Different Strengths Of Interaction Research Articles

Direct nitrous oxide decomposition with CoOx-CeO2 catalysts

The focus of the performed studies were CoOx-CeO2 oxide catalysts for nitrous oxide decomposition. All CoOx-CeO2 systems exhibit similar or higher activity than the undoped cobalt catalyst. It has been found that in temperatures up to 800°C in a N2O–Ar stream cobalt in these catalysts is in the form of Co3O4. At higher temperatures it is reduced to CoO. In a N2O–O2–Ar stream Co3O4 is the main cobalt-containing phase in the entire studied temperature range. The obtained results revealed that the activity of CoOx-CeO2 systems with a high cobalt loading increases with temperature only up to 800°C in a N2O–Ar stream. Upon further temperature increase the activity of these catalysts decreases, as in the case of the undoped cobalt catalyst. This is due to the reduction of Co3O4 to CoO. Hence, when oxygen is present in the feed and cobalt is in the form of Co3O4, the activity is higher. In contrast, the activity of catalysts with the cobalt molar ratio no greater than 0.64 is the same in both N2O–Ar and N2O–O2–Ar streams and increases with temperature in the entire studied range (700–850°C). It has been demonstrated that at 850°C in a N2O–Ar stream CoOx-CeO2 systems contain two types of CoO, which require different conditions to be oxidized. This is a result of a different strength of interaction with CeO2. It can be concluded that the activity of CoOx-CeO2 systems results from the activity of Co3O4 and of the cobalt oxide–ceria interface. The share of each component is determined by the cobalt content.

Computer Simulation of n‐Butylamine‐Intercalated α‐Zirconium Phosphate

AbstractMolecular dynamics simulation was carried out to study the structure properties of α‐Zirconium Phosphate (α‐ZrP) loaded with n‐butylamine molecules. Two minimum‐energy configurations of α‐ZrP with interlayer distances 12.7 and 17.0 Å were found from the simulation. The structure properties of n‐butylmine, α‐ZrP and also interaction between n‐butylamine and α‐ZrP were analyzed. The different phase behavior was found due to the different strength of interaction between NH2 in n‐butylamine and O in PO4 of α‐ZrP.

Interactions of B-class complex proteins involved in tepal development in Phalaenopsis orchid

In our previous studies, we identified four DEFICIENS (DEF)-like genes and one GLOBOSA (GLO)-like gene involved in floral organ development in Phalaenopsis equestris. Revealing the DNA binding properties and protein-protein interactions of these floral homeotic MADS-box protein complexes (PeMADS) in orchids is crucial for the elucidation of the unique orchid floral morphogenesis. In this study, the interactome of B-class PeMADS proteins was assayed by the yeast two-hybrid system (Y2H) and glutathione S-transferase (GST) pull-down assays. Furthermore, the DNA binding activities of these proteins were assessed by using electrophoretic mobility shift assay (EMSA). All four DEF-like PeMADS proteins interacted individually with the GLO-like PeMADS6 in Y2H assay, yet with different strengths of interaction. Generally, the PeMADS3/PeMADS4 lineage interacted more strongly with PeMADS6 than the PeMADS2/PeMADS5 lineage did. In addition, independent homodimer formation for both PeMADS4 (DEF-like) and PeMADS6 (GLO-like) was detected. The protein-protein interactions between pairs of PeMADS proteins were further confirmed by using a GST pull-down assay. Furthermore, both the PeMADS4 homodimer and the PeMADS6 homodimer/homomultimer per se were able to bind to the MADS-box protein-binding motif CArG. The heterodimeric complexes PeMADS2-PeMADS6, PeMADS4-PeMADS6 and PeMADS5-PeMADS6 showed CArG binding activity. Taken together, these results suggest that various complexes formed among different combinations of the five B-class PeMADS proteins may increase the complexity of their regulatory functions and thus specify the molecular basis of whorl morphogenesis and combinatorial interactions of floral organ identity genes in orchids.

High-resolution photoelectron spectroscopy of self-assembled mercaptohexanol monolayers on gold surfaces

Mercaptohexanol (MCH) monolayers assembled on gold surfaces were investigated by means of high-resolution X-ray photoemission spectroscopy (XPS). The presence of three chemical states of sulfur was detected which exhibit different strength of interaction with the gold surface. Comparing the relative intensities of the corresponding subspectra allowed to estimate which fraction of the deposited MCH molecules is not bound to the metal surface via the thiol group, and thus, the characterization of the quality of the self-assembled monolayer (SAM). The number of sulfur atoms bound to the gold surface decreased when part of the the hydroxyl endgroup of the assembled MCH molecules is substituted by DNA duplexes. Long-term irradiation experiments on MCH layers revealed that soft X-ray radiation induces damage of the SAMs, accompanied with a preferential cleavage of both hydroxyl groups and hydrogen atoms from the alkane chains, leading in turn to a rearrangement of those MCH molecules which were not bound to the gold surface during the SAM preparation. The fraction of molecules which are bound to the metal via the thiol group, however, is practically not affected by the irradiation with soft X-rays.

