Aminoacids Absorption

The iron absorption is enhanced when soluble monomeric complexes are formed (in the presence of e.g. proteins, aminoacids, ascorbic acid, EDTA, citric acid etc.) [13]. 

M. A. Palacios, A. Varga, M. Gomez, C. Camara, F. Gavilanes, Evaluation of acid hydrolysis of proteins on Se-aminoacids and trimethylselenonium species by liquid chromatography-microwave digestion-hydride generation-atomic absorption spectrometry, Quim. Anal., 18 (1999), 163-168. 

The phthalimide functional group has absorption and ET properties which make it very attractive in terms of PET processes in which it is the oxidizing species. The application of phthalimide derivatives in carbon-carbon bond forming processes with electron-donating groups such as ethers, thioethers, amines, arenes, carboxylates, etc., has been reviewed. A PET decarboxylation-cycliz-ation sequence has been used for the synthesis of medium-sized (8-16) heterocyclic ring systems (15) from AT-phthaloylanthranilic amides coupled to ca-aminoacids (14). The same PET protocol has been used to convert di-, tri-, and tetrapeptides into cyclopeptides with a minimum of protection and activation... 

As previously mentioned, tryptophanase is inhibited by a variety of different amino acids, which react with the PLP-cofactor to form covalent intermediates (102), but the structure of the substrate prevents completion of the reaction pathway. At equilibrium, these quasisubstrates generally form intense absorption bands in the 500-nm region of the spectrum, which result from the accumulation of a stable quinonoidal species. Phillips et al. (105) utilized RSSF in conjunction with SWSF studies to investigate the mechanisms of reaction for various aminoacid analogs of i-Trp in order to determine substrate structural elements important both for substrate binding and reactivity with the enzyme (structures 6-9). 

Investigations of approaches to (3-lactams through (3-aminoacid derivatives have resulted in the synthesis of a cholesterol absorption inhibitor 64 <96JOC834l>, the development of phosphorodimorpholidic halides as condensing agents <96MI656>, and a new synthesis of the thienamycin intermediate 65 <97CC565>. 

Some of the fluorophores native to cells are NADH, flavins and aromatic aminoacids constituents of proteins (e.g., tryptophan, tyrosine, phenylalanine). Various porphyrins and lipopigments such as ceroids, lipofuscin, which are end products of lipid metabolism, also fluoresce. In addition, some important endogenous fluorophores are present in the extracellular structures of tissues. For example, collagen and elastin, present in the extracellular matrix (ECM), fluoresce as a result of cross-linking between amino acids. The absorption and emission spectra of some endogenous fluorophores are shown in Figure 3 (Katz and Alfano, 2000). 

Conformational studies on non-natural poly-a-aminoacids containing the nitroaromatic chromophore in the side-chain, and on derivatives of [L-Trp] and [L-His] showed that, in the presence of bulky substituents the side-chain chromophores cannot assume an ordered array around the a-helical backbone. This fact is probably responsible for the absence of strong perturbation from the side-chain chromophores in the amide CD absorption region. 

Ho, W. S., Sartoii, G., and Stogryn, E. L., 1990, Absorbent Composition Containing a Severely Hindered Amine Mixture With Amine Salts and/or Aminoacid Additives for the Absorption of H2S from Fluid Mixtures Containing CO2, US Patent 4,961,873, Oct 9. 

Electronic transitions of the carbazole chromophores afford a highly sensitive probe for studies of carbazole-containing polymers in respect of their absorption and emission characteristics as well as of either inherent or induced circular dichroism. They have been conveniently employed to describe microstructural characteristics of carbazole-containing polymers, including homopolymers of carbazolated a-aminoacids and of vinylated carbazoles with chiral substituents. Data obtained are entirely consistent with interpretation of polymer structures derived from related UV absorption, excimer fluorescence emission and NMR studies and are especially valuable as a completely new indication of copolymer sequence distributions. 

Rowe, P.B. and Wyngaarden, J.B. 1968. Glutamine phosphoribosyl-pyrophosphate amidotransferase. Purification, substructure aminoacid composition and absorption spectra. J. Biol. Chem. 245 6373-6383. 

---