Interaction Of Aromatic Amino Acids Research Articles

Formation of lipid corona on Ag nanoparticles and its impact on Ag+ ion dissolution and aggregation of Ag nanoparticles against external stimuli

The application of lipid coated nanoparticles has been expanding in nanoscience over the past few years. Lipid corona formation is one of the novel ways for the lipid conjugation around the nanoparticles. Although several properties of nanoparticles and lipids are well reported in literature in last few years, the dependency of lipid corona formation on metallic core and surface ligands is poorly understood. The aggregation, surface oxidation and metal ions dissolution of nanoparticles limit their usefulness in various applications. Besides all the reported methods to overcome all of these limitations, lipid corona could be an alternative, feasible, and more efficient method. In the current manuscript, we investigate the interaction of aromatic amino acids (tyrosine and tryptophan) functionalized silver nanoparticles (Ag-Tyr and Ag-Trp NPs) with different surface charged and phase states lipid vesicles and compare them with the reported amino acid functionalized gold nanoparticles (Au-AA NPs). The effectiveness of different zwitterionic and positively charged lipid coated Ag-Tyr and Ag-Trp NPs to prevent the aggregation and Ag+ ion dissolution of Ag NPs against different external stimuli (acidic pH, high NaCl concentration, and freeze-thaw cycles) are investigated. Our results reveal that surface ligands around the NPs play crucial role for lipid corona formation irrespective of the metallic core of NPs. Although all the lipid coated Ag NPs exhibit greater stability against external stimuli than native Ag NPs, zwitterionic lipid coated Ag NPs is better choice than positively charged lipid coated Ag NPs. This study on lipid corona and its stability will help the nanoresearcher to choose the suitable lipid for lipid corona formation.

Features of l-Tryptophan Solvation in Some Water–Organic Mixtures at T = 298.15 K

The effect of changes in the composition of some water–organic mixtures on the thermodynamic parameters of dissolution and solvation of l-tryptophan was studied by the method of calorimetry of dissolution at T = 298.15 K. To explain the experimental results, the enthalpic coefficients of pairwise interactions between l-tryptophan and organic cosolvent molecules and the energy contributions of the side chain to the energy of intermolecular interactions are calculated, and the influence of some properties of organic solvents on these interactions is estimated. All the data obtained were compared with those for l-phenylalanine to reveal the influence of the side chain structure on the energy of intermolecular interactions of aromatic amino acids with organic solvent molecules in aqueous solutions.

Adsorption of Aromatic Amino Acids on Gallium Nitride Nanotubes - A Computational ONIOM Investigation

In this study, we have considered the interaction of aromatic amino acids (AAAs), i.e., Phenylalanine (Phen), Histidine (His), Tyrosine (Tyr), and Tryptophan (Trp), with different Gallium Nitride Nanotubes (GaNNTs). For optimization, we have used molecular mechanics (MM) method for GaNNTs and density functional theory (DFT) for aromatic amino acids respectively. We have investigated the interaction between AAAs and GaNNTs using ONIOM methods. We have found that aromatic amino acids are well encapsulated inside the wall of the GaNNTs. For different structures of GaNNTs chiral (10, 5), (12, 6) and armchair (10, 10), (12, 12) it has been found that the adsorption energy (Eads) of all AAAs range from -24.058 to -60.907 kcal/mol.

Biomolecular Interactions and Biological Responses of Emerging Two-Dimensional Materials and Aromatic Amino Acid Complexes.

