ABSTRACT
Functionalization is a widely-used strategy to modulate and optimize the properties of materials towards various applications, including sensing, catalysis, and energy generation. While the influence of sulfur-functionalization of carbon materials and oxides like ZnO and TiO2 has been studied, far less research has been devoted to analyzing sulfur-functionalization of CuO and other transition metal oxide nanomaterials. Here, we report sulfur-functionalization of copper(ii) oxide nanosheets synthesized by using a soft-templating procedure, with sulfur-addition based on hydrogen sulfide gas as a source. The resulting sulfur-functionalization does not change the overall crystal structure and morphology of the CuO nanosheets, but leads to a decrease in surface hydroxyl groups. Sulfur induces a semiconductor-to-conductor state transition of the CuO nanosheets, which is supported by computational modeling. The metallic transition results from shifting of the Fermi level into the valence band due to formation of Cu-S bonds on the surface of the CuO nanosheets.
ABSTRACT
Multinucleated skeletal muscle fibers form through the fusion of myoblasts during development and regeneration. Previous studies identified myomaker (Tmem8c) as a muscle-specific membrane protein essential for fusion. However, the specific function of myomaker and how its function is regulated are unknown. To explore these questions, we first examined the cellular localization of endogenous myomaker. Two independent antibodies showed that whereas myomaker does localize to the plasma membrane in cultured myoblasts, the protein also resides in the Golgi and post-Golgi vesicles. These results raised questions regarding the precise cellular location of myomaker function and mechanisms that govern myomaker trafficking between these cellular compartments. Using a synchronized fusion assay, we demonstrated that myomaker functions at the plasma membrane to drive fusion. Trafficking of myomaker is regulated by palmitoylation of C-terminal cysteine residues that allows Golgi localization. Moreover, dissection of the C terminus revealed that palmitoylation was not sufficient for complete fusogenic activity suggesting a function for other amino acids within this C-terminal region. Indeed, C-terminal mutagenesis analysis highlighted the importance of a C-terminal leucine for function. These data reveal that myoblast fusion requires myomaker activity at the plasma membrane and is potentially regulated by proper myomaker trafficking.