Practical Study into Enhancing IgG Immobilisation on Screen-Printed Electrodes for Environmental Applications

This work is focused on the influence of pH and applied potential for the immobilisation of rabbit IgG on a carbon screen-printed electrode. The orientation of IgG molecule at the surface is fundamental for activity and reproducibility of the immunosensor. As the electrode potential is increased a particular order may be brought to the immobilised antibodies, i.e. the antibodies adapt a more favourable arrangement on the surface to facilitate better binding. The response increased when changing the pH from basic to acidic medium and the reverse trend was observed for the limit of detection (LOD). When a potential was applied to the electrode, the response generally decreased and the LOD increased in the order acidic > basic > neutral pH. The LODs obtained from antibodies immobilised at acidic pH and + 100 mV were better than the LODs obtained at other conditions.     

Solid-phase synthesis of the cyclic lipononadepsipeptide [N-Mst(Ser1), d-Ser4, L-Thr6, L-Asp8, L-Thr9]syringotoxin

An optimized solid-phase strategy for the preparation of the cyclic lipononadepsipeptide [N-Mst(L-Ser1), D-Ser4, L-Thr6, L-Asp8, L-Thr9]syringotoxin is reported. The strategy is based on the use of a mild orthogonal protection scheme and the incorporation of the nonproteinogenic amino acid (Z)-Dhb into the peptide chain as the dipeptide Fmoc-Thr(tBu)-(Z)-Dhb-OH. The didehydrodipeptide was synthesized by a water-soluble carbodiimide-induced beta-elimination of a protected dipeptide containing a residue of Thr with its free hydroxy side chain unprotected.     

Design and synthesis of push-pull chromophores for second-order nonlinear optics derived from rigidified thiophene-based pi-conjugating spacers.

Two series of push-pull chromophores built around thiophene-based pi-conjugating spacers rigidified either by covalent bonds or by noncovalent intramolecular interactions have been synthesized and characterized by UV-vis spectroscopy, electric field induced second harmonic generation (EFISH) and differential scanning calorimetry. Comparison of the linear and second-order nonlinear optical properties of chromophores based on a covalently bridged dithienylethylene (DTE) spacer with those of their analogues based on open chain DTE shows that the rigidification of the spacer produces a considerable bathochromic shift of the absorption maximum together with a dramatic enhancement of the molecular quadratic hyperpolarizability (mu beta) which reaches values among the highest reported so far. A second series of NLO-phores has been derived from a 2,2'-bi(3,4-ethylenedioxythiophene) (BEDOT) pi-conjugating spacer. As indicated by X-ray and UV-vis data, rigidification of the spacer originates in that case, from noncovalent intramolecular interactions between sulfur and oxygen atoms. Again, comparison with the parent compounds based on an unsubstituted bithiophene spacer reveals a marked red shift of the absorption maximum and a large enhancement of mu beta. In an attempt to distinguish the contribution of the electronic and geometrical effects of the ethylenedioxy group, a third series of NLO-phores based on 3,4-ethylenedioxythiophene (EDOT) and 3,4-dihexyloxythiophene spacers has been synthesized. Comparison with compounds based on unsubstituted thiophene shows that, despite a red shift of lambda(max), introduction of alkoxy groups leads to a decrease of mu beta. Theoretical calculations indicate that this effect results from a decrease of the dipole moment (mu) caused by the auxiliary electron-donor alkoxy groups on the thiophene ring. In contrast, replacement of BT by BEDOT produces an increase of mu, which associated with the noncovalent rigidification of the BT system accounts for the observed enhancement of mu beta.     

Stereoselective synthesis of trans-2,3-disubstituted pyrrolidines via addition to N-acyliminium ions

An efficient and stereoselective synthesis of trans-2,3-disubstituted pyrrolidines is described. The intermolecular alkylation of racemic N-acyliminium ions generated in situ from the corresponding 3-substituted lactams proceeds stereoselectively and in high yield.     

