Analysis of 'ARN' naphthenic acids by high temperature gas chromatography and high performance liquid chromatography

Examination by high temperature GC (HTGC) of the methyl esters of the so-called 'ARN' naphthenic acids from crude oils of North Sea UK, Norwegian Sea and West African oilfields revealed the distributions of resolved 4-8 ring C80 tetra acids and trace amounts of other acids. Whilst all three oils contained apparently the same major acids, the proportions of each differed, possibly reflecting the growth temperatures of the archaebacteria from which the acids are assumed to have originated. The structures of the 4, 5, 7 and 8 ring acids are tentatively assigned by comparison with the known 6 ring acid and related natural products and an HPLC method for the isolation of the individual acids is described. ESI-MS of individual acids isolated by preparative HPLC established the elution order of the 4-8 ring acids on the HPLC and HTGC systems and revealed the presence of previously unreported acids tentatively identified as C81 and C82 7 and 8 ring analogues.     

Adsorption behavior of acidic and basic proteins onto citrate-coated Au surfaces correlated to their native fold, stability, and pI

The adsorption of eight different proteins (alpha-lactalbumin (types I and III), bovine serum albumin, hemoglobin, myoglobin, cytochrome c, alpha-casein, and lysozyme) onto a model anionic surface was performed at equivalent bulk (solvent, ionic strength, pH) and surface conditions. Adsorption was monitored on a quartz crystal microbalance with dissipation monitoring (QCM-D) with citrate-coated gold surfaces as adsorbents and has been correlated to native fold stability determined from near- and far-UV circular dichroism (CD) measurements. The proteins studied here were chosen based on their pI and documented knowledge about their structural stability and flexibility. Protein adsorption was found to be independent of global protein charge. Rather, binding occurs through oppositely charged patches on protein and surface. Moreover, data indicate that there is a correlation between secondary and tertiary structure stability and the adsorption characteristics at interfaces. Also, protein surface coverage, layer thickness, and flexibility can be tuned as a function of deposition method. This is discussed in terms of adsorption/spreading kinetics and intermolecular (protein-surface and protein-protein) interactions. Adsorption to surfaces can induce formation of supramolecular structures such as micelles (in the case of alpha-Cas) and multilayers (as for Hb). In the case of alpha-casein, this phenomenon depends on the deposition method and protein concentration. When ranking the surface coverage for proteins added in excess, the order is Lyz < Cyt c < Mb < BSA < alpha-La I < alpha-Cas < alpha-La III < Hb, which can be correlated to the proteins ability to form supramolecular structures (alpha-Cas, Hb), overall conformational flexibilities, and ability to form stable intermediates.     

Mechanistic studies of UV assisted [4 + 2] cycloadditions in synthetic efforts toward vibsanin E

Quantum chemical DFT calculations at the B3LYP/6-31G(d) level have been used to study the stereochemical course of the photochemical cycloaddition of enone 9 with dienes. The observed products of this photochemically induced cycloaddition showed a stereoselectivity, which is opposite to what would be expected by FMO considerations. The quantum chemical calculations revealed that the unusual stereoselectivity of the reaction can be rationalized by assuming a stereospecific photochemical cis-trans isomerization of enone 9 to trans isomer 9a followed by a thermal Diels-Alder reaction of the diene onto the highly reactive trans enone. The photochemical reaction step involves the selective formation of a twisted triplet intermediate, which accounts for the selectivity of the reaction.     

Determination of liposome–buffer distribution coefficients of charged drugs by capillary electrophoresis frontal analysis

The potential of using CE frontal analysis (CE‐FA) to study the interactions between a range of charged low molecular weight drug substances and liposomes was evaluated. The liposomes used were net negatively charged and consisted of 2‐oleoyl‐1‐palmitoyl‐sn‐glycero‐3‐phosphocholine and 1,2‐dipalmitoyl‐sn‐glycero‐3‐phosphate monosodium salt in a ratio of 80/20 mol%. Apparent distribution coefficients (D_mem), defined as the molar concentration of drug substance in the membrane phase divided by the molar concentration of drug substance in the aqueous phase, were successfully determined for six positively and eight negatively charged drug substances with log D_mem ranging from 1.35 to 3.63. The extent of liposome–buffer distribution was found to be dependent on the drug concentration. The results obtained with the developed CE‐FA method were in good agreement with results obtained by equilibrium dialysis. Furthermore, the CE‐FA method was faster, less labor intensive and required smaller sample volumes (～50 μL) compared with equilibrium dialysis. Thus, CE‐FA is an efficient and useful tool for the characterization of interactions between liposomes and low molecular weight drug substances.     

