Bond Memory in Dynamically Determined Stereoselectivity

The carboborative ring contraction of cyclohexenes exhibits an abnormal selectivity pattern in which a formally concerted double migration gives rise to predominant but not exclusive inversion products. In dynamic trajectories, the inversion and retention products are formed from the same transition state, and the trajectories accurately account for the experimental product ratios. The unusual origin of the selectivity is the dynamically retained non-equivalence of newly formed versus pre-existing bonds after the first bond migration.

Hexahydropyrrolo[2,3-b]indole Compounds as Potential Therapeutics for Alzheimer's Disease

Alzheimer's disease (AD) is the most common form of dementia among the elderly and has become a leading public health concern worldwide. It represents a huge economic and psychological burden to caregivers and families. The presence of extracellular amyloid beta (Aβ) plaques is one of the hallmarks of this neurodegenerative disorder. Amyloid plaques are comprised of aggregates of Aβ peptides, mainly Aβ₄₂, originated by the cleavage of the amyloid precursor protein (APP). Aβ is a crucial target for the treatment of AD, but to date, no effective treatment for the clearance of Aβ has been found. We have identified four new hexahydropyrroloindoles (HPI) synthetic compounds that are able to inhibit the aggregation of Aβ₄₂ and/or disaggregate the fibril. Docking experiments suggest that the nonpolar component of the interaction of compounds with Aβ₄₂ contributes favorably to the binding free energy of each complex. Molecular dynamics simulations suggested fibril disaggregating activity of compounds 1 via interaction with hydrophobic moieties of the fibril. Consistently, compounds 1 and 2 were able to mitigate Aβ₄₂ fibrils induced death in rat pheochromocytoma cells (PC 12). One of the compounds reduces the formation of Aβ aggregates in vivo and the paralysis associated with Aβ toxicity in Caenorhabditis elegans. Our study thus augments efforts for the identification and characterization of new agents that may help stop or delay the progression of AD.

Alkene Synthesis by Photocatalytic Chemoenzymatically Compatible Dehydrodecarboxylation of Carboxylic Acids and Biomass

Direct conversion of renewable biomass and bioderived chemicals to valuable synthetic intermediates for organic synthesis and materials science applications by means of mild and chemoselective catalytic methods has largely remained elusive. Development of artificial catalytic systems that are compatible with enzymatic reactions provides a synergistic solution to this enduring challenge by leveraging previously unachievable reactivity and selectivity modes. We report herein a dual catalytic dehydrodecarboxylation reaction that is enabled by a crossover of the photoinduced acridine-catalyzed O-H hydrogen atom transfer (HAT) and cobaloxime-catalyzed C-H-HAT processes. The reaction produces a variety of alkenes from readily available carboxylic acids. The reaction can be embedded in a scalable triple-catalytic cooperative chemoenzymatic lipase-acridine-cobaloxime process that allows for direct conversion of plant oils and biomass to long-chain terminal alkenes, precursors to bioderived polymers.

Highly Stereoselective and Catalytic Desulfitative C-O and C-I Dienylation with Sulfolenes: the Importance of Basic Additives

Conjugated dienes and polyenes are central structural motifs of natural products, and key synthetic intermediates in organic synthesis and materials science. We describe herein a palladium-catalyzed dienylation of aryl, heteroaryl, and vinyl triflates, nonaflates and iodides that were previously identified as recalcitrant substrates for the sulfolene-mediated catalytic dienylation. The method has now been successfully expanded to C-O and C-I dienylation, demonstrating broad scope with respect to sulfonates, iodides and sulfolenes. The reactions proceed with high regio- and stereoselectivity, and efficiency that are strongly influenced by basic additives, whose influence on the reaction performance was systematically studied.

Efficient synthesis of 3-sulfolenes from allylic alcohols and 1,3-dienes enabled by sodium metabisulfite as a sulfur dioxide equivalent

We present herein an efficient and practical method for a gram scale synthesis of 3-sulfolenes using sodium metabisulfite as a safe, inexpensive, and easy to handle sulfur dioxide equivalent. Diversely-substituted 3-sulfolenes can be prepared by reacting a variety of 1,3-dienes or allylic alcohols with sodium metabisulfite in aqueous hexafluoroisopropanol (HFIP) or in aqueous methanol in the presence of potassium hydrogen sulfate. Advantageously, the method enables conversion of allylic alcohols directly to 3-sulfolenes, bypassing intermediate 1,3-dienes.

Organoboron chemistry comes to light: recent advances in photoinduced synthetic approaches to organoboron compounds

Photoinduced synthetic approaches to organoboron compounds have attracted significant attention in the recent years. Photochemical activation of organic molecules enables generation of reactive intermediates from a variety of precursors, resulting in borylation methods with improved and broader substrate scopes. The review summarizes recent developments in the area of photoinduced reactions of organoboron compounds with an emphasis on borylation of haloarenes, amine derivatives, and redox-active esters of carboxylic acids, as well as photoinduced rearrangements of organoboron compounds and photoinduced synthesis of organoboron compounds from alkenes and alkynes.

