Reactive methacrylate systems for dental bioadhesives

The procedure of restoring missing crown part of a human tooth with use of experimental materials, including new functional dimethacrylate monomers, is presented. The essential steps are precise evaluation of root canal cavities and providing a good adhesion of restorative materials to tooth structures. Magnetic resonance microscopy is considered to be a valuable supporting technique in restorative dentistry.     

The Sequential Building of Chiral Macrocyclic Bis‐β‐Lactams by Double Staudinger–Cu‐Catalyzed Azide–Alkyne Cycloadditions

A novel approach for the synthesis of macrocyclic bis‐β‐lactams based on the Cu‐catalyzed alkyne–azide cycloaddition (CuAAC) is reported. The procedure is general and allows access to a full range of diastereomerically or enantiomerically pure macrocyclic cavities in good yields. The incorporation of chiral oxazolidinone fragments at C3 in the β‐lactam rings allows the total enantiocontrol of the process.     

Considerations in the design of a microwave induced plasma utilizing the TM010 cavity for optical emission spectroscopy

A procedure is presented to determine the resonant frequency shift of the TM₀₁₀ cavity when dielectric material (the plasma discharge tube) is inserted. This allows convenient adjustment of the cavity diameter to yield a resonance frequency near 2.450 GHz when the plasma is ignited.The design of a unique plasma discharge tube is presented. This discharge tube utilizes a tangential plasma support gas flow (He or Ar) to generate a suspended plasma discharge which does not touch the wall of the discharge tube. The resulting discharge has superior spatial and temporal stability compared to previously reported plasma discharges.The use of TM₀₁₀ resonant cavities having 2 and 3 cm internal thicknesses is discussed. These cavities result in physically longer plasmas providing greater analyte residence times and enhanced analytical performance. Results with and without prior aerosol desolvation are presented.     

Dopamine Oxidation at Per(6‐deoxy‐6‐thio)‐α‐Cyclodextrin Monolayer Modified Gold Electrodes

The gold electrode is functionalized by sequential self‐assembly of a monolayer of the title thiolated cyclodextrin with and without dopamine included in the cavities. The structure of α‐cyclodextrin modified gold electrode is carefully characterized using STM and AFM. Surface complexation of dopamine is examined and its association constant is evaluated. Chemical reactions accompanying the electrode process of dopamine, which interfere in the electrochemical dopamine determination, are described and the conditions to avoid them are proposed. Dopamine incorporated in the α‐cyclodextrin sites anchored to the electrode surface was found to provide electrochemical contact of the electrode with the solution‐resident dopamine. Dopamine present in the α‐cyclodextrin cavities has different properties compared to dopamine in the bulk buffer solution and can act as a mediator for the dopamine molecules diffusing to the electrode. This unique mediation effect leads to improvement of the sensitivity of dopamine determination using the α‐cyclodextrin modified electrode and a procedure for the determination of dopamine in large excess of ascorbate is proposed.     

Design of Ligand Binding to an Engineered Protein Cavity Using Virtual Screening and Thermal Up-shift Evaluation

Summary Proteins could be used to carry and deliver small compounds. As a tool for designing ligand binding sites in protein cores, a three-step virtual screening method is presented that has been optimised using existing data on T4 lysozyme complexes and tested in a newly engineered cavity in flavodoxin. The method can pinpoint, in large databases, ligands of specific protein cavities. In the first step, physico-chemical filters are used to screen the library and discard a majority of compounds. In the second step, a flexible, fast docking procedure is used to score and select a smaller number of compounds as potential binders. In the third step, a finer method is used to dock promising molecules of the hit list into the protein cavity, and an optimised free energy function allows discarding the few false positives by calculating the affinity of the modelled complexes. To demonstrate the portability of the method, several cavities have been designed and engineered in the flavodoxin from Anabaena PCC 7119, and the W66F/L44A double mutant has been selected as a suitable host protein. The NCI database has then been screened for potential binders, and the binding to the engineered cavity of five promising compounds and three tentative non-binders has been experimentally tested by thermal up-shift assays and spectroscopic titrations. The five tentative binders (some apolar and some polar), unlike the three tentative non-binders, are shown to bind to the host mutant and, importantly, not to bind to the wild type protein. The three-step virtual screening method developed can thus be used to identify ligands of buried protein cavities. We anticipate that the method could also be used, in a reverse manner, to identify natural or engineerable protein cavities for the hosting of ligands of interest.     

