Spherical Silica Functionalized by 2-Naphthalene Methanol Luminophores as a Phosphorescence Sensor

Photoluminescence is known to have huge potential for applications in studying biological systems. In that respect, phosphorescent dye molecules open the possibility to study the local slow solvent dynamics close to hard and soft surfaces and interfaces using the triplet state (TSD: triplet state solvation dynamics). However, for that purpose, probe molecules with efficient phosphorescence features are required with a fixed location on the surface. In this article, a potential TSD probe is presented in the form of a nanocomposite: we synthesize spherical silica particles with 2-naphthalene methanol molecules attached to the surface with a predefined surface density. The synthesis procedure is described in detail, and the obtained materials are characterized employing transmission electron microscopy imaging, Raman, and X-ray photoelectron spectroscopy. Finally, TSD experiments are carried out in order to confirm the phosphorescence properties of the obtained materials and the route to develop phosphorescent sensors at silica surfaces based on the presented results is discussed.

Intramolecular Charge Transfer of 1-Aminoanthraquinone and Ultrafast Solvation Dynamics of Dimethylsulfoxide

The intramolecular charge transfer (ICT) of 1-aminoanthraquinone (AAQ) in the excited state strongly depends on its solvent properties, and the twisted geometry of its amino group has been recommended for the twisted ICT (TICT) state by recent theoretical works. We report the transient Raman spectra of AAQ in a dimethylsulfoxide (DMSO) solution by femtosecond stimulated Raman spectroscopy to provide clear experimental evidence for the TICT state of AAQ. The ultrafast (~110 fs) TICT dynamics of AAQ were observed from the major vibrational modes of AAQ including the νC-N + δCH and νC=O modes. The coherent oscillations in the vibrational bands of AAQ strongly coupled to the nuclear coordinate for the TICT process have been observed, which showed its anharmonic coupling to the low frequency out of the plane deformation modes. The vibrational mode of solvent DMSO, νS=O showed a decrease in intensity, especially in the hydrogen-bonded species of DMSO, which clearly shows that the solvation dynamics of DMSO, including hydrogen bonding, are crucial to understanding the reaction dynamics of AAQ with the ultrafast structural changes accompanying the TICT.

Solvation dynamics-powered structure and function of multi-molecular cellular systems exemplified by non-equilibrium cereblon-degrader-CK1α ternary complex formation

Cellular functions are executed via a form of analog computing that is based on the switchable covalent and non-covalent states of multi-molecular fluxes (i.e., time-dependent species/state concentrations) operating in the non-linear dynamics regime. We and others have proposed that the non-covalent states and state transitions of aqueous fluxes are powered principally by the storage and release of potential energy to/from the anisotropic H-bond network of solvating water (which we refer to as the 'solvation field'), which is a key tenet of a first principles theory on cellular structure and function (called Biodynamics) that we outlined previously. This energy is reflected in water occupancy as a function of solute surface position, which can be probed computationally using WATMD software. In our previous work, we used this approach to deduce the structural dynamics of the COVID main protease, including substrate binding-induced enzyme activation and dimerization, and product release-induced dimer dissociation. Here, we examine: 1) The general relationships between surface composition/topology and solvation field properties for both high and low molecular weight (HMW and LMW) solutes. 2) The general means by which structural dynamics are powered by solvation free energy, which we exemplify via binding between the E3 ligase CUL4A/RBX1/DDB1/CRBN, LMW degraders, and substrates. We propose that degraders organize the substrate binding surface of cereblon toward complementarity with native and neo substrates, thereby speeding the association rate constant and incrementally slowing the dissociation rate constant. 3) Structure-activity relationships (SAR) based on complementarity between the solvation fields of cognate protein-ligand partners exemplified via LMW degraders.