Automated,high performance,flow-through chemiluminescence microarray for the multiplexed detection of phycotoxins

A novel multiplexed immunoassay for the analysis of phycotoxins in shellfish samples has been developed. Therefore, a regenerable chemiluminescence (CL) microarray was established which is able to analyze automatically three different phycotoxins (domoic acid (DA), okadaic acid (OA) and saxitoxin (STX)) in parallel on the analysis platform MCR3. As a test format an indirect competitive immunoassay format was applied. These phycotoxins were directly immobilized on an epoxy-activated PEG chip surface. The parallel analysis was enabled by the simultaneous addition of all analytes and specific antibodies on one microarray chip. After the competitive reaction, the CL signal was recorded by a CCD camera. Due to the ability to regenerate the toxin microarray, internal calibrations of phycotoxins in parallel were performed using the same microarray chip, which was suitable for 25 consecutive measurements. For the three target phycotoxins multi-analyte calibration curves were generated. In extracted shellfish matrix, the determined LODs for DA, OA and STX with values of 0.5 ± 0.3 μg L⁻¹, 1.0 ± 0.6 μg L⁻¹, and 0.4 ± 0.2 μg L⁻¹ were slightly lower than in PBS buffer. For determination of toxin recoveries, the observed signal loss in the regeneration was corrected. After applying mathematical corrections spiked shellfish samples were quantified with recoveries for DA, OA, and STX of 86.2%, 102.5%, and 61.6%, respectively, in 20 min. This is the first demonstration of an antibody based phycotoxin microarray.     

On the Solvent‐free Structure of a Jäger‐type Cobalt(II) N2O2‐Chelate Complex

A combined synchrotron X‐ray and density functional theory (DFT) study on the structure of a Jäger‐type N₂O₂ chelate complex was carried out. The ethoxy‐substituted bis(3‐oxo‐enaminato)cobalt(II) complex ( 1 ) was an original sample from the laboratory of the late Professor Ernst‐G. Jäger (University of Jena, Germany). Single‐crystal X‐ray analysis revealed essentially flat molecules of 1 , which are unsolvated and coordinatively unsaturated. The DFT calculations on the isolated molecule predict a planar structure for the non‐hydrogen atoms, which is a local minimum on the energy surface. The crystal packing is achieved through off‐set stacking (staircase arrangement), resulting in a herringbone pattern in the space group P2₁2₁2₁. The structure of 1 is compared to known structures of related bis(3‐oxo‐enaminato)cobalt(II) complexes ( 2 – 4 ). Original bulk material of 1 was investigated by scanning electron microscopy (SEM), powder X‐ray diffraction (PXRD), melting point determination, and infrared (IR) spectroscopy.     

Chemiluminescence microarrays in analytical chemistry: a critical review

Multi-analyte immunoassays on microarrays and on multiplex DNA microarrays have been described for quantitative analysis of small organic molecules (e.g., antibiotics, drugs of abuse, small molecule toxins), proteins (e.g., antibodies or protein toxins), and microorganisms, viruses, and eukaryotic cells. In analytical chemistry, multi-analyte detection by use of analytical microarrays has become an innovative research topic because of the possibility of generating several sets of quantitative data for different analyte classes in a short time. Chemiluminescence (CL) microarrays are powerful tools for rapid multiplex analysis of complex matrices. A wide range of applications for CL microarrays is described in the literature dealing with analytical microarrays. The motivation for this review is to summarize the current state of CL-based analytical microarrays. Combining analysis of different compound classes on CL microarrays reduces analysis time, cost of reagents, and use of laboratory space. Applications are discussed, with examples from food safety, water safety, environmental monitoring, diagnostics, forensics, toxicology, and biosecurity. The potential and limitations of research on multiplex analysis by use of CL microarrays are discussed in this review. Figure

Achievements in the development of CL microarray analysis platforms     

Gold Carbenoids: Lessons Learnt from a Transmetalation Approach

Carbophilic catalysts that are based on Au^I allow a host of different nucleophiles to be added across various π systems. 1 – 3 Although many of these reactions are thought to proceed via gold carbenoids, the challenge to observe and characterize these putative intermediates has basically been unmet. 4 The current mechanistic interpretation therefore largely relies on indirect evidence and computational data, some of which are subject to debate. 5 In an attempt to fill this gap, we pursued a potential route to gold carbenoids by formal transmetalation of chromium or tungsten Fischer carbene complexes with [LAu]⁺. Whereas this transformation proceeds with exceptional ease as long as a stabilizing heteroelement is present on the carbene center, it stops half‐way in its absence. Rather unusual bimetallic arrays are formed, which allow the charge density to delocalize over several positions. The obvious difficulty of releasing an “unstabilized” gold carbenoid has potential mechanistic implications for the understanding of π‐acid catalysis in general.     

