Sugar analog synthesis by in vitro biocatalytic cascade: A comparison of alternative enzyme complements for dihydroxyacetone phosphate production as a precursor to rare chiral sugar synthesis.

Carbon-carbon bond formation is one of the most challenging reactions in synthetic organic chemistry, and aldol reactions catalysed by dihydroxyacetone phosphate-dependent aldolases provide a powerful biocatalytic tool for combining C-C bond formation with the generation of two new stereo-centres, with access to all four possible stereoisomers of a compound. Dihydroxyacetone phosphate (DHAP) is unstable so the provision of DHAP for DHAP-dependent aldolases in biocatalytic processes remains complicated. Our research has investigated the efficiency of several different enzymatic cascades for the conversion of glycerol to DHAP, including characterising new candidate enzymes for some of the reaction steps. The most efficient cascade for DHAP production, comprising a one-pot four-enzyme reaction with glycerol kinase, acetate kinase, glycerophosphate oxidase and catalase, was coupled with a DHAP-dependent fructose-1,6-biphosphate aldolase enzyme to demonstrate the production of several rare chiral sugars. The limitation of batch biocatalysis for these reactions and the potential for improvement using kinetic modelling and flow biocatalysis systems is discussed.

Iron, Copper, and Zinc Concentration in Aß Plaques in the APP/PS1 Mouse Model of Alzheimer's Disease Correlates with Metal Levels in the Surrounding Neuropil.

The metal ions of iron, copper, and zinc have long been associated with the aggregation of ß-amyloid (Aß) plaques in Alzheimer's disease; an interaction that has been suggested to promote increased oxidative stress and neuronal dysfunction. We examined plaque metal load in the hippocampus of APP/PS1 mice using X-ray fluorescence microscopy to assess how the anatomical location of Aß plaques was influenced by the metal content of surrounding tissue. Immunohistochemical staining of Aß plaques colocalized with areas of increased X-ray scattering power in unstained tissue sections, allowing direct X-ray based-assessment of plaque metal levels in sections subjected to minimal chemical fixation. We identified and mapped 48 individual plaques in four subregions of the hippocampus from four biological replicates. Iron, Cu, and Zn areal concentrations (ng cm-2) were increased in plaques compared to the surrounding neuropil. However, this elevation in metal load reflected the local metal makeup of the surrounding neuropil, where different brain regions are enriched for different metal ions. After correcting for tissue density, only Zn levels remained elevated in plaques. This study suggests that the in vivo binding of Zn to plaques is not simply due to increased protein deposition.

Therapeutic targeting and rapid mobilization of endosteal HSC using a small molecule integrin antagonist.

The inherent disadvantages of using granulocyte colony-stimulating factor (G-CSF) for hematopoietic stem cell (HSC) mobilization have driven efforts to identify alternate strategies based on single doses of small molecules. Here, we show targeting α9ß1/α4ß1 integrins with a single dose of a small molecule antagonist (BOP (N-(benzenesulfonyl)-L-prolyl-L-O-(1-pyrrolidinylcarbonyl)tyrosine)) rapidly mobilizes long-term multi-lineage reconstituting HSC. Synergistic engraftment augmentation is observed when BOP is co-administered with AMD3100. Impressively, HSC in equal volumes of peripheral blood (PB) mobilized with this combination effectively out-competes PB mobilized with G-CSF. The enhanced mobilization observed using BOP and AMD3100 is recapitulated in a humanized NODSCIDIL2Rγ(-/-) model, demonstrated by a significant increase in PB CD34(+) cells. Using a related fluorescent analogue of BOP (R-BC154), we show that this class of antagonists preferentially bind human and mouse HSC and progenitors via endogenously primed/activated α9ß1/α4ß1 within the endosteal niche. These results support using dual α9ß1/α4ß1 inhibitors as effective, rapid and transient mobilization agents with promising clinical applications.

Total Synthesis of Ustiloxin D Utilizing an Ammonia-Ugi Reaction.

