Simultaneous determination of Fe(II) and Fe(III) in waters by capillary isotachophoresis

An ITP method for the simultaneous determination of Fe(II) and Fe(III) in waters, based on separation of their EDTA and fluoride complexes, respectively, was developed. The leading electrolyte used consists of chlorides, La(III) as co-counter ion and is buffered with β-alanine to pH = 3.5. The terminating electrolyte contains caproic acid and L-histidine (pH = 4.5). The method was validated and tested with samples of artificial, ground and treated water with good results, comparable to those obtained by other analytical techniques. Fe(II) and Fe(III) up to 20 mg/L were measured with an RSD = 1.4–1.5% and detection and determination limits of 0.8–0.9 and 3.0–3.5 mg/L, respectively. The ITP method can be recommended for routine utilization in hydroanalytical laboratories.     

An efficient synthesis of nitrogen-containing heterocycles via a tandem carbenoid N-H insertion/ring-closing metathesis sequence

A series of five- to eight-membered nitrogen-containing heterocycles were prepared via a general and efficient one-pot, two-component sequence featuring rhodium-catalyzed insertion of a vinyl-substituted α-diazocarbonyls into the N-H bond of a series of tert-butoxycarbonyl-(Boc)-protected amines, followed by ring-closing metathesis catalyzed by ruthenium benzylidene complexes. This methodology allows easy and convenient access to highly functionalized azacycloalkenes in moderate yields and excellent chemoselectivity in a single transformation.     

Accelerating molecular dynamic simulation on graphics processing units

We describe a complete implementation of all‐atom protein molecular dynamics running entirely on a graphics processing unit (GPU), including all standard force field terms, integration, constraints, and implicit solvent. We discuss the design of our algorithms and important optimizations needed to fully take advantage of a GPU. We evaluate its performance, and show that it can be more than 700 times faster than a conventional implementation running on a single CPU core. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2009