Lipid-driven molecular complexes

Three dimensional structure of the Aquila Rift of magnetized neutral gas is\ninvestigated by analyzing HI and CO line data. The projected distance on the\nGalactic plane of the HI arch of the Rift is ~250 pc from the Sun. The HI arch\nemerges at l~ 30 deg, reaches to altitudes as high as ~ 500 pc above the plane\nat l~ 350deg, and returns to the disk at l~270 deg. The extent of arch at\npositive latitudes is ~1 kpc and radius is ~100 pc. The eastern root is\nassociated with the giant molecular cloud complex, which is the main body of\nthe optically defined Aquila Rift. The HI and molecular masses of the Rift are\nestimated to be M_HI~1.4x10^5Msun and M_H2 ~3x10^5 Msun. Gravitational energies\nto lift the gases to their heights are E_grav: HI ~1.4x10^51 and E_grav: H_2\n~0.3x10^51 erg, respectively. Magnetic field is aligned along the HI arch of\nthe Rift, and the strength is measured to be B~10 microG using Faraday rotation\nmeasures of extragalactic radio sources. The magnetic energy is estimated to be\nE_mag~1.2x10^51 erg. A possible mechanism of formation of the Aquila Rift is\nproposed in terms of interstellar magnetic inflation by a sinusoidal Parker\ninstability of wavelength of ~2.5 kpc and amplitude ~500 pc.\n

The pro-inflammatory, leukocyte-derived S100A12 protein occurs as calcium-dependent oligomers in serum, while EDTA plasma from the majority of healthy individuals contains only monomers. Addition of 5 mM EDTA to serum leads to a rapid dissociation of the oligomers in most samples. However, using gel permeation chromatography, we have found that sera from some patients and seemingly healthy individuals contain molecular complexes in the 400–1000 kDa range reacting with anti-S100A12 even in the presence of EDTA; for these we introduce the name ERAC (EDTA Resistant S100A12 Complexes). Based upon monoclonal antibodies and the lateral flow principle, we have developed a quantitative rapid ERAC test giving results within 10 minutes. The highest prevalence of ERAC positivity was found in sera from patients with concomitant rheumatoid arthritis and coronary heart disease. The structure of ERAC is not yet known. Further studies are needed to analyse the mechanism behind the appearance of ERAC and the possible association with inflammatory-related diseases.

Osteotropic β-cyclodextrin for local bone regeneration

Open-framework germanates are a group of germanium oxides with a well-defined porous structure, suitable for ion-exchange and gas adsorption applications. Recently, Ni incorporation into the porous structure by establishing Ge-O-Ni bonds with the molecular complexes [Ni(H2N(CH2)2NH2)2] was realized. We investigate the optical and electronic features of these systems (SUT-1 and SUT-2) from first principles. To describe the photophysical behavior, we analyze the bonding between the Ni and nearest-neighboring atoms and simulate the absorption spectra. Because of their optical characteristics, germania-based nanomaterials are expected to be essential components of future optical and electronic devices. We discuss to what extent molecular transition-metal complexes embedded into porous germanium oxide can modify the optical response to potentially expand the area of applications.

— The phosphorescence of oxygen in the liquid phase and in a solution in carbon tetrachloride was studied upon excitation at a wavelength of 765 nm using an LED array as a source of direct optical excitation. A comparison is made of the observed efficiency of oxygen phosphorescence at a wavelength of 1270 nm upon its excitation at a wavelength of 765 nm with its excitation at other wavelengths, which partially or completely coincide with the absorption lines of molecular oxygen complexes. Key words: phosphorescence, singlet oxygen, molecular complexes, optical excitation, LED matrices.

Unveiling the nature and the distribution of surface sites in heterogeneous catalysts, and for the Phillips catalyst (CrO3/SiO2) in particular, is still a grand challenge despite more than 60 years of research. Commonly used references in Cr K-edge XANES spectral analysis rely on bulk materials (Cr-foil, Cr2O3) or molecules (CrCl3) that significantly differ from actual surface sites. In this work, we built a library of Cr K-edge XANES spectra for a series of tailored molecular Cr complexes, varying in oxidation state, local coordination environment, and ligand strength. Quantitative analysis of the pre-edge region revealed the origin of the pre-edge shape and intensity distribution. In particular, the characteristic pre-edge splitting observed for Cr(III) and Cr(IV) molecular complexes is directly related to the electronic exchange interactions in the frontier orbitals (spin-up and -down transitions). The series of experimental references was extended by theoretical spectra for potential active site structures and used for training the Extra Trees machine learning algorithm. The most informative features of the spectra (descriptors) were selected for the prediction of Cr oxidation states, mean interatomic distances in the first coordination sphere, and type of ligands. This set of descriptors was applied to uncover the site distribution in the Phillips catalyst at three different stages of the process. The freshly calcined catalyst consists of mainly Cr(VI) sites. The CO-exposed catalyst contains mainly Cr(II) silicates with a minor fraction of Cr(III) sites. The Phillips catalyst exposed to ethylene contains mainly highly coordinated Cr(III) silicates along with unreduced Cr(VI) sites.

