Ab initiocalculations of the physical properties of ionic crystals

Abstract

The Arg-Gly-Asp (RGD) peptide sequence is known as a cell recognition site for numerous adhesive proteins present in the extracellular matrix (ECM) and in blood. Whilst surface immobilized RGD groups enhance cell attachment, RGD components present in solution can effectively inhibit cell attachment by competing with endogenous ligands for the same recognition site. In contrast to the widely reported binding to cell integrin, this study demonstrates a new RGD feature: its inhibitive effect on fibrinogen adsorption. Through a combined analysis of spectroscopic ellipsometry, neutron reflection and dual polarization interferometry, we show that the kinetic process of fibrinogen adsorption as a model pro-coagulant at the silica/solution interface and in the absence of any cells can be substantially reduced by the addition of RGD in solution and that the extent of the reduction is dependent on the relative concentration of RGD.

Microporous cesium salts of tetravalent Keggin-type polyoxotungstates Cs4[SiW12O40], Cs4[PW11O39(Sn-n-C4H9)], and Cs4[PW11O39(Sn-OH)] and their adsorption properties

“…8B), the Cs + -heteropoly anion mismatch can be avoided. On the basis of the anion vacancy model, we calculated the number of anion vacancies per unit weight of the Cs salt by using: (3) where N defect , F W , and N A are the number of the anion vacancies per unit weight of the Cs salt (g -1 ), the formula weight of the Cs salt, and Avogadro's number, respectively. If the heteropoly anion is a sphere with a diameter of 1.1 nm [44], the total volume of the anion vacancies per unit weight of the Cs salt (V defect , cm 3 g -1 ) can be calculated by using:…”

“…These Cs salts had highly developed micropores with small external surface areas, regardless of the presence or absence of functional groups (n-butyl and hydroxyl). We discuss the mechanism for the formation of micropores in terms of the crystal structures and morphology of the particles and in comparison with that for Cs 3 [PW 12 O 40 ]. In addition, the effects of n-butyl and hydroxyl groups on the adsorption properties were investigated by measuring the adsorption isotherms of various adsorbates.…”

“…Ionic crystals, which are important families of crystalline materials, have been attracting considerable interest because of their unique chemical and physical properties, which depend on their crystalline structures and constituent ions [1][2][3][4][5][6][7][8][9]. Normally, cations and anions are densely packed in the crystal lattice, with the coordination numbers determined by the relative sizes and charges of the constituent ions since the Coulombic forces are strong and directionless.…”

Lattice dynamics and the ferroelectric and antiferrodistorsive instabilities in a bulk crystal and thin films of SrZrO3

“…To accomplish this, for each ion, we calcu lated the forces where E tot is the total energy of the crystal, which is the sum of the contributions from the energies of the Cou lomb interaction, the short range interaction, and the dipole interaction: E Coulomb + E short + E dipole . It should be noted that all the contributions to the total energy of the crystal in our model were described by the ana lytical expressions (see review [8]); therefore, the first derivative of the energy was not calculated by numeri cal differentiation, but it was also described by the analytical expressions, which could be easily obtained from the expression presented for the total energy in review [8]. Then, each ion was displaced in the direc tion of the forces acting on it; thereafter, the forces acting on the ions were again calculated, and the pro cedure was repeated until the forces at each ion exceeded the value of 2 meV/Å.…”

“…Details of the model were described in the review by Maksimov et al [8]. The calculation of the aforementioned parameters for the bulk SrZrO 3 crys tal was carried out only for the cubic phase of this…”