Facile electrochemical affinity measurements of small and large molecules.

A novel miniaturized sensor for electrochemical detection that contains graphene- and gold nanoparticles was functionalized with proteins. Using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) it was possible to observe and quantify interactions of molecules with these proteins. The protein binders included carbohydrate ligands as small as carbohydrates up to COVID-19 spike protein variants engaged in protein-protein interactions. The system uses off-the-shelf sensors combined with an affordable potentiostat and yet is sensitive enough for small ligand binding.

Hydrogen Evolution Electrocatalysis with a Molecular Cobalt Bis(alkylimidazole)methane Complex in DMF: a Critical Activity Analysis.

[Co(HBMIMPh2 )2 ](BF4 )2 (1) [HBMIMPh2 =bis(1-methyl-4,5-diphenyl-1H-imidazol-2-yl)methane] was investigated for its electrocatalytic hydrogen evolution performance in DMF using voltammetry and during controlled potential/current electrolysis (CPE/CCE) in a novel in-line product detection setup. Performances were benchmarked against three reported molecular cobalt hydrogen evolution reaction (HER) electrocatalysts, [Co(dmgBF2 )2 (solv)2 ] (2) (dmgBF2 =difluoroboryldimethylglyoximato), [Co(TPP)] (3) (TPP=5,10,15,20-tetraphenylporphyrinato), and [Co(bapbpy)Cl](Cl) (4) [bapbpy=6,6'-bis-(2-aminopyridyl)-2,2'-bipyridine], showing distinct performances differences with 1 being the runner up in H2 evolution during CPE and the best catalyst in terms of overpotential and Faradaic efficiency during CCE. After bulk electrolysis, for all of the complexes, a deposit on the glassy carbon electrode was observed, and post-electrolysis X-ray photoelectron spectroscopy (XPS) analysis of the deposit formed from 1 demonstrated only a minor cobalt contribution (0.23 %), mainly consisting of Co2+ . Rinse tests on the deposits derived from 1 and 2 showed that the initially observed distinct activity was (partly) preserved for the deposits. These observations indicate that the molecular design of the complexes dictates the features of the formed deposit and therewith the observed activity.

A high-resolution 4D terrestrial laser scan dataset of the Kijkduin beach-dune system, The Netherlands.

Sandy coasts form the interface between land and sea and their morphologies are highly dynamic. A combination of human and natural forcing results in morphologic changes affecting both nature values and coastal safety. Terrestrial laser scanning (TLS) is a technique enabling near-continuous monitoring of the changing morphology of a sandy beach-dune system with centimetre-order accuracy. In Kijkduin, The Netherlands, a laser scanner sampled one kilometre of coast at hourly intervals for about six months. This resulted in over 4,000 consecutive topographic scans of around one million points each, at decimetre-order point spacing. Analysis of the resulting dataset will offer new insights into the morphological behaviour of the beach-dune system at hourly to monthly time scales, ultimately increasing our fundamental scientific understanding of these complex geographic systems. It further provides the basis for developing novel algorithms to extract morphodynamic and geodetic information from this unique 4D spatiotemporal dataset. Finally, experiences from this TLS setup support the development of improved near-continuous 3D observation of both natural and anthropogenic scenes in general.

Combining metal-metal cooperativity, metal-ligand cooperativity and chemical non-innocence in diiron carbonyl complexes.

Several metalloenzymes, including [FeFe]-hydrogenase, employ cofactors wherein multiple metal atoms work together with surrounding ligands that mediate heterolytic and concerted proton-electron transfer (CPET) bond activation steps. Herein, we report a new dinucleating PNNP expanded pincer ligand, which can bind two low-valent iron atoms in close proximity to enable metal-metal cooperativity (MMC). In addition, reversible partial dearomatization of the ligand's naphthyridine core enables both heterolytic metal-ligand cooperativity (MLC) and chemical non-innocence through CPET steps. Thermochemical and computational studies show how a change in ligand binding mode can lower the bond dissociation free energy of ligand C(sp3)-H bonds by ∼25 kcal mol-1. H-atom abstraction enabled trapping of an unstable intermediate, which undergoes facile loss of two carbonyl ligands to form an unusual paramagnetic (S = ) complex containing a mixed-valent iron(0)-iron(i) core bound within a partially dearomatized PNNP ligand. Finally, cyclic voltammetry experiments showed that these diiron complexes show catalytic activity for the electrochemical hydrogen evolution reaction. This work presents the first example of a ligand system that enables MMC, heterolytic MLC and chemical non-innocence, thereby providing important insights and opportunities for the development of bimetallic systems that exploit these features to enable new (catalytic) reactivity.

Support vector regression for high-resolution beach surface moisture estimation from terrestrial LiDAR intensity data.