The present work experimentally investigates the interaction of aromatic amino acids viz., tyrosine, tryptophan, and phenylalnine with novel two-dimensional (2D) materials including graphene, graphene oxide (GO), and boron nitride (BN). Photoluminescence, micro-Raman spectroscopy, and cyclic voltammetry were employed to investigate the nature of interactions and possible charge transfer between 2D materials and amino acids. Graphene and GO were found to interact strongly with aromatic amino acids through π-π stacking, charge transfer, and H-bonding. Particularly, it was observed that both physi and chemisorption are prominent in the interactions of GO/graphene with phenylalanine and tryptophan while tyrosine exhibited strong chemisorption on graphene and GO. In contrast, BN exhibited little or no interactions, which could be attributed to localized π-electron clouds around N atoms in BN lattice. Lastly, the adsorption of amino acids on 2D materials was observed to considerably change their biological response in terms of reactive oxygen species generation. More importantly, these changes in the biological response followed the same trends observed in the physi and chemisorption measurements.

Site specific interaction of aromatic amino acids with ZnO nanotubes: A density functional approach

The fast growing application of inorganic nanostructures for biomedical purposes has led to an increasing demand for further studies to obtain deeper understanding on the interactions between biomolecules and nanostructures at the atomic level. In this regard, a group of amino acids (AA) are the subject of the present study; in which density functional theory (DFT) is employed to investigate the interaction between aromatic amino acids (AAs) and Zinc oxide single walled nanotubes (SWNT) to identify the effective parameters for the biomedical applications. The structural changes and site specific binding nature of the bio-conjugated system are examined in detail. The results show that nanotube’s curvature is an effective factor in the magnitude of binding energy, since by decrease of nanotubes’ curvature the binding energy increases. Examination of the interactions between ZnO SWNTs and different binding sites of aromatic AAs indicates that the charge-solvent structure involving aromatic ring site of AAs is energetically more favorable. In this configuration the bonding is mediated by hybridization of π orbitals in aromatic ring and the d orbitals of Zinc atoms. The results of this study support the possible capability of ZnO SWNTs in detection of amino acids which shows the promising application of ZnO SWNTs in biosensing purposes.

Equivalent Isopropanol Concentrations of Aromatic Amino Acids Interactions with Lipid Vesicles.

We show that the interaction of aromatic amino acids with lipid bilayers can be characterized by conventional 1D [Formula: see text]H NMR spectroscopy using reference spectra obtained in isopropanol-d8/D[Formula: see text]O solutions. We demonstrate the utility of this method with three different peptides containing tyrosine, tryptophan, or phenylalanine amino acids in the presence of 1,2-dioleoyl-sn-glycero-3-phosphocholine or 1,2-dioleoyl-sn-glycero-3-phosphoserine lipid membranes. In each case, we determine an equivalent isopropanol concentration (EIC) for each hydrogen site of aromatic groups, in essence constructing a map of the chemical environment. These EIC maps provide information on relative affinities of aromatic side chains for either PC or PS bilayers and also inform on amino acid orientation preference when bound to membranes.

A theoretical study on the interaction of aromatic amino acids with graphene and single walled carbon nanotube

In this study we have investigated the interaction of phenylalanine (Phe), histidine (His), tyrosine (Tyr), and tryptophan (Tryp) molecules with graphene and single walled carbon nanotubes (CNTs) with an aim to understand the effect of curvature on the non-covalent interaction. The calculations are performed using density functional theory and the Moller-Plesset second-order perturbation theory (MP2) within linear combination of atomic orbitals-molecular orbital (LCAO-MO) approach. Using these methods, the equilibrium configurations of these complexes were found to be very similar, i.e., the aromatic rings of the amino acids prefer to orient in parallel with respect to the plane of the substrates, which bears the signature of weak pi-pi interactions. The binding strength follows the trend: His<Phe<Tyr<Tryp. Although the qualitative trend in binding energy is almost similar between the planar graphene and rolled nanotube structure but they differ in terms of the absolute magnitude. For the nanotube, the binding strength of these molecules is found to be weaker than the graphene sheet. To get an insight about the nature of these interactions, we have calculated the polarizability of the aromatic motifs of the amino acids. Remarkably, we find excellent correlation between the polarizability and the strength of the interaction; the higher the polarizability, greater is the binding strength. Moreover, we have analyzed the electronic densities of state spectrum before and after adsorption of the amino acid moieties. The results reveal that the Fermi level of the free CNT is red-shifted by the adsorption of the amino acids and the degree of shift is consistent with the trend in polarizability of these molecules.

