Multi-C−C/C−N-Coupled Light-Emitting Aliphatic Terpolymers: N−H-Functionalized Fluorophore Monomers and High-Performance Applications

To circumvent costly fluorescent labeling, five nonconventional, multifunctional, intrinsically fluorescent aliphatic terpolymers ( 1 – 5 ) have been synthesized by C−C/C−N-coupled, solution polymerization of two non-emissive monomers with protrusions of fluorophore monomers generated in situ. These scalable terpolymers were suitable for sensing and high-performance exclusion of Cu^II, logic function, and bioimaging. The structures of the terpolymers, in situ attachment of fluorescent monomers, aggregation-induced enhanced emission, bioimaging ability, and super adsorption were investigated by ¹H and ¹³C NMR, EPR, FTIR, X-ray photoelectron, UV/Vis, and atomic absorption spectroscopy, thermogravimetric analysis, high-resolution transmission electron microscopy, dynamic light scattering, solid-state fluorescence, fluorescence imaging, and fluorescence lifetime measurements, as well as by isotherm, kinetics, and thermodynamic studies. The geometries and electronic structures of the fluorophores and the absorption and emission properties of the terpolymers were examined by DFT, time-dependent DFT, and natural transition orbital analyses. For 1 , 2 , and 5 , the limits of detection were determined to be 1.03×10⁻⁷, 1.65×10⁻⁷, and 1.77×10⁻⁷ m , respectively, and the maximum adsorption capacities are 1575.21, 1433.70, and 1472.21 mg g⁻¹, respectively.     

Hydrogen bond breaking mechanism and water reorientational dynamics in the hydration layer of lysozyme

The mechanism and the rate of hydrogen bond-breaking in the hydration layer surrounding an aqueous protein are important ingredients required to understand the various aspects of protein dynamics, its function, and stability. Here, we use computer simulation and a time correlation function technique to understand these aspects in the hydration layer of lysozyme. Water molecules in the layer are found to exhibit three distinct bond-breaking mechanisms. A large angle orientational jump of the donor water molecule is common among all of them. In the most common ( approximately 80%) bond-breaking event in the layer, the new acceptor water molecule comes from the first coordination shell (initially within 3.5 A of the donor), and the old acceptor water molecule remains within the first coordination shell, even after the bond-breaking. This is in contrast to that in bulk water, in which both of the acceptor molecules involve the second coordination shell. Additionally, the motion of the incoming and the outgoing acceptor molecules involved is not diffusive in the hydration layer, in contrast to their observed diffusive motion in the bulk. The difference in rotational dynamics between the bulk and the hydration layer water molecules is clearly manifested in the calculated time-dependent angular van Hove self-correlation function ( G(theta, t)) which has a pronounced two-peak structure in the layer, and this can be traced to the constrained translational motion in the layer. The longevity of the surrounding hydrogen bond network is found to be significantly enhanced near a hydrophilic residue.     

Diffusion constant of a nonspecifically bound protein undergoing curvilinear motion along DNA

The mechanism of a protein's diffusion along a DNA segment is a subject of much current interest because of the involvement of this diffusion in numerous biological processes, including the recognition of DNA sequences and chemical modifications of DNA. In this work we present a theoretical derivation of the diffusion coefficient of a nonspecifically bound protein, assuming that the protein follows a helical track along the DNA. It is shown that, for protein-sized molecules, the principal contribution to the total translational friction comes from the curvilinear motion along the helix, and this contribution is given by 6pietaRR(oc)(2) + 8pietaR(3), where R is the protein radius, ROC is the distance of separation between the center of mass of the protein and the helical axis of DNA, and eta is the viscosity of the medium. The translational diffusion of the protein along the helical track of DNA is thus predicted to have a nearly R(-3) size dependence, not the R(-1) dependence characterizing simple translational diffusion. It is shown that this expression gives rather good estimates of the translational diffusion coefficient measured in single molecule experiments.     

Wurtzite CuGaS2 with an In-Situ-Formed CuO Layer Photocatalyzes CO2 Conversion to Ethylene with High Selectivity

We present surface reconstruction-induced C−C coupling whereby CO₂ is converted into ethylene. The wurtzite phase of CuGaS_2. undergoes in situ surface reconstruction, leading to the formation of a thin CuO layer over the pristine catalyst, which facilitates selective conversion of CO₂ to ethylene (C₂H₄). Upon illumination, the catalyst efficiently converts CO₂ to C₂H₄ with 75.1 % selectivity (92.7 % selectivity in terms of R_electron) and a 20.6 μmol g⁻¹ h⁻¹ evolution rate. Subsequent spectroscopic and microscopic studies supported by theoretical analysis revealed operando-generated Cu²⁺, with the assistance of existing Cu⁺, functioning as an anchor for the generated *CO and thereby facilitating C−C coupling. This study demonstrates strain-induced in situ surface reconstruction leading to heterojunction formation, which finetunes the oxidation state of Cu and modulates the CO₂ reduction reaction pathway to selective formation of ethylene.     

Vibrational phase relaxation of O–H stretch in bulk water: Role of large amplitude angular jumps and negative cross-correlations among the forces on the O–H bond

The ultrafast vibrational phase relaxation of O–H stretch in bulk water is investigated in molecular dynamics simulations. The dephasing time (T₂) of the O–H stretch in bulk water calculated from the frequency fluctuation time correlation function (C_ω(t)) is in the range of 70–80 femtosecond (fs), which is comparable to the characteristic timescale obtained from the vibrational echo peak shift measurements using infrared photon echo [W.P. de Boeij, M.S. Pshenichnikov, D.A. Wiersma, Ann. Rev. Phys. Chem. 49 (1998) 99]. The ultrafast decay of C_ω(t) is found to be responsible for the ultrashort T₂ in bulk water. Careful analysis reveals the following two interesting reasons for the ultrafast decay of C_ω(t). (A) The large amplitude angular jumps of water molecules (within 30–40 fs time duration) provide a large scale contribution to the mean square vibrational frequency fluctuation and gives rise to the rapid spectral diffusion on 100 fs time scale. (B) The projected force, due to all the atoms of the solvent molecules on the oxygen (F_O(t)) and hydrogen (F_H(t)) atom of the O–H bond exhibit a large negative cross-correlation (NCC). We further find that this NCC is partly responsible for a weak, non-Arrhenius temperature dependence of the dephasing rate.