Search results for "Interaction"

Spectrophotometric determinations of binding constants between cyclodextrins and aromatic nitrogen substrates at various pH values

2001

The inclusion capacity of native β-cyclodextrin (1) and mono-(6-amino-6-deoxy)-β-cyclodextrin (2) versus aromatic compounds having a nitro or an amino group or both has been investigated at three different pH values. Molecular interactions in inclusion complexes have also been investigated by means of molecular mechanics (MM2/QD) models. Electrostatic and van der Waals interactions and the formation of a hydrogen bond between the donor amino group and the oxygen atom of the secondary hydroxyl group seem to be the more important contributions in determining complex stability. The inclusion capacity of two different cyclodextrins versus aromatic compounds has been investigated at three differ…

Estimation of pKa shifts in weak polyacids using a simple molecular model: effects of strong polybases, hydrogen bonding and divalent counterion bind…

2004

Abstract The pKa values of ionizable groups in macromolecules can be significantly different than those of the isolated groups in solution. We have estimated theoretically the changes in the dissociation constant of a weak acid (a) in the vicinity of another ionizable group (b) on the basis of the theoretical approach by Hill (J. Am. Chem. Soc. 78 (1956) 3330) for matching pairs of interacting sites on two large molecules. Three cases are considered for group b: the strong base, the same weak acid as group a with hydrogen bonding between them, and the same weak acid as group a with divalent counterion binding. The pKa shifts are evaluated in each case as a function of the interaction energy…

2014

The interest in RNA modification enzymes surges due to their involvement in epigenetic phenomena. Here we present a particularly informative approach to investigate the interaction of dye-labeled RNA with modification enzymes. We investigated pseudouridine (Ψ) synthase TruB interacting with an alleged suicide substrate RNA containing 5-fluorouridine (5FU). A longstanding dogma, stipulating formation of a stable covalent complex was challenged by discrepancies between the time scale of complex formation and enzymatic turnover. Instead of classic mutagenesis, we used differentially positioned fluorescent labels to modulate substrate properties in a range of enzymatic conversion between 6% and…

Interaction in POSS-poly(ethylene-co-acrylic acid) nanocomposites

2013

Use of polyhedral oligomeric silsesquioxane (POSS) in polymer-based nanocomposites is promising for the design of high-performance materials for several applications. In this study, nanocomposites based on ethylene-acrylic acid (EAA) copolymer and POSS molecules were prepared by melt mixing. In particular, partial cage POSS with different pendent organic groups was used to investigate the interaction between the –OH groups of POSS and the acrylic functionalities of the matrix. All nanocomposites were characterized by mechanical, rheological, thermal and spectroscopic analyses. In addition, PE-POSS compounds were prepared under the same processing conditions for sake of comparison. The POSS …

Incorporation of Membrane Proteins in Solid-Supported Lipid Layers

1995

Binding of water-soluble, globular proteins to anionic model membranes

2009

Abstract The role of electrostatics is studied in the adsorption of proteins to negatively charged (phosphatidylcholine/phosphatidylglycerol, PC/PG) and neutral (PC) small unilamellar vesicles (SUVs). For model proteins the interaction is monitored vs . pH at low ionic strength. The adsorption behaviour of lysozyme, myoglobin and albumin (isoelectronic point, p I 5–11) is investigated in SUVs, along with changes of the fluorescence emission spectra of the charged proteins, via their adsorption on SUVs. Significant adsorption of the proteins to negatively charged SUVs is found only at pH values, where the number of positive charge moieties exceeds the number of negative charge moieties on th…

A Flory–Huggins thermodynamic approach for predicting sorption equilibrium in ternary polymer systems

1989

The Flory–Huggins theory as modified by Pouchlý has been applied to calculate preferential (λ) and total (Y) sorption coefficients for a ternary polymer system. The ternary interaction function (ϕ1ϕ2ϕ3GT(u1, ϕ3)) is described as the product of three independent binary functions. This expression allows prediction of λ and Y from binary interaction parameters χ, χ, g, g, and g12(ϕ10). Three ternary polymer systems are used to check the validity of the expression. Moreover for polymer systems in which the parameters g and/or g are unknown, a procedure to evaluate them has been developed and verified on systems for which sufficient experimental information is available.

Intra-Helical Salt Bridge Contribution to Membrane Protein Insertion.

2021

ABSTRACTSalt bridges between negatively (D, E) and positively charged (K, R, H) amino acids play an important role in protein stabilization. This has a more prevalent effect in membrane proteins where polar amino acids are exposed to a very hydrophobic environment. In transmembrane (TM) helices the presence of charged residues can hinder the insertion of the helices into the membrane. This can sometimes be avoided by TM region rearrangements after insertion, but it is also possible that the formation of salt bridges could decrease the cost of membrane integration. However, the presence of intra-helical salt bridges in TM domains and their effect on insertion has not been properly studied ye…

Magneto-structural versatility of copper(II)-3-phenylpropionate coordination polymers with N-donor coligands.

2015

A novel series of copper(II) coordination polymers [Cu2(O2CC8H9)4(pyz)]n (1), [Cu2(O2CC8H9)4(dps)]n (2), {[Cu(O2CC8H9)2(dps)(H2O)]·H2O}n (3), {[NaCu(O2CC8H9)2(bpm)(NO3)]·H2O}n (4), and [Cu4(O2CC8H9)6(OH)2(bpp)2]n (5) [O2CC8H9− = 3-phenylpropionate anion, pyz = pyrazine, dps = di(4-pyridyl)sulfide, bpm = 2,2′-bipyrimidine, and bpp = 1,3-bis(4-pyridyl)propane] have been synthesized and magneto-structurally investigated. Compounds 1 and 2 belong to a large group of copper(II) carboxylates where bis-monodentate pyz (1) and dps (2) ligands connect the paddle-wheel [CuII2(μ-O2CC8H9)4] units leading to alternating copper(II) chains. The structure of 3 consists of uniform chains of trans-[CuII(O2CC…

Interactions between polymer brush-coated spherical nanoparticles: the good solvent case.

2011

The interaction between two spherical polymer brushes is studied by molecular dynamics simulation varying both the radius of the spherical particles and their distance, as well as the grafting density and the chain length of the end-grafted flexible polymer chains. A coarse-grained bead-spring model is used to describe the macromolecules, and purely repulsive monomer-monomer interactions are taken throughout, restricting the study to the good solvent limit. Both the potential of mean force between the particles as a function of their distance is computed, for various choices of the parameters mentioned above, and the structural characteristics are discussed (density profiles, average end-to…