INTRAMOLECULAR EXCITED ENERGY TRANSFER PATHWAYS IN PROTEINS

The transfer of energy perturbations within protein structure is an important phenomenon in many biological processes. In particular, the transfer of energy perturbations within a molecule in the absence of electron transfer is critical to the understanding of such processes as signaling involving receptors, channels, and enzymes among others, and to the design and development of relevant conducting materials. In this work, we have proposed a mechanism to explain this nonradiative, nonelectron energy transfer based on the π-orbital interactions of aromatic amino acids. Additionally, some theoretical background and possible computational approaches are presented as support for the proposal.

A Preference for Edgewise Interactions between Aromatic Rings and Carboxylate Anions: The Biological Relevance of Anion−Quadrupole Interactions

Noncovalent interactions are quite important in biological structure-function relationships. To study the pairwise interaction of aromatic amino acids (phenylalanine, tyrosine, tryptophan) with anionic amino acids (aspartic and glutamic acids), small molecule mimics (benzene, phenol or indole interacting with formate) were used at the MP2 level of theory. The overall energy associated with an anion-quadrupole interaction is substantial (-9.5 kcal/mol for a benzene-formate planar dimer at van der Waals contact distance), indicating the electropositive ring edge of an aromatic group can interact with an anion. Deconvolution of the long-range coplanar interaction energy into fractional contributions from charge-quadrupole interactions, higher-order electrostatic interactions, and polarization terms was achieved. The charge-quadrupole term contributes between 30 to 45% of the total MP2 benzene-formate interaction; most of the rest of the interaction arises from polarization contributions. Additional studies of the Protein Data Bank (PDB Select) show that nearly planar aromatic-anionic amino acid pairs occur more often than expected from a random angular distribution, while axial aromatic-anionic pairs occur less often than expected; this demonstrates the biological relevance of the anion-quadrupole interaction. While water may mitigate the strength of these interactions, they may be numerous in a typical protein structure, so their cumulative effect could be substantial.

Characterisation of the interactions of aromatic amino acids with diacetyl phosphatidylcholine

Download options Please wait... Article information DOI https://doi.org/10.1039/B312184D Article type Paper Submitted 01 Oct 2003 Accepted 05 Dec 2003 First published 21 Jan 2004 Download Citation Phys. Chem. Chem. Phys., 2004,6, 1012-1017 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Characterisation of the interactions of aromatic amino acids with diacetyl phosphatidylcholine J. M. Sanderson and E. J. Whelan, Phys. Chem. Chem. Phys., 2004, 6, 1012 DOI: 10.1039/B312184D To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Social activity Tweet Share Search articles by author John M. Sanderson Eleanor J. Whelan

Binding constants for aromatic amino acids and their derivatives with sulfobutyl ether β-cyclodextrin determined using capillary electrophoresis

The binding interaction of aromatic amino acids, their glycine dipeptides and some tryptophan derivatives with sulfobutyl ether fi-cyclodextrin (SBE7-fi-CD), an anionic cyclodextrin, in phosphate buffer (pH3, 5, 7 and 9) was studied using capillary electrophoresis (CE) chromatography. L-Trp, L-Tyr and L-Phe were the amino acids evaluated. Gly-L-Trp, L-Trp-Gly, Gly-L-Phe, L-Phe-Gly, Gly-L-Tyr and L-Tyr-Gly were studied as glycine dipeptides. N-acetyl-L-Trp, N-acetyl-L-Trp ethylester and L-Trp ethylester were used as L-Trp derivatives. For all the amino acids and the dipeptides, binding constants were higher at pH3 presumably because of the interaction between largely cationic amino acids/peptides at this pH and the anionic SBE7-fi-CD. The order of binding with the Trp series was Trp ethylester>N-acetyl-Trp ethylester>Trp>N-acetyl-Trp. These results support the conclusion that the interaction between amino acids/peptides and SBE7-fi-CD depends on charge and the neighboring functional groups. This study shows that SBE7-fi-CD can interact with amino acids and their derivatives and that a positive charge on the molecule facilitates the interaction.

