A low-cost, disposable card for rapid polymerase chain reaction

A low-cost, disposable card for rapid polymerase chain reaction (PCR) was developed in this work. Commercially available, adhesive-coated aluminum foils and polypropylene films were laminated with structured polycarbonate films to form microreactors in a card format. Ice valves [1] were employed to seal the reaction chambers during thermal cycling and a Peltier-based thermal cycler was configured for rapid thermal cycling and ice valve actuation. Numerical modeling was conducted to optimize the design of the PCR reactor and investigate the thermal gradient in the reaction chamber in the direction of sample thickness. The PCR reactor was experimentally characterized by using thin foil thermocouples and validated by a successful amplification of 10 copy of E. coli tuf gene in 27 min.     

Calorimetric, spectroscopic, and model studies provide insight into the transport of Ti(IV) by human serum transferrin

Evidence suggests that transferrin can bind Ti(IV) in an unhydrolyzed form (without bound hydroxide or oxide) or in a hydrolyzed form. Ti(IV) coordination by N,N'-di(o-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid (HBED) at different pH values models the two forms of Ti(IV)-loaded transferrin spectrally and structurally. 13C NMR and stopped-flow kinetic experiments reveal that when the metal is delivered to the protein using an unhydrolyzed source, Ti(IV) can coordinate in the typical distorted octahedral environment with a bound synergistic anion. The crystal structure of TiHBED obtained at low pH models this type of coordination. The solution structure of the complex compares favorably with the solid state from pH 3.0 to 4.0, and the complex can be reduced with E1/2 = -641 mV vs NHE. Kinetic and thermodynamic competition studies at pH 3.0 reveal that Ti(citrate)3 reacts with HBED via a dissociative mechanism and that the stability of TiHBED (log beta = 34.024) is weaker than that of the Fe(III) complex. pH stability studies show that Ti(IV) hydrolyzes ligand waters at higher pH but still remains bound to HBED until pH 9.5. Similarly, at a pH greater than 8.0 the synergistic anion that binds Ti(IV) in transferrin is readily displaced by irreversible metal hydrolysis although the metal remains bound to the protein until pH 9.5. Thermal denaturation studies conducted optically and by differential scanning calorimetry reveal that Ti(IV)-bound transferrin experiences only minimal enhanced thermal stability unlike when Fe(III) is bound. The C- and N-lobe transition Tm values shift to a few degrees higher. The stability, competition, and redox studies performed provide insight into the possible mechanism of Ti2-Tf transport in cells.     

Determination of Total Reduced Thiol Levels in Plasma Using a Bromide Substituted Quinone

The exploitation of 2‐bromo‐1,4‐naphthoquinone (NQBr) as a selective redox label for the determination of reduced thiol functionalities (RSH) has been investigated. The system is selective for RSH functionality, giving distinct voltammetric signals for glutathione and cysteine but can also be adapted for broad spectrum thiol detection. Ion chromatographic protocols based on conductimetric detection enable total RSH analysis (protein and monomolecular moieties) within human plasma. Bromide released through the reaction can be easily quantified and integrated within normal IC measurements. The efficacy of the approach has been assessed and the response validated through comparison with the standard colorimetric technique.     

Resolution of (R,S)-flurbiprofen catalysed by dry mycelia in organic solvent

Mycelia of Aspergillus oryzae display high enantioselectivity towards (R)-flurbiprofen and can be efficiently used in pure organic solvent for the resolution of (R,S)-flurbiprofen through esterification. The use of the lyophilized mycelia facilitates the separation process so that in one step the two enantiomers of flurbiprofen, which are both valuable for pharmaceutical applications, can be easily separated. The biotransformation can be carried out in different apolar solvents using different primary alcohols as nucleophiles under very mild conditions.     

Six‐coordinate Co2+ with imidazole,NH3, and H2O ligands: Approaching spin crossover

Octahedral, six‐coordinate Co²⁺ can exist in two spin states: S = 3/2 and S = 1/2. The difference in energy between high spin (S = 3/2) and low spin (S = 1/2) is dependent on both the ligand mix and coordination stereochemistry. B3LYP calculations on combinations of neutral imidazole, NH₃, and H₂O ligands show that low‐spin isomers are stabilized by axial H₂O ligands and in structures that also include trans pairs of equatorial NH₃ and protonated imidazole ligands, spin crossover structures are predicted from spin state energy differences. Occupied Co d orbitals from the DFT calculations provide a means of estimating effective ligand strength for homoleptic and mixed ligand combinations. These calculations suggest that in a labile biological system, a spin crossover environment can be created. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

Reactions of CF3CH2I+O(3P): competing mechanisms of HF elimination

Ab initio density functional and molecular orbital calculations provide singlet and triplet electronic potential energy surfaces for the reactions of CF3CH2I+O(3P) leading to OI and HF eliminations, reactions which have been the subject of recent experimental studies. A barrier to OI formation occurs on the triplet potential energy surface; there is no reverse barrier to OI formation on the singlet pathway. Findings suggest that two competing pathways may form HF. One is an addition-insertion-elimination process involving insertion of O into the C-I bond. The alternate path involves OI elimination, addition of an O atom to CF3CH2, and subsequent HF elimination. The computed reactant pathways and energetics are discussed in relation to recent experiments.     

