Zel'Manov's Theorem for Primitive Jordan-Banach Algebras

The following result is well known and easy to prove (see [14,Theorem 2.2.6]). Theorem 0. If A is a primitive associative Banach algebra, thenthere exists a Banach space X such that A can be seen as a subalgebraof the Banach algebra BL(X) of all bounded linear operatorson X in such a way that A acts irreducibly on X and the inclusionABL(X) is continuous. In fact, if X is any vector space on which the primitive Banachalgebra A acts faithfully and irreducibly, then X can be convertedin a Banach space in such a way that the requirements in Theorem0 are satisfied and even the inclusion ABL(X) is contractive. Roughly speaking, the aim of this paper is to prove the appropriateJordan variant of Theorem 0.     

Tailoring orthogonal proteomic routines to understand protein separation during ion exchange chromatography

Surface charge, molecular weight, and folding state are known to influence protein chromatographic behaviour onto ion exchangers. Experimentally, information related to such factors can be gathered via 2-DE methods. The application of 2-D PAGE under denaturing/reducing conditions was already shown to reveal separation trends within a large protein population from cell extracts. However, ion-exchange chromatography normally runs under native conditions. A tailored protocol consisting in a first separation based on IEF on Immobiline strips under native conditions followed by a second dimension SDS-PAGE run was adopted. The chromatographic versus electrophoretic separation behaviours of two model proteins, thaumatin (TAU) and BSA, were compared to better understand which proteomic routine would be better suited to anticipate IEX chromatographic separations. It was observed that the information contained in the pI value obtained with the adapted 2-DE protocol showed better correlation with the IEX chromatographic behaviour. On the other hand, chromatographic separations performed in the presence of urea as a denaturant have demonstrated the potential influence of hydrodynamic radius/conformation on protein separation. Moreover, the information provided by such 2-D system correlated well with the chromatographic behaviour of an additional set of pure proteins. An initial prediction of protein ion-exchange chromatographic behaviour could be possible utilizing an experimental approach based on 2-DE running under milder chemical conditions. This technique provides information that more closely resembles the separation behaviour observed with a complex biotechnological feedstock.     

A comparison of homogeneous and biphasic hydrogenation systems of macrocyclic lactones with in situ formed rhodium complexes

Homogeneous and biphasic hydrogenation of avermectins catalyzed by rhodium complexes in situ formed from [RhCl(COD)]₂ and triphenylphosphine or sulphonated arylphosphines, respectively, was studied under mild reaction conditions. Effects of adding TBAB and bis-QACs as phase transfer agents, Tween? 80 as non-ionic surfactant, β-cyclodextrin as inverse phase-transfer agent, and triphenylphosphine as co-ligand, are reported for the biphasic system.     

Assessing adsorbent-biomass interactions during expanded bed adsorption onto ion exchangers utilizing surface energetics

Biomass adhesion onto an adsorbent matrix or "interaction" as well as biological particle co-adhesion or "aggregation" can severely affect the overall performance of many direct-contact methods for downstream processing of bioproducts. Studies to quantitatively describe this biomass-adsorbent interaction were developed utilizing surface energetics. An indirect thermodynamic approach via contact angle and zeta potential measurements was utilized. Intact yeast cells, yeast homogenates, and disrupted bacterial paste were employed as model system. Various surfaces that are relevant to biochemical and environmental applications were characterized. The extended Derjaguin, Landau, Verwey, Overbeek (XDLVO) theory was found to appropriately predict biomass adhesion behaviour. It was observed that cell attachment onto anion-exchange supports is promoted by strong and close interaction within a secondary energy minimum followed by moderate multilayer cell aggregation. On the other hand, cell interaction with cation-exchange materials can take place within a reversible secondary energy minimum and at longer separation distance. The influence of particle charge and size, as well as the influence of the nature of the material under study were summarized in the form of energy vs. distance profiles. These investigations lead to many process-related conclusions: (a) process buffer conductivity windows can be recommended for anion-exchange chromatography (AEX) vs. cation-exchange chromatography (CEX) systems, (b) increased hydrodynamic shear is required to prevent biomass attachment onto AEX as compared to CEX, and (c) aggregation phenomena is a function of contact time and biomass concentration. Understanding biomass-adsorbent interaction at the particle (local) level is opening the pave for optimized operation of expanded bed adsorption methods at the process (macro) scale. A universal methodological approach is presented to guide both process and material design.     

