Amino acids soil peptides

Dietary copper intake is approximately 1-2 mg/day. Quoted copper contents of foods are unreliable. While some foods, such as meats and shellfish, have consistently high concentrations, others such as dairy produce are consistently low in copper. However, the copper content of cereals and fruits varies greatly with soil copper content and the method of food preparation. Estimates of copper intake should include water copper content, and the permitted upper copper concentration for drinking water is 2mg L. Approximately 10% of dietary copper is absorbed in the upper intestine, transported in the blood loosely bound to albnmin, certain amino acids and peptides. Finally, most of the ingested copper is taken np by the liver. Copper homeostasis is critically dependent on the liver becanse this organ provides the only physiologically relevant mechanism for excretion of this metal. 

Various examples of solid-state NMR applications are collected in the final Section 4. This section is divided into subsections depending on the type of the material studied (4.1) organic solids (4.2) pharmaceutical and biomedical applications (4.3) amino acids and peptides (4.4) proteins (4.5) membrane proteins and lipids (4.6) polymers (4.7) carbonaceous materials and soils (4.8) organometallic and coordination compounds (4.9) glasses and amorphous solids (4.10) surface science and catalysis, and (4.11) inorganic and other related solids. 

Hydrolysis reactions occur by nucleophilic attack at a carbon single bond, involving either the water molecule directly or the hydronium or hydroxyl ion. The most favorable conditions for hydrolysis, e.g. acidic or alkaline solutions, depend on the nature of the bond which is to be cleaved. Mineral surfaces that have Bronsted acidity have been shown to catalyze hydrolysis reactions. Examples of hydrolysis reactions which may be catalyzed by the surfaces of minerals in soils include peptide bond formation by amino acids which are adsorbed on clay mineral surfaces and the degradation of pesticides (see Chapter 22). 

A comparison of the mean amino acid composition of the soils with those of algae, bacteria, fungi, and yeasts showed the greatest similarity to that of bacteria. [4] This suggests, perhaps not too surprisingly, a major role for microorganisms in the synthesis in the soil of amino acids, peptides and proteins from plant and animal residues, and also explains the relatively uniform amino acid composition in different soils. 

As to the origins of the major N compounds identified, it is possible that at least a portion of some of these compounds are pyrolysis products of amino acids, peptides, proteins, [18] and porphyrins (a component of chlorophyll), [19] or originate from the microbial decomposition of plant lignins and other phenolics in the presence of ammonia. [20] Of considerable interest are the identifications aromatic and aliphatic nitriles. Nitriles can be formed from amines with the loss of 2 H2, from amides with the loss of H20, and also by reacting n-alkanoic acid with NH3. [21] The detection of long-chain alkyl- and dialkyl-nitriles points to the presence in the soil or SOM of long-chain amines... 

From the data presented herein and in earlier publications, [16,17, 28] it is possible to deduce the following distribution of total N in soils proteinaceous materials (proteins, peptides, and amino acids) 40%, amino sugars 5%, heterocyclic N compounds (including purines and pyrimidines) 35 %, and NH3 20% with about 1/4 of the NH3 fixed as NH4 to clay minerals. Thus, proteinaceous materials and heterocyclic N compounds are the major soil N components. 

L. Verma, J.P. Martin and K. Haider, Decomposition of carbon-14-labeled proteins, peptides, and amino acids free and complexed with humic polymers, Soil Sci. Soc. Am. Proc. 39 (1975) 279-284. 

Freeze-dried DOM samples collected with the siphon-elution system (Kuzyakov and Siniakina, 2001) for the first time showed diurnal dynamics in the molecular-chemical composition of maize rhizodeposits (Kuzyakov et al., 2003). In a forthcoming study with maize, Melnitchouck et al. (2005) showed that amino acids, especially aspartic acid, asparagine, glutamic acid, phenylalanine, leucine and isoleucine contributed to the more intensive rhizodeposition during daytime than during nighttime. Furthermore, the maximum of thermal volatilization of peptides at low pyrolysis temperature in Figure 14.8 indicates the rhizodeposition or microbial formation of free amino acids rather than amino acids bound in peptides or trapped in soil humic substances. 

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