1990-34-7

Upstream product

• 100-02-7 4-nitro-phenol 
• 1218-34-4 N-acetyl-DL-tryptophan 
• 54-12-6 Trp 

Relevant academic research and scientific papers

Targeting peptides with an iron-based oxidant: Cleavage of the amino acid backbone and oxidation of side chains

The oxidation of protected amino acids using an iron-based oxidant is described. Substrates of the general formula Ac-X-NHtBu, where X = Gly (1), Ala (2), Val (3), Phe (4), Tyr (5), Trp (6), and Met (7) were constructed to model individual amino acid residues within a polypeptide chain. Oxidation of 1 by the iron catalyst [FeII(N4Py)(MeCN)](ClO4)2 (8) and KHSO5 leads to scission of the amino acid backbone and produces N-acetylformamide as the major product. Decomposition of the iron-based oxidant [FeIV(O)(N4Py)]2+, derived from 8, is slower in the presence of 2,2-d2-1 (96% D) than with 1, giving a kinetic isotope effect of 4.8, which is consistent with [FeIV(O)(N4Py)]2+ cleaving an α-CH bond of 1. Aliphatic amino acid substrates 2 and 3 do not react with [FeIV(O)(N4Py)]2+ under the same conditions used with 1. With substrates 4-7 oxidation of the amino acid side chain is observed. Decomposition of [FeIV(O)(N4Py)]2+ upon treatment with 10 equiv of 1 and 4-7 revealed that 5 is the most reactive toward the FeIVO species. Pseudo-first-order rate constants of 17.0(5) × 10-3, 3.15(8) × 10-3 and 5.8(2) × 10-5 s-1 were obtained for decomposition of [FeIV(O)(N4Py)]2+ ([Fe] = 1 mM, 1:1 H2O/MeCN) by 6, 7, and 1, respectively. Copyright

Fluorescence anisotropy and mobility of dansyl fluorophore in labelled homologous alkanes

Using the steady-state and time-resolved fluorescence anisotropy, the mobility of 5-(dimethylamino)naphthalene-1-sulfonyl (dansyl) fluorophore in homologous 1-[2-acetamido-3-(1H-indol-3-yl)propanamido[-n-]5-(dimethylamino)naphthalene-1-s ulfonamido]alkanes 1 was studied in binary solvents glycerol-water. Steady-state fluorescence data were evaluated by the generalized Perrin equation and the micro-Brownian motion of dansyl fluorophore was described by means of average characteristics (rotational relaxation times) of the rotational relaxation spectrum. The rotational relaxation time of "fast" motions caused by torsional vibrations of single bonds within the rotational-isomeric states decreases with increasing number of methylene groups in homologous compounds. The rotational relaxation time of "slow" motions due to conformational changes of the chain between the tryptophane and dansyl fluorophore remains at first approximately constant with increasing number of methylene groups but increases considerably for long aliphatic chains. The observed decrease in the rate of conformational changes of a long aliphatic chain is probably due to intramolecular interaction of parts of the methylene chain in a medium with high water content. The values of activation enthalpy ΔH+ and activation entropy ΔS≠ calculated from experimental data corroborate such interpretation. Time-resolved anisotropy of dansyl fluorophore at a particular binary solvent composition confirmed the shape of rotational relaxation spectrum and the measured rotational correlation times have been discussed. The time-dependent decays of anisotropy supported our previous interpretation in terms of intramolecular association of the long aliphatic chain in polar medium.