Search results for "tryptophan"

L-Tryptophan on Cu(111): engineering a molecular labyrinth driven by indole groups

2015

The present article investigates the adsorption and molecular orientation of L-Tryptophan, which is both an essential amino acid important for protein synthesis and of particular interest for the development of chiral molecular electronics and biocompatible processes and devices, on Cu(111) using scanning tunneling microscopy and spectroscopy at 55 K and at room temperature. The arrangement of chemisorbed L-Tryptophan on the copper surface varies with both temperature and surface coverage. At low coverage, small clusters form on the surface irrespective of temperature, while at high coverage an ordered chain structure emerges at room temperature, and a tightly packed structure forms a molec…

Redox intermediates of plant and mammalian peroxidases: a comparative transient-kinetic study of their reactivity toward indole derivatives.

2002

Abstract A comparative study on the reactivity of five indole derivatives (tryptamine, N-acetyltryptamine, tryptophan, melatonin, and serotonin), with the redox intermediates compound I (k2) and compound II (k3) of the plant enzyme horseradish peroxidase (HRP) and the two mammalian enzymes lactoperoxidase (LPO) and myeloperoxidase (MPO), was performed using the sequential-mixing stopped-flow technique. The calculated bimolecular rate constants (k2, k3) revealed substantial differences regarding the oxidizability of the substrates by redox intermediates at pH 7.0 and 25°C. With HRP it was shown that k2 and k3 are mainly determined by the reduction potential (E°′) of the substrate with k2 bei…

ARGININE, HISTIDINE AND TRYPTOPHAN IN PEPTIDE SYNTHESIS. THE INDOLE FUNCTION OF TRYPTOPHAN

1990

ChemInform Abstract: Arginine, Histidine, and Tryptophan in Peptide Synthesis. The Indole Function of Tryptophan

2010

Synthesis and in Vitro Evaluation of Biotinylated RG108:  A High Affinity Compound for Studying Binding Interactions with Human DNA Methyltransferases

2006

Small-molecule inhibitors of DNA methyltransferases such as RG108 represent promising candidates for cancer drug development. We report the synthesis and in vitro analysis of a biotinylated RG108 conjugate, 2-(1,3-dioxo-1,3-dihydro-isoindol-2-yl)-3-(5-[3-[5-(2-oxo-hexahydro-thieno[3,4-d]imidazol-4-yl)pentanoylamino]propoxy]-1H-indol-3-yl)propionic acid (bio-RG108), for the evaluation of interactions with DNA methyltransferase enzymes. The structural design of the chemically modified inhibitor was aided by molecular modeling, which suggested the possibility for extensive chemical modifications at the 5-position of the tryptophan moiety in RG108. The inhibitory activity of the corresponding d…

Regio- and stereo-selectivity in the intramolecular quenching of the excited benzoylthiophene chromophore by tryptophan

2000

Laser flash photolysis studies on the photobehaviour of a series of bichromophoric derivatives bearing benzoylthiophene and tryptophan groups have shown that the efficiency of the intramolecular quenching process depends on both the stereochemistry of the chiral centers and the relative ketone versus tryptophan orientation. Perez Prieto, Julia, Julia.Perez@uv.es

Thermal aggregation of bovine serum albumin at different pH: comparison with human serum albumin.

2007

We report here a study on thermal aggregation of BSA at two different pH values selected to be close to the isoelectric point (pI) of this protein. Our aim is to better understand the several steps and mechanisms accompanying the aggregation process. For this purpose we have performed kinetics of integrated intensity emission of intrinsic and extrinsic dyes, tryptophans and ANS respectively, kinetics of Rayleigh scattering and of turbidity. The results confirm the important role played by conformational changes in the tertiary structure, especially in the exposure of internal hydrophobic regions that promote intermolecular interactions. We also confirm that the absence of electrostatic repu…

Effects of photodynamic processes and ultraviolet light on duck and hen egg-white lysozymes.

1973

— The photochemical yields for inactivation and amino acid destruction in hen and duck egg-white lysozyme are presented. Duck lysozyme II is devoid of histidine but it has two more tyrosine residues than does hen lysozyme. The data indicate that sensitized oxidation of the single histidine residue of hen lysozyme is of no significance for the inactivation of this lysozyme. The ultraviolet destruction of tryptophan and cystine residues appears to be equally related with the loss in enzymatic activity of hen lysozyme. In the case of duck lysozyme, however, the ultraviolet inactivation appears to be predominantly governed by the destruction of cystine residues.

New amide and dioxopiperazine derivatives from leaves of Breynia nivosa

2017

The first chemical investigation of leaves of Breynia nivosa from Nigeria resulted in the isolation of two new amide derivatives breynivosamides A and B (1 and 2) and two new dioxopiperazine derivatives breynivosines A and B (4 and 5) together with seven known compounds (3, 6-11). The structures of the new compounds were elucidated by 1D, 2D NMR and HRESIMS data as well as by comparison with the literature. All isolated compounds were tested for the cytotoxic and antimicrobial activities. Only cristatin A (6) showed cytotoxicity against the L5178Y mouse lymphoma cell line with an IC50 value of 13.9μM while breynivosamide A (1) exhibited moderate antimicrobial activity against Mycobacterium …

Cooperative Transition in the Conformation of 24-Mer Tarantula Hemocyanin upon Oxygen Binding

2005

Hemocyanins are large respiratory proteins of arthropods and mollusks, which bind oxygen with very high cooperativity. Here, we investigated the relationship between oxygen binding and structural changes of the 24-mer tarantula hemocyanin. Oxygen binding of the hemocyanin was detected following the fluorescence intensity of the intrinsic tryptophans. Under the same conditions, structural changes were monitored by the non-covalently bound fluorescence probe Prodan (6-propionyl-2-(dimethylamino)-naphthalene), which is very sensitive to its surroundings. Upon oxygen binding of the hemocyanin a red shift of 5 nm in the emission maximum of the label was observed. A comparison of oxygen binding c…