Phase transitions in K3AlF6

Phase transitions in the elpasolite-type K₃AlF₆ complex fluoride were investigated using differential scanning calorimetry, electron diffraction and X-ray powder diffraction. Three phase transitions were identified with critical temperatures , and . The α-K₃AlF₆ phase is stable below T₁ and crystallizes in a monoclinic unit cell with a=18.8588(2)Å, b=34.0278(2)Å, c=18.9231(1)Å, β=90.453(1)° (a=2a_c−c_c, b=4b_c, c=a_c+2c_c; a_c, b_c, c_c—the basic lattice vectors of the face-centered cubic elpasolite structure) and space group I2/a or Ia. The intermediate β phase exists only in very narrow temperature interval between T₁ and T₂. The γ polymorph is stable in the T₂<T<T₃ temperature range and has an orthorhombic unit cell with a=36.1229(6)Å, b=17.1114(3)Å, c=12.0502(3)Å (a=3a_c−3c_c, b=2b_c, c=a_c+c_c) at 250 °C and space group Fddd. Above T₃ the cubic δ polymorph forms with a_c=8.5786(4)Å at 400 °C and space group . The similarity between the K₃AlF₆ and K₃MoO₃F₃ compounds is discussed.     

Preparation and Crystal Structure of a New Uranyl Sulfate Templated by a Bis-isothiouronium Cation

Crystals of a new uranyl sulfate (C₂N₄H₈S₂)[UO₂(SO₄)₂] · 0.3H₂O ( 1 ) templated by a relatively rare bis-isothiouronium cation, were formed upon evaporation of aqueous solutions containing uranyl acetate, thiourea, and excess sulfuric acid. The new compound is orthorhombic, P2₁2₁2₁, a = 6.928(2) Å, b = 13.398(3) Å, c = 15.225(3) Å, Z = 2. Its crystal structure is comprised of [UO₂(SO₄)₂] moieties linked by hydrogen bonds formed between the template cations and terminal oxygen atoms of the sulfate tetrahedra. The C₂N₄H₈S₂²⁺ template is most likely formed in situ during a redox reaction between uranyl cation and thiourea in a strongly acidic medium, with UO₂²⁺ partially reduced to U⁴⁺.     

Extraction products from <Emphasis Type="Italic">Miscanthus</Emphasis> var. ‘Soranovskii’

The chemical structures of Miscanthus var. ‘Soranovskii’ lignin fractions released via extraction of lignin from the lignocellulosic feedstock using moderately heated acetone under atmospheric pressure, without acidic and alkaline catalysts, were studied. A blend of Miscanthus stems and leaves was pretreated with water under thermobaric conditions. The acetone organosolv process subsequently afforded a substance related to a lignin-like matter-acetone organosolv Miscanthus lignin (AOML). Non-destructive analytical techniques such as FTIR spectroscopy, gas chromatography-mass spectrometry, size-exclusion chromatography, and 2D NMR were used. The IR and NMR spectroscopies revealed the AOML structure to comprise all the three major types of phenylpropane units: guaiacyl (G), syringyl (S), and p-hydroxyphenyl (H). The resultant acetone-organosolv lignin exhibits good solubility in polar solvents, moderate solubility in aromatic chemicals, and is insoluble in non-polar solvents, exhibiting the physicochemical properties of a thermoplastic polymer with a softening point of 67.0°C (onset 33.0°C, endset 81.5°C).     

Synthesis and Evaluation of GdIII‐Based Magnetic Resonance Contrast Agents for Molecular Imaging of Prostate‐Specific Membrane Antigen

Magnetic resonance (MR) imaging is advantageous because it concurrently provides anatomic, functional, and molecular information. MR molecular imaging can combine the high spatial resolution of this established clinical modality with molecular profiling in vivo. However, as a result of the intrinsically low sensitivity of MR imaging, high local concentrations of biological targets are required to generate discernable MR contrast. We hypothesize that the prostate‐specific membrane antigen (PSMA), an attractive target for imaging and therapy of prostate cancer, could serve as a suitable biomarker for MR‐based molecular imaging. We have synthesized three new high‐affinity, low‐molecular‐weight Gd^III‐based PSMA‐targeted contrast agents containing one to three Gd^III chelates per molecule. We evaluated the relaxometric properties of these agents in solution, in prostate cancer cells, and in an in vivo experimental model to demonstrate the feasibility of PSMA‐based MR molecular imaging.     

