Point of care creatinine measurement for diagnosis of renal disease using a disposable microchip

A point‐of‐care device for the determination of elevated creatinine levels in blood is reported. This device potentially offers a new and simple clinical regime for the determination of creatinine that will give huge time savings and removal of several steps of determination. The test employs a disposable prefilled microchip and the handheld Medimate Multireader®. By optimizing the analytical conditions it was found that the LOD of the proposed method was 87 μM creatinine, close to the normal human serum levels that are in the range of 60 to 100 μM. A statistical analysis of the residual shows a normal distribution, indicating the absence of systematic errors in the proposed method. The test can be used to distinguish patients with renal insufficiency (creatinine levels >100 μM) from healthy persons. Long‐term monitoring could furthermore distinguish between acute renal failure and chronic kidney disease by the rate of creatinine concentration rise.     

Free energy simulation of helical transitions

An umbrella sampling method for the calculation of free energies for helical transitions is presented. The method biases structures toward helices of a desired radius and pitch. Although computationally complex, the method has negligible overhead in actual applications. To illustrate the method, calculations of the helical free energy landscape of several peptides are presented for both the CHARMM and the AMBER force fields. © 2012 Wiley Periodicals, Inc.     

A new and efficient catalytic isomerization of cis- and trans-epoxides

We report new ruthenium-catalyzed cis-trans isomerization of various functionalized epoxides. Enantiospecific isomerization of chiral epoxides is achieved without loss of enantiopurity, and epimerization occurs only at the epoxide carbon of the activating group.     

Access to multinuclear salen complexes using olefin metathesis

The use of olefin metathesis as a construction tool for multimetallic salen-based structures is described. The approach involves mono- and diallyl-functionalized metallosalen complexes that can be directly coupled by metathesis leading to dimetallic species or mixtures of linear and cyclic oligomers. The metathesis of bis-allyl Ni(salen) complexes has been studied in detail. At high concentration it is possible to selectively obtain di-Ni species rather than heavier oligomers while under dilute conditions cyclic rather than linear oligomers are preferentially obtained. A mono-allyl Zn(salphen) complex was efficiently coupled using metathesis to give the di-Zn(salphen) product, which was subsequently transmetalated with a variety of metals to yield dimetallic salens of potential catalytic interest. Finally, a tetranuclear Zn(4) macrocycle was also prepared using buildings blocks obtained by metathesis from commercially available precursors. The methods described herein allow for the facile construction of multi-centered Schiff base complexes of catalytic or supramolecular interest.     

Memristive port-Hamiltonian Systems

The port-Hamiltonian modelling framework is extended to a class of systems containing memristive elements and phenomena. First, the concept of memristance is generalised to the same generic level as the port-Hamiltonian framework. Second, the underlying Dirac structure is augmented with a memristive port. The inclusion of memristive elements in the port-Hamiltonian framework turns out to be almost as straightforward as the inclusion of resistive elements. Although a memristor is a resistive element, it is also a dynamic element since the associated Ohmian laws are rather expressed in terms of differential equations. This means that the state space manifold, as naturally defined by the storage elements, is augmented by the states associated with the memristive elements. Hence the order of complexity is, in general, defined by the number of storage elements plus the number of memristors in the system. Apart from enlarging our repertoire of modelling building blocks, the inclusion of memristive elements in the existing port-Hamiltonian formalism possibly opens up new ideas for controller synthesis and design.     

Selective Extraction and Transport of the [PtCl6]2− Anion through Outer‐Sphere Coordination Chemistry

Platinum recovery : Tripodal receptors incorporating urea, amido or sulfonamido hydrogen‐bond donors show high loading and selectivity for extraction of [PtCl₆]^2? over chloride (present in 60‐fold excess) from a low pH aqueous phase to organic media (see figure). The formation of neutral 2:1 [LH]⁺/[PtCl₆]^2? packages in organic solvents is supported by single‐crystal X‐ray structure determinations.

     

A Mechanistic Analysis of the Palladium‐Catalyzed Formation of Branched Allylic Amines Reveals the Origin of the Regio‐ and Enantioselectivity through a Unique Inner‐Sphere Pathway

A recently reported palladium‐catalyzed allylic substitution of vinyl‐substituted cyclic carbonates (VCCs) with aryl amines represents a rare example of a regio‐ and enantioselective synthesis of α,α‐disubstituted allylic N‐aryl amines. However, the underlying reasons for this unusual selectivity profile remain elusive. In the present work, density functional theory (DFT) calculations in combination with mechanistic control experiments were performed to elucidate in detail this allylic amination manifold and the origin of the regio‐ and enantioselectivity. The combined data show that after oxidative addition of the VCC to Pd⁰, the nucleophilic attack via an originally proposed outer‐sphere pathway gives, however, the opposite regioisomer compared to the experimental results. Instead, nucleophilic attack of the amine reagent via a unique type of chelation‐assisted, inner‐sphere pathway accounts for the experimentally observed “branched” regioselectivity and high enantio‐control.