Recent developments in computer vision-based analytical chemistry: A tutorial review

Chemical analysis based on colour changes recorded with imaging devices is gaining increasing interest. This is due to its several significant advantages, such as simplicity of use, and the fact that it is easily combinable with portable and widely distributed imaging devices, resulting in friendly analytical procedures in many areas that demand out-of-lab applications for in situ and real-time monitoring. This tutorial review covers computer vision-based analytical (CVAC) procedures and systems from 2005 to 2015, a period of time when 87.5% of the papers on this topic were published. The background regarding colour spaces and recent analytical system architectures of interest in analytical chemistry is presented in the form of a tutorial. Moreover, issues regarding images, such as the influence of illuminants, and the most relevant techniques for processing and analysing digital images are addressed. Some of the most relevant applications are then detailed, highlighting their main characteristics. Finally, our opinion about future perspectives is discussed.     

Two-dimensional miscibility studies--the analysis of interaction between long-chain alcohols and semifluorinated alkanes

This work presents the results of phase behavior studies of two-dimensional (2D) binary systems involving semifluorinated alkanes (SFAs) and fatty alcohols. Four different SFAs were selected for investigations: (i) with a short and branched perfluorinated moiety (iF3H20), (ii) with a short and normal perfluorinated chain (F4H20), (iii) with a long and branched perfluorinated fragment (iF9H20), and (iv) with a long and normal perfluorinated group (F10H20). Two alcohols were selected to mix with the above-mentioned SFAs: tetradecanol and docosanol. The measurements were based on surface pressure/area isotherms in addition to Brewster angle microscope (BAM) imaging. Dependencies of the collapse surface pressure and the compression modulus vs the monolayer composition together with the excess free energy of mixing values, complemented with BAM images, enabled us to draw some general conclusions regarding the phase behavior of the investigated mixed systems. Generally, it has been noticed that the addition of docosanol into an SFA monolayer exerts a condensing effect, contrary to tetradecanol. Moreover, SFAs with a long perfluorinated segment mix to a larger extent with alcohols as compared to their analogues having a short perfluorinated moiety. The resultant phase diagrams for all the investigated eight mixtures are presented and discussed.     

Stereoselective synthesis of eight-membered cyclic ethers by tandem Nicholas reaction/ring-closing metathesis: a short synthesis of (+)-cis-Lauthisan

[STRUCTURE: SEE TEXT] Cis-2,8-disubstituted oxocanes and the parent unsaturated precursors were prepared from the corresponding Co2(CO)6-cycloalkynic ethers. Key steps in such synthesis were the ether linkage formation by intermolecular Nicholas reaction, RCM of the suitable acyclic dienyl ether and montmorillonite K-10 induced isomerization of the complexed cycloalkyne. A short synthesis of (+)-cis-lauthisan taking advantage of the developed methodology is described.     

Dihydrogen Catalysis of the Reversible Formation and Cleavage of CH and NH Bonds of Aminopyridinate Ligands Bound to (η5‐C5Me5)IrIII

This study focuses on a series of cationic complexes of iridium that contain aminopyridinate (Ap) ligands bound to an (η⁵‐C₅Me₅)Ir^III fragment. The new complexes have the chemical composition [Ir(Ap)(η⁵‐C₅Me₅)]⁺, exist in the form of two isomers ( 1⁺ and 2⁺ ) and were isolated as salts of the BAr_F^? anion (BAr_F=B[3,5‐(CF₃)₂C₆H₃]₄). Four Ap ligands that differ in the nature of their bulky aryl substituents at the amido nitrogen atom and pyridinic ring were employed. In the presence of H₂, the electrophilicity of the Ir^III centre of these complexes allows for a reversible prototropic rearrangement that changes the nature and coordination mode of the aminopyridinate ligand between the well‐known κ²‐N,N′‐bidentate binding in 1⁺ and the unprecedented κ‐N,η³‐pseudo‐allyl‐coordination mode in isomers 2⁺ through activation of a benzylic C?H bond and formal proton transfer to the amido nitrogen atom. Experimental and computational studies evidence that the overall rearrangement, which entails reversible formation and cleavage of H?H, C?H and N?H bonds, is catalysed by dihydrogen under homogeneous conditions.