Identification and characterization of endonuclein binding proteins: evidence of modulatory effects on signal transduction and chaperone activity

Background  

We have previously identified endonuclein as a cell cycle regulated WD-repeat protein that is up-regulated in adenocarcinoma of the pancreas. Now, we aim to investigate its biomedical functions.     

Watching nanoparticles form: an in situ (small-/wide-angle X-ray scattering/total scattering) study of the growth of yttria-stabilised zirconia in supercritical fluids

Understanding nanoparticle-formation reactions requires multi-technique in situ characterisation, since no single characterisation technique provides adequate information. Here, the first combined small-angle X-ray scattering (SAXS)/wide-angle X-ray scattering (WAXS)/total-scattering study of nanoparticle formation is presented. We report on the formation and growth of yttria-stabilised zirconia (YSZ) under the extreme conditions of supercritical methanol for particles with Y(2)O(3) equivalent molar fractions of 0, 4, 8, 12 and 25 %. Simultaneous in situ SAXS and WAXS reveals a quick formation (seconds) of sub-nanometre amorphous material forming larger agglomerates with subsequent slow crystallisation (minutes) into nanocrystallites. The amount of yttria dopant is shown to strongly affect the crystallite size and unit-cell dimensions. At yttria-doping levels larger than 8 %, which is known to be the stoichiometry with maximum ionic conductivity, the strain on the crystal lattice is significantly increased. Time-resolved nanoparticle size distributions are calculated based on whole-powder-pattern modelling of the WAXS data, which reveals that concurrent with increasing average particle sizes, a broadening of the particle-size distributions occur. In situ total scattering provides structural insight into the sub-nanometre amorphous phase prior to crystallite growth, and the data reveal an atomic rearrangement from six-coordinated zirconium atoms in the initial amorphous clusters to eight-coordinated zirconia atoms in stable crystallites. Representative samples prepared ex situ and investigated by transmission electron microscopy confirm a transformation from an amorphous material to crystalline nanoparticles upon increased synthesis duration.     

Superfluidity of neutron matter: (II). Triplet pairing

The possibility of neutron triplet pairing and superfluidity in neutron star matter is investigated, and the energy gap and corresponding critical temperature is calculated or estimated as a function of Fermi momentum or density. The calculations are performed for a “one-pion-exchange gaussian” potential, and compared with the results for neutron and proton singlet pairing and superfluidity calculated earlier.The results indicate that neutron superfluidity, corresponding specifically to ³P₂ state pairing, may exist in a high-density shell in the nuclear-matter region of a neutron star, i.e. for 1.6 × 10¹⁴g/cm³ < ρ < 1.4 × 10¹⁵g/cm³, and the maximum self-consistent energy gap is Δ⁰₁k_F ≈ 0.6 MeV and Δ⁰₃(k_F) ≈ 0.1 MeV for an effective mass $\text{m}{}^1\text{≈ 0.75}\text{and}\text{k}{}_{\mathrm{<mtext>F</mtext>}}\text{≈ 2.1}\text{fm}{}^{\mathrm{?1}}$, i.e. for a mas ? ≈ 5.2 × 10¹⁴g/cm³. For $\text{m}{}^1\text{= 1.0}$ we get correspondingly Δ⁰₁(k_F) ≈ 3.3 MeV and Δ⁰₃(k_F) ≈ 0.6 MeV for k_F ≈ 2.2 fm^?1.     

Maghemite in basalt studied by Mössbauer spectroscopy in external magnetic field

In the present study, we investigate the feasibility of detecting and determining the presence of maghemite in rock samples, by obtaining Mössbauer spectra in an external magnetic field of 1.6 T at room temperature. The interaction of the external magnetic field and the magnetic moments of the sublattices will induce differential shifts in the peak positions. By this method, we can assign some lower limit of the amount of maghemite in the sample. The results are compared with a model for a mixture of maghemite and stoichiometric magnetite.     

In-situ studies of catalysts by XAFS and Mössbauer spectroscopy

The unique advantages of XAFS and Mössbauer spectioscopy applied to studies of catalysts are discussed. These advantages include the importantin situ capability, as well as the possibility to provide information on X-ray amorphous materials. The successful use of the two techniques is demonstrated by examples of two important technical catalyst systems, hydrotreating and ammonia synthesis catalysts, representing supported and unsupported catalysts.

     

FTIR spectroscopy of ethyl benzoate-titanium tetrachloride complexes with application to supported Ziegler-Natta catalysts

Several methods using linear predictionz-transformation and autoregression have been applied to FTIR spectral analysis to reduce noise and improve resolution of an emission spectrum obtained from the truncated interferogram.