Electrochemical melting-curve analysis

Genotyping technologies need to tackle issues of cost-effectiveness, flexibility, and mutiplexability to meet the ever-increasing demands for clinical diagnostics, addressing the future medical paradigm. Here we report on a facile method for the rapid detection of mutations using electrochemical melting-curve analysis. The concept is based on the use of an immobilised probe hybridised to the mutant region of a ferrocene labelled amplicon. Following hybridisation, the temperature is ramped and the dissociation of the ferrocene labelled DNA from the electrode surface is monitored using differential pulse voltammetry. Using a model system consisting of short probe and target, the proposed approach was demonstrated to clearly discriminate between complementary and mismatch duplexes. The melting temperature of the surface confined DNA duplex was observed to be markedly lower than that obtained in solution, with melting temperatures of 38 and 59 °C, observed, respectively. The approach can be extended to array based melting-curve analysis, allowing the simultaneous detection of multiple mutations, as well as for genosensor design.     

Investigation into the voltammetric behaviour and detection of selenium(IV) at metal electrodes in diverse electrolyte media

The voltammetric behaviour of selenium(IV) was studied at platinum and gold electrodes in sulphuric acid, perchloric acid and potassium chloride media as a basis for its voltammetric detection. The best voltammetric behaviour was recorded at gold electrodes with perchloric acid as the supporting electrolyte. The concomitant presence of metals, such as copper or lead, and of model biomolecules, such as bovine serum albumin, in the solution resulted in a deterioration of the electrochemical response for selenium(IV). Quantitative detection of selenium(IV) by square wave anodic stripping voltammetry at both a millimetre-sized gold disc electrode and a microband electrode array revealed linear responses to selenium concentration in the ranges 5–15 μM and 0.1–10 μM, respectively, with 60 s preconcentration. The sensitivities were 6.4 μA μM⁻¹ cm⁻² and 100 μA μM⁻¹ cm⁻² at the disc and the microband array, respectively. The detection limit at the microband electrode array was 25 nM, illustrating the potentiality of such microelectrodes for the development of mercury-free analytical methods for the trace detection of selenium(IV).     

Thermoelectric power,Coulomb correlation and charge transfer in TCNQ salts

We show how the amount of charge transfer for a large class of TCNQ systems can be simply deduced from a measurement of the high temperature saturation value of the thermoelectric power. Of particular interest is the value - 60 μV/°K characteristic of a quarter-filled correlated band, and found in almost all 2 : 1 TCNQ salts.     

Structure-retention and mobile phase-retention relationships for reversed-phase high-performance liquid chromatography of several hydroxythioxanthone derivatives in binary acetonitrile-water mixtures

The reversed-phase high-performance liquid chromatographic (RP-HPLC) behavior of some newly synthesized hydroxythioxanthone derivatives using binary acetonitrile-water mixtures as mobile phase has been examined. First, the variation in the retention time of each molecule as a function of mobile phase properties was studied by Kamlet-Taft solvatochromic equations. Then, the influences of molecular structure of the hydroxythioxanthone derivatives on their retention time in various mobile phase mixtures were investigated by quantitative structure-property relationship (QSPR) analysis. Finally, a unified model containing both the molecular structure parameters and mobile phase properties was developed to describe the chromatographic behavior of the systems studied. Among the solvent properties, polarity/polarizability parameter (π^*) and hydrogen-bond basicity (β), and among the solute properties, the most positive local charge (MPC), the sum of positive charges on hydrogen atoms contributing in hydrogen bonding (SPCH) and lipophilicity index (log P) were identified as controlling factors in the RP-HPLC behavior of hydroxythioxanthone derivatives in actonitrile-water binary solvents.     

The effect of polarons on the conductivity of the narrow-band Hubbard chain

We consider a half-filled, narrow band Hubbard chain with Holstein-type electron-phonon coupling to a set of intramolecular vibrational modes. We allow for dispersion in the vibrational spectrum and show, in the limit of zero temperature, that contrary to some recent results the one-electron density of states vanishes at the Fermi energy and the d.c. conductivity does not diverge as the inverse temperature.     

