Amino nitrogen decrease

Hydrogen sulfide production is highly correlated to must composition (29). Lack of pantothenate or zinc stimulates hydrogen sulfide production, as does an excess of iron or copper (29) as free amino nitrogen decreases, hydrogen sulfide production may increase (61). 

Group IV substituents, especially the trimethylsilyl group, apparently enhance the electron affinity of aromatic systems. The effect is particularly noticeable in aniline derivatives. The strong electron-releasing effect of the amino group decreases the electron affinity of the aniline derivatives and hinders reduction to the radical anions. Nitroanilines may be reduced to radical anions (65). The only other aniline radical anions that have been reported bear silyl substituents either at nitrogen (62) or on the ring (83, 85, 86). 

Nitrogen values more than triple on adding ammonium nitrate. The mor the straw is rotted, the less nitrogen can be hydrolyzed with hydrochloric acid. A part of the nitrogen in the lignin fractions is fixed as a-amino nitrogen. The quantity decreases from 60% of total nitrogen content in fresh straw to about 20% in rotted straw. A remarkable decrease could be observed for the methoxyl content. This fact can be explained by an enzymatic demethylation process. 

Carbon-13 shift values of aliphatic amines [337-339] collected in Table 4.42 indicate that the y effect is about — 4.5 ppm for primary, secondary, and tertiary amines. The a effect, however, increases while the ft effect decreases with an increasing degree of alkylation at the amino nitrogen. Analogously to alkanols, two increment systems can be used to predict alkyl carbon shifts of amines according to eq. (4.12 a, b), based on the reference shifts of corresponding alkanes (R —H) or the methyl homologs (R —CH3) [337, 338] (Table 4.43). 

However, when a free amino group is present (Ri) in compounds VIII and IX, the unpaired electrons of the amino nitrogen atom may influence the electronegativity of the carbonyl carbon atom and thereby decrease its tendency to withdraw electrons from the adjacent a-carbon... 

Introduction of a silyl group at the position a to the nitrogen decreases the oxidation potentials of organonitrogen compounds by at most 0.3 V (Table 7)31. fi- and y-silyl groups do not cause a significant decrease in the oxidation potential. The introduction of a silyl group directly on the amino nitrogen atom does not decrease the oxidation potentials of amines. 

When promoted by sodium hydroxide, the Maillard reaction, as evidenced by a decrease in amino nitrogen, is reversible on addition of acid. However, if the reaction proceeds near neutrality in the presence of phosphate, this is not so.168... 

Activation of the polyol pathway results in a decrease of NADPH and NAD+ these are necessary cofactors in redox reactions throughout the body. The decreased concentration of these cofactors leads to decreased synthesis of reduced glutathione, nitric oxide, myoinositol and taurine. Myoinositol is particularly required for the normal function of nerves. Sorbitol may also glycate the amino nitrogen on proteins such as collagen, forming AGEs. 

The three-atom chain between position 10 and the amino nitrogen is required. Shortening or lengthening the chain nt this position drastically decreases activity. The three-atom chain length may be necessary to bring the protonated amino nitrogen into proximity with the 2-.substituent. 

These compounds were synthesized because it was noticed that several competitive inhibitors of the NMDA receptor had alpha-amino carboxylic acid and phosphonic acid functionalities separated by 3-5 carbons. All of the inhibitors shown in Fig. 11.11 have K- values for inhibition of the NMDA receptor of 10 juM or less. In general, nitrogen substituents larger than those shown decrease receptor affinity. In addition, substitution on the second nitrogen decreases affinity. 

Using the cyclic voltamperometric method, oxidation potentials of some 2V-aminoazoles have been measured (Table VII). All compounds thus investigated give only a one-electron oxidation wave. The oxidation process is practically irreversible, and this represents instability in the radical-cations thus formed. Comparison of the oxidation of A -amino- and N-methyl-benzazoles indicates that the A-amino groups decreases the Ep value on the average by 0.2 V. Probably, this is explained by an overlap of the heterocycle 7r-orbitals with that of the unshared electron pair of the amine nitrogen atom, providing some stabilization of the radical-cation. 

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