Highly sensitive and selective turn-on fluorescent chemosensors for Hg2+ based on thioacetal modified pyrene.

This work reports a facile strategy for the synthesis of water-soluble fluorescent probes Pyr1 and Pyr2, which have carboxyl and hydroxyl group in the side chain of thioacetal moiety, respectively. Pyr1-2 exhibit exclusively selective turn-on fluorescence response towards Hg2+ over other cations, based on intramolecular charge transfer (ICT) mechanism. Upon addition of Hg2+, the thioacetal moiety in Pyr1-2 can be converted to aldehyde group, which is confirmed by 1H NMR titrations. The detection limits for Pyr1-2 are less than 1.80nM in aqueous media, lower than the maximum allowable level of Hg2+ in drinking water by EPA. Moreover, Pyr2 have been successfully used for fluorescence imaging of Hg2+ in living cells, demonstrating potential application in biological science.

Targeting human telomeric and c-myc G-quadruplexes with alkynylplatinum(II) terpyridine complexes under molecular crowding conditions.

The interactions between alkynylplatinum(II) terpyridine complexes 1-3 and the G-quadruplex DNA, including c-myc and telomeric quadruplex DNA, are investigated both in dilute solution and under molecular crowding conditions. The UV-vis absorption spectroscopy, circular dichroism and molecular docking studies suggest that 1-3 associate with telomeric and c-myc G-quadruplexes via groove binding, and electrostatic interactions. Experimental studies indicate that under molecular crowding conditions (in the presence of 40wt% PEG 200), 1-2 show weak affinity for c-myc, while 3 still displays high affinity and selectivity for c-myc. On the other hand, 1-3 act as efficient and selective ligand for telomeric quadruplex DNA under molecular crowding conditions. The complex 3 exhibits excellent cytotoxicity against A549, K562 and SGC-7901, with IC50 values that are 35.0-fold, 10.0-fold, and 12.1-fold lower than the values of cisplatin under the same conditions, respectively.

The effect of amphiphilic polymers on the association, morphology and photophysical properties of hypocrellin coordination polymer/fullerene assemblies.

The yttrium coordination polymer of pyrene modified hypocrellin A (Y(3+)-PyrHA) is synthesized and characterized. The methoxydiglycol malonate modified fullerene can be included in the cavity of Y(3+)-PyrHA in organic solution and buffer solution containing amphiphilic polymers, such as polyvinyl pyrrolidone (PVP), pluronic F127 and P123. The interaction between an amphiphilic polymer and Y(3+)-PyrHA plays an important role in controlling the size and morphology of Y(3+)-PyrHA/fullerene. TEM images of Y(3+)-PyrHA/fullerene in 1% F127 and P123 show nanoparticles in the size range 10-60 nm, while TEM images of Y(3+)-PyrHA/fullerene in 1% PVP display large-scale aggregation. Singlet oxygen is generated by irradiation of the polymer solution of Y(3+)-PyrHA/fullerene in the presence of oxygen. The electron paramagnetic resonance (EPR) spin trapping and 9,10-dimethoxyanthracene-2-sulfonic acid sodium salt (MAS) photooxidation results suggest that in 1% P123 solution Y(3+)-PyrHA/fullerene exhibits a higher singlet oxygen quantum yield than Y(3+)-PyrHA and the corresponding fullerene.

Synthesis and photophysical properties of a supramolecular host-guest assembly constructed by fullerenes and tryptamine modified hypocrellin.

The metal coordination polymer of hypocrellin A bearing tryptamine motif (M-DTrpHA) can include fullerene via a two-point interaction, involving π-π stacking and electron donor-acceptor interaction. The 1:1 host-guest system M-DTrpHA/fullerene exhibits a moderate association constant K(a) (6.62 × 10(4) to 6.46 × 10(5) M(-1)). Both of the metal ions in M-DTrpHA and the substituents connected to the fullerene core play important roles in stabilizing the M-DTrpHA/fullerene complex. Transient absorption spectral and NIR absorption spectral results demonstrate that, in the M-DTrpHA/fullerene system, efficient photoinduced electron transfer from the tryptamine group in M-DTrpHA to fullerene may occur, resulting in a long-lived fullerene anion radical. The observed order of quantum yield (Φ(ET)(T)) and rate constants (K(ET)(T)) for electron transfer via (3)C(60)(*) is Y(3+)-DTrpHA > La(3+)-DTrpHA > DTrpHA, consistent with their binding ability to C(60). The nanostructure of M-DTrpHA is rearranged to form an interpenetrating network after interaction with fullerene.

