Effect of Guest–Host Hydrogen Bonding on Thermodynamic Stability of Clathrate Hydrates: Diazine Isomers

Guest–host hydrogen bonding strongly affects the physical properties of clathrate hydrate, such as the thermodynamic stability, water dynamics, and dielectric properties, but attempts to quantify the effects of hydrogen bonding on these properties are rare thus far. As a preliminary work, this study investigates methane clathrate hydrates with three diazine isomers, pyrazine, pyrimidine, and pyridazine, which expect nearly the same van der Waals volumes due to their similar molecular shapes and sizes, and their guest–host hydrogen-bonding behaviors. The crystal structures of all three binary diazine + CH₄ hydrate phases were identified as a cubic <i>Fd</i>3̅<i>m</i> structure, including diazine molecules in the 5¹²6⁴ cavity, commonly termed as structure II hydrate, by a high-resolution powder diffraction pattern analysis. The phase equilibrium curves of their clathrate hydrates were obtained by the <i>P–T</i> trajectory of the hydrate formation and dissociation process, and the thermodynamic stability trend was well-explained by the guest–host hydrogen bonding behavior as evaluated by the molecular polarities, proton affinities, and ring-breathing vibration frequencies of the three diazine isomers obtained from Raman spectroscopy. This study provides useful information that contributes to the realization of the expansion of the thermodynamics of clathrate hydrates to include guest–host hydrogen-bonding interactions

Decoding the Parkinson’s Symphony: PARIS, Maestro of Transcriptional Regulation and Metal Coordination for Dopamine Release

Parkin interacting substrate (PARIS) is a pivotal transcriptional regulator in the brain that orchestrates the activity of various enzymes through its intricate interactions with biomolecules, including nucleic acids. Notably, the binding of PARIS to insulin response sequences (IRSs) triggers a cascade of events that results in the functional loss in the substantia nigra, which impairs dopamine release and, subsequently, exacerbates the relentless neurodegeneration. Here, we report the details of the interactions of PARIS with IRSs via classical zinc finger (ZF) domains in PARIS, namely, PARIS(ZF2–4). Our biophysical studies with purified PARIS(ZF2–4) elucidated the binding partner of PARIS, which generates specific interactions with the IRS1 (5′-TATTTTT, Kd = 38.9 ± 2.4 nM) that is positioned in the promoter region of peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α). Mutational and metal-substitution studies demonstrated that Zn(II)–PARIS(ZF2–4) could recognize its binding partner selectively. Overall, our work provides submolecular details regarding PARIS and shows that it is a transcriptional factor that regulates dopamine release. Thus, PARIS could be a crucial target for therapeutic applications

Surface-Originated Weak Confinement in Tetrahedral Indium Arsenide Quantum Dots

While the shape-dependent quantum confinement (QC) effect in anisotropic semiconductor nanocrystals has been extensively studied, the QC in facet-specified polyhedral quantum dots (QDs) remains underexplored. Recently, tetrahedral nanocrystals have gained prominence in III–V nanocrystal synthesis. In our study, we successfully synthesized well-faceted tetrahedral InAs QDs with a first excitonic absorption extending up to 1700 nm. We observed an unconventional sizing curve, indicating weaker confinement than for equivalently volumed spherical QDs. The (111) surface states of InAs QDs persist at the conduction band minimum state even after ligand passivation with a significantly reduced band gap, which places tetrahedral QDs at lower energies in the sizing curve. Consequently, films composed of tetrahedral QDs demonstrate an extended photoresponse into the short-wave infrared region, compared to isovolume spherical QD films