Reverse micelles as a catalyst for the nucleophilic aromatic substitution between glutathione and 2,4-dinitrochlorobenzene

The nucleophilic aromatic substitution (SNAr) between GSH and 2,4-dinitrochlorobenzene was studied in reverse micellar systems composed of limited amounts of water, a surfactant with a polar head and a nonpolar tail, and the organic solvent 2,2,4-trimethylpentane. When the surfactant was positively charged and contained an aromatic ring in the polar head, the second-order rate constant was increased by approximately two orders of magnitude as compared to that in aqueous solution. The rate enhancement could be attributed to the stabilization of the negatively charged Meisenheimer σ-complex by the positively charged polar head and the weak aromatic ring’s electric quadrupole interactions of the surfactant. The reaction rate in reverse micelles composed of neutral polar head groups (Triton X-100) was increased by 3-fold, which may be explained by the interactions of the hydroxy groups of Triton molecules with the π-system of the Meisenheimer complex. An inverse relationship between the molar concentration [H2O]/[surfactant] ratio, which reflects the inclusive volume of the reverse micellar particle, and the rate enhancement was observed for positively charged or hydroxy-containing reverse micelles, but opposite results were obtained with negatively charged reverse micelles. These reverse micellar systems thus mimic the active site of a detoxification enzyme, glutathione transferase, in which stabilization of the Meisenheimer complex by a positively charged arginine residue, on-edge quadrupole interactions of aromatic amino acids, and the hydroxy group of tyrosine or threonine have been proposed in the enzyme-catalysed SNAr conjugation.

Interactions of aromatic amino acids with gastric secretagogues in humans

To determine the interactions of phenylalanine and tryptophan with gastric secretagogues, acid secretory studies were performed in 10 healthy subjects. Phenylalanine and tryptophan potentiated the gastric secretory responses following low doses of pentagastrin, whereas their effects on acid secretion stimulated by low doses of histamine or the cholinergic bethanecol were additive. Phenylalanine and tryptophan did not increase maximal acid output stimulated by pentagastrin, histamine, or bethanecol. Doses of the H2-receptor antagonist ranitidine, the prostaglandin E1 analogue misoprostol, atropine, and somatostatin that produced ≈50% inhibition of pentagastrin-stimulated acid secretion significantly inhibited phenylalanine- and tryptophan-stimulated acid secretion. After the combination of either phenylalanine or tryptophan with pentagastrin, the H2-receptor antagonist significantly inhibited gastric acid secretion, whereas somatostatin, atropine, and the prostaglandin E1 analogue were not effective. These results indicate that both phenylalanine and tryptophan potentiate gastric acid secretion stimulated by a submaximal dose of pentagastrin, whereas their effects on histamine- and bethanecol-stimulated secretion are additive. The potentiating effects of phenylalanine and tryptophan on pentagastrin-stimulated acid secretion depend, at least in part, on intact histamine pathways.

Interaction of aromatic amino acids with gossypol

The aromatic amino acids L‐tryptophan, L‐tyrosine and L‐phenylalanine complex with gossypol at pH 7.6, resulting in negative CD bands at 424–426 nm and 300 nm and a positive band at 355 nm. The association constant and free energy change for complex formation have been calculated from the amplitude of the CD band at 420 nm. The interaction is weak. The association constant for complex formation increases with the hydrophobicity of amino acid. The effect of additives on the reaction has also been determined.

The interaction of aromatic amino acids with rat liver phenylalanine hydroxylase.