Coherent control protocol for separating energy-transfer pathways in photosynthetic complexes by chiral multidimensional signals

Adaptive optimizations performed using a genetic algorithm are employed to construct optimal laser pulse configurations that separate spectroscopic features associated with the two main energy-transfer pathways in the third-order nonlinear optical response simulated for the Fenna-Matthews-Olson (FMO) photosynthetic complex from the green sulfur bacterium Chlorobium tepidum. Superpositions of chirality-induced tensor components in both collinear and noncollinear pulse configurations are analyzed. The optimal signals obtained by manipulating the ratios of various 2D spectral peaks reveal detailed information about the excitation dynamics.     

Engineering of a redox protein for DNA-directed assembly

Engineered enzyme conjugate of the small laccase enzyme from Streptomyces coelicolor and zinc finger DNA binding domain from Zif268 is demonstrated to bind double stranded DNA in a site specific manner while retaining enzymatic activity.     

Analytic energy gradient for second-order Møller-Plesset perturbation theory based on the fragment molecular orbital method

The first derivative of the total energy with respect to nuclear coordinates (the energy gradient) in the fragment molecular orbital (FMO) method is applied to second order M?ller-Plesset perturbation theory (MP2), resulting in the analytic derivative of the correlation energy in the external self-consistent electrostatic field. The completely analytic energy gradient equations are formulated at the FMO-MP2 level. Both for molecular clusters (H(2)O)(64) and a system with fragmentation across covalent bonds, a capped alanine decamer, the analytic FMO-MP2 energy gradients with the electrostatic dimer approximation are shown to be complete and accurate by comparing them with the corresponding numeric gradients. The developed gradient is parallelized with the parallel efficiency of about 97% on 32 Pentium4 nodes connected by Gigabit Ethernet.     

Mixed Co/Fe oxide nanoparticles in block copolymer micelles

Small iron oxide and Co-doped iron oxide nanoparticles (NPs) were synthesized in a commercial amphiphilic block copolymer, poly(ethylene oxide)-b-poly(methacrylic acid) (PEO 68-b-PMAA8), in aqueous solutions. The structure and composition of the micelles containing guest molecules (metal salts) or NPs (metal oxides) were studied using transmission electron microscopy, dynamic light scattering, X-ray photoelectron spectroscopy, and X-ray powder diffraction. The enlarged micelle cores after incorporation of metal salts are believed to be formed by both PMAA blocks containing metal species and penetrating PEO chains. The nanoparticle size distributions in PEO 68-b-PMAA8 were determined using small-angle X-ray scattering (SAXS) in bulk. Two independent methods for SAXS data interpretation for comprehensive analysis of volume distributions of metal oxide NPs showed presence of both small particles and larger entities containing metal species which are ascribed to organization of block copolymer micelles in bulk. The magnetometry measurements revealed that the NPs are superparamagnetic and their characteristics depend on the method of the NP synthesis. The important advantage of the PEO 68-b-PMAA8 stabilized magnetic nanoparticles described in this paper is their remarkable solubility and stability in water and buffers.     

Competition between lipases and monoglycerides at interfaces

Tensiometry (the pendant drop technique), interfacial shear rheology, and ellipsometry have been used to study the effect of polar lipids that are generated during fat digestion on the behavior of lipases at the oil-water interface. Both Sn-1,3 regiospecific and nonregiospecific lipases have been used, and a noncatalytically active protein, beta-lacloglobulin, has been used as reference in the interfacial shear rheology experiments. The results from the pendant drop measurements and the interfacial rheology studies were in agreement with each other and demonstrated that the Sn-2 monoglyceride, which is one of the lipolysis products generated when a Sn-1,3 regiospecific lipase catalyzes triglyceride hydrolysis, is very interfacially active and efficiently expels the enzyme from the interface. Ellipsometry conducted at the liquid-liquid interface showed that the lipase forms a sublayer in the aqueous phase, just beneath the monoglyceride-covered interface. Sn-1/3 monoglycerides do not behave this way because they are rapidly degraded to fatty acid and glycerol and the fatty acid (or the fatty acid salt) does not have enough interfacial activity to expel the lipase from the interface. Since the lipases present in the gastrointestinal tract are highly Sn-1,3 regiospecific, we believe that the results obtained can be transferred to the in vivo situation. The formation of stable and amphiphilic Sn-2 monoglycerides can be seen as a self-regulatory process for fat digestion.