Rapid Detection of the Antibiotic Sulfamethazine in Pig Body Fluids by Paper Spray Mass Spectrometry

We report herein a practical method for nonlethal detection of the antibiotic sulfamethazine in pig body fluids via the combination of simple extraction and paper spray mass spectrometry (PS-MS). This method requires minimal sample preparation while still providing high sensitivities and accuracies in complex matrices including pig whole blood (LOD = 7.9 μg/L; recovery = 95.4–103.7%), pig serum (LOD = 11.5 μg/L; recovery = 103.2–106.2%), and synthetic urine (LOD = 11.2 μg/L; recovery = 99.1–103.2%). Given a known correlation between the level of sulfamethazine in body fluids and edible tissues, this method shows great promise as a practical and nonlethal solution for rapid testing of the drug, which can substantially aid managerial decision in the livestock industry

Strand displacement and duplex invasion into double-stranded DNA by pyrrolidinyl peptide nucleic acids

The so-called acpcPNA system bears a peptide backbone consisting of 4′-substituted proline units with (2′R,4′R) configuration in an alternating combination with (2S)-amino-cyclopentane-(1S)-carboxylic acids. acpcPNA forms exceptionally stable hybrids with complementary DNA. We demonstrate herein (i) strand displacements by single-stranded DNA from acpcPNA-DNA hybrids, and by acpcPNA strands from DNA duplexes, and (ii) strand invasions by acpcPNA into double-stranded DNA. These processes were studied in vitro using synthetic oligonucleotides and by means of our concept of wavelength-shifting fluorescent nucleic acid probes, including fluorescence lifetime measurements that allow quantifying energy transfer efficiencies. The strand displacements of preannealed 14mer acpcPNA-7mer DNA hybrids consecutively by 10mer and 14mer DNA strands occur with rather slow kinetics but yield high fluorescence color ratios (blue:yellow or blue:red), fluorescence intensity enhancements, and energy transfer efficiencies. Furthermore, 14mer acpcPNA strands are able to invade into 30mer double-stranded DNA, remarkably with quantitative efficiency in all studied cases. These processes can also be quantified by means of fluorescence. This remarkable behavior corroborates the extraordinary versatile properties of acpcPNA. In contrast to conventional PNA systems which require 3 or more equivalents PNA, only 1.5 equivalents acpcPNA are sufficient to get efficient double duplex invasion. Invasions also take place even in the presence of 250 mM NaCl which represents an ionic strength nearly twice as high as the physiological ion concentration. These remarkable results corroborate the extraordinary properties of acpcPNA, and thus acpcPNA represents an eligible tool for biological analytics and antigene applications. © The Royal Society of Chemistry 2015

The kinetics and mechanism of the organo-iridium catalysed racemisation of amines

The dimeric iodo-iridium complex [IrCp*I2 ]2 (Cp*=pentamethylcyclopentadiene) is an efficient catalyst for the racemisation of secondary and tertiary amines at ambient and higher temperatures with a low catalyst loading. The racemisation occurs with pseudo-first-order kinetics and the orresponding four rate constants were obtained by monitoring the time dependence of the concentrations of the (R) and (S) enantiomers starting with either pure (R) or (S) and show a first-order dependence on catalyst concentration. Low temperature 1H NMR data is consistent with the formation of a 1:1 complex with the amine coordinated to the iridium and with both iodide anions still bound to the metal-ion, but at the higher temperatures used for kinetic studies binding is weak and so no saturation zero-order kinetics are observed. A cross-over experiment with isotopically labelled amines demonstrates the intermediate formation of an imine which can dissociate from the iridium complex. Replacing the iodides in the catalyst by other ligands or having an amide substituent in Cp* results in a much less effective catalysts for the racemisation of amines. The rate constants for a deuterated amine yield a significant primary kinetic isotope effect kH/kD = 3.24 ndicating that hydride transfer is involved in the rate-limiting step

Synthesis of Structurally Diverse N-Substituted Quaternary-Carbon-Containing Small Molecules from α,α-Disubstituted Propargyl Amino Esters.

N-containing quaternary stereocenters represent important motifs in medicinal chemistry. However, due to their inherently sterically hindered nature, they remain underrepresented in small molecule screening collections. As such, the development of synthetic routes to generate small molecules that incorporate this particular feature are highly desirable. Herein, we describe the diversity-oriented synthesis (DOS) of a diverse collection of structurally distinct small molecules featuring this three-dimensional (3D) motif. The subsequent derivatisation and the stereoselective synthesis exemplified the versatility of this strategy for drug discovery and library enrichment. Chemoinformatic analysis revealed the enhanced sp3 character of the target library and demonstrated that it represents an attractive collection of biologically diverse small molecules with high scaffold diversity.ERC (FP7/2007-2013; 279337/DOS) Marie Curie Fellowship (2013-IEF-626191) AstraZeneca IDB Cambridge International Scholarshi

Synthesis and properties of novel nucleopeptides

SIGLEAvailable from British Library Document Supply Centre-DSC:D192156 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Fluorogenic PNA probes

Fluorogenic oligonucleotide probes that can produce a change in fluorescence signal upon binding to specific biomolecular targets, including nucleic acids as well as non-nucleic acid targets, such as proteins and small molecules, have applications in various important areas. These include diagnostics, drug development and as tools for studying biomolecular interactions in situ and in real time. The probes usually consist of a labeled oligonucleotide strand as a recognition element together with a mechanism for signal transduction that can translate the binding event into a measurable signal. While a number of strategies have been developed for the signal transduction, relatively little attention has been paid to the recognition element. Peptide nucleic acids (PNA) are DNA mimics with several favorable properties making them a potential alternative to natural nucleic acids for the development of fluorogenic probes, including their very strong and specific recognition and excellent chemical and biological stabilities in addition to their ability to bind to structured nucleic acid targets. In addition, the uncharged backbone of PNA allows for other unique designs that cannot be performed with oligonucleotides or analogues with negatively-charged backbones. This review aims to introduce the principle, showcase state-of-the-art technologies and update recent developments in the areas of fluorogenic PNA probes during the past 20 years