Mei Hong

Simple whole-cell biodetection and bioremediation of heavy metals based on an engineered lead-specific operon.

A lead-specific binding protein, PbrR, and promoter pbr from the lead resistance operon, pbr, of Cupriavidus metallidurans CH34 was incorporated into E. coli in conjunction with an engineered downstream RFP (red fluorescence protein), which allowed for highly sensitive and selective whole-cell detection of lead ions. The subsequent display of PbrR on the E. coli cell surface permitted selective adsorption of lead ions from solution containing various heavy metal ions. The surface-engineered E. coli bacteria effectively protected Arabidopsis thaliana seed germination from the toxicity of lead ions at high concentrations. Engineering the E. coli bacteria harboring these lead-specific elements from the pbr operon may potentially be a valuable general strategy for biodetection and bioremediation of toxic heavy metal ions in the environment.

Amino acid mediated mesopore formation in LTA zeolites

Mesoporous LTA zeolites have been hydrothermally synthesized by using amino acids as a mesoporogen. Amino acids of carnitine, lysine, or their salt derivatives were able to generate disordered mesopores of 10–20 nm within single crystalline LTA zeolites. Unlike other mesopore generating templates such as surfactants or polymers, the amino acid templates could be easily removed by washing with water, eliminating the energy-intensive calcination step. A possible crystallization process involving three-dimensional assembly of amino acid templates via hydrogen bonding and electrostatic interaction was proposed, as it was found that hydrogen bonding is crucial in hierarchical structure generation, and that hydroxyl group shielded acetyl carnitine yielded no mesopores. The obtained hierarchically mesoporous LTA zeolites exhibited a remarkably higher adsorption capacity (264 mg g−1) for catalase enzyme, and retained greater enzyme activity (>90%) than did conventional LTA.

Core–shell zeolite Y with ant-nest like hollow interior constructed by amino acids and enhanced catalytic activity

Core–shell zeolite Y containing an ant-nest like hollow interior has been synthesized in the presence of natural amino acids. Time-resolved characterization of zeolite samples revealed the gradual development of three-dimensionally interconnected mesoporous channels via an intermediate stage of spatially aligned cavities in the core, which did not follow either a classical or a reversed crystal growth route. Comparative experiments suggested coordinative construction actions of amino acids, the interpenetration of which into the internal weak points of the aluminosilicate framework takes place simultaneously with zeolite crystallization. At the point of complete zeolite growth, amino acids in aggregated domains begin disassembling the zeolite interior forming a network of channels while maintaining the external zeolite shell thickness of 165 nm and morphologically similar to conventional faujasite. The core–shell zeolite Y samples exhibit superior crystallinity and enhanced catalytic activity for Friedel–Crafts benzylation of toluene.

Halloysite nanotube-based electrospun ceramic nanofibre mat: a novel support for zeolite membranes

Some key parameters of supports such as porosity, pore shape and size are of great importance for fabrication and performance of zeolite membranes. In this study, we fabricated millimetre-thick, self-standing electrospun ceramic nanofibre mats and employed them as a novel support for zeolite membranes. The nanofibre mats were prepared by electrospinning a halloysite nanotubes/polyvinyl pyrrolidone composite followed by a programmed sintering process. The interwoven nanofibre mats possess up to 80% porosity, narrow pore size distribution, low pore tortuosity and highly interconnected pore structure. Compared with the commercial α-Al2O3 supports prepared by powder compaction and sintering, the halloysite nanotube-based mats (HNMs) show higher flux, better adsorption of zeolite seeds, adhesion of zeolite membranes and lower Al leaching. Four types of zeolite membranes supported on HNMs have been successfully synthesized with either in situ crystallization or a secondary growth method, demonstrating good universality of HNMs for supporting zeolite membranes.

The small molecule fluorescent probes for gasotransmitters

In the biological system, there are various gas molecules, which play key roles in the system. Specially, NO, CO and H 2 S are recognized as gasotransmitters, involving in the signal transduction and related biological events. Even though remarkable advance in the field has been made these years, the roles of gasotransmitters in the biological systems are not fully understood. For further exploration of the functions of gasotransmitters, fast, high selective and high sensitive analysis and imaging methods are highly required. Development on these methods has become an important cross discipline among chemical biology, bioinorganic chemistry, pharmacy and medicine. The current review focuses on the development of the small molecule fluorescent probes for gasotransmitters in recent years, and hopefully this work would attract the interest of the field.

Facile synthesis of macrocyclic peptide toxins of GpTx-1 and its analogue

GpTx-1, a 34-residue peptide cross-linked by three disulfide bridges, originally isolated from the venom of the tarantula Grammostola porter, and its analogue GpTx-1-71 ([Ala5,Phe6,Leu26,Arg28]GpTx-1) are highly potent pharmaceutical inhibitor candidates to voltage-gated sodium channels, currently in preclinical development. GpTx-1 and its analogue for drug development had previously been obtained by adopting a tedious stepwise solid phase peptide synthesis strategy. Herein, we present a flexible and highly practical strategy by converging three segments based on C-terminal proline residues. This approach provided a reliable and convenient synthetic route which could greatly facilitate GpTx-1 based drug developments for pain relief. Solution NMR structural analysis and electrophysiology evaluation verified the compositional and functional characteristics of the two macrocyclic peptides, which are consistent with previous studies.

Zeolite Y microspheres with perpendicular mesochannels and metal@Y heterostructures for catalytic and SERS applications

The control over particle shape and internal architecture offers promise to better realize catalytic activity and selectivity through structural optimization but remains a challenge for crystalline zeolite frameworks. This work describes a facile one-pot strategy to synthesize uniform zeolite Y microspheres through epitaxial hydrogen bonding and entropic hydrophobic interactions using simple mono-alcohols as zeolite growth modifiers with judicious adjustment of synthesis parameters. The internal architecture can be fine-tuned by the co-presence of L-carnitine which creates hidden defects. Unprecedented wheel-like mesoporous channels are created within the microspheres by acid attack of the induced weak points. Moreover, the combination of zeolite Y microspheres with other materials is expected to impart additional properties due to the hybrid nature of the resulting nanocomposites and the perpendicular mesochannels for alleviated diffusion. As demonstrated, Pd2+-exchanged microspheres exhibit remarkably enhanced catalytic activity and recyclability for C–C coupling reactions, and metal doped Ag@Y microspheres allow for fast sensing by surface-enhanced Raman scattering (SERS), achieving orders of magnitude lower detection limit for water soluble molecules.

The small molecule optical probes for gases with potential medical applications

Various gas molecules exist in the life systems. According to their functions, they can be divided into: signaling gas molecules (gasotransmitters) and non-signaling gas molecules. Similar to the gasotransmitters, the non-signaling gas molecules are of great potential and can be valuable in medical applications, such as serving as specific index for disease status and treating medical conditions. Since their distributions and concentrations are closely related to the health status, selective detection and imaging of these gas molecules is very important. Electrochemistry and mass spectroscopy are traditional methods to detect such gas molecules. However, these methods need expensive instruments and complicated data processing. Recently, optical probes have been emerged as important tools in detecting gas molecules with simple operations. The current review focuses on the recent development on the optical probes for the non-signaling gas molecules.