Electrochemical Detection of a Dengue-related Oligonucleotide Sequence Using Ferrocenium as a Hybridization Indicator.

A simple method for electrochemical detection of a synthetic 20-bpoligonucleotide sequence related with dengue virus genome was developed. Acomplimentary DNA probe sequence was electrostatically immobilized onto a glassycarbon electrode modified with chitosan. Electrochemical detection of hybridizationbetween probe and target was performed by cyclic voltammetry, using ferrocene (Fc ) as ahybridization label. After hybridization, the peak current response of Fc oxidationincreased around 26%. A higher voltammetric decay rate constant (kd) and a lower half-lifeperiod (t1/2) for the interaction of Fc with dsDNA compared to those with ssDNAquantitatively characterize the different strengths of interaction with both types of DNA.By combining the simplicity of DNA immobilization onto a chitosan film and suitablevoltammetric detection of hybridization concomitant with ferrocene attachment, a gooddiscrimination between ssDNA and dsDNA was obtained.

CW EPR, echo-detected EPR, and field-step ELDOR study of molecular motions of nitroxides ino-terphenyl glass: Dynamical transition, dynamical heterogeneity and β-relaxation

Continuous-wave electron paramagnetic resonance (CW EPR), echo-detected (ED) EPR, and field-step electron-electron double resonance (FS ELDOR) were simultaneously applied to study molecular motions of nitroxide spin probes of two different types in glassyo-terphenyl. A strong linear temperature dependence of the overall splitting of the CW EPR lineshape was found for nitroxide Tempone and only a weak one for a phenyl-ring-containing imidasoline nitroxide. The linear temperature dependence of the splitting is explained within the model of harmonic librations. The assessed libration frequency for Tempone is of the order of 3·1012 rad/s. The observed remarkable difference between the two nitroxides is explained by the different strength of interactions between guest and host molecules and by dynamical heterogeneity of the glass. The nonlinear temperature dependence above 250 K is attributed to the onset of anharmonic motion that is postulated in a number of neutron scattering and Mossbauer spectroscopy studies for molecular glasses and proteins (the so-called dynamical transition). Above 245 K also ED EPR spectra change drastically, which may be explained on the same ground. Magnetization transfer was observed in FS ELDOR for nitroxide Tempone, with a time constant around 10−5 s. It was found to be almost temperature-independent between 160 K and 265 K and was attributed to the Johari-Goldstein β-relaxation process. For the phenyl-ring-containing imidasoline nitroxide this transfer was not observed, which may be explained again by the dynamical heterogeneity of the glass and by small effectivity of the β-relaxation process in this case.

WOx/ZrO2 Catalysts Prepared by Anionic Exchange: In Situ Raman Investigation from the Precursor Solutions to the Calcined Catalysts

W/ZrO(2) catalysts were prepared using anionic exchange of peroxotungstate species with hydroxyl groups of zirconium hydroxide at low pH. The solids were dried and calcined under air at 700 degrees C. Each step of this novel method of preparation was investigated by Raman spectroscopy. A reference sample was also prepared by incipient wetness impregnation of ZrO(2).n(H2O) with an ammonium tungstate solution and characterized throughout its preparation process. Complementary data were collected from X-ray diffraction, chemical analysis, surface area measurements, and thermal analysis. The Raman spectra of the H2WO4-H2O2 precursor solutions evidenced the presence of (W2O3(O2)4(H2O)2)(2-) dimers. These low-nuclearity species were exchanged with zirconium hydroxide at low pH. The Raman spectra of the dried solids did not reveal peroxotungstate species but were typical of tetrahedral (WO4)(2-) species. A slight agglomeration of W species was observed with an increase in the W content. However, for an equivalent W loading, a higher W dispersion was obtained by anionic exchange, compared to the impregnation method. Furthermore, a remarkable homogeneity of the exchanged samples was evidenced by the micro-Raman spectra. The in situ Raman spectra recorded during calcination characterized both crystalline phases and supported tungsten species. Significant modifications were observed during the calcination process. The exchanged and the impregnated samples, with the same W loading, evidenced a similar type of tungsten species with one W=O bond. However, their behavior during calcination up to 700 degrees C was different. This was attributed to different strengths of interaction with the support. Moreover, the spectra recorded after calcination on various points of the exchanged sample with a high W content revealed a better spatial homogeneity than the impregnated one.

