化学•材料最新文献

Highly polar solvents are generally considered to significantly quench the luminous emission of rare-earth doping luminescence materials. In this work, we reported a counterintuitive luminescence phenomenon in Dy/Eu@Gd-MOFs. Their photoluminescence (PL) behaviors in propanol/butanol isomers exhibit trends of emission intensity that inversely correlate with solvent polarity. This phenomenon should not be simplistically ascribed to quenching induced solely by reabsorption, solvent effects, or high-frequency vibrational groups. The structural differences among propanol and butanol isomers result in diversified high-frequency and fingerprint-region vibrational modes. When these vibrations resonate with the critical energy gap, they nonradiative decay in the sensitizer through vibrational coupling, thereby steering energy toward the activator. Time-resolved spectra acquired at different temperatures provide a detailed analysis and evidence for this opinion. These findings give an unconventional interpretation for solvent-induced luminescence quenching in rare-earth luminescence materials, enabling a novel route for modulating their excited states through solvent engineering.

Hydrogen bonds (H-bonds) are central to biomolecular structure and dynamics. Although H-bonds are typically characterized by well-defined proton positions, proton delocalization has been proposed to play a role in facilitating enzyme catalysis and allostery in some systems. Experimentally locating protons is difficult, hampering the study of proton mobility in H-bonds. We used neutron crystallography, atomic resolution X-ray bond length analysis, and large quantum mechanics/molecular mechanics-Born-Oppenheimer molecular dynamics (QM/MM-BOMD) simulations to comprehensively characterize the shared proton/deuteron in a Glu-Asp low-barrier hydrogen bond (LBHB) in the bacterial protein YajL that is a conventional H-bond in the homologous disease-associated human protein DJ-1. X-ray bond length analysis of protiated and perdeuterated DJ-1 and YajL shows no significant effect of deuteron substitution on these carboxylic acid-carboxylate H-bonds but does reveal an effect at the active site glutamic acid near a cysteine thiolate. Residues in an H-bonded network that might favor LBHB formation in YajL were interrogated by the mutation of homologous residues in DJ-1. A distal DJ-1 substitution increases proton delocalization in the Glu-Asp H-bond, demonstrating that mutations within extended H-bond networks can modulate proton transfer barriers in carboxylic acid-carboxylate H-bonds. In addition, proton mobility in the H-bond is correlated with dimer-spanning motions in the QM/MM-BOMD simulations of YajL and DJ-1. Our results show that proton delocalization can be tuned using combined bioinformatic, structural, and computational information, opening the possibility of using engineered proton delocalization as a probe of H-bonding environments and as a tool to test hypotheses about LBHB function.