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Tryptophan Side Chain (tryptophan + side_chain)

Distribution by Scientific Domains

Chemistry	83%

Selected Abstracts

Calculated Raman Optical Activity Signatures of Tryptophan Side Chains

CHEMPHYSCHEM, Issue 15 2008
Christoph R. Jacob Dr.
Raman optical activity: The different local chirality of an adjacent group can cause a different sign of the ROA intensity of an amino-acid side chain (here tryptophan, see picture centre), even though the normal mode is unchanged. Calculated spectra clearly confirm that ROA spectroscopy can be utilized to determine the absolute conformation of tryptophan side chains in proteins (see figure, left and right). [source]

Re-evaluation of intramolecular long-range electron transfer between tyrosine and tryptophan in lysozymes

FEBS JOURNAL, Issue 17 2003
Evidence for the participation of other residues
One-electron oxidation of six different c-type lysozymes from hen egg white, turkey egg white, human milk, horse milk, camel stomach and tortoise was studied by gamma- and pulse-radiolysis. In the first step, one tryptophan side chain is oxidized to indolyl free radical, which is produced quantitatively. As shown already, the indolyl radical subsequently oxidizes a tyrosine side chain to the phenoxy radical in an intramolecular reaction. However this reaction is not total and its stoichiometry depends on the protein. Rate constants also vary between proteins, from 120·s,1 to 1000·s,1 at pH 7.0 and room temperature [extremes are hen and turkey egg white (120·s,1) and human milk (1000·s,1)]. In hen and turkey egg white lysozymes we show that another reactive site is the Asn103,Gly104 peptidic bond, which gets broken radiolytically. Tryptic digestion followed by HPLC separation and identification of the peptides was performed for nonirradiated and irradiated hen lysozyme. Fluorescence spectra of the peptides indicate that Trp108 and/or 111 remain oxidized and that Tyr20 and 53 give bityrosine. Tyr23 appears not to be involved in the process. Thus new features of long-range intramolecular electron transfer in proteins appear: it is only partial and other groups are involved which are silent in pulse radiolysis. [source]

Peptide conformational changes induced by tryptophan,phosphocholine interactions in a micelle

BIOPOLYMERS, Issue 5 2002
Jonathan W. Neidigh
Abstract Sodium dodecylsulfate (SDS) and dodecylphosphocholine (DPC) micelles are often used to mimic the membrane- or receptor-bound states of peptides in NMR studies. From the present examination of a 26-residue analog of exendin-4 (TrEX4) by NMR and CD in water, aqueous 30% trifluoroethanol (TFE), and bound to both SDS and DPC micelles, it is clear that these two lipid micelles can yield very different peptide structures. The Trp-cage fold (also observed in 30% TFE) is present when TrEX4 is bound to SDS micelles; however, tertiary structure is absent in the presence of DPC micelles. The loss of tertiary structure is attributed to an energetically favorable interaction (estimated as 2,3 kcal/mol) of the tryptophan side chain with the phosphocholine head groups. These dramatic structural differences suggest that care must be taken when using either SDS or DPC to mimic the membrane- or receptor-bound states. © 2002 Wiley Periodicals, Inc. Biopolymers 65: 354,361, 2002 [source]

Tryptophan ,-Electron System Capping a Copper(I) Binding Site,A New Organometallic Bonding Mode in Proteins

CHEMBIOCHEM, Issue 11 2008
Olaf Kühl Dr.
,2 -Arene coordination (dotted lines) from the aromatic tryptophan side chain to CuI (red) in the prokaryotic CuI -transport protein CusF represents a new organometallic interaction in biology. [source]

Role of Arginine in Protein Refolding, Solubilization, and Purification

BIOTECHNOLOGY PROGRESS, Issue 5 2004
Kouhei Tsumoto
Recombinant proteins are often expressed in the form of insoluble inclusion bodies in bacteria. To facilitate refolding of recombinant proteins obtained from inclusion bodies, 0.1 to 1 M arginine is customarily included in solvents used for refolding the proteins by dialysis or dilution. In addition, arginine at higher concentrations, e.g., 0.5,2 M, can be used to extract active, folded proteins from insoluble pellets obtained after lysing Escherichia coli cells. Moreover, arginine increases the yield of proteins secreted to the periplasm, enhances elution of antibodies from Protein-A columns, and stabilizes proteins during storage. All these arginine effects are apparently due to suppression of protein aggregation. Little is known, however, about the mechanism. Various effects of solvent additives on proteins have been attributed to their preferential interaction with the protein, effects on surface tension, or effects on amino acid solubility. The suppression of protein aggregation by arginine cannot be readily explained by either surface tension effects or preferential interactions. In this review we show that interactions between the guanidinium group of arginine and tryptophan side chains may be responsible for suppression of protein aggregation by arginine. [source]