We have examined the interaction of hepatic phenylalanine hydroxylase with the phenylalanine analogs, tryptophan and the diastereomers of 3-phenylserine (beta-hydroxyphenylalanine). Both isomers of phenylserine are substrates for native phenylalanine hydroxylase at pH 6.8 and 25 degrees C, when activity is measured with the use of the dihydropteridine reductase assay coupled with NADH in the presence of the synthetic cofactor, 6-methyl-5,6,7,8-tetrahydropterin. However, while erythro-phenylserine exhibits simple Michaelis-Menten kinetics (Km = 1.2 mM, Vmax = 1.2 mumol/min X min) under these conditions, the threo isomer exhibits strong positive cooperativity (S0.5 = 4.8 mM Vmax = 1.4 mumol/min X mg, nH = 3). Tryptophan also exhibits cooperativity under these conditions (S0.5 = 5 mM, Vmax = 1 mumol/min X mg, nH = 3). The presence of 1 mM lysolecithin results in a hyperbolic response of phenylalanine hydroxylase to tryptophan (Km = 4 mM, Vmax = 1 mumol/min X mg) and threo-phenylserine (Km = 2 mM, Vmax = 1.4 mumol/min X mg). erythro-Phenylserine is a substrate for native phenylalanine hydroxylase in the presence of the natural cofactor, L-erythro-tetrahydrobiopterin (BH4) (Km = 2 mM, Vmax 0.05 mumol/min X mg, nH = 2). Preincubation of phenylalanine hydroxylase with erythro-phenylserine results in a 26-fold increase in activity upon subsequent assay with BH4 and erythro-phenylserine, and hyperbolic kinetic plots are observed. In contrast, both threo-phenylserine and tryptophan exhibit negligible activity in the presence of BH4 unless the enzyme has been activated. The product of the reaction of phenylalanine hydroxylase with either isomer of phenylserine was identified as the corresponding p-hydroxyphenylserine by reaction with sodium periodate and nitrosonaphthol. With erythro-phenylserine, the hydroxylation reaction is tightly coupled (i.e. 1 mol of hydroxyphenylserine is formed for every mole of tetrahydropterin cofactor consumed), while with threo-phenylserine and tryptophan the reaction is largely uncoupled (i.e. more cofactor consumed than product formed). Erythro-phenylserine is a good activator, when preincubated with phenylalanine hydroxylase (A0.5 = 0.2 mM), with a potency about one-third that of phenylalanine (A0.5 = 0.06 mM), while threo-phenylserine (A0.5 = 6 mM) and tryptophan (A0.5 approximately 10 mM) are very poor activators. Addition of 4 mM tryptophan or threo-phenylserine or 0.2 mM erythro-phenylserine to assay mixtures containing BH4 and phenylalanine results in a dramatic increase in the hydroxylation at low concentrations of phenylalanine.(ABSTRACT TRUNCATED AT 400 WORDS)

Interaction of aromatic amino acids in D and L forms with 3,4-dihydroxyphenylalanine decarboxylase from pig kidney.

Interaction of aromatic amino acids in D and L forms with 3,4-dihydroxyphenylalanine decarboxylase from pig kidney.

Stacking specificity and polarization. Comparative synopsis of affinity data.

AbstractAn explanation is given of the specificity of stacking associations based on suggestions of the contribution of dipole‐induced dipole interactions, which emphasize bond moments as the origin of the polarizing power and polarizability of the π‐electron ring system concerned. This explanation is consistent with our own experimental data and with those of other authors on nucleoside self‐association, the mixed interaction of different nucleic acid constituents, and the interaction of aromatic amino acids with nucleosides, nucleotides, and nucleic acids.

Interaction of aromatic amino acids with neutral polyadenylic acid.

The aromatic amino acids tryptophan, phenylalanine, and histidine interact with singlestranded polyadenylic acid [poly(A)] as observed by proton magnetic resonance spectroscopy. The chemical shift of the C(2) and C(8) protons of the adenine moiety of poly(A) is consistent with a destacking of the initially partly-stacked polynucleotide chain by the intercalation of the planar ring structure. The relative magnitude of this interaction is tryptophan>phenylalanine>histidine.