Organocatalytic asymmetric synthesis of alpha,alpha-disubstituted alpha-amino acids and derivatives

It is shown that racemic oxazolones are excellent reagents for the synthesis of chiral quaternary amino acids and its derivatives by the diastereo- and enantioselective nucleophilic addition to alpha,beta-unsaturated aldehydes catalyzed by diarylprolinol silyl ethers. The scope of this new organocatalytic reaction is demonstrated for different oxazolones having aromatic and alkyl groups at the reactive carbon atom and different aromatic and aliphatic substituted alpha,beta-unsaturated aldehydes, for which the stereoselective reaction proceeds with good yield, moderate to good to very high diastereoselectivity, and very high enantioselectivity. The potential of the reaction is shown for the synthesis of optically active alpha,alpha-disubstituted alpha-amino acids, alpha-quaternary proline derivatives, amino alcohols, lactams, and tetrahydropyranes. Furthermore, we have calculated by DFT-methods the transition-state structures that account for both the diastereo- and enantioselectivity observed for the addition of oxazolones to the alpha,beta-unsaturated aldehydes. For one class of compounds, the stereoselectivity is controlled by a hydrogen-bonding interaction of the enolate-form of the oxazolone with an ortho-hydroxy-phenyl substituent of the alpha,beta-unsaturated aldehyde, whereas the benzhydryl-protecting group in the oxazolone determines the diastereo- and enantioselectivity in a more general manner for both aromatic and aliphatic alpha,beta-unsaturated aldehydes.     

Magnetic nanoparticles coated with polyaniline to stabilize immobilized trypsin

It is reported the synthesis of magnetic nanoparticles via the chemical co-precipitation of Fe ³⁺ ions and their preparation by coating them with polyaniline. The electronic micrograph analysis showed that the mean diameter for the nanoparticles is ～15 nm. FTIR, powder X-ray diffraction and Mössbauer spectroscopy were used to understand the chemical, crystallographic and ⁵⁷Fe hyperfine structures for the two samples. The nanoparticles, which exhibited magnetic behavior with relatively high spontaneous magnetization at room temperature, were identified as being mainly formed by maghemite (γFe₂O₃). The coated magnetic nanoparticles (sample labeled “mPANI”) presented a real ability to bind biological molecules such as trypsin, forming the magnetic enzyme derivative (sample “mPANIG-Trypsin”). The amount of protein and specific activity of the immobilized trypsin were found to be 13±5 μg of protein/mg of mPANI (49.3 % of immobilized protein) and 24.1±0.7 U/mg of immobilized protein, respectively. After 48 days of storage at 4 ^°C, the activity of the immobilized trypsin was found to be 89 % of its initial activity. This simple, fast and low-cost procedure was revealed to be a promising way to prepare mPANI nanoparticles if technological applications addressed to covalently link biomolecules are envisaged. This route yields chemically stable derivatives, which can be easily recovered from the reaction mixture with a magnetic field and recyclable reused.     

A metal-complex-tolerant CuAAC 'click' protocol exemplified through the preparation of homo- and mixed-metal-coordinated [2]rotaxanes

A series of mono- and bis-metallated [2]rotaxanes has been prepared using a CuAAC 'click' protocol that is compatible with metal-coordinated building blocks and ligands; the methodology provides a general means for appending a metal ion or complex to an organic scaffold via Cu(I)-catalysed 'click' chemistry, even when the molecule contains redox-active or kinetically labile metals or vacant ligand sites.     

Global screening of protein chromatographic behavior on ion exchangers from a complex cell proteome. Towards in silico downstream processing of bioproducts

Protein separation during ion-exchange chromatography implies complex physicochemical events. This work has evaluated the chromatographic behaviour of a complex cell proteome on commercial agarose-based adsorbents. Various ligand types in the cation- and anion-exchange mode were studied. ANX-Sepharose, a weak anion exchanger, performed similarly to the strong anion exchanger-type materials. Proteomic tools were applied in order to understand protein separation. Experimental evidence showed a correlation between apparent isoelectric point distributions and the mobile phase conductivity. Molecular weight distributions were unaffected by the elution position. On the basis of two-dimensional electrophoresis, operational windows were described having typical minor contaminants. These could be annotated for future implementation of in silico downstream processing.     

The Moment Problem for a Sobolev Inner Product

The concepts of definite and determinate Sobolev moment problem are introduced. The study of these questions is reduced to the definiteness or determinacy, respectively, of a system of classical moment problems by means of a canonical decomposition of the moment matrix associated with a Sobolev inner product in terms of Hankel matrices.     

CdTe epilayers for uses in optical waveguides

CdTe epilayers have been grown by vapor phase epitaxy (VPE) on glass, MgO, sapphire, LiNbO₃ and mica substrates. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) studies show the good structural quality of the epilayers. In these epilayers, a few optical modes were excited with a 1.33-μm laser. The measured propagation losses were in the range between 5 dB/cm and less than 0.5 dB/cm. From dark-mode m-lines, the epilayer thickness was found to be in the 1–3 μm range, in good accord with that obtained by SEM measurements. The refractive index obtained from the fitting is also in good accord with that of bulk CdTe. Received: 7 October 1999 / Accepted: 13 March 2000 / Published online: 5 July 2000