Pak-Ho Chan

Benzothiazole-substituted benzofuroquinolinium dye: a selective switch-on fluorescent probe for G-quadruplex

A new switch-on fluorescent probe containing the natural product cryptolepine analogue benzofuroquinolinium moiety (binding scaffold) and a benzothiazole moiety (signalling unit) shows a remarkable fluorescence enhancement selective for the G-quadruplex nucleic acid structure. Binding studies revealed that the highly selective response of the fluorescent probe arises from end-stack binding to G-quadruplex.

Identification of a New Class of FtsZ Inhibitors by Structure-Based Design and in Vitro Screening

The Filamenting temperature-sensitive mutant Z (FtsZ), an essential GTPase in bacterial cell division, is highly conserved among Gram-positive and Gram-negative bacteria and thus considered an attractive target to treat antibiotic-resistant bacterial infections. In this study, a new class of FtsZ inhibitors bearing the pyrimidine-quinuclidine scaffold was identified from structure-based virtual screening of natural product libraries. Iterative rounds of in silico studies and biological evaluation established the preliminary structure-activity relationships of the new compounds. Potent FtsZ inhibitors with low micromolar IC₅₀ and antibacterial activity against S. aureus and E. coli were found. These findings support the use of virtual screening and structure-based design for the rational development of new antibacterial agents with innovative mechanisms of action.

Surface properties of polyester fabrics induced by excimer laser processing

Abstract Induced properties of polyester fabric due to irradiation of excimer laser, including surface luster, wettability, dyeability and stability of the resulting micro-structures in the fibre surface are investigated. After excimer laser treatment, the irradiated polyester fabric samples exhibit better hydrophobicity at room temperature and the dyeability of the fabric is improved. The study on surface reflectance shows that excimer laser treatment results in a reduction and a more uniform distribution of fabric glossiness: the treated polyester fabric samples have a silk-like appearance. Scanning electron microscope (SEM) observation reveals that the resulting structures on the fibre surface is virtually unaffected by hot air and hot water and is chemically as stable as its untreated counterpart.

Trityl-derivatized carbohydrates immobilized on a polystyrene microplate

Carbohydrate biosensors, including carbohydrate arrays, are attracting increased attention for the comprehensive and high-throughput investigation of protein-carbohydrate interactions. Here, we describe an effective approach to fabricating a robust microplate-based carbohydrate array capable of probing protein binding and screening for inhibitors in a high-throughout manner. This approach involves the derivatization of carbohydrates with a trityl group through an alkyl linker and the immobilization of the trityl-derivatized carbohydrates (mannose and maltose) onto microplates noncovalently to construct carbohydrate arrays. The trityl carbohydrate derivative has very good immobilization efficiency for polystyrene microplates and strong resistance to aqueous washing. The carbohydrate arrays can probe the interactions with the lectin Concanavalin A and screen this protein for the well-known inhibitors methyl alpha-D-mannopyranoside and methyl alpha-D-glucopyranoside in a high-throughput manner. The method described in this paper represents a convenient way of fabricating robust noncovalent carbohydrate arrays on microplates and offers a convenient platform for high-throughput drug screening.

A tricarbonyl rhenium(I) complex with a pendant pyrrolidinium moiety as a robust and recyclable catalyst for chemical fixation of carbon dioxide in ionic liquid

A novel Re(I) complex covalently anchored with a pyrrolidinium moiety was successfully synthesized and used as an efficient and recyclable catalyst in the cycloaddition of CO2 with epoxides under mild reaction conditions to give excellent isolated yield and selectivity of cyclic carbonates in pyrrolidinium ionic liquid.

Amyloid fibrils as rapid and efficient nano-biosorbents for removal of dye pollutants

This study demonstrates the promising role of amyloid fibrils as rapid and efficient nano-biosorbents for removal of dye pollutants in water. Amyloid fibrils of hen lysozyme, which are highly ordered protein nanofibers, can be prepared easily in one step under green and mild aqueous conditions. Results of zeta-potential and fluorescence measurements indicate that lysozyme nanofibers bear positive/negative charges and hydrophobic regions along their fibrillar structures. These special structural properties enable lysozyme nanofibers to adsorb the anionic dyes Reactive Black 5 and Acid Blue 29 and the cationic dye Victoria Blue B rapidly and efficiently, presumably through multiple intermolecular interactions (e.g. electrostatic attraction and hydrophobic interaction); the adsorption equilibrium for these dyes can be reached within 15 min, and a dye removal efficiency of over 60% can be achieved in industrial wastewater. Lysozyme nanofibers are also compatible with magnetite nanoparticles to form magnetic nanofibers, which can provide rapid and convenient dye removals through the application of an external magnetic field and maintain high dye removal efficiency (92–99%) after undergoing 20 cycles of desorption.

