Degradation of Human Serum Albumin by Infrared Free Electron Laser Enhanced by Inclusion of a Salen-Type Schiff Base Zn (II) Complex

Disassembly of Amyloid Fibril with Infrared Free Electron Laser

Amyloid fibril causes serious amyloidosis such as neurodegenerative diseases. The structure is composed of rigid β-sheet stacking conformation which makes it hard to disassemble the fibril state without denaturants. Infrared free electron laser (IR-FEL) is an intense picosecond pulsed laser that is oscillated through a linear accelerator, and the oscillation wavelengths are tunable from 3 μm to 100 μm. Many biological and organic compounds can be structurally altered by the mode-selective vibrational excitations due to the wavelength variability and the high-power oscillation energy (10-50 mJ/cm²). We have found that several different kinds of amyloid fibrils in amino acid sequences were commonly disassembled by the irradiation tuned to amide I (6.1-6.2 μm) where the abundance of β-sheet decreased while that of α-helix increased by the vibrational excitation of amide bonds. In this review, we would like to introduce the IR-FEL oscillation system briefly and describe combination studies of experiments and molecular dynamics simulations on disassembling amyloid fibrils of a short peptide (GNNQQNY) from yeast prion and 11-residue peptide (NFLNCYVSGFH) from β2-microglobulin as representative models. Finally, possible applications of IR-FEL for amyloid research can be proposed as a future outlook.

Rigid Schiff Base Complex Supermolecular Aggregates as a High-Performance pH Probe: Study on the Enhancement of the Aggregation-Caused Quenching (ACQ) Effect via the Substitution of Halogen Atoms

Optical signals of pH probes mainly driven from the formation or rupture of covalent bonds, whereas the changes in covalent bonds usually require higher chemical driving forces, resulting in limited sensitivity and reversibility of the probes. The exploration of high-performance pH probes has been a subject of intense investigation. Herein, a new pH probe has been developed, with optical property investigation suggesting the probe has excellent signal-to-noise ratio, and fluorescence intensity shows exponential growth, combined with a visible color change, as pH increased from 5.1 to 6.0; Moreover, the probe has outstanding stability and reversibility, with more than 90% of the initial signal intensity remaining after 30 cycles. In order to better understand the special fluorescence behavior of the reported probe, the non-halogenated isomer is introduced for comparison, combined with the results of structural analysis, quantitative calculation and optical experiments, and the possible mechanism of the special supramolecular aggregation-caused quenching effect induced by the halogen atom is discussed.

The Physical Chemistry and Chemical Physics (PCCP) Section of the International Journal of Molecular Sciences in Its Publications: The First 300 Thematic Articles in the First 3 Years

The Physical Chemistry and Chemical Physics Section (PCCP Section) is one of the youngest among the sections of the International Journal of Molecular Sciences (IJMS)-the year 2021 will only mark three years since its inception [...].

Influences of polarizability effect of alkyl group and homoring competition effect of substituents on the NMR spectra of salen-type Schiff base

Salen-type Schiff bases are a kind of important compounds and are widely used. In order to explore the effect of alkyl groups and substituents attached to aromatic ring on the chemical shifts, 63 title compounds were synthesized. Their ¹ H NMR and ¹³ C NMR spectra were obtained; and the effects of the alkyl chain length and substituents on the chemical shifts (δ_H (CHN), δ_C (CHN), δ_H (OH), and δ_C (COH)) were studied. The results show that (1) the alkyl polarizability effect index (PEI) has an important influence on the chemical shifts of the above four atoms, with the increase of PEI, the values of δ_H (CHN) and δc(CHN) decrease, and the values of δ_H (OH) and δ_C (COH) increase. (2) The influence of substituent X attached to aromatic ring on the chemical shift is related to its position by taking OH or CHN as reference. As for the effect of substituent on the chemical shifts, the effect of Hammett constant σ(X)_OH and excited-state substituent parameter σ CC ex X  OH with OH as reference are different from that ofσ(X)_CHN and σ CC ex X  CH  N with CHN as reference, and there is a "homoring competition effect" of the substituent. (3) The effect of the cross-interaction between X and OH on the chemical shift is also significantly different due to the different position of X. Quantitative correlation equations against chemical shifts were built for the four atoms, and the stability and prediction ability of the obtained equations were confirmed by leave-one-out cross validation.

Photo-Tunable Azobenzene-Anthraquinone Schiff Base Copper Complexes as Mediators for Laccase in Biofuel Cell Cathode

Induced chirality (achiral target in chiral matrix such as proteins) sometimes play a useful role in evaluating supramolecular systems involving biomolecules. Enzymatic fuel cells, which generate electricity via enzymatic redox reactions at electrodes hold a significant potential for sustainable power. Bacterial laccase, a multi-copper oxidase, was used in the cathodic compartment of the enzymatic biofuel cells because of its low redox potential. Three new salen Cu(II) complexes were designed and investigated as mediators. The Schiff base ligands consisted of both a redox-active (anthraquinone) and a photochromic (azobenzene) moiety. The interaction between laccase and a mediator was examined with induced circular dichroism (CD) and the docking tool to observe in which of the laccase domains the mediators bind as well as study the photo-induced tuning of both the cis-trans photoisomerization and orientation by the Weigert effect. Both the electrochemical and photochromic properties are also discussed and compared using density functional theory (DFT), time-dependent (TD)-DFT, and docking simulations.