Measurement of the Curvature-Dependent Surface Tension in Nucleating Colloidal Liquids

The curvature dependence of the surface tension is central to the nucleation of liquids, but remains difficult to access experimentally and predict theoretically. This curvature dependence arises from the curvature-dependent molecular structure, which, for small nuclei, can deviate significantly from that of the planar liquid interface. Simulations and density functional theory have been used to predict this curvature dependence, however with contradicting results. Here, we provide the first direct measurement of the curvature-dependent surface tension in nucleating colloidal liquids. We employ critical Casimir forces to finely adjust colloidal particle interactions and induce liquid nucleation, and image individual nuclei at the particle scale to measure their curvature-dependent surface tension directly from thermally excited surface distortions. Using continuum models, we elucidate the interplay between nucleus structure, particle pair potential, and surface tension. Our results reveal a 20% lower surface tension for nuclei of critical size compared to bulk liquids, leading to 3 orders of magnitude higher nucleation rates, thus highlighting the importance of surface tension curvature corrections for accurate prediction of nucleation rates.

Highly Regio- and Stereoselective Catalytic Synthesis of Conjugated Dienes and Polyenes

Conjugated dienes and polyenes are typically synthesized by sequential introduction of C═C bonds. Here, we report a practical and scalable, catalytic dienylation that is highly regio- and stereoselective for both C═C bonds. The reaction is enabled by a stereoselective palladium-catalyzed cross-coupling that is preceded by a regioselective base-induced ring opening of readily available sulfolenes. The dienylation reaction is particularly useful for the synthesis of synthetically challenging dienes containing cis double bonds. We also show that the reaction can serve as a synthetic platform for the construction of conjugated polyenes.

Characterization and Applications of Marine Microbial Enzymes in Biotechnology and Probiotics for Animal Health

Marine microorganisms have been recognized as potential sources of novel enzymes because they are relatively more stable than the corresponding enzymes derived from plants and animals. Enzymes from marine microorganisms also differ from homologous enzymes in terrestrial microorganisms based on salinity, pressure, temperature, and lighting conditions. Marine microbial enzymes can be used in diverse industrial applications. This chapter will focus on the biotechnological applications of marine enzymes and also their use as a tool of marine probiotics to improve host digestion (food digestion, food absorption, and mucus utilization) and cleave molecular signals involved in quorum sensing in pathogens to control disease in aquaculture.

Synthesis of triphenylamines via ligand-free selective ring-opening of benzoxazoles or benzothiazoles under superparamagnetic nanoparticle catalysis

Synthesis of triphenylamines via ligand-free selective ring-opening of benzoxazoles or benzothiazoles with aryl halides under CuFe₂O₄ superparamagnetic nanoparticle catalysis.

Positron-emission tomography/computed tomography imaging in head and neck oncology: An update

Cancers of the head and neck account for more than half a million cases worldwide annually, with a significant majority diagnosed as squamous cell carcinoma (HNSCC). Imaging studies such as contrast-enhanced computed tomography (CT), magnetic resonance imaging (MRI) and ¹⁸F-2-fluoro-2-deoxy-D-glucose positron-emission tomography/computed tomography (¹⁸F-FDG PET/CT) are widely used to determine the presence and extent of tumors and metastatic disease, both before and after treatment. Advances in PET/CT imaging have allowed it to emerge as a superior imaging modality compared to both CT and MRI, especially in detection of carcinoma of unknown primary, cervical lymph node metastasis, distant metastasis, residual/recurrent cancer and second primary tumors, often leading to alteration in management. PET/CT biomarker may further provide an overall assessment of tumor aggressiveness with prognostic implications. As new developments emerged leading to better understanding and use of PET/CT in head and neck oncology, the aim of this article is to review the roles of PET/CT in both pre- and post-treatment management of HNSCC and PET-derived parameters as prognostic indicators.

Critical Casimir forces for colloidal assembly

Critical Casimir forces attract increasing interest due to their opportunities for reversible particle assembly in soft matter and nano science. These forces provide a thermodynamic analogue of the celebrated quantum mechanical Casimir force that arises from the confinement of vacuum fluctuations of the electromagnetic field. In its thermodynamic analogue, solvent fluctuations, confined between suspended particles, give rise to an attractive or repulsive force between the particles. Due to its unique temperature dependence, this effect allows in situ control of reversible assembly. Both the force magnitude and range vary with the solvent correlation length in a universal manner, adjusting with temperature from fractions of the thermal energy, k B T, and nanometre range to several ten kT and micrometer length scale. Combined with recent breakthroughs in the synthesis of complex particles, critical Casimir forces promise the design and assembly of complex colloidal structures, for fundamental studies of equilibrium and out-of-equilibrium phase behaviour. This review highlights recent developments in this evolving field, with special emphasis on the dynamic interaction control to assemble colloidal structures, in and out of equilibrium.

