Electron Microscopic Study of Products Containing β-Cyclodextrin

The advantageous properties of cyclodextrin (CD) derivatives have been applied in various fields of drug production. Their presence in physical powder mixtures increases the flow characteristics, which can be improved still further if isodimensional particles and homogeneous dispersive products are produced by spray-embedding. An account is given of an electron microscopic study of such products.     

Involvement of an Oxidation‐Reduction Equilibrium in Chromium‐Mediated Enantioselective Nozaki–Hiyama Reactions

Ligand induced enantioselective versions of the chromium(II)‐mediated Nozaki–Hiyama reaction to homoallyl alcohols proved to be very difficult to achieve, especially if any other nucleophile than the parent allylchromium(III) species was applied. Also, the reaction is frequently accompanied by the formation of oxidation side products, predominantly allyl ketones. This can be explained by an Oppenauer–(Meerwein–Ponndorf Verley) type mechanism (OMPV reaction). The addition of an enantiopure ligand to racemic chromium homoallyl alcoholate intermediates produced enantiomerically enriched homoallyl alcohols with an enantiomeric excess of up to 32%. This observation not only supports that the proposed OMPV oxidation‐reduction equilibrium plays a crucial role in Nozaki–Hiyama reactions, but also proves its involvement in enantioselective versions.     

Crystal structure of the di-haem cytochrome c peroxidase from Pseudomonas aeruginosa

BACKGROUND: Cytochrome c peroxidase from Pseudomonas aeruginosa (PsCCP) represents a new class of peroxidases which work without the need to create a semi-stable free radical for catalysis. The enzyme is located in the bacterial periplasm where its likely function is to provide protection against toxic peroxides. The soluble 323-residue single polypeptide chain contains two covalent c-type haems with very different properties: one of them is a low-potential (-330 mV) centre where hydrogen peroxide is reduced (the peroxidatic site); the other is a high-potential (+320 mV) centre which feeds electrons to the peroxidatic site from soluble electron-shuttle proteins such as cytochrome c and azurin. RESULTS: The crystal structure of the oxidized form of PsCCP has been determined to 2.4 A resolution by multiple isomorphous replacement, and refined to an R-factor of 19.2%. PsCCP is organized into two domains, both of them containing a covalent c-haem in a structure reminiscent of class 1 cytochromes c. The domains are related by a quasi-twofold axis. The domain interface holds a newly discovered calcium-binding site with an unusual set of ligands. CONCLUSIONS: The likely function of the calcium site is to maintain the structural integrity of the enzyme and/or to modulate electron transfer between the two haem domains. The low-potential haem has two histidine axial ligands (His55 and His71) and the high-potential haem is ligated by His201 and Met275. There are no polar residues at the peroxidatic site in the inactive oxidized enzyme. The structure suggests that, in the half-reduced functional form of the enzyme, the low-potential haem has to shed His71 in order to make the enzyme catalytically competent. This process is likely to trigger a reorganization of the active site, and may introduce a new residues into the haem pocket.     

Structure-function relationships of alkyl-lysophospholipid analogs in selective antitumor activity

This investigation was initiated in order to delineate the structure-function relationship of the anticancer alkyllysophospholipids and assess their degree of selective cytotoxicity toward neoplastic cells. A series of glycerol phosphocholine analogs with varying substitutions in thesn-1 andsn-2 position were tested for their inhibitory activity as measured by thymidine incorporation, clonogenic assays and effects on protein kinase C activity against a series of human leukemic cell lines and healthy bone marrow progenitor cells. The IC₅₀ was determined for each of the compounds in each cell line and healthy bone marrow cells following a 4-h incubation. The data indicated that a 16–18 carbon chain at thesn-1 coupled with a short substitution atsn-2 had the broadest antitumor activity and was the least toxic to normal bone marrow cells. The results provide a number of useful leads toward the design and development of potentially more active phospholipid compounds.     

Photosynthetic reaction centers/ITO hybrid nanostructure

Photosynthetic reaction center proteins purified from Rhodobacter sphaeroides purple bacterium were deposited on the surface of indium tin oxide (ITO), a transparent conductive oxide, and the photochemical/-physical properties of the composite were investigated. The kinetics of the light induced absorption change indicated that the RC was active in the composite and there was an interaction between the protein cofactors and the ITO. The electrochromic response of the bacteriopheophytine absorption at 771 nm showed an increased electric field perturbation around this chromophore on the surface of ITO compared to the one measured in solution. This absorption change is associated with the charge-compensating relaxation events inside the protein. Similar life time, but smaller magnitude of this absorption change was measured on the surface of borosilicate glass. The light induced change in the conductivity of the composite as a function of the concentration showed the typical sigmoid saturation characteristics unlike if the photochemically inactive chlorophyll was layered on the ITO. In this later case the light induced change in the conductivity was oppositely proportional to the chlorophyll concentration due to the thermal dissipation of the excitation energy. The sensitivity of the measurement is very high; few picomole RC can change the light induced resistance of the composite.     

