Decay of the transient Cu(B)-CO complex is accompanied by formation of the heme Fe-CO complex of cytochrome cbb(3)-CO at ambient temperature: evidence from time-resolved Fourier transform infrared spectroscopy

Time-resolved step-scan Fourier infrared spectroscopy has been used to study the CO-bound cbb(3)-type cytochrome c oxidase from Pseudomonas stutzeri at room temperature. We observe a single band in the FTIR spectrum at 1956 cm(-1) (beta-form). The time-resolved data indicate that upon photolysis, CO is transferred from heme b(3) (nu(CO) = 1956 cm(-1)) to CuB (nu(CO) = 2064 cm(-1)). The decay of the 2065 cm(-1) peak (t(1/2) = 120 +/- 16 ms) and the development of the 1956 cm(-1) peak (t(1/2) = 144 +/- 8 ms ) suggest that formation of the Fe-CO complex is concurrent with the decay of the CuB-CO complex. The intensity ratio of the Fe-CO/CuB-CO (2.15) remains constant for all data points, and thus we conclude that no fraction of CO escapes the binuclear center at 293 K.     

Über die Wirkung von Auxochromen in Flavyliumsalzen,II. 5,6-Benzo-flavyliumsalze

Analogously to the 7-hydroxyflavyliumion the 5,6-benzoflavyliumion affects auxochromes in 4′-position not as strongly as the flavylium ion. In the flavylium series the dimethyl-amino group e.g. causes a bathochromic effect of 137 nm; in the 5,6-benzoflavylium series however the bathochromic effect is only 109 nm. The absorption maxima of both series converge; in the case of the dimethylamino group the convergence amounts to 28 nm.     

In situ SAXS investigation of dibromomethane adsorption in ordered mesoporous silica

A SAXS/WAXS apparatus with the aid of a specially designed sample cell capable for performing both SAXS and WAXS experiments was used for adsorption studies in nanoporous materials. The applicability of the instrument for structural investigations and its ability for adsorption experiments because of the advanced sample environment were demonstrated by carrying out in situ SAXS measurements during gas physisorption. SAXS profiles of ordered mesoporous silica were measured at selected equilibrium points alongside a dibromomethane (CH₂Br₂) adsorption isotherm at 293 K. SBA-15 was the adsorbent of choice because it consists of a regular 2D hexagonal array of cylindrical mesopores that gives rise to Bragg reflections in the small-angle regime. CH₂Br₂ was selected as a contrast-matching fluid because it has almost the same electron density as silica. We obtained high-quality data comparable to those resulting from experiments performed in synchrotron light sources which produce intense beams of x-rays and support advanced instrumentation for high-resolution diffraction and SAXS studies. The Bragg peaks of the pore lattice are clearly visible for the evacuated sample and at the early stages of the adsorption process. The intensity decrease and the elimination of the Bragg peaks for the saturated sample suggest that an almost perfect contrast matching was achieved. A model has been used for monitoring the fluid condensation and evaporation regime in SBA-15 by taking into account both the Bragg scattering and the diffuse scattering for spatially random pore filling. The results show the absence of spatial correlations between filled pores suggesting random pore filling.     

Losartan Interactions with 2-Hydroxypropyl-β-CD

Losartan potassium salt (LSR) is a well-known antihypertensive drug with proven beneficial effects on human health. Its formulation with the non-toxic 2-hydroxypropyl-β-cyclodextrin (2-HP-β-CD) could improve its pharmacological profile. Thus, its molecular interactions are studied using a combination of Differential Scanning Calorimetry (DSC), Nuclear Magnetic Resonance (NMR) and Molecular Dynamics (MD). First, its complexation is shown through Differential Scanning Calorimetry as lyophilization provided distinct thermal properties in comparison to the mixture. The complexation is further proved by utilizing the chemical shift changes in the complexation and T1 values. Furthermore, the reversible favorable complexation was shown by MD calculations. Such physical chemical properties provide evidence that this formulation must be further explored through biological experiments.     

Principles of demineralization: modern strategies for the isolation of organic frameworks. Part I. Common definitions and history

In contrast to biomineralization phenomena, that are among the most widely studied topics in modern material and earth science and biomedicine, much less is systematized on modern view of demineralization. Biomineralized structures and tissues are composites, containing a biologically produced organic matrix and nano- or microscale amorphous or crystalline minerals. Demineralization is the process of removing the inorganic part, or the biominerals, that takes place in nature via either physiological or pathological pathways in organisms. In vitro demineralization processes, used to obtain mechanistic information, consist in the isolation of the mineral phase of the composite biomaterials from the organic matrix. Physiological and pathological demineralization include, for example, bone resorption mediated by osteoclasts. Bioerosion, a more general term for the process of deterioration of the composite biomaterials represents chemical deterioration of the organic and mineral phase followed by biological attack of the composite by microorganisms and enzymes. Bioerosional organisms are represented by endolithic cyanobacteria, fungi, algae, plants, sponges, phoronids and polychaetes, mollusks, fish and echinoids.In the history of demineralization studies, the driving force was based on problems of human health, mostly dental caries. In this paper we summarize and integrate a number of events, discoveries, milestone papers and books on different aspect of demineralization during the last 400 years. Overall, demineralization is a rapidly growing and challenging aspect of various scientific disciplines such as astrobiology, paleoclimatology, geomedicine, archaeology, geobiology, dentistry, histology, biotechnology, and others to mention just a few.     

Chemistry in Molten Alkali Metal Polyselenophosphate Fluxes. Influence of Flux Composition on Dimensionality. Layers and Chains in APbPSe(4), A(4)Pb(PSe(4))(2) (A = Rb, Cs), and K(4)Eu(PSe(4))(2)

The reaction of Pb and Eu with a molten mixture of A(2)Se/P(2)Se(5)/Se produced the quaternary compounds APbPSe(4), A(4)Pb(PSe(4))(2) (A = Rb,Cs), and K(4)Eu(PSe(4))(2). The red crystals of APbPSe(4) are stable in air and water. The orange crystals of A(4)Pb(PSe(4))(2) and K(4)Eu(PSe(4))(2) disintegrate in water and over a long exposure to air. CsPbPSe(4) crystallizes in the orthorhombic space group Pnma (No. 62) with a = 18.607(4) ?, b = 7.096(4) ?, c = 6.612(4) ?, and Z = 4. Rb(4)Pb(PSe(4))(2) crystallizes in the orthorhombic space group Ibam (No. 72) with a = 19.134(9) ?, b = 9.369(3) ?, c = 10.488(3) ?, and Z = 4. The isomorphous K(4)Eu(PSe(4))(2) has a = 19.020(4) ?, b = 9.131(1) ?, c = 10.198(2) ?, and Z = 4. The APbPSe(4) have a layered structure with [PbPSe(4)](n)()(n)()(-) layers separated by A(+) ions. The coordination geometry around Pb is trigonal prismatic. The layers are composed of chains of edge sharing trigonal prisms running along the b-direction. [PSe(4)](3)(-) tetrahedra link these chains along the c-direction by sharing edges and corners with the trigonal prisms. A(4)M(PSe(4))(2) (M = Pb, Eu) has an one-dimensional structure in which [M(PSe(4))(2)](n)()(n)()(-) chains are separated by A(+) ions. The coordination geometry around M is a distorted dodecahedron. Two [PSe(4)](3)(-) ligands bridge two adjacent metal atoms, using three selenium atoms each, forming in this way a chain along the c-direction. The solid state optical absorption spectra of the compounds are reported. All compounds melt congruently in the 597-620 degrees C region.