hem.html

Hem

Synthesis and Electrocatalytic Activity of [FeFe]-Hydrogenase Model Complexes with Non-Innocent Chelating Nitrogen-Donor Ligands

To probe the influence of redox non‐innocent ligands on a well‐known class of [FeFe]‐hydrogenase models, three new asymmetrically disubstituted diiron complexes of the general formula (µ‐SRS)[Fe(CO)3][Fe(CO)(N‐N)] {SRS = propane‐1,3‐dithiolate (pdt) or benzene‐1,2‐dithiolate (bdt), and N‐N = 2,2′‐bipyridine (bipy) or 2,2′‐bipyrimidine (bpym)} have been synthesized from their parent hexacarbonyls and characterized. The new complexes, (µ‐pdt)Fe2(CO)4(κ2‐bpym) (2), (µ‐bdt)Fe2(CO)4(κ2‐bipy) (3), and (µ‐bdt)Fe2(CO)4(κ2‐bpym) (4), were fully characterized by spectroscopic and electrochemical techniques, and the results are compared to those of a related complex, (µ‐pdt)Fe2(CO)4(κ2‐bipy) (1). The crystal structures of 2–4 show that, in each complex, the two iron units are in an eclipsed orientation, and the N‐N ligand lies in the basal plane. IR spectra and electrochemical analyses indicate that electron density at the iron centers decreases in the order 1 > 2 > 3 > 4. Furthermore, compound 2 undergoes a ligand‐centered reduction at the same potential that the hexacarbonyl precursor undergoes its first reduction. However, unlike the 2,2′‐bipy derivatives 1 and 3, the 2,2′‐bpym complexes 2 and 4 are not effective catalysts for electrochemical proton reduction from acetic acid

Using Surface Amide Couplings to Assemble Photocathodes for Solar Fuel Production Applications

International audienceA facile surface amide-coupling method was examined to attach dye and catalyst molecules to silatrane-decorated NiO electrodes. Using this method, electrodes with a push–pull dye were assembled and characterized by photoelectrochemistry and transient absorption spectroscopy. The dye-sensitized electrodes exhibited hole injection into NiO and good photoelectrochemical stability in water, highlighting the stability of the silatrane anchoring group and the amide linkage. The amide-coupling protocol was further applied to electrodes that contain a molecular proton reduction catalyst for use in photocathode architectures. Evidence for catalyst reduction was observed during photoelectrochemical measurements and via femtosecond-transient absorption spectroscopy demonstrating the possibility for application in photocathodes

Visualizing biomolecular electrostatics in virtual reality with UnityMol‐APBS

International audienceVirtual reality is a powerful tool with the ability to immerse a user within a completely external environment. This immersion is particularly useful when visualizing and analyzing interactions between small organic molecules, molecular inorganic complexes, and biomolecular systems such as redox proteins and enzymes. A common tool used in the biomedical community to analyze such interactions is the APBS software, which was developed to solve the equations of continuum electrostatics for large biomolecular assemblages. Numerous applications exist for using APBS in the biomedical community including analysis of protein ligand interactions and APBS has enjoyed widespread adoption throughout the biomedical community. Currently, typical use of the full APBS toolset is completed via the command line followed by visualization using a variety of two-dimensional external molecular visualization software. This process has inherent limitations: visualization of three-dimensional objects using a two-dimensional interface masks important information within the depth component. Herein, we have developed a single application, UnityMol-APBS, that provides a dual experience where users can utilize the full range of the APBS toolset, without the use of a command line interface, by use of a simple \ac{GUI} for either a standard desktop or immersive virtual reality experience

De novo Sequencing and Native Mass Spectrometry Reveals Hetero-Association of Dirigent Protein Homologs and Potential Interacting Proteins in Forsythia × intermedia

The discovery of dirigent proteins (DPs) and their functions in plant phenol biochemistry was made over two decades ago with Forsythia × intermedia. Stereo-selective, DP-guided, monolignol-derived radical coupling in vitro was then reported to afford the optically active lignan, (+)-pinoresinol from coniferyl alcohol, provided one-electron oxidase/oxidant capacity was present. It later became evident that DPs have several distinct sub-families. In vascular plants, DPs hypothetically function, along with other essential enzymes/proteins (e.g. oxidases), as part of lignin/lignan forming complexes (LFCs). Herein, we used an integrated bottom-up, top-down, and native mass spectrometry approach to detect potential interacting proteins in a DP-enriched solubilized protein fraction from Forsythia × intermedia, via adaptation of our initial report of DP solubilization and purification. Because this hybrid species lacks a published genome, de novo sequencing was performed using publicly available transcriptome and genomic data from closely related species. We detected and identified two new DP homologs, which appear to form hetero-trimers. Molecular dynamics simulations suggest that similar hetero-trimers were possible between Arabidopsis DP homologs with comparable sequence similarity. Other identified proteins in the DP-enriched preparation were putatively associated with DP function or the cell wall. Although their co-occurrence after extraction and chromatographic separation is suggestive for components of a protein complex in vivo, none were found to form stable complexes with DPs under the specific experimental conditions we have explored. Nevertheless, our integrated mass spectrometry method development helps prepare for future investigations directed to detect hypothetical LFCs and other related complexes isolated from plant biomass fractionation