Two‐step cavitation in semi‐crystalline polymer during stretching at temperature below glass transition

Cavitation behavior in poly(4‐methyl‐1‐pentene) upon stretching below glass transition temperature was investigated by in situ ultra‐small angle X‐ray scattering technique. Strong stress‐whitening was observed indicating an extensive occurrence of cavitation in the material during tensile deformation below Tg. The X‐ray scattering patterns suggest oriented disc‐shaped cavities with normal mostly parallel to the stretching direction occurred. Structural parameters of such cavities such as thickness, radius, and tilting angle of the normal of the disc with respect to the stretching direction have been successfully calculated using a model fitting procedure. The results exhibited a two‐step process of cavitation that small amount of large cavities appeared first and then small cavities were triggered extensively in the samples at larger strains. This two‐step cavitation phenomenon can be weakened after the quenched sample was annealed or the sample was prepared by slow cooling. This peculiar two‐step cavitation process can be understood as a result of high frozen in internal stress in quenched sample that led to local failure of the materials. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 2007–2014     

Solubilization of prothionamide with micelles of an amphiphilic acrylic acid oligomer with thiohexyl terminal groups and preparation of postoperative cavity filling formulations

An amphiphilic oligomer was prepared by telomerization of acrylic acid in the presence of n-hexyl mercaptan. The structure, molecular weight, critical micelle concentration, and ζ-potential of the oligomer, and also its particle-size distribution in aqueous solution were determined. The product allows solubilization of prothiondamide antituberculosis drug. A procedure was suggested for preparing a filling formulation containing prothionamide for filling postoperative cavities in connective tissue.     

Measurement of Ibuprofen Binding to Mixed Monolayers Containing β-Cyclodextrin Active Sites

A molecular imprinting method involving a three-step sequential self-assembly procedure was applied to prepare gold electrodes responsive towards ibuprofen. The electrode modified with the cyclodextrin derivative binds ferrocene to form an electroactive complex with the ferrocene oxidation current decreasing in the presence of ibuprofen in the solution. The competition of ferrocene and ibuprofen for the cyclodextrin cavities in the monolayer provided a means for the determination of the binding constants of ibuprofen with two derivatives of lipoylamide β-cyclodextrin of different hydrophobicity.     

II. Cesium leaching in CsA and CsX zeolites: use of blocking agents to inhibit the cesium cation mobility

Cesium-exchanged A and X zeolites were loaded with cesium acetate species and thermally treated in order to inhibit the mobility of exchangeable cesium cations. The proposed procedure seems to block the cavities channels avoiding the releasing of cesium cations under the leaching conditions. The cesium impregnated species did not induce strong structural modifications if they are used in small amounts (0.2 meq/g zeolite), but they promote transformation toward cesium orthosilicate if they are loaded in amounts as high as 2 meq/g zeolite. This orthosilicate retains safely the cesium as it is a component of the lattice.     

Estimation of the minimum pore size sufficient for capillary hysteresis

A procedure for determination of the minimum pore sizes suitable for the formation of an adsorption-desorption hysteresis loop was developed. Conditions for the formation of hysteresis in infinite rectangular channels and in the cavities restricted along three directions (spheres, rectangular parallelepipeds) and in channels with different cross-sections and limited lengths are considered. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 18–28, January, 2008.     

Fluorescence spectroscopic investigation of the interaction between triphenyltin and humic acids

The interaction between triphenyltin (TPT) and humic acid (HA) was investigated using UV-vis and fluorescence spectra techniques. The experimental results showed that the fluorescence quenching of HA by TPT was a result of the interaction of TPT with HA. The binding constant K(b) and corresponding thermodynamic parameters were measured at different temperatures. The binding of TPT molecule to HA is a spontaneous molecular interaction procedure in which entropy increased and Gibbs free energy decreased. Hydrophobic interaction force plays a major role in stabilizing the TPT-HA complex. The three-dimensional fluorescence contour spectra revealed that TPT could enter into the hydrophobic cavities in some domain of HA.     

Comparison of substructural epitopes in enzyme active sites using self-organizing maps

Summary This paper presents a new algorithm to compare substructural epitopes in protein binding cavities. Through the comparison of binding cavities accommodating well characterized ligands with cavities whose actual guests are yet unknown, it is possible to draw some conclusions on the required shape of a putative ligand likely to bind to the latter cavities. To detect functional relationships among proteins, their binding-site exposed physicochemical characteristics are described by assigning generic pseudocenters to the functional groups of the amino acids flanking the particular active site. The cavities are divided into small local regions of four pseudocenters having the shape of a pyramid with triangular basis. To find similar local regions, an emergent self-organizing map is used for clustering. Two local regions within the same cluster are similar and form the basis for the superpositioning of the corresponding cavities to score this match. First results show that the similarities between enzymes with the same EC number can be found correctly. Enzymes with different EC numbers are detected to have no common substructures. These results indicate the benefit of this method and motivate further studies.     

Electronic state of small and large cavities for methane hydrate

It is well known that methane hydrate is aggregates of small and large hydrogen bonded water cavities (composed of 12 pentagonal faces of 20 water molecules, and 12 pentagonal and two hexagonal faces of 24 water molecules, respectively) where one methane molecule is encaged. We calculated the methane molecule in vacuum, the small and large cavities by ab initio MO method to clarify the electronic state. The proton of methane in the cavities is shown to form the weak hydrogen bond (O...H[bond]C) between methane and four water molecules, and the H-bond lengths and energies in the small and large cavities were estimated as (0.293 nm, 6.8 kJ/mol) and (0.309 nm, 5.2 kJ/mol), respectively. The calculated values of symmetric C[bond]H stretching frequencies and (13)C-NMR chemical shieldings of the methane in the two cluster cavities show good agreement with the experimental ones observed by Sum et al. and Ripmeester and coworker, respectively.     

