in the stomach depends on the nitrate and nitrite intake. 

When hydroxypteridines are considered, it must be borne in mind that these compounds exist principally in the pteridinone forms, containing thermodynamically stable amide functions, and consequently have low reactivity. Their stability towards acid and alkali correlates well with the number of electron-donating groups which apparently redress the deficit of ir-electrons located at the ring nitrogen atoms. Quantitative correlations can be seen in the decomposition studies of various pteridinones (Table 7). These results are consistent with the number of the oxy functions and their site at the pteridine nucleus. The... 

Coleman et al. have performed a preliminary structure/activity study for a series of analogues of 77 [149]. They found that removal of the naphthoate moiety (88 Scheme 11.11) dramatically reduced the yield of DNA alkylation, while replacement of the NH2 group with O-benzyl (89 and 90) abolished DNA alkylation completely. Compound 91 alkylated DNA with reduced efficiency, so this effect is not simply due to a requirement for a hydrogen bond donor at this position. Perhaps the amide is required at this position to increase the ability of the C=0 to act as a hydrogen bond acceptor. Importantly, they found a strong correlation between the extent of in vitro DNA alkylation and cell culture cytotoxicity. 

Then the AH values of sulphoxides and amides were correlated with Taft s a affording the following equation ... 

The second problem involves the measurement of pKa values for carbonyl and thiocarbonyl derivatives. Grieg and Johnson (157) have pointed out that the measurement of pKa values for very weak bases (11) is an inaccurate and arbitrary process. Of particular difficulty for our purposes is the fact that different carbonyl derivatives may require different acidity functions. As a result of this situation, no attempt was made to make correlations of pKa data for carbonyl and thiocarbonyl derivatives with eq. (2). Because accurate pKa values can be measured for imines, these values were correlated with eq. (2), although the conformational problem remains. The imine sets were first studied by Charton and Charton (73), who correlated them with eq. (2). No correlations of data for carbonyl or thiocarbonyl derivatives with eq. (2) are extant in the literature. Bhaskar, Gosavi, and Rao (158) have reported that AG values for complex formation of substituted thioureas with iodine are a linear function of the Taft a values. Drago, Wenz, and Carlson (159) have reported similar results for complex formation between iodine and substituted amides. Oloffson (160) has reported a linear relationship between -AH for the complex of substituted N,N-dimethylamides with SbCls and the ffj constants. 

Amides, alkaline hydrolysis, 215 Anharmonic systems, direct evaluation of quantum time-correlation functions, 93 Apollo DSP—160, CHARMM performance, 129/ simulations, solvent effects, 83... 

Of the other physico-chemical data available to us we found good predictive correlations between the spectra and the degree of amidation (Fig. 6)... 

The data from sensory evaluation and texture profile analysis of the jellies made with amidated pectin and sunflower pectin were subjected to Principal component analysis (PC) using the statistical software based on Jacobi method (Univac, 1973). The results of PC analysis are shown in figure 7. The plane of two principal components (F1,F2) explain 89,75 % of the variance contained in the original data. The attributes related with textural evaluation are highly correlated with the first principal component (Had.=0.95, Spr.=0.97, Che.=0.98, Gum.=0.95, Coe=0.98, HS=0.82 and SP=-0.93). As it could be expected, spreadability increases along the negative side of the axis unlike other textural parameters. 

The jellies made with sunflower pectin and amidated pectin (level 1%) are very similar (in so far as texture is concerned) but as the polynomial correlation (degree 2) suggests, above 0.7% of sunflower pectin the overall acceptance decreases probably due to the appearance of perceived in-mouth sensations described as greasy and clammy and leading to an unfavourable appreciation. 

The authors expressed PKA consisting of 353 amino acids, of which eight are prolines. Resonances of 274 backbone amide peaks were visible in the spectrum, of which 191 were assigned. It was possible to assign resonances for the N- and C-terminal sequences, the majority of the N-lobe, including the glycine-rich loop, and most of the solvent-exposed residues of the C-lobe. This enabled a determination of the structure for the more flexible parts of the structure. However, many correlations were missing for the... 

Molecular geometrical differences between the amides (225) and (226), the latter having the more pyramidal arrangement around nitrogen, have been correlated with the known differences in their solvolytic behaviour. 

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