Biocatalytic Implant of Pt Nanoclusters into Glucose Oxidase: A Method to Electrically Wire the Enzyme and to Transform It from an Oxidase to a Hydrogenase

The enzyme glucose oxidase (GOx) reduces, in the presence of glucose and under anaerobic conditions, PtCl₆²⁻ to Pt nanoclusters (NCs) that are implanted in the protein. The assembly of the Pt NC/GOx hybrid on a dithiol monolayer yields an electrically contacted enzyme electrode, and the bioelectrocatalytic oxidation of glucose is activated (turnover rate ca. 2780 ± 70 s⁻¹). The Pt NC/GOx hybrid is also used, under anaerobic conditions, as a biocatalyst for H₂ evolution

Entropic Attraction Condenses Like-Charged Interfaces Composed of Self-Assembled Molecules

Like-charged solid interfaces repel and separate from one another as much as possible. Charged interfaces composed of self-assembled charged-molecules such as lipids or proteins are ubiquitous. The present study shows that although charged lipid-membranes are sufficiently rigid, in order to swell as much as possible, they deviate markedly from the behavior of typical like-charged solids when diluted below a critical concentration (ca. 15 wt %). Unexpectedly, they swell into lamellar structures with spacing that is up to four times shorter than the layers should assume (if filling the entire available space). This process is reversible with respect to changing the lipid concentration. Additionally, the research shows that, although the repulsion between charged interfaces increases with temperature, like-charged membranes, remarkably, condense with increasing temperature. This effect is also shown to be reversible. Our findings hold for a wide range of conditions including varying membrane charge density, bending rigidity, salt concentration, and conditions of typical living systems. We attribute the limited swelling and condensation of the net repulsive interfaces to their self-assembled character. Unlike solids, membranes can rearrange to gain an effective entropic attraction, which increases with temperature and compensates for the work required for condensing the bilayers. Our findings provide new insight into the thermodynamics and self-organization of like-charged interfaces composed of self-assembled molecules such as charged biomaterials and supramolecular assemblies that are widely found in synthetic and natural constructs