New method of identifying morphine in urine samples using nanoparticle-dendrimer-enzyme hybrid system

The incorporation of morphine (MOR) into the nanoparticle structure is a viable alternative to traditional enzyme usage. It has good biological potential to separate MOR from real urine samples. In this study, a new method of MOR identification in real urine samples was synthesized using the β-glucuronidase-dendrimer poly amidoamine (PAMAM) enzyme hybrid system. Replacing MOR in dendrimer cavities significantly reduces enzyme consumption. The replacement technique is done in dendrimer cavities in two stages as an alternative to β-glucuronidase enzyme and even MOR. In this paper, firstly, PAMAM dendrimer G2 was synthesized based on silica. The β-glucuronidase enzyme was replaced inside its dendrimer cavities and the compound was released into a real urine sample containing MOR. The enzyme was extracted from dendrimer cavities. The MOR- β-glucuronidase enzyme bond broke. In the next stage of the process, free MOR entered the PAMAM dendrimer G2 cavities. MOR was detected in real urine samples.     

Structure of interparticle space in great noncrystalline packings of Lennard-Jones atoms and its influence on diffusional mobility of admixture particles

Models of 100,000 atoms interacting with Lennard-Jones potential have been constructed using the Monte Carlo method at different densities and temperatures. In these models, the structure of empty space is investigated in which the test particle with a diameter smaller than the diameter of matrix atoms can move. The percolation thresholds, when “infinite” cavities penetrating all model space arise, are found. A change of density and temperature of matrix preparation leads to a non trivial redistribution of volume between cavities of different type. By the method of molecular dynamics it is found that the usual (Einsteinian) law of diffusion is established rather quickly, on average. However, the laws for test particles moving in cavities of different type are more complex and specific to each kind of cavities. It should result in different course of chemical reaction in different local areas of a matrix.     

Local kinetics of cavitation in hydrogen-exposed EPDM using in-situ X-Ray tomography: Focus on free surface effect and cavity interaction

Decompression failure in high-pressure gas exposed rubbers has almost only been studied at a global scale so far. In the present study in hydrogen-exposed EPDM, the growth kinetics of cavities was visualized and quantified at the cavity scale using 3D in-situ X-ray micro-tomography with an emphasis on interaction effects and boundary conditions. The volume evolution of cavities was processed and the inflation rate and maximum volume were calculated. The boundary conditions of selected cavities was analysed in terms of distance to the free surface as well as distance to other cavities. Proximity to the free surface was found to be a driving force for evolution of cavities up to a certain range beyond which the growth kinetics are more driven by other factors such as time of nucleation. Within the range made accessible by the current spatial resolution, no clear interaction effect was pointed out between close cavities.     

Asymmetric bridging of interconnected pores by encased semiflexible macromolecules

An increase of chain rigidity of macromolecule encased in interconnected cavities leads to bridging conformational transition in which polymer molecule at certain conditions spans the cavities. This is a similar phenomenon to that described for flexible chains on increase of confinement. Chain stiffness introduces, however, a delicate effect of interplay between confinement, chain stiffness, and concentration that leads to a breakup of symmetric bridging conformation to a striking asymmetric conformation even in the symmetric system of cavities. We provide the first data on this transition with complex translocation landscape and offer a tentative explanation.     

Microfabrication of cavities in polydimethylsiloxane using DRIE silicon molds

We present a novel method to create cavities in PDMS that is simple and exhibits wide process latitude allowing control over the radius of curvature to form shallow concave pits or deep spherical cavities.     

Enveloping triangulation method for detecting internal cavities in proteins and algorithm for computing their surface areas and volumes

Detection and quantitative characterization of the internal cavities in proteins remain an important topic in studying protein structure and function. Here we propose a new analytical method for detecting the existence of cavities in proteins. The method is based on constructing the special enveloping triangulation enclosing the cavities. Based on this method, we develop an algorithm and a fortran package, CAVE, for computing volumes and surface areas of cavities in proteins. We first test our method and algorithm in some artificial systems of spheres and find that the calculated results are consistent with exact results. Then we apply the package to compute volumes and surface areas of cavities for some protein structures in the Protein Data Bank. We compare our calculated results with those obtained by some other methods and find that our approach is reliable.     

Electron microtomography: A new method for studying the spatial structure of catalysts

The spatial arrangement of active component (Pt) particles on the surface of a support (Sibunit globule) has been studied by bright-field electron tomography. A tomographic attachment for a standard specimen holder and tomographic grids have been designed. The tomographic procedure has been refined, and adequate tilt series alignment and tomographic reconstruction algorithms have been chosen. The 3D distribution of the active component in the catalyst grain has been studied: particles hidden in micropores have been directly observed, and the size of the pores connecting internal cavities with the exterior has been estimated.