Polyoxoniobates as molecular building blocks in thin films
in Dalton Transactions (accepted). Link
Abstract: Niobium oxide thin films have been prepared by spin-coating aqueous solutions of tetramethylammonium salts of the isostructural polyoxometalate clusters [Nb10O28]6- , [TiNb10O28]7- and [Ti2Nb8O28]8- onto silicon wafers, and annealing them. The [Nb10O28]6- cluster yields films of Nb2O5 in the orthorhombic and monoclinic crystal phases when annealed at 800 °C and 1,000 °C, respectively, whereas the [TiNb10O28]7- and [Ti2Nb8O28]8- clusters yield the monoclinic crystal phases of Ti2Nb12O29 and TiNb2O7 (titanium-niobium oxides) in different ratios. We also demonstrate a protocol for depositing successive layers of metal oxide films. Finally, we explore factors affecting the roughness of the films.
Computational exploration of heterometal substitution into the decaniobate framework, [Nb10O28]6-
in Phys. Chem. Chem. Phys., 2021, 23, 10402-10408. Link
Abstract: The factors governing the substitution of group 4B–12B metals into the decaniobate framework are explored using density functional theory in order to ascertain whether (1) recently isolated [MNb9O28]x− clusters are kinetic or thermodynamic products, (2) density functional theory is a sufficient level of theory to accurately predict substitution patterns in polyoxometalates where ion pairing and other effects may operate, and (3) it can be used to guide future synthetic efforts. Computations using restricted, unrestricted and open-shell density functional theory at PBE0/def2-tzvp were found to correctly predict substitution patterns in known clusters, and were subsequently used to calculate the relative energies of a large series of [MNb9O28]x− clusters, to reveal trends and suggest potential synthetic approaches. OPBE/def2-tzvp correctly predicted favoured spin states of known substituted decametalates.
Polyoxometalates as Effective Nano-inhibitors of Amyloid Aggregation of Pro-inflammatory S100A9 Protein Involved in Neurodegenerative Diseases
in ACS Appl. Mater. Interfaces, 2021, 13(23), 26721-26734.
Chaudhary, Himanshi; Iaschishyn, Igor A.; Romanova, Nina V.; Rambaran, Mark A.; Musteikyte, Greta; Smirnovas, Vytautas; Holmboe, Michael; Ohlin, C. André; Svedruzić, Zelsko M.; Morozova-Roche, Ludmilla A.
Abstract: Pro-inflammatory and amyloidogenic S100A9 protein is central to the amyloid-neuroinflammatory cascade in neurodegenerative diseases. Polyoxometalates (POMs) constitute a diverse group of nanomaterials, which showed potency in amyloid inhibition. Here, we have demonstrated that two selected nanosized niobium POMs, Nb10 and TiNb9, can act as potent inhibitors of S100A9 amyloid assembly. Kinetics analysis based on ThT fluorescence experiments showed that addition of either Nb10 or TiNb9 reduces the S100A9 amyloid formation rate and amyloid quantity. Atomic force microscopy imaging demonstrated the complete absence of long S100A9 amyloid fibrils at increasing concentrations of either POM and the presence of only round-shaped and slightly elongated aggregates. Molecular dynamics simulation revealed that both Nb10 and TiNb9 bind to native S100A9 homo-dimer by forming ionic interactions with the positively charged Lys residue-rich patches on the protein surface. The acrylamide quenching of intrinsic fluorescence showed that POM binding does not perturb the Trp 88 environment. The far and near UV circular dichroism revealed no large-scale perturbation of S100A9 secondary and tertiary structures upon POM binding. These indicate that POM binding involves only local conformational changes in the binding sites. By using intrinsic and 8-anilino-1-naphthalene sulfonate fluorescence titration experiments, we found that POMs bind to S100A9 with a Kd of ca. 2.5 μM. We suggest that the region, including Lys 50 to Lys 54 and characterized by high amyloid propensity, could be the key sequences involved in S1009 amyloid self-assembly. The inhibition and complete hindering of S100A9 amyloid pathways may be used in the therapeutic applications targeting the amyloid-neuroinflammatory cascade in neurodegenerative diseases.
Based on a plethora of experiments and advanced geochemical analysis techniques, Hussein Kanbar in the Holmboe group (Department of Chemistry/UMU), in a collaboration with PhD student Fredrik Olajos and Professor Göran Englund from the Department of Ecology and Environmental Sciences/UMU, has published a paper in the Journal of Soils and Sediments, detailing the mineral and geochemical characteristics of Holocene lake sediments from the Hotagen lake in west Sweden (Jämtland). Read more here:
Kanbar, H.J., Tran Le, T., Olajos, F. et al. Tracking mineral and geochemical characteristics of Holocene lake sediments: the case of Hotagen, west-central Sweden. J Soils Sediments (2021). https://doi.org/10.1007/s11368-021-03012-y
Our planet has more organic carbon in its fragile soil layers than all the carbon on land and atmosphere combined. The Holmboe group is now hiring a PhD student (4 year minimum) and offering one postdoc fellowship (2 years) for two separate but similar projects focusing on the molecular interactions between natural organic molecules and mineral surfaces.
In order to focus on the molecular scale, the research will utilize various experimental methods and molecular dynamics simulations (extracting for instance free energy profiles as shown below), and why not also virtual reality!
To apply for the PhD position, please visit this link.
To apply for the postdoc fellowship financed by the Kempe Foundations, please visit this link.
Yun J., Kumar A, Removski N., Shchukarev A., Link N., Boily J.-F., Bertram A.K. 2021. Effects of Inorganic Acids and Organic Solutes on the Ice Nucleating Ability and Surface Properties of Potassium-Rich Feldspar. ACS Earth Space Chem. (in press).
Using microelectrodes, we revealed a gateway for ion transport in bubbles pinned on hematite and on gold!
Harizi V, Nha TPT, Berisha A, Boily JF. 2021. A gateway for ion transport on gas bubbles pinned onto solids. Commun. Chem. 4, 43.
Bishop JL, Yeşilbaş M, Hinman NW, Burton ZMF, Englert PAJ, Toner JD, McEwen AS, Gulick VC, Gibson EK, Koeberl C. 2021. Martian subsurface cryosalt expansion and collapse as trigger for landslides. Sci. Adv. 7, eabe4459.
Using soil analogues, the group showed how cryosalts can trigger landslides on Mars. This suggests the martian environment is still dynamic and active today, which is important for future human exploration on Mars. A portion of the experimental work was done in JF Boily’s laboratory.