Mono and dinuclear arene ruthenium complexes containing 6,7-dimethyl-2,3-di(pyridine-2-yl)quinoxaline as chelating ligand: Synthesis and molecular structure

The mononuclear cations of the general formula [(η⁶-arene)RuCl(dpqMe₂)]⁺ (dpqMe₂ = 6,7-dimethyl-2,3-di(pyridine-2-yl)quinoxaline; arene = C₆H₆, 1; C₆H₅Me, 2; p-PrⁱC₆H₄Me, 3; C₆Me₆, 4) as well as the dinuclear dications [(η⁶-arene)₂Ru₂Cl₂(μ-dpqMe₂)]²⁺ (arene = C₆H₆, 5; C₆H₅Me, 6; p-PrⁱC₆H₄Me, 7; C₆Me₆, 8) have been synthesised from 6,7-dimethyl-2,3-di(pyridine-2-yl)quinoxaline (dpqMe₂) and the corresponding chloro complexes [(η⁶-C₆H₆)Ru(μ-Cl)Cl]₂, [(η⁶-C₆H₅Me)Ru(μ-Cl)Cl]₂, [(η⁶-p-PrⁱC₆H₄Me)Ru(μ-Cl)Cl]₂ and [(η⁶-C₆Me₆)Ru(μ-Cl)Cl]₂, respectively. The X-ray crystal structure analyses of [1][PF₆], [3][PF₆] and [6][PF₆]₂ reveal a typical piano-stool geometry around the metal centre; in the dinuclear complexes the two chloro ligands, with respect to each other, are found to be trans oriented.     

Synthesis,structures and mass spectrometry of lanthanide nitrate complexes with tricyclohexylphosphine oxide

The complexes Ln(NO₃)₃(OPCy₃)₃(EtOH)_x (Cy = cyclohexyl, C₆H₁₁x = 0 for Ln = Eu, Er, x = 0.5 for Ln = La, Nd and x = 1 for Ln = Tm, Yb) have been prepared by reaction of lanthanide nitrates with Cy₃PO in ethanol. The single crystal X-ray structures for Ln = La, Nd, Eu, Er, Tm and Yb are reported. The structures for Ln = La–Eu have two molecules in the unit cell in which the nitrates are all bound as bidentate ligands. The unit cell for Ln = Er contains two distinct molecules; one with three bidentate nitrates and one with two bidentate and one monodentate nitrate. The Tm and Yb complexes have one molecule in the unit cell with two bidentate and one monodentate nitrate ligands. The monodentate nitrates are hydrogen bonded to ethanol in the Tm and Yb structures but not in the Er complex. The infrared spectra of the three classes of complex do not readily permit identification of the monodentate nitrate groups. Electrospray mass spectrometry indicates that redistribution/ionisation reactions occur in solution. Ions formed by solvolysis reactions are attributed to gas phase processes associated with the electrospray technique. Tandem mass spectrometry for the La, Ho and Yb complexes shows that in the gas phase loss of Cy₃PO is the sole fragmentation pathway for all but the Yb complex where the higher energy required for initial fragmentation leads to a more complex fragmentation pattern.     

Synthesis of TiO2 nanoparticles on the Au(111) surface

The growth of titanium oxide nanoparticles on reconstructed Au(111) was investigated by scanning tunneling microscopy and x-ray photoelectron spectroscopy. Ti was deposited by physical-vapor deposition at 300 K. Regular arrays of titanium nanoparticles form by preferential nucleation of Ti at the elbow sites of the herringbone reconstruction. The titanium oxide nanoclusters were synthesized by subsequent exposure to O(2) at 300 K. Two-and three-dimensional titanium oxide nanocrystallites form during annealing in the temperature range from 600 to 900 K. At the same time, the Au(111) surface assumes a serrated 110-oriented step-edge morphology suggesting step-edge pinning by titanium oxide nanoparticles. The oxidation state of the titanium oxide nanoparticles varies with annealing temperature. Specifically, annealing to 900 K results in the formation of stoichiometric TiO(2) nanocrystals as judged by the Ti(2p) binding energies measured in the x-ray photoelectron data. The nanodispersed TiO(2) on Au(111) is an ideal system to test the various models proposed for the enhanced catalytic reactivity of supported Au nanoparticles.