Trisomic Ts65Dn mice show direct parallels with many phenotypes of Down syndrome (DS), including effects on the structure of cerebellum and hippocampus. A small segment of Hsa21 known as the 'DS critical region' (DSCR) has been held to contain a gene or genes sufficient to cause impairment in learning and memory tasks involving the hippocampus. To test this hypothesis, we developed Ts1Rhr and Ms1Rhr mouse models that are, respectively, trisomic and monosomic for this region. Here, we show that trisomy for the DSCR alone is not sufficient to produce the structural and functional features of hippocampal impairment that are seen in the Ts65Dn mouse and DS. However, when the critical region is returned to normal dosage in trisomic Ms1Rhr/Ts65Dn mice, performance in the Morris water maze is identical to euploid, demonstrating that this region is necessary for the phenotype. Thus, although the prediction of the critical region hypothesis was disproved, novel gene dosage effects were identified, which help to define how trisomy for this segment of the chromosome contributes to phenotypes of DS.

Photoelectrocatalysis of the oxygen evolution reaction remains a primary challenge for development of tandem-absorber solar fuel generators due to the lack of a photoanode with broad solar spectrum utilization, a large photovoltage, and stable operation. Bismuth vanadate with a 2.4−2.5 eV band gap has shown the most promise becauses its photoactivity down to 0.4 V vs RHE is sufficiently low to couple to a lower-gap photocathode for fuel synthesis. Through development of photoanodes based on the FeWO 4 structure, in particular, Fe-rich variants with addition of about 6% Bi, we demonstrate the same 0.4 V vs RHE turn-on voltage with a 2 eV band gap metal oxide, enabling a 2-fold increase in the device efficiency limit. Combinatorial exploration of materials composition and processing facilitated synthesis of n-type variants of this typical p-type semiconductor that exhibit much higher photoactivity than previous implementations of FeWO 4 in solar photochemistry. The photoanodes are particularly promising for solar fuel applications given their stable operation in acid and base.

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The discovery of conductive and magnetic two-dimensional (2D) materials is critical for the development of next generation spintronics devices. Coordination chemistry in particular represents a highly versatile, though underutilized, route toward the synthesis of such materials with designer lattices. Here, we report the synthesis of a conductive, layered 2D metal–organic kagome lattice, Mn 3 (C 6 S 6 ), using mild solution-phase chemistry. Strong geometric spin frustration in this system mediates spin freezing at low temperatures, which results in glassy magnetic dynamics consistent with a rare geometrically frustrated (topological) spin glass. Notably, we show that this geometric frustration engenders a large, tunable exchange bias of 1625 Oe in Mn 3 (C 6 S 6 ), providing the first example of exchange bias in a coordination solid or a topological spin glass. Exchange bias is a critical component in a number of spintronics applications, but it is difficult to rationally tune, as it typically arises due to structural disorder. This work outlines a new strategy for engineering exchange bias systems using single-phase, crystalline lattices. More generally, these results demonstrate the potential utility of geometric frustration in the design of new nanoscale spintronic materials.

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Chemical alloying is a powerful approach to tune the electronic structure of semiconductors, 36 and has led to the synthesis of ternary and quaternary two-dimensional (2D) dichalcogenide 37 semiconductor alloys (e.g. MoSSe 2 , WSSe 2 etc.). To date, most studies have been focused on 38 determining the chemical composition by evaluating the optical properties, primarily via 39 photoluminescence and reflection spectroscopy of these materials in the 2D monolayer limit.However, a comprehensive study of alloying in multilayer films with direct measurement of 41 electronic structure, combined with first principles theory, is required for a complete understanding 42 of this promising class of semiconductors. We have combined first-principles density functional 43 theory calculations with experimental characterization of MoS 2(1-x) Se 2x (where x ranges from 0 to 44 1) alloys using X-ray photoelectron spectroscopy to evaluate the valence and conduction band 45 edge positions in each alloy. Moreover, our observations reveal that the valence band edge energies 46 for molybdenum sulfide/selenide alloys increase as a function of increasing selenium 47 concentration. These experimental results agree well with the results of density functional theory 48 calculations showing a similar trend in calculated valence band edges. Our studies suggest that 49 alloying is an effective technique for tuning the band edges of transition-metal dichalcogenides, 50 with implications for applications such as solar cells and photoelectrochemical devices.

Multivalent ligand-receptor interaction provides the fundamental basis for the hypothetical notion that high binding avidity relates to the strong force of adhesion. Despite its increasing importance in the design of targeted nanoconjugates, an understanding of the physical forces underlying the multivalent interaction remains a subject of urgent investigation. In this study, we designed three vancomycin (Van)-conjugated dendrimers G5(Van) ( n = mean valency = 0, 1, 4) for bacterial targeting with generation 5 (G5) poly(amidoamine) dendrimer as a multivalent scaffold and evaluated both their binding avidity and physical force of adhesion to a bacterial model surface by employing surface plasmon resonance (SPR) spectroscopy and atomic force microscopy. The SPR experiment for these conjugates was performed in a biosensor chip surface immobilized with a bacterial cell-wall peptide Lys-d-Ala-d-Ala. Of these, G5(Van) bound most tightly with a K of 0.34 nM, which represents an increase in avidity by 2 or 3 orders of magnitude relative to a monovalent conjugate G5(Van) or free vancomycin, respectively. By single-molecule force spectroscopy, we measured the adhesion force between G5(Van) and the same cell-wall peptide immobilized on the surface. The distribution of adhesion forces increased in proportion to vancomycin valency with the mean force of 134 pN at n = 4 greater than 96 pN at n = 1 at a loading rate of 5200 pN/s. In summary, our results are strongly supportive of the positive correlation between the avidity and adhesion force in the multivalent interaction of vancomycin nanoconjugates.

In the search for photoanode materials with band gaps suitable for utilization in solar fuel generation, approximately 1.2–2.8 eV, theory-guided experiments have identified a variety of materials that meet the band gap requirements and exhibit operational stability in harsh photoelectrochemical environments. In particular, M-V-O compounds (M is a transition metal or main group element) with VO4 structural motifs were predicted to show a remarkably wide range of band energetics (>3 eV variation in the energy of valence band maximum) and characteristics, depending on the M and crystal structure, which is beyond the extent of electronic structured tuning observed in previously studied families of metal oxide photoanodes. While this finding guided experimental discovery of new photoanode materials, explicit experimental verification of the theoretical prediction of the tunable electronic structure of these materials has been lacking to date. In this study, we use X-ray photoelectron spectroscopy and Kelvin probe microscopy to experimentally investigate the electronic structure of M-V-O photoanodes, enabling comparison to theory on a common absolute energy scale. The results confirm the prediction that band edge energies of ternary vanadates vary significantly with metal cations. The valence band variation of approximately 1 eV observed here is larger than that reported in any analogous class of metal oxide semiconductors and demonstrates the promise of tuning the metal oxide electronic structure to enable efficient photoelectrocatalysis of the oxygen evolution reaction and beyond. Because midgap states can hamper realization of the high photovoltage sought by band edge tuning, we analyze the electronic contributions of oxygen vacancies for the representative photoanode V4Cr2O13 to guide future research on the development of high-efficiency metal oxide photoanodes for solar fuel technology.