Total synthesis of the highly functionalized cyclic peptide natural product, ustiloxin D, has been achieved in a convergent manner. Our strategy incorporates an asymmetric allylic alkylation to construct the tert-alkyl aryl ether linkage between the dopa and isoleucine residues. The elaborated ß-hydroxydopa derivative is rapidly converted to a linear tripeptide through an ammonia-Ugi reaction. Subsequent cyclization and global deprotection affords ustiloxin D in six steps from a known ß-hydroxydopa derivative.

A general method for interconversion of boronic acid protecting groups: trifluoroborates as common intermediates.

We have developed a general protocol for the interconversion of diverse protected boronic acids, via intermediate organotrifluoroborates. N-Methyliminodiacetyl boronates, which have been hitherto resistant to direct conversion to trifluoroborates, have been shown to undergo fluorolysis at elevated temperatures. Subsequent solvolysis of organotrifluoroborates in the presence of trimethylsilyl chloride and a wide range of bis-nucleophiles enables the generation of a variety of protected boronic acids.

Design of non-aggregating variants of Aß peptide.

Self association of the amyloid-ß (Aß42) peptide into oligomers, high molecular weight forms, fibrils and ultimately neuritic plaques, has been correlated with progressive cognitive decline in Alzheimer's disease. Thus, insights into the drivers of the aggregation pathway have the capacity to significantly contribute to our understanding of disease mechanism. Functional assays and a three-dimensional crystal structure of the P3 amyloidogenic region 18-41 of Aß were used to identify residues important in self-association and to design novel non-aggregating variants of the peptide. Biophysical studies (gel filtration, SDS-PAGE, dynamic light scattering, thioflavin T assay, and electron microscopy) demonstrate that in contrast to wild type Aß these targeted mutations lose the ability to self-associate. Loss of aggregation also correlates with reduced neuronal toxicity. Our results highlight residues and regions of the Aß peptide important for future targeting agents aimed at the amelioration of Alzheimer's disease.

Naturally occurring polyphenolic inhibitors of amyloid beta aggregation.

Alzheimer's disease is the most common neurodegenerative disease and is one of the main causes of death in developed countries. Consumption of foods rich in polyphenolics is strongly correlated with reduced incidence of Alzheimer's disease. Our study has investigated the biological activity of previously untested polyphenolic compounds in preventing amyloid ß aggregation. The anti-aggregatory potential of these compounds was assessed using the Thioflavin-T assay, transmission electron microscopy, dynamic light scattering and size exclusion chromatography. Two structurally related compounds, luteolin and transilitin were identified as potent inhibitors of Aß fibril formation. Computational docking studies with an X-ray derived oligomeric structure offer a rationale for the inhibitory activity observed and may facilitate development of improved inhibitors of Aß aggregation and toxicity.

Structural insights into the interaction of platinum-based inhibitors with the Alzheimer's disease amyloid-ß peptide.

Extended X-ray absorption fine structure spectroscopy, mass spectrometry, dynamic light scattering and density functional theory are combined to derive structural models for the interaction of neurotoxicity-ablating platinum-based compounds with the amyloid-ß peptide.

Enhanced photovoltaic efficiency via light-triggered self-assembly.

Light-initiated, radical and hydrogen-bond induced self-assembly of bis-acetamido-functionalized triarylamines is demonstrated to occur in strongly dipolar "push-pull" molecules. This self-assembly process results in the formation of self-assembled nanostructures which in turn increase the efficiency of organic photovoltaic devices.

Synthesis of ß,γ-dihydroxyhomotyrosines by a tandem Petasis-asymmetric dihydroxylation approach.

Petasis reactions of substituted styrenylboronic acids and glyoxylic acid, employing tert-butylsulfinamide as the 'amine' component, proceed with high stereoselectivity to produce ß,γ-dehydrohomoarylalanine derivatives. Subsequent asymmetric dihydroxylation under neutral conditions gives the corresponding protected ß,γ-dihydroxyhomoarylalanines with up to 15:1 dr. The method has been exploited in the efficient, stereoselective synthesis of protected ß,γ-dihydroxyhomotyrosine, a component of the antifungal cyclic peptide echinocandin B.