Synthesis of new lariat ethers containing polycyclic phenols and heterocyclic aromatic compound on graphite surface via mannich reaction

Synthesis of novel lariat ethers containing polycyclic phenols and heterocyclic aromatic compound using graphite via Mannich reaction are herein described. For this purpose N-(methoxymethyl) azacrown ether 4 was synthesized in nearly quantitative yield. The reaction of N-(methoxymethyl) azacrown ether 4 with polycyclic phenols and heterocyclic aromatic compound was performed in 10-20 min in the presence of graphite. The graphite powder can be reused up to five times after simple washing with acetone.     

Low-medium resolution HLA-DQ2/DQ8 typing for coeliac disease predisposition analysis by colorimetric assay

Coeliac disease is an inflammation of the small intestine, occurring in genetically susceptible individuals triggered by the ingestion of gluten. Human Leukocyte Antigens (HLA) DQ2 and DQ8 gene have been identified as key genetic factors in coeliac disease as they are presented in almost 100 % of the patients. These genes are encoded by the combination of certain alleles in the DQA and DQB region of chromosome 6. Specifically, DQA1*05:01 and DQB1*02:01 alleles for serologically defined leukocyte antigen DQ2 cis, DQA1*05:05 and DQB1*02:02 for DQ2 trans and DQA1*03:01 and DQB1*03:02 alleles for the DQ8. Specific identification of these alleles is a challenge due to the high number of alleles that have been identified so far: 46 in the DQA region and 160 in the DQB region (as of IMGT/HLA Database 10/2011 release). In the reported work, the development of a multiplex colorimetric assay for the low to medium HLA typing of the DQ2 and DQ8 genes is presented. The optimisation of probe design and assay conditions, performed by both surface plasmon resonance and enzyme-linked oligonucleotide assay, are reported. Finally, the performances of the developed typing platform were validated by the analysis of real patient samples and HLA typing, compared with those obtained using hospital based typing technology and an excellent correlation obtained.     

Phase transitions in iridium oxide films

We report studies of SIROFs by differential thermal analysis (DTA), evolved gas analysis (EGA), and scanning electron microscopy (SEM). SIROFs undergo an irreversible exothermic transition at ≈300°C associated with ≈1 eV energy release and no decomposition. There is a second endothermic transition at ≈700°C, which is associated with dehydration. After undergoing the first transition, SIROFs lose their good electrochromic and electrocatalytic properties.     

The Behaviors of Ferro-Magnetic Nano-Particles In and Around Blood Vessels under Applied Magnetic Fields

In magnetic drug delivery, therapeutic magnetizable particles are typically injected into the blood stream and magnets are then used to concentrate them to disease locations. The behavior of such particles in-vivo is complex and is governed by blood convection, diffusion (in blood and in tissue), extravasation, and the applied magnetic fields. Using physical first-principles and a sophisticated vessel-membrane-tissue (VMT) numerical solver, we comprehensively analyze in detail the behavior of magnetic particles in blood vessels and surrounding tissue. For any blood vessel (of any size, depth, and blood velocity) and tissue properties, particle size and applied magnetic fields, we consider a Krogh tissue cylinder geometry and solve for the resulting spatial distribution of particles. We find that there are three prototypical behaviors (blood velocity dominated, magnetic force dominated, and boundary-layer formation) and that the type of behavior observed is uniquely determined by three non-dimensional numbers (the magnetic-Richardson number, mass Péclet number, and Renkin reduced diffusion coefficient). Plots and equations are provided to easily read out which behavior is found under which circumstances ( Fig. 5, Fig. 6, Fig. 7 and Fig. 8). We compare our results to previously published in-vitro and in-vivo magnetic drug delivery experiments. Not only do we find excellent agreement between our predictions and prior experimental observations, but we are also able to qualitatively and quantitatively explain behavior that was previously not understood.