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Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels1are essential for pacemaking activity and neural signalling2,3. Drugs inhibiting HCN1 are promising candidates for management of neuropathic pain4and epileptic seizures5. The general anaesthetic propofol (2,6-di-iso-propylphenol) is a known HCN1 allosteric inhibitor6with unknown structural basis. Here, using single-particle cryo-electron microscopy and electrophysiology, we show that propofol inhibits HCN1 by binding to a mechanistic hotspot in a groove between the S5 and S6 transmembrane helices. We found that propofol restored voltage-dependent closing in two HCN1 epilepsy-associated polymorphisms that act by destabilizing the channel closed state: M305L, located in the propofol-binding site in S5, and D401H in S6 (refs. 7,8). To understand the mechanism of propofol inhibition and restoration of voltage-gating, we tracked voltage-sensor movement in spHCN channels and found that propofol inhibition is independent of voltage-sensor conformational changes. Mutations at the homologous methionine in spHCN and an adjacent conserved phenylalanine in S6 similarly destabilize closing without disrupting voltage-sensor movements, indicating that voltage-dependent closure requires this interface intact. We propose a model for voltage-dependent gating in which propofol stabilizes coupling between the voltage sensor and pore at this conserved methionine–phenylalanine interface in HCN channels. These findings unlock potential exploitation of this site to design specific drugs targeting HCN channelopathies.

An in-depth study of the class of cationic materials [Ag(4,4′-bipy)+][X–] (where X–= CH3CO2–, NO3–, BF4–, ClO4–, and MnO4–) has led to key insights on the relationship between anion hydration energy, material structure, solubility, and stability. Since these materials show promise for their potential as water remediation tools, understanding their properties in detail is of significant importance. The structure of the starting and ending materials is the main driving force behind the resultant stability and solubility and can be successfully used to predict the ion exchange capabilities. The solubility trend was determined to be, from most soluble to least soluble, X–= CH3CO2–> NO3–∼ BF4–> ClO4–> MnO4–. Kinetics and thermal stability also follow predictable trends but involve additional factors. For instance, the kinetics of NO3–to MnO4–exchange was much slower than expected based on that seen for NO3–to ClO4–. Powder X-ray diffraction (PXRD) and Fourier transform infrared spectroscopy (FTIR) were used to characterize the materials. Solubility was determined by inductively coupled plasma optical emission spectroscopy (ICP-OES) analysis. Ion exchange was analyzed with ion chromatography (IC) and ultraviolet–visible spectroscopy (UV–vis), and thermal stability was determined with thermogravimetric analysis (TGA).

Varied distributions of soil chemicals were compared to known activity areas at the Wilson-Slack site, a 19th century historic farmstead/blacksmith complex in northern Delaware. Calcium and magnesium were not clearly correlated with specific activity areas. Potassium and phosphorus were not correlated with animal penning areas but were correlated with a machine shop/blacksmithing area. Low pH values were correlated with organic-rich midden deposits.