Zhong-Lin Lu

Methods for the detection and determination of nitrite and nitrate: A review

Various techniques for the determination of nitrite and/or nitrate developed during the past 15 years were reviewed in this article. 169 references were covered. The detection principles and analytical parameters such as matrix, detection limits and detection range of each method were tabulated. The advantages and disadvantages of various methods were evaluated. In comparison to other methods, spectrofluorimetric methods have become more attractive due to its facility availability, high sensitivity and selectivity, low limits of detection and low-cost.

Persistent Organic Nanopores Amenable to Structural and Functional Tuning

Rigid macrocycles 2, which share a hybrid backbone and the same set of side chains while having inner cavities with different inward-pointing functional groups, undergo similar nanotubular assembly as indicated by multiple techniques including (1)H NMR, fluorescence spectroscopy, and atomic force microscopy. The formation of tubular assemblies containing subnanometer pores is also attested by the different transmembrane ion-transport behavior observed for these macrocycles. Vesicle-based stopped-flow kinetic assay and single-channel electrophysiology with planar lipid bilayers show that the presence of an inward-pointing functional (X) group in the inner cavity of a macrocyclic building block exerts a major influence on the transmembrane ion-transporting preference of the corresponding self-assembling pore. Self-assembling pores with inward-pointing amino and methyl groups possess the surprising and remarkable capability of rejecting protons but are conducive to transporting larger ions. The inward-pointing groups also resulted in transmembrane pores with a different extent of positive electrostatic potentials, leading to channels having different preferences for transporting chloride ion. Results from this work demonstrate that synthetic modification at the molecular level can profoundly impact the property of otherwise structurally persistent supramolecular assemblies, with both expected tunability and suprisingly unusual behavior.

Effective and reversible DNA condensation induced by bifunctional molecules containing macrocyclic polyamines and naphthyl moieties

A series of bifunctional molecules containing macrocyclic polyamines [12]aneN(3) and naphthyl moieties 1-3(a, b) have been designed and synthesized through efficient N-alkylation and copper-mediated alkyne-azide click reactions. Experiments on gel electrophoresis, dynamic light scattering and atomic force microscopy confirmed that 2b and 3b with two [12]aneN(3) units efficiently induced the DNA condensation at the concentration of 120 μM in less than 5 min. The condensation mechanism was studied by EB displacement fluorescence spectra, viscosity titration, and ionic strength effects. The condensation process was found to be reversible, and the presence of both naphthyl and [12]aneN(3) units in the molecules was proved to be necessary for the effective DNA condensation inductions. Cytotoxicity assay showed that the presence of triazole moieties can result in lower toxicity.

Controlling Ion-Sensing Specificity of N-Amidothioureas: From Anion-Selective Sensors to Highly Zn2+-Selective Sensors by Tuning Electronic Effects

N-Amidothioureas bearing nitro groups showed different sensitivities to various anions, while those with methoxy moieties exhibited the sensitive and selective fluorescence turn-on property for Zn(2+) in aqueous solution and in cells. N-Amidothioureas can therefore be adjusted from anion-selective sensors to Zn(2+)-selective sensors by varying the electronic effects of their substituents.

Syntheses of bifunctional molecules containing [12]aneN 3 and carbazol moieties as effective DNA condensation agents

Bifunctional molecules containing macrocyclic polyamine [12]aneN3 and carbazol units, 1–4, have been efficiently synthesized and fully characterized. Through gel electrophoresis, atomic force microscopy, and dynamic light scattering experiments, compounds 3 and 4b bearing both [12]aneN3 and carbazol moieties showed effective DNA condensation ability at the concentration of 80 μM. Investigations from EB displacement fluorescence spectra, viscosity titration, and ionic strength effects revealed that the effective DNA condensation comes from the appropriate combination of carbazol and [12]aneN3 units in the bifunctional molecules, and the DNA condensation process is reversible. The incorporation of triazole units in the molecules clearly reduced the cytotoxicity.