Beach Surface Moisture (BSM) is a key attribute in the coastal investigations of land-atmospheric water and energy fluxes, groundwater resource budgets and coastal beach/dune development. In this study, an attempt has been made for the first time to estimate BSM from terrestrial LiDAR intensity data based on the Support Vector Regression (SVR). A long-range static terrestrial LiDAR (Riegl VZ-2000) was adopted to collect point cloud data of high spatiotemporal resolution on the Ostend-Mariakerke beach, Belgium. Based on the field moisture samples, SVR models were developed to retrieve BSM, using the backscattered intensity, scanning ranges and incidence angles as input features. The impacts of the training samples' size and density on the predictive accuracy and generalization capability of the SVR models were fully investigated based on simulated BSM-intensity samples. Additionally, we compared the performance of the SVR models for BSM estimation with the traditional Stepwise Regression (SR) method and the Artificial Neural Network (ANN). Results show that SVR could accurately retrieve the BSM from the backscattered intensity with high reproducibility (average test RMSE of 0.71% ± 0.02% and R2 of 0.98% ± 0.002%). The Radial Basis Function (RBF) was the most suitable kernel for SVR model development in this study. The impacts of scanning geometry on the intensity could also be accurately corrected in the process of estimating BSM by the SVR models. However, compared to the SR method, the predictive accuracy and generalization performance of SVR models were significantly dependent on the training samples' coverage, size and distribution, suggesting the need for the training samples of uniform distribution and representativeness. The minimum size of training samples required for SVR model development was 54. Under this condition, SVR performed similarly to ANN with a test RMSE of 1.06%, but SVR still performed acceptably (with an RMSE of 1.83%) even using extremely few training samples (only 16 field samples of uniform distribution), far better than the ANN (with an RMSE of 4.02%).

Electrocatalytic Proton Reduction by a Cobalt Complex Containing a Proton-Responsive Bis(alkylimdazole)methane Ligand: Involvement of a C-H Bond in H2 Formation.

Homogeneous electrocatalytic proton reduction is reported using cobalt complex [1](BF4 )2 . This complex comprises two bis(1-methyl-4,5-diphenyl-1H-imidazol-2-yl)methane (HBMIM Ph 2 ) ligands that contain an acidic methylene moiety in their backbone. Upon reduction of [1](BF4 )2 by either electrochemical or chemical means, one of its HBMIM Ph 2 ligands undergoes deprotonation under the formation of dihydrogen. Addition of a mild proton source (acetic acid) to deprotonated complex [2](BF4 ) regenerates protonated complex [1](BF4 )2 . In presence of acetic acid in acetonitrile solvent [1](BF4 )2 shows electrocatalytic proton reduction with a kobs of ≈200 s-1 at an overpotential of 590 mV. Mechanistic investigations supported by DFT (BP86) suggest that dihydrogen formation takes place in an intramolecular fashion through the participation of a methylene C-H bond of the HBMIM Ph 2 ligand and a CoII -H bond through formal heterolytic splitting of the latter. These findings are of interest to the development of responsive ligands for molecular (base)metal (electro)catalysis.

Tropylium-Promoted Oxidative Functionalization of Tetrahydroisoquinolines.

Structural modification of the tetrahydroisoquinoline (THIQ) framework is of significant interest to organic chemists due to its central role in heterocyclic and medicinal chemistry. Here we demonstrate an efficient metal-free method for the oxidative functionalization of THIQs at the C1 position, which is amenable to a diverse range of C-C coupling reactions. These reactions proceed through a hydride abstraction involving the tropylium ion followed by quenching the generated iminium intermediates with nucleophiles to afford THIQ derivatives with excellent efficiencies and interesting selectivities.

Simultaneous detection of Anaplasma and Ehrlichia species in ruminants and detection of Ehrlichia ruminantium in Amblyomma variegatum ticks by reverse line blot hybridization.

The detection of Anaplasma and Ehrlichia species is usually based on species-specific PCR assays, since no assay is yet available which can detect and identify these species simultaneously. To this end, we developed a reverse line blot (RLB) assay for simultaneous detection and identification of Anaplasma and Ehrlichia species in domestic ruminants and ticks. In a PCR the hypervariable V1 region of the 16S ribosomal RNA (rRNA) gene was amplified with a set of primers unique for members of the genera Anaplasma and Ehrlichia [Int. J. Syst. Evol. Microbiol. 51 (2001) 2145]. Amplified PCR products from blood of domestic ruminants or Amblyomma variegatum tick samples were hybridized onto a membrane to which eight species-specific oligonucleotide probes and one Ehrlichia and Anaplasma catch-all oligonucleotide probe were covalently linked. No DNA was amplified from uninfected blood, nor from other hemoparasites such as Theileria annulata, or Babesia bigemina. The species-specific probes did not cross-react with DNA amplified from other species. E. ruminantium, A. ovis and another Ehrlichia were identified by RLB in blood samples collected from small ruminants in Mozambique. Finally, A. variegatum ticks were tested after feeding on E. ruminantium infected sheep. E. ruminantium could be detected in adult ticks even if feeding of nymphs was carried out 3.5 years post-infection. In conclusion, the developed species-specific oligonucleotide probes used in an RLB assay can simultaneously detect and identify several Ehrlichia and Anaplasma species. However, as no quantitative data for the detection limit are available yet, only positive results are interpretable at this stage.