Characterization of Xenopus egg membrane microdomains containing uroplakin Ib/III complex: roles of their molecular interactions for subcellular localization and signal transduction.

A single-transmembrane protein uroplakin III (UPIII) and its tetraspanin binding-partner uroplakin Ib (UPIb) are members of the UP proteins that were originally identified in mammalian urothelium. In Xenopus laevis eggs, these proteins: xUPIII and xUPIb, are components of the cholesterol-enriched membrane microdomains or "rafts" and involved in the sperm-egg membrane interaction and subsequent egg activation signaling via Src tyrosine kinase at fertilization. Here, we investigate whether the xUPIII-xUPIb complex is in close proximity to CD9, a tetraspanin that has been implicated in the sperm-egg fusion in the mouse and GM1, a ganglioside typically enriched in egg rafts. Preparation of the egg membrane microdomains using different non-ionic detergents (Brij 98 and Triton X-100), chemical cross-linking, co-immunoprecipitation, in vitro kinase assay and in vitro fertilization experiments demonstrated that GM1, but not CD9, is in association with the xUPIII-xUPIb complex and contributes to the sperm-dependent egg activation. Transfection experiments using HEK293 cells demonstrated that xUPIII and xUPIb localized efficiently to the cholesterol-dependent membrane microdomains when they were co-expressed, whereas co-expression of xUPIII and CD9, instead of xUPIb, did not show this effect. Furthermore, xUPIII and xUPIb were shown to suppress kinase activity of the wild type, but not a constitutively active form of, Xenopus Src protein co-expressed in HEK293 cells. These results provide novel insight into the molecular architecture of the egg membrane microdomains containing xUPIII, xUPIb and Src, which may contribute to the understanding of sperm-egg interaction and signaling during Xenopus fertilization.

Uroplakin III, a novel Src substrate in Xenopus egg rafts, is a target for sperm protease essential for fertilization.

In a previous study, we identified Xenopus egg uroplakin III (xUPIII), a single-transmembrane protein that localized to lipid/membrane rafts and was tyrosine-phosphorylated upon fertilization. An antibody against the xUPIII extracellular domain abolishes fertilization, suggesting that xUPIII acts not only as tyrosine kinase substrate but also as a receptor for sperm. Previously, it has been shown that the protease cathepsin B can promote a transient Ca2+ release and egg activation as seen in fertilized eggs (Mizote, A., Okamoto, S., Iwao, Y., 1999. Activation of Xenopus eggs by proteases: possible involvement of a sperm protease in fertilization. Dev. Biol. 208, 79-92). Here, we show that activation of Xenopus eggs by cathepsin B is accompanied by tyrosine phosphorylation of egg-raft-associated Src, phospholipase Cgamma, and xUPIII. Cathepsin B also promotes a partial digestion of xUPIII both in vitro and in vivo. A synthetic xUPIII-GRR peptide, which contains a potential proteolytic site, inhibits the cathepsin-B-mediated proteolysis and tyrosine phosphorylation of xUPIII and egg activation. Importantly, this peptide also inhibits sperm-induced tyrosine phosphorylation of xUPIII and egg activation. Protease activity that digests xUPIII in an xUPIII-GRR peptide-sensitive manner is present in Xenopus sperm. Several protease inhibitors, which have been identified to be inhibitory toward Xenopus fertilization, are shown to inhibit sperm-induced tyrosine phosphorylation of xUPIII. Uroplakin Ib, a tetraspanin UP member, is found to be associated with xUPIII in egg rafts. Our results highlight novel mechanisms of fertilization signaling by which xUPIII serves as a potential target for sperm protease essential for fertilization.