Monitoring the aggregation of the tau protein is a key protocol for elucidating the pathogenic mechanism of Alzheimer's disease. In the present article, [Ru(phen)2dppzidzo]2+, a “light switch” ruthenium(II) complex, was presented as a new monitoring probe for the aggregation of a tau R3 peptide, the third repeat unit of the tau microtubule-binding domain. Having little impact on the aggregation process, large fixed Stokes shift and small background luminescence made the complex a better probe for monitoring the aggregation process and quantitatively detecting tau filaments compared to thioflavin S, a commonly used fluorescent dye for staining neurofibrillary tangles and monitoring tau aggregation. Furthermore, a long luminescence lifetime of this complex could also expand its potential usage in the detection of tau filaments in the presence of short-lived fluorescent backgrounds.

A piperidine-modified calix[4]arene derivative was synthesized and its structure was confirmed with X-ray diffraction data. UV–visible spectroscopy was used to study its molecular recognition of rare earth ions. The results revealed the calix[4]arene derivative could separate tight metal picrate ion pairs by complexation with the rare earth metal ions in tetrahydrofuran. Resolution of the UV–visible spectra with chemometric methods revealed that the derivative and the rare earth ions Eu3+, Dy3+, and Tb3+ formed ML2 complexes with stability constants of 108.26, 108.29, and 107.41 respectively.Graphical abstractX-ray crystal structure of the piperidine-modified calix[4]arene derivative PD–CA, which has strong molecular recognition effect to some rare earth metals as Eu3+, Dy3+ and Tb3+.Highlights► X-ray data shows piperidine-modified calix[4]arene molecule enclosed three DMF molecules. ► UV spectra revealed it can transform metal picrate tight ion pairs into separated ones. ► Chemometric resolution of the UV spectra revealed the formation of ML2 complexes. ► The stable constants of these complexes were calculated respectively.

This paper presents the preparation of novel thiacalixarene (TCA) covalently functionalized multiwalled carbon nanotubes (MWCNTs) and an enhanced differential pulse anodic stripping voltammetric procedure for the determination of trace amounts of Pb2+ ions, which relies on the selective accumulation of the metals at a TCA-MWCNT-modified glassy carbon electrode. Through a combination of thiacalixerene’s excellent selective recognition and the outstanding electronic properties of MWCNTs, this electrode material shows excellent selectivity and high sensitivity for electrochemical detection of Pb2+ ions. The stripping response is highly linear (R = 0.999) over a Pb2+ concentration range of 2 × 10–10 to 1 × 10–8 mol/L, and the limit of detection is 4 × 10–11 mol/L. Furthermore, the determination of Pb2+ (10–7 mol/L) in the presence of an equal amount of interfering Sn2+ ions yielded well-separated signals. To understand the molecular interaction mechanism between the TCA molecules and metal ions (Pb2+ and Sn2+), theoretical computations were performed. The results demonstrate that the Pb2+/Sn2+ ions could stably adsorb onto the TCA molecules, and there is significant electron delocalization between Pb2+/Sn2+ and sulfur atoms in the TCA molecule.