NMR diffusion as a novel tool for measuring the association constant between cyclodextrin and guest molecules

In this paper we introduce the use of diffusion measurements by nuclear magnetic resonance (NMR) spectroscopy for determining association constants of weak and very weak interactions between cyclodextrin and guest molecules, as long as both the free and complexed guest molecules are soluble to an extent that allows good sensitivity in the NMR experiment. The experimental setup and data analysis is discussed for three different guest molecules: l-phenylalanine, l-leucine and l-valine, representing different strengths of interaction. The underlying assumptions are discussed and the scope of the method (range of K a values, requirements to the guest molecule) are discussed. The method's main advantage is its general applicability independent of chromogenic or electrochemical properties of the guest molecule. Whereas calorimetric methods that exhibit a similar generality, are applicable mainly to strong interactions, NMR diffusion measurements are applicable to weaker interactions down to the theoretical limit of 1 M −1, the upper limit for K a values to be determined by it is approximately 200. A further advantage of the method is the low amount of sample needed. The method is in principle applicable to any case of molecular recognition between a host and guest molecule leading to weak interactions.

Structure/property relationships in nematic liquid crystal/polymer alignment layer interactions

The interactions occurring at the interface between a liquid crystal (LC) and the walls of a LC cell have been studied using microsecond time resolved Fourier transform infrared (FTIR) spectroscopy. We have found that, by varying the structure of the alignment layers, different rates of electro-optical response could be achieved. These differences stem from the different strengths of interactions between the LC and the alignment layers. No specific, strong interactions (i.e. hydrogen bonding) were found by a direct analysis of the spectra. By calculating the local dipole moment of the polymer films using semi-empirical molecular orbital methods, a direct correlation between the electro-optical behavior and dipole moment was found for several polymers with similar base structures. This shows that the interactions at the LC/alignment layer interface are dominated by dipole–dipole forces.

Role of adsorption in zeolite-catalyzed hydrocarbon cracking reaction

The activity for hydrocarbon cracking of zeolite catalysts depends on the type of zeolite and steam treatment. By comparing the activities of different zeolites under the condition where the catalyst did not undergo deactivation and the product distributions were identical, and presumably for the monomolecular mechanism, it was found that there were no differences in the chemical properties of the active sites in the zeolites. The apparent differences in catalytic activities among zeolites could be attributed to different concentrations of adsorbed alkane reactants, which is a consequence of the different strength of interaction of the alkyl groups with the zeolite walls. The latter may also be a significant contribute to the observed different strengths of interaction of alkyl amines with the Bronsted acid sites in zeolites.

Superfluidity of indirect excitons in a quantum dot

The superfluidity and Bose–Einstein condensation of indirect excitons in coupled quantum dots or trapped atoms with induced dipole momenta (or dipole molecules) are studied by path-integral Monte Carlo simulations. The temperature dependencies of superfluid and Bose-condensed fraction are calculated at different strengths of interaction. Using Kosterlitz–Thouless recursion relations, we also predict the critical temperature in a macroscopic system of indirect excitons.

FTi.r. and potentiometric study of basic polymer behaviour in the free form, in different bulks, in both solid state and aqueous solution

The behaviour of the polymer N 2LL having a poly(amidoamine) structure [obtained by polyaddition of N, N′-dimethyl-1,4-diaminobutane to 1,4-bis(acryloyl)piperazine], was studied by Fourier transform infrared spectroscopy and potentiometric techniques in the free form, blended, surface grafted and in a network with polyurethane. The different strengths of interaction via hydrogen bond of the N 2LL chain were evaluated in the different bulks, which showed that the polymeric chains have similar behaviour when in the linear form and anchored at one end to the surface of the polyurethane support, or when both ends are fastened. The different hydrophilic character of the N 2LL polymer and polyurethane chains is responsible for differences in behaviour in the solid state and in aqueous solution.

LEED structure analysis of p(2 × 2)S/Ni(100)

With adsorption of sulfur on Ni(100) a streaky p(2 × 2) LEED pattern appears at coverage θ = 0.25. In spite of the corresponding existence of some disorder in the adlayer a LEED structure analysis of satisfying quality could be performed (Pendry R-factor R = 0.21). Sulfur adsorbs in the hollow site with an adsorption height of 1.25 ± 0.03 Å. The topmost substrate layer spacing is changed from 1% contraction as derived for the clean surface to 0.5 ± 1% expansion. The nickel atoms below the adsorbed sulfur are shifted down by 0.07 ± 0.05 Å whereas the other atoms of the second substrate layer are not affected. The results are discussed to be in line with those obtained recently for the c(2 × 2)S structure and the similar superstructures observed with adsorption of oxygen. The observation of some unavoidable disorder in the p(2 × 2)S layer is discussed and contrasted to the similar but well-ordered phase of p(2 × 2)O/Ni(100) investigated earlier. The differences between the two systems are interpreted to be due to the different strength of interaction of the adsorbates with the substrate, in agreement with the details of the structural results.