A Switch‐On Fluorescence Assay for Bacterial β‐Lactamases with Amyloid Fibrils as Fluorescence Enhancer and Visual Tool

Herein is described the development of a novel switch-on fluorescence assay for detecting β-lactamases. The fluorescence assay comprises two components: solid beads coated with a β-lactam antibiotic, which is linked to an environment-sensitive fluorophore (dansylaminothiophenol, DTA), and amyloid fibrils of hen lysozyme (acting as fluorescence enhancer and visual tool). In the presence of the clinically significant TEM-1 β-lactamase, the DTA-antibiotic complex on the solid beads is hydrolyzed, thus releasing the DTA dye into solution. The DTA dye is only weakly fluorescent in solution but gives strong green fluorescence upon binding to lysozyme fibrils. These strongly fluorescent DTA-bound fibrils can be easily visualized by the naked eye upon illumination of the sample with a simple UV lamp. The fluorescence assay can detect TEM-1 at low concentration (0.01 nM). In contrast, no observable fluorescence appears when the fluorescence assay is performed on samples without the TEM-1 β-lactamase.

Ethylenediamine-modified amyloid fibrils of hen lysozyme with stronger adsorption capacity as rapid nano-biosorbents for removal of chromium(VI) ions

We report the development of ethylenediamine-modified amyloid fibrils (nanofibers) of hen lysozyme as rapid nano-biosorbents for removing toxic chromium(VI) ions in water. Ethylenediamine was covalently conjugated with the –COO− groups on positively charged lysozyme nanofibers through the formation of amide bonds using N-hydroxysuccinimide (NHS) and 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) as the activating agents. Mass spectrometric results indicate that about 42% of lysozyme molecules in nanofibers are conjugated with ethylenediamine. The resulting ethylenediamine-modified lysozyme nanofibers, which have higher net positive charges as a result of the reduction in the number of –COO− groups through ethylenediamine conjugations, can adsorb Cr(VI) (existing as negatively charged chromate) rapidly in water and have stronger Cr(VI) adsorption capacity in acidic, neutral and alkaline media (pH 3.0–11.0) compared to unmodified lysozyme nanofibers. Results of the Langmuir isotherm model reveal that the adsorption sites on modified lysozyme nanofibers have higher affinity for Cr(VI) with respect to those on unmodified lysozyme nanofibers. Ethylenediamine-modified lysozyme nanofibers can maintain their Cr(VI) removal efficiency (∼60%) after undergoing a series of desorption steps using NaCl as the desorbing agent. Ethylenediamine/–COO− conjugations can increase the adsorption capacities of lysozyme nanofibers for Cr(VI) in industrial wastewater (qe = 0.68 mg g−1) and river water (qe = 1.90 mg g−1) compared to those of unmodified lysozyme nanofibers (qe = 0.40 and 1.44 mg g−1 for industrial wastewater and river water, respectively).

Covalent immobilization of carbohydrates on sol–gel-coated microplates

Carbohydrate microarrays have attracted increasing attention in recent years because of their ability to monitor biologically important protein-carbohydrate interactions in a high-throughput manner. Here we have developed an effective approach to immobilizing intact carbohydrates directly on polystyrene microtiter plates coated with amine-functionalized sol-gel monolayers. Lectin binding was monitored by fluorescence spectroscopy using these covalent arrays of carbohydrates that contained six mono- and di-saccharides on the microplates. In addition, binding affinities of lectin to carbohydrates were also quantitatively analyzed by determining IC(50) values of lectin-specific antibody with these arrays. Our results indicate that microplate-based carbohydrate arrays can be efficiently fabricated by covalent immobilization of intact carbohydrates on sol-gel-coated microplates. The microplate-based carbohydrate arrays can be applied for screening of protein-carbohydrate interactions in a high-throughput manner.

Correction: Amyloid fibrils as rapid and efficient nano-biosorbents for removal of dye pollutants

Correction for ‘Amyloid fibrils as rapid and efficient nano-biosorbents for removal of dye pollutants’ by Wai-Hong Leung et al., RSC Adv., 2015, 5, 90022–90030.