Slow evaporation of a solution of 5,6-dicyano[1,2,5]selenodiazolo[3,4-b]pyrazine (1) and 18-crown-6 (2) in tetrahydrofuran (THF) yields the 14·23 THF2 (3) molecular crystal complex. The composition of 3 differs from the 1:1 stoichiometry typical for molecular complexes of 1,2,5-chalcogenadyazole derivatives with crown ethers. The structure of 3 is determined by single crystal X-Ray diffraction. The crystal packing of 3 is formed by π-stacking interactions between the molecules of 1 and by strongly shortened Se⋯O contacts between the molecules of 1 and 2. The Se⋯O contacts meet the geometric criteria of chalcogen bonding.

1. Molecular charge-transfer complexes have been prepared from transition-metal chelates based on heterosubstituted benzo [b] thiophenes. 2. The electronic absorption spectra and x-ray photoelectron spectra of the molecular complexes indicate that besides an intermolecular π-π* interaction, there is a local donor-acceptor interaction between the coordinated metal ion of the chelate and a chlorine atom in the acceptor. 3. A correlation is observed between the electronegativity of the heteroatom and the donor power of the chelate.

We report the unprecedented electrocatalytic activity of a series of molecular nickel thiolate complexes (1–5) in reducing CO2 to C1–3 hydrocarbons on carbon paper in pH‐neutral aqueous solutions. Ni(mpo)2 (3, mpo=2‐mercaptopyridyl‐N‐oxide), Ni(pyS)3− (4, pyS=2‐mercaptopyridine), and Ni(mp)2− (5, mp=2‐mercaptophenolate) were found to generate C3 products from CO2 for the first time in molecular complex. Compound 5 exhibits Faradaic efficiencies (FEs) of 10.6 %, 7.2 %, 8.2 % for C1, C2, C3 hydrocarbons respectively at −1.0 V versus the reversible hydrogen electrode. Addition of CO to the system significantly promotes the FEC1–C3 to 41.1 %, suggesting that a key Ni−CO intermediate is associated with catalysis. A variety of spectroscopies have been performed to show that the structures of nickel complexes remain intact during CO2 reduction.

A method to visualize the equilibrium between molecular complexes (MCs) and trigonal bipyramidal (TB) adducts for ArSeBr2Ar′ has been devised. The TB formation causes large downfield shifts for the ipso carbons δ(Ci), whereas the upfield shifts are characteristic for δ(Ci) in the MC formation. Therefore, the equilibrium is clearly proved if such an ArSeAr′ is prepared that shows an upfield shift at one of ipso carbons, whereas the other goes downfield, when bromine is added to the ArSeAr′ solution. The halogen‐induced chemical shifts (Δδ) are measured for 4‐YC6H4SePh (1a–1g), 2‐YC6H4SePh (2d, 2e, 2h), 2‐YC6H4SeC6H4Br‐p(3d, 3e, 3h), 2‐O2NC6H4SeC6H4Y‐p (4a, 4e, 4i), and 2,4‐(O2N)2C6H3SeC6H4Y‐p (5a, 5e, 5i), where Y = H (a), OMe (b), Me (c), Cl (d), Br (e), COOEt (f), NO2(g), I (h), and t‐Bu (i). Positive values (downfield shifts) are observed for both δ(Ci) in2and3, positive and negative values are recorded for each δ(Ci) in4, and negative values are detected for both δ(Ci) in5. The equilibrium between MC's and TB adducts is clearly shown in4. The equilibrium constants K (K = [MC]/[TB]) are also calculated: they are ca. 0.20 for2and3and 0.16, 0.33, and 0.73 for4i, 4a, and4e, respectively. The contribution of MC is negligible in1a, and the contribution of the TB adduct is negligible in5. The results show that TB adducts become unstable relative to MCs, when the effective electronegativity of the selenium atom and/or the bulkiness around the atom in a selenide are increased. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:369–379, 2001

