A generalized formulation of ion-π electron interactions: role of the nonelectrostatic component and probe of the potential parameter transferability

The intermolecular potentials for hexafluorobenzene (HFBz) and 1,3,5-trifluorobenzene (TFBz) interacting with alkali (M(+); M = Li, Na, K, Rb, Cs) and halogen (X(-); X = F, Cl, Br, I) ions are provided as a combination of electrostatic and nonelectrostatic terms. The ion-HFBz and ion-TFBz electrostatic components are formulated as a sum of Coulombic potentials associated with the interactions between the ion charge and point charges on the molecular frame, whose distributions are consistent with the permanent quadrupole moment of HFBz and TFBz, respectively. The corresponding nonelectrostatic components are represented as a sum of effective potential functions, each one having a specific physical meaning, related to ion-molecular bond pair interactions. In the present paper, we test the transferability of the ion-bond potential parameters. Moreover, the powerfulness of the model is analyzed by comparing predicted binding energies and equilibrium geometries for the family of M(+)-HFBz, X(-)-HFBz, M(+)-TFBz, and X(-)-TFBz systems with available ab initio results.     

A fluorescence probe study of the mixed surfactant vesicles

Vesicle can be prepared from aqueous mixtures of simple commercially available, single-tailed canonic and anionic surfactants. In this work, the I3/I1 value, Ie/ Im value, and fluorescence lifetime of pyrene in different systems (see the preparation of samples) were determined. Hie essential affecting factors in the formation of vesicle can be deduced from the obtained results. It showed that large vesicle must form naturally before sonication in 0.082 M octyltrimethylammonium bromide and sodium laurate pH = 9.2 aqueous solution. While after sonication, only small vesicle exists, which can be proved further through electron microscope.     

The role of probe–probe interactions on the hybridization of double-stranded DNA targets onto DNA-modified magnetic microparticles

In this work, we have studied the effect of different probe lengths and surface densities on the hybridization of a 181-bp polymerase chain reaction product to probes tethered onto magnetic microparticles. Hybridization was shown to be favored by longer probes but only at probe surface densities where probe-to-probe interactions are absent. From these results, a simple rule was inferred for determining maximum surface densities above which hybridization signals decreased. According to this rule, if the average surface area occupied by an immobilized probe (Σ) is larger than the projected surface area of each tethered probe molecule (S _ss ), hybridization efficiency increases with surface density, whereas the reverse occurs when Σ −  S _ss  < 0.     

Synthesis of a flavonoid fluorescent probe for the detection of sulfur dioxide derivatives and cell imagingEI北大核心CSCD

A novel fluorescent probe HMQC was synthesized for HSOf detection by coupling flavonoid derivatives with 3-quinoline salt. In PBS buffer solution, the probe showed high selectivity, good sensitivity (58 nmol/L) and rapid response (150 s) for the detection of HSO3−. The possible sensing mechanism of the probe was discussed by nuclear magnetic hydrogen spectroscopy, mass spectrometry and theoretical calculation, indicating that the addition reaction between HSO3− and the C