Establishing a quality assurance plan for nucleic acid-based diagnostic laboratories: from planning to implementation

Nucleic acid-based technologies have opened new perspectives in diagnosis, prognosis, and treatment in clinical medicine. To maintain patient confidence in this rapidly expanding field and to provide the highest standard of analysis, strict laboratory quality assurance procedures must be followed. While impressive break-through are taking place in this field, the need for an appropriate and suitable quality assurance (QA) plan for nucleic acid-based diagnostic laboratories must be a top priority. In this study, we developed a systematic QA plan for this kind of diagnostic laboratories that would enable us to assure the highest quality standards of their services. We focus on those labs that would like to start introducing a quality system for the first time and discuss the most appropriate ways to pave the way to implement a QA plan from the beginning. This QA plan is suitable for any nucleic acid-based techniques laboratory regardless of the field or services provided.     

Photophysical properties of a new series of water soluble iridium bisterpyridine complexes functionalised at the 4' position

Four new hetero- and homo-leptic iridium(III) bisterpyridine complexes have been prepared which incorporate aniline (tpy-φ-NH(2)), benzoic acid (tpy-φ-COOH), and benzyl alcohol (tpy-φ-CH(2)OH) substituents at the 4' positions of the tpy ligands (tpy = 2,2':6',2'-terpyridine, φ = phenylene). The electrochemical behaviour and ground and excited state spectroscopic properties of the complexes are reported, and the X-ray crystal structures of a homoleptic benzyl alcohol [Ir(tpy-φ-CH(2)OH)(2)](PF(6))(3), homoleptic aniline [Ir(tpy-φ-NH(2))(2)](PF(6))(3), and heteroleptic benzyl alcohol/aniline substituted complex [Ir(tpy-φ-CH(2)OH)(tpy-φ-NH(2))](PF(6))(3) have been solved. Complexes with aniline substituents were found to display absorption bands at around 430 nm corresponding to intraligand charge transfer (ILCT) that are sensitive to changes in solvent and pH. Strong emission in the visible region involving the ILCT state is observed in two of the complexes (Φ(e) = 0.7% and 2.6%) in acetonitrile. In the heteroleptic aniline/benzyl alcohol complex the Stokes shift is shown to be linearly related to solvent polarisability according to the Lippert equation, but only for solvents with weak hydrogen bonding interactions. Additionally, in water, emission from the ILCT state is quenched and only weak ligand centred (LC) emission is observed. The long lifetimes and quantum yields of these complexes make them interesting candidates for probes in sensing applications, especially [Ir(tpy-φ-CH(2)OH)(tpy-φ-NH(2))(2)](PF(6))(3) due to its unusual sensitivity to the solvent environment.     

Palladium Aryl Sulfonate Phosphine Catalysts for the Copolymerization of Acrylates with Ethene

The reaction of 2‐[bis(2‐methoxy‐phenyl)phosphanyl]‐4‐methyl‐benzenesulfonic acid (a) and 2‐[bis(2′,6′‐dimethoxybiphenyl‐2‐yl)phosphanyl]benzenesulfonic acid (b) with dimethyl(N,N,N′,N′‐tetramethylethylenediamine)‐palladium(II) (PdMe₂(TMEDA)) leads to the formation of TMEDA bridged palladium based polymerization catalysts ( 1a and 1b ). Upon reaction with pyridine, two mononuclear catalysts are formed ( 2a and 2b ). These catalysts are able to homopolymerize ethylene and also copolymerize ethylene with acrylates or with norbornenes. With ligand b , high molecular weight polymers are formed in high yields, but higher comonomer incorporations are obtained with ligand a .

     

Ultra-performance liquid chromatography/time-of-flight mass spectrometry based metabolomics of raw and steamed Panax notoginseng

At present, metabolite profiling is of growing importance in herbal medicine fields such as breeding, formulation, quality control and clinical trials. This preliminary study indicated that ultra-performance liquid chromatography/time-of-flight mass spectrometry (UPLC/TOFMS)-based metabolomics allows direct detection of down-stream derivatives of metabolites, arising from the herbal formulation process. This analytical approach allows the discrimination and tentative authentication of unique biomarkers related to different herbal extracts using unsupervised multivariate principal component analysis (PCA). The tentative identification of biomarkers is complemented significantly by the accurate mass measurement of TOFMS and the high resolution and high retention time reproducibility rendered by UPLC. The application of this approach in herbal extract discrimination and ginsenoside biomarker discovery of raw and steamed Panax notoginseng (Burk.) F.H. Chen is demonstrated and discussed.     