D–A–D type chromophores with aggregation-induced emission and two-photon absorption: synthesis, optical characteristics and cell imaging

Three novel D–A–D type chromophores, consisting of substituted triphenylamine and aggregation-induced emission (AIE)-active tetraphenylethylene moieties, 1 (with two ethoxy groups), 2 (with two hydroxyl groups), 3 (non-substituted), were synthesized and characterized. Their one-photon excited fluorescence (OPEF) quantum yields (ΦF) and lifetimes (τ) in organic solutions increased with the increase of the electron-donating ability of the substituents on the triphenylamine unit, i.e., 1 > 2 > 3. By means of dynamic light scattering and scanning electron microscopy, it was found that the higher hydrophobicity of 1 resulted in larger particle sizes and a strong AIE effect. 1 and 2 showed good two-photon excited fluorescence (TPEF) and two-photon absorption cross-sections (σ) (4230 and 4004, respectively) and proved to have good biocompatibility. Both compounds 1 and 2 were successfully applied in cell imaging based on their OPEF and TPEF properties. This work clearly implies that these chromophores can be finely tuned for different optical properties and applications through varying the electron-donating ability, hydrophobicity, and cytotoxicity of the substituents.

Fluorescent sensors based on [12]aneN3-modified BODIPY: Discrimination of different biological thiols in aqueous solution and living cells.

Two fluorescent probes, 1 and 2, derived from borondipyrromethene (BODIPY) modified with macrocyclic polyamine [12]aneN3, were synthesized and applied in the discrimination of cysteine (Cys), homocysteine (Hcy), and glutathione (GSH) with absorption and fluorescent spectroscopy in comparison. It was found that Boc-protected 1 showed highly sensitive and selective recognition of GSH over Cys and Hcy; while probe 2 was able to distinguish the three different thiols due to their different reactivities. With its water-solubility, rapid responsiveness, high sensitivity and low cytotoxicity, probe 2 was successfully applied in the fast detection of three biothiols in living cells.

Hexakis(m-phenylene ethynylene) Macrocycles with Multiple H-Bonding Side Chains and Modified Cavities: Altered Stacking Strength and Persistent Tubular Assembly

Hexakis(m-phenylene ethynylene) macrocycles 1 bearing multiple hydrogen-bonding side chains and containing inner cavities modified with different functional groups are synthesized based on Pd-catalyzed (Sonogashira) coupling of monomeric building blocks to trimeric precursors that are recombined and coupled to give macrocycles with different substitution patterns of inward-pointing groups. Examining four representative macrocycles indicates that they all undergo the same helical tubular assembly previously observed for macrocycle 1a but with different stacking strengths.

Synthesis of [12]aneN3-dipeptide conjugates as metal-free DNA nucleases.

In this Letter, a series of macrocyclic polyamine [12]aneN(3)-dipeptide conjugates as a new type of metal-free nucleases were synthesized and fully characterized with (1)H NMR, (13)C NMR, IR, and HR-MS. Results indicate that these conjugates can bind to calf thymus DNA mainly through electrostatic interaction and can cleave the plasmid DNA at 200 μM (pH 7.2, 37°C), with an acceleration of 10(6)-fold via hydrolytic pathway.

Gemini-Type Tetraphenylethylene Amphiphiles Containing [12]aneN3 and Long Hydrocarbon Chains as Nonviral Gene Vectors and Gene Delivery Monitors

Four gemini amphiphiles decorated with triazole-[12]aneN3 as the hydrophilic moiety and various long hydrocarbons as hydrophobic moieties, 1-4, were designed to form micelles possessing the aggregation-induced emission (AIE) property for gene delivery and tracing. All four amphiphiles give ultralow critical micelle concentrations, are pH-/photostable and biocompatible, and completely retard the migration of plasmid DNAs at low concentrations. The DNA-binding abilities of the micelles were fully assessed. The coaggregated nanoparticles of 1-4 with DNAs could convert back into AIE micelles. In vitro transfections indicated that lipids 1 and 2 and their originated liposomes bearing decent delivering abilities have great potentials as nonviral vectors. Finally, on the basis of the transfection and the transitions between condensates and micelles, lipid 2 was singled out as the first example for real-time tracing of the intracellular deliveries of nonlabeled DNA, which provides spatiotemporal messages about the processes of condensate uptake and DNA release.