The Crystalline Molecular Complex between Cationic Surfactant and Some Additive Systems: II. Complex Formation with Basic Substances as Additives

The complex-formation reactions between iodine and aza-18-crown-6 (1,4,7,10,13-pentaoxa-16-azacyclooctadecane), 7,16-diaza-18-crown-6 (1,4,10,13-tetraoxa-7,16-diazacyclooctadecane and 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane (cryptand C222) have been studied spectrophotometrically in chloroform solution at various temperatures. In the cases of 7,16-diaza-18-crown-6 and cryptand C222 the resulting 1 : 2 (macrocycle to iodine) molecular complex is formulated as (macrocycle ⋯ I+)I3–, while with aza-18-crown-6 a 2 : 2 molecular complex of the type [(macrocycle)2⋯ I+]I3– is formed. The spectrophotometric results, as well as conductance measurements, revealed that the gradual release of triiodide ion from its contact ion pair in the molecular complex into solution is the rate-determining step of the reaction. The formation constants of the resulting molecular complexes were evaluated from computer fitting of absorbance vs. mole ratio data and found to vary in the order cryptand C222 > 7,16-diaza-18-crown-6 > aza-18-crown-6. The enthalpy and entropy of complexation of iodine with aza- and 7,16-diaza-18-crown-6 were determined from the temperature dependence of the formation constants. In both cases, the complexation reactions are enthalpy stabilized, but entropy destabilized.

The directing effect of coordinating ligands in the formation of uranium molecular complexes has been well established, but the role of counterions in metal-ligand interactions remains ambiguous and requires further investigation. In this work, we describe the targeted isolation, through the choice of alkali-metal ions, of a family of tetravalent uranium sulfates, showing the influence of the overall topology and, unexpectedly, the UIV nuclearity upon the inclusion of such countercations. Analyses of the structures of uranium(IV) oxo/hydroxosulfate oligomeric species isolated from consistent synthetic conditions reveal that the incorporation of Na+ and Rb+ promotes the crystallization of 0D discrete clusters with a hexanuclear [U6O4(OH)4(H2O)4]12+ core, whereas the larger Cs+ ion allows for the isolation of a 2D-layered oligomer with a less condensed trinuclear [U3(O)]10+ center. This finding expands the prevalent view that counterions play an innocent role in molecular complex synthesis, affecting only the overall packing but not the local oligomerization. Interestingly, trends in nuclearity appear to correlate with the hydration enthalpies of alkali-metal cations, such that the alkali-metal cations with larger hydration enthalpies correspond to more hydrated complexes and cluster cores. These findings afford new insights into the mechanism of nucleation of UIV, and they also open a new path for the rational design and synthesis of targeted molecular complexes.

Aqueous mixtures of cornstarch and Pluronic® F127 studied by experimental and computational techniques

Renal dysplasia, the major cause of childhood renal failure in humans, arises from perturbed renal morphogenesis and molecular signaling during embryogenesis. Recently, we discovered induction of molecular crosstalk between Smad1 and beta-catenin in the TgAlk3QD mouse model of renal medullary cystic dysplasia. Our finding that Myc, a Smad and beta-catenin transcriptional target and effector of renal epithelial dedifferentiation, is misexpressed in dedifferentiated epithelial tubules provided a basis for investigating coordinate transcriptional control by Smad1 and beta-catenin in disease. Here, we report enhanced interactions between a molecular complex consisting of Smad1, beta-catenin and Tcf4 and adjacent Tcf- and Smad-binding regions located within the Myc promoter in TgAlk3QD dysplastic renal tissue, and Bmp-dependent cooperative control of Myc transcription by Smad1, beta-catenin and Tcf4. Analysis of nuclear extracts derived from TgAlk3QD and wild-type renal tissue revealed increased levels of Smad1/beta-catenin molecular complexes, and de novo formation of chromatin-associated Tcf4/Smad1 molecular complexes in TgAlk3QD tissues. Analysis of a 476 nucleotide segment of the 1490 nucleotide Myc genomic region upstream of the transcription start site demonstrated interactions between Tcf4 and the Smad consensus binding region and associations of Smad1, beta-catenin and Tcf4 with oligo-duplexes that encode the adjacent Tcf- and Smad-binding elements only in TgAlk3QD tissues. In collecting duct cells that express luciferase under the control of the 1490 nucleotide Myc genomic region, Bmp2-dependent stimulation of Myc transcription was dependent on contributions by each of Tcf4, beta-catenin and Smad1. These results provide novel insights into mechanisms by which interacting signaling pathways control transcription during the genesis of renal dysplasia.