Insulin-lecithin interaction in non-aqueous solvents and its change after application of a static electric field.

The interaction between dipalmitoyl lecithin and egg lecithin with insulin was studied in a non-aqueous solvent such as dioxane-chloroform (1:1) by dielectric constant measurements and absorption spectra. The electrostatic character of the interaction results from the dielectric measurements and the effect of an external application of a static electric field (F = 30 kV/cm) is apparently related to the strength of such an interaction. The different strength of interaction of insulin with the two types of lecithins results also from experiments with a two-phase system.

An equivalent circuit for the quantitative description of inter-receptor coupling in the retina of the desert antCataglyphis bicolor

1. An ionic equivalent circuit model is developed for the purpose of quantifying the strengths of electrical coupling existing between certain receptor cells in the compound eye ofCataglyphis bicolor which show wavelength dependence in the slopes of their ‘V logI’ relations and orientations of maximum PS (Mote and Wehner, 1980). It combines the pure electrical equivalent of the plasma membrane, as proposed by Finkelstein and Mauro (1963), and a closed series circuit such that Kirchhoff's laws are applicable. 2. The model is applied to hypothetical pairs of cells with different sensitivities and different strengths of interaction. It predicts that cells are most strongly coupled when at rest and most weakly coupled when most active. When one is active and the second is not then “apparent rectification” can occur since the coupling strength is not symmetrical. This means that both “resting” and “dynamic” coupling coefficients must be considered. Transition between these modes causes irregularities in the ‘V logI’ relation of a weakly excited cell which is coupled to a strongly excited cell. 3. The model is then applied to data obtained from photoreceptors in the compound eye ofCataglyphis. It adequately simulates the wavelength dependence of both the ‘V logI’ relation (Fig. 6) and the orientation of maximum PS (Fig. 7) measured in these cells. In its simplest form the model permits an estimate of the coupling coefficients which are greater than 0.6 for strongly coupled cells and less than 0.4 for weakly coupled cells. 4. A hypothetical treatment of pairs of coupled cells under conditions approaching the natural situation in the animal's environment suggests that super-numerary analyzers of polarized light in the u.v. could arise through receptor coupling in certain ommatidial types found in the eye ofCataglyphis.

Interaction of poly( l-lysine) and copolymers of lysine with immobilized DNA

Sonicated DNA has been covalently attached to Sepharose 4B by a carbodiimide method [Rickwood, P. (1972) Biochim. Biophys. Acta 269, 47–50] which minimizes modification of the DNA and matrix. Columns of this material have been used to study the interaction between cationic polypeptides and DNA. When poly( l-lysine) is bound to such columns at low ionic strength and then eluted with a linear salt gradient the polypeptide elutes over a broad range of salt concentration, presumably reflecting different strengths of interaction with various sites on the DNA. The broadness of the elution profile cannot be attributed to heterogeneity in the poly( l-lysine) sample but rather to the AT GC content of various DNA sites. Studies with other polypeptides, poly( l-Lys 79, l-Leu 21) and poly-( l-Lys- l-Ala-Gly), as well as studies at different temperatures, have helped to clarify the possible roles of conformational mobility, polypeptide hydrophobicity, and the presence of contiguous lysines in determining the strength of interaction of polypeptides and proteins with DNA sites.

Perturbation approach to the free energy of solution

A perturbation treatment, based on a statistical approach due to Longuet-Higgins, is developed for the free energy of solution. By assuming that the different free energies of solution within a set of closely-related molecules arise solely from the different strengths of interactions of the molecules with the solvent, the thermal contribution to the activity coefficient of a solute, 2 should be related to that of a reference solute, 2′, by [graphic omitted] The results for four sets of alkane isomers in seven solvents confirm the validity of this equation.

Superparamagnetic effects in thin films

The experimental and theoretical concept concerning the magnetic properties of 2-dimensional arrangements of small particles with different strengths of interaction is discussed. Taking into account recent results on isolated small single-domain particles, a representation for a whole scale of possible structures from these to closely packed ferromagnetic films is given, using a molecular field formalism. The interaction considered may be much weaker than the full ferromagnetic exchange coupling. The resultant collective magnetization M of such aggregates of small particles may be considerably lower than their spontaneous magnetization M s . A transition temperature T A towards occurrence of superparamag-netism may appear that is well below the Curie temperature Θ of the individual particles. These effects seem to be consistent with experimental data obtained by a number of authors using various methods of measurement. Observations of time effects at magnetization reversals in very thin films also support the aforementioned model.