New Cu(II) complexes with polydentate chelating Schiff base ligands: Synthesis, structures, characterisations and biochemical activity studies

We have reported herein the synthesis of three new Cu(II) complexes of tri- and tetradentate Schiff base ligands containing N₃ or N₄ donor set along with terminal NNN⁻ or SCN⁻ ligands: [L¹Cu(NCS)]ClO₄ (1), [L²Cu(NCS)₂] (2) and [L³Cu(NNN)]ClO₄ (3) [L¹ = NC₅H₄C(CH₃)=N(CH₂)₃N=C(CH₃)C₅H₄N, L²= Me₂N–(CH₂)₃–N=C(CH₃)C₅H₄N and L³ = NC₅H₄CH=N–(CH₂)₄–N=CHC₅H₄N]. The complexes have been systematically characterised by elemental, spectroscopic and electrochemical techniques. Antimicrobial activities of the Schiff base ligands and their metal complexes have been studied using the disc diffusion method on the strains of Candida tropicalis and Bacillus megaterium. Structures of all the complexes have been unequivocally established from single crystal X-ray diffraction analyses that show the monomeric units containing a five-coordinated copper center in highly distorted square pyramidal geometry with thiocyanate or azide anion coordinated as terminal ligand. The complexes 1 and 3 crystallise in monoclinic (P2₁/c) and 2 in triclinic (P-1) space group, respectively.     

Prediction of cytochrome P450 3A4, 2D6, and 2C9 inhibitors and substrates by using support vector machines

Statistical learning methods have been used in developing filters for predicting inhibitors of two P450 isoenzymes, CYP3A4 and CYP2D6. This work explores the use of different statistical learning methods for predicting inhibitors of these enzymes and an additional P450 enzyme, CYP2C9, and the substrates of the three P450 isoenzymes. Two consensus support vector machine (CSVM) methods, "positive majority" (PM-CSVM) and "positive probability" (PP-CSVM), were used in this work. These methods were first tested for the prediction of inhibitors of CYP3A4 and CYP2D6 by using a significantly higher number of inhibitors and noninhibitors than that used in earlier studies. They were then applied to the prediction of inhibitors of CYP2C9 and substrates of the three enzymes. Both methods predict inhibitors of CYP3A4 and CYP2D6 at a similar level of accuracy as those of earlier studies. For classification of inhibitors of CYP2C9, the best CSVM method gives an accuracy of 88.9% for inhibitors and 96.3% for noninhibitors. The accuracies for classification of substrates and nonsubstrates of CYP3A4, CYP2D6, and CYP2C9 are 98.2 and 90.9%, 96.6 and 94.4%, and 85.7 and 98.8%, respectively. Both CSVM methods are potentially useful as filters for predicting inhibitors and substrates of P450 isoenzymes. These methods generally give better accuracies than single SVM classification systems, and the performance of the PP-CSVM method is slightly better than that of the PM-CSVM method.     

Synthesis and molecular and extended structures for a diaminonaphthalene-derived bis(amido)stannylene

The cyclic bis(amido)tin(II) compound Sn[1,8-((iPrN)2C10H6] (2) was isolated from the reaction of Li2[1,8-((iPrN)2C10H6] (1) and SnCl2. Solid-state structural analysis of 2 showed it to be a mononuclear species with a pyramidal Sn center as part of a nonplanar metallaheterocycle. The packing diagram of 2 revealed an extended one-dimensional head-to-tail chain structure with short intermolecular Sn/arene-C interactions. Computational examination of 2 (DFT/PW91 and MP2 with 6-31G* and 6-311G** basis functions) indicated that the optimum gas-phase structure of 2,which displays a Sn center in the plane of the naphthyl backbone with a slightly twisted metallaheterocycle, is approximately 24 kcal/mol lower in energy than the X-ray structure. The solid-state geometry of 2 is attributed to the intermolecular donation of the naphthalene pi-electrons to a Lewis acidic Sn center, which leads to the observed supramolecular structure. The crystal structure of 1 is also reported.     

Effect of oxygen fraction on local entropy generation in a hydrogen–air burner

This study considers numerical simulation of the combustion of hydrogen with air, including oxygen and nitrogen, in a burner and the numerical solution of local entropy generation rate due to the high temperature and velocity gradients in the combustion chamber. The effects of equivalence ratio (ϕ) and oxygen percentage (γ) on the combustion and entropy generation rate are investigated for different ϕs (from 0.5 to 1.0) and γs (from 10 to 30%). The combustion is simulated for the fuel mass flow rate providing the same heat transfer rate to the combustion chamber in the each case. The numerical calculation of combustion is performed individually for all cases with the help of the Fluent CFD code. Furthermore, a computer program has been developed to calculate numerically the volumetric entropy generation rate distributions and the other thermodynamic parameters by using the results of the calculations performed with the FLUENT code. The calculations bring out that the increase of ϕ (or the decrease of λ) reduces significantly the reaction rate levels. The average temperatures in the combustion chamber increase about 70 and 23% with the increases of γ (from 10 to 30%) and ϕ (from 0.5 to 1.0), respectively. With the increase of γ from 10 to 30%, the volumetric local entropy generation rates decrease about 9 and 4% in the cases of ϕ=0.5 and 1.0, respectively, and while the total entropy generation rates decrease exponentially, the merit numbers increase. The useful energy transfer rate to irreversibility rate therefore improves as the oxygen percentage increases.