Redox‐Neutral α,β‐Difunctionalization of Cyclic Amines

In contrast to the continuously growing number of methods that allow for the efficient α‐functionalization of amines, few strategies exist that enable the direct functionalization of amines in the β‐position. A general redox‐neutral strategy is outlined for amine β‐functionalization and α,β‐difunctionalization that utilizes enamines generated in situ. This concept is demonstrated in the context of preparing polycyclic N,O‐acetals from simple 1‐(aminomethyl)‐β‐naphthols and 2‐(aminomethyl)‐phenols.     

Metal/Metal Redox Isomerism Governed by Configuration

A pair of diastereomeric dinuclear complexes, [Tp′(CO)BrW{μ-η²-C,C′-κ²-S,P-C₂(PPh₂)S}Ru(η⁵-C₅H₅)(PPh₃)], in which W and Ru are bridged by a phosphinyl(thiolato)alkyne in a side-on carbon P,S-chelate coordination mode, were synthesized, separated and fully characterized. Even though the isomers are similar in their spectroscopic properties and redox potentials, the like-isomer is oxidized at W while the unlike-isomer is oxidized at Ru, which is proven by IR, NIR and EPR-spectroscopy supported by spectro-electrochemistry and computational methods. The second oxidation of the complexes was shown to take place at the metal left unaffected in the first redox step. Finally, the tipping point could be realized in the unlike isomer of the electronically tuned thiophenolate congener [Tp′(CO)(PhS)W{μ-η²-C,C′-κ²-S,P-C₂(PPh₂)S}Ru(η⁵-C₅H₅)-(PPh₃)], in which valence trapped W^III/Ru^II and W^II/Ru^III cationic species are at equilibrium.     

The structure of N-Pyrid-2-yl-iminotriphenylphosphorane,C23H19N2P

M_r = 353.9, monoclinic, P 2₁/c, a = 11.371(4), b = 11.391(5), c = 14.699(11) Å, β = = 97.78(2)⁰, Z = 4, V = 1888.6(6) ų, D_x = 1.28 Mgm⁻³, final R = 0.052 for 2360 independent reflections excluding those with |F₀| < 5 σ(F₀). Intensities were measured with an automatic diffractometer. The PN C- part of the molecule is nearly coplanar with the pyridinring (torsion angle 6.4°). The P atom and the N(2) atom of the pyridinring overlap with their van der Waals spheres and have nearly the position with the maximum of steric hindrance. This conformation of the molecule is the consequence of a conjugation between the Ph₃P=N-group and the N-standing pyridine ring as well as of an attraction between the P atom and the N(2) atom.     

The structure of Dimethylaminomethanediphosphonic Acid,C3H11NO6P2

M_r = 218.9, monoclinic, P 2₁/c, a = 6.870(1), b = 10.824(2), c = 11.337(2) Å, β = = 94.59(2)⁰, Z = 4, V = 840.5(3) ų, D_x = 1.73 Mgm⁻³. Final R = 0.033 for 2648 independent reflections, excluding those with |F₀| < 3σ(F₀). Intensities were measured with an automatic diffractometer. This organophosphorous compound is characterized by two P C bonds. Four symmetrically independent intermolecular hydrogen bonds determine the threedimensional packing of the molecules and the unique chemical properties of the campound.     

The crystal and molecular structure of 1,12-dibromododecane,C12H24Br2

The α,ω-dihaloalcanes could serve as model compounds for polyethylenes in further studies of infrared and Raman-spectra. The 1,12-dibromododecane, belonging to this class of compounds, has the monoclinic space group P 2₁/a with the cell parameters a = 24.8 Å, b = 5.40 Å, c = 5.50 Å, β = 99°, Z = 2. The preparation of crystals was very difficult. The crystal finally used gives only few and bad X-ray data measured by film method (equiinclination Weissenberg). Therefore the accuracy of the structure determination is not high, but the result is reliable and has model character for related compounds. All molecules are ordered with their long molecular axes parallel to the (401) planes of the unit cell. There are alternating plane layers of bromine atoms on the one hand and aliphatic parts of the molecules on the other hand, both parallel to the (100)-planes. This molecular arrangement explains well the spectroscopic and crystal optical properties of the structure and also of related compounds like 1,10-dibromodecane and 1,18-dibromooctadecane.