Use of sweet sorghum juice for lactic acid fermentation: preliminary steps in a process optimization

BACKGROUND: Lactic acid has many applications in the chemical industries and it can be produced economically by microorganisms using biomass raw materials of different origins. Sweet sorghum juice is a high sugar content raw material with potential for lactic acid production because after hydrolysis of its sucrose content the remaining glucose and fructose can supply the carbon demand of most lactic acid bacteria. However, satisfying the nitrogen and B‐vitamin needs of the bacteria by supplementation with yeast extract and/or other alternative nitrogen‐containing supplements can make the process too expensive. RESULTS: Using a statistical optimization process much of the yeast extract can be replaced by a cheaper alternative nitrogen source, namely wheat gluten. This resulted in a fermentation with 99% lactic acid yield and 3.04 g L^?1 h^?1 volumetric productivity. CONCLUSION: Using response surface methodology (RSM) media optimization was performed for lactic acid fermentation with an industrially acceptable result, reducing the costs of raw materials by half, replacing yeast extract by an alternative nitrogen source and applying yeast extract only as a source of micro‐elements (vitamins, salts, etc.) Copyright © 2010 Society of Chemical Industry     

Interdependence of the thermal properties and electronic structure of Y1Ba2CuxO y , (1.5≤x≤9) ceramics

A definite correlation between the thermal and electronic properties of Y₁Ba₂Cu _x O _y perovskite materials has been observed using differential thermal analysis (DTA) and X-ray fluorescence spectroscopy (XFS). The compound Y₁Ba₂Cu₃O_7?z shows anomalous transition enthalpy and copper-oxygen hybridization with respect to other compounds with different copper content.     

Anaerobic crystallisation of an isopenicillin N synthase.Fe(II).substrate complex demonstrated by X-ray studies

Isopenicillin N synthase (IPNS) was cocrystallised with ferrous sulphate and its substrate, delta-(L-alpha-aminoadipoyl)-L-cysteinyl-D-valine (Aad-Cys-Val). Vital to the successful procedure was the maintenance of a rigorously anaerobic environment. Hanging-drop vapour-diffusion crystallisation experiments, using lithium sulphate as the precipitant produced three crystal forms. Form I crystals, with a plate habit, diffracted X-rays to at least 0.11-nm resolution at the European Synchrotron Radiation Facility and belong to the space group P2(1)2(1)2(1), with unit-cell dimensions a = 4.68, b = 7.15, c = 10.10 nm. Their asymmetric unit contains a single IPNS.Fe(II).Aad-Cys-Val complex with a solvent content of 38.5%. Form II crystals, with a hexagonal habit, diffract X-rays to at least 0.21 nm resolution at the European Synchrotron Radiation Facility and belong to the space group P3(1)21, with unit-cell dimensions a = 10.10, b = 10.10, c = 11.567 nm. Their asymmetric unit also contains a single IPNS.Fe(II).Aad-Cys-Val complex with a solvent content of 69.5%. Form III crystals, needles, do not show well-ordered diffraction. Although all three forms were initially produced in crystallisation experiments under identical conditions, appropriate micro and streak seeding allows selective crystallisation of form I or form II crystals. Extended X-ray-absorption fine-structure studies on a crystalline slurry of the form I crystals demonstrate the presence of an Fe-S(Aad-Cys-Val) bond length of 0.234 +/- 0.003 nm.     

Translation Invariance in the Polynomial Kernel Space and Its Applications in kNN Classification

In this paper, a new technique is presented to measure dissimilarity in kernel space providing scaling and translation invariance. The motivation comes from signal/image processing, where classifiers are often required to ensure invariance against linear transforms, since in many cases linear transforms do not affect the content of a signal/image for a human observer. We examine the theoretical background of linear invariance in the polynomial kernel space, introduce the centered correlation and centered Euclidean dissimilarity in kernel space, deduce formulas to compute it efficiently and test the proposed dissimilarity measures with the kNN classifier. The experimental results show that the presented techniques are highly competitive in similarity or dissimilarity based classification methods.