Elementary depinning processes of magnetic domain walls under fields and currents

The probability laws associated to domain wall depinning under fields and currents have been studied in NiFe and FePt nanowires. Three basic domain wall depinning processes, associated to different potential landscapes, are found to appear identically in those systems with very different anisotropies. We show that these processes constitute the building blocks of any complex depinning mechanism. A Markovian analysis is proposed, that provides a unified picture of the depinning mechanism and an insight into the pinning potential landscape.

Switchable spin-current source controlled by magnetic domain walls

Using nonlocal spin injection, spin-orbit coupling, or spincaloritronic effects, the manipulation of pure spin currents in nanostructures underlies the development of new spintronic devices. Here, we demonstrate the possibility to create switchable pure spin current sources, controlled by magnetic domain walls. When the domain wall is located at a given point of the magnetic circuit, a pure spin current is injected into a nonmagnetic wire. Using the reciprocal measurement configuration, we demonstrate that the proposed device can also be used as a pure spin current detector. Thanks to its simple geometry, this device can be easily implemented in spintronics applications; in particular, a single current source can be used both to induce the domain wall motion and to generate the spin signal.

Controlling colloidal morphologies by critical Casimir forces

Active control over the assembly of colloidal and nanoparticles has important applications for the design of new nanostructured materials, but it is a difficult task. Here, a new method is presented to control the morphology of colloidal aggregates using critical Casimir forces. Via direct temperature control of critical Casimir forces, the particles are assembled into aggregates with well-defined architecture.

Detection of domain-wall position and magnetization reversal in nanostructures using the magnon contribution to the resistivity

We show that magnetization reversal detection can be achieved at room temperature using the contribution of magnons to resistivity, in 50 nm wide nanowires with either perpendicular anisotropy (FePt) or in-plane magnetization (NiFe). Even though these nanowires are made from single layers, simple magnetoresistance measurements can be used to measure switching fields, or to detect the position of a domain wall along a nanowire. Surprisingly, in NiFe nanowires, and for applied fields nearly parallel to the wire, the magnon contribution is found to dominate the classical anisotropic magnetoresistance.

Successful AV fistula creation does not lead to higher catheter use: the experience by the Northwest Renal Network 16 Vascular Access Quality Improvement Program. Four years follow-up

BACKGROUND

In 2002, the Center for Medicare and Medicaid Services (CMS) required all 18 Renal Networks to participate in a Vascular Access Quality Improvement Program (QIP). The Northwest Renal Network (NWRN 16) chose to increase arteriovenous fistula (AVF) use. NWRN 16 hypothesized that strategies which targeted the improvement of AVF rate and the reduction of catheter use were the same. In December 2001, 44.2% of hemodialysis (HD) patients in the NWRN 16 received HD using an AVF which met the Dialysis Outcome Quality Initiative (K/DOQI) 40% AVF guideline for prevalent patients. However, 43% of HD facilities (2869 patients) had less than 40% of AVF and higher HD catheter rates than the average Network catheter rates (25.0 vs. 20.3%). To address the needs of underperforming facilities, NWRN 16 provided education and tools for their vascular access decision makers to promote AVF creation and catheter reduction.

METHODS

In 2002, NWRN 16 sponsored four regional workshops targeted at nephrologists, vascular surgeons, HD nurses, and interventional radiologists.

RESULTS

Percentage of AVFs in use in invited facilities increased from 31.3% pre-intervention to 56.2% at 4 yrs: 78% increase (99% confidence interval: 77.8% to 81.5%). Percentage of catheters increased from 25% to 25.8%: 3.2% change over 4 yrs (99% confidence interval: 2.5% to 4%).

CONCLUSION

The success of Network 16's AVF interventions demonstrates the effectiveness of Network education promoting multidisciplinary teamwork, and innovative strategies to increase dramatically AVF use without substantial increase in catheter use.

Creation of secondary AV fistulas from failed hemodialysis grafts: the role of routine vein mapping

Pre-existing forearm grafts lead to dilatation of upper arm veins of the ipsilateral arm that greatly facilitates the creation of secondary arteriovenous fistulas (AVF). In this retrospective review of 18 patients, the routine and periodical revision of failed grafts were discontinued. Vein mapping by physical examination or Duplex studies was performed prior to graft failure and a secondary AVF was created when the graft failed. Using this management strategy, an AVF creation success rate of 95% was achieved despite high incidence of co-morbidity factors within the patient population. This success rate demonstrates the value of vein selection by vascular mapping prior to graft failure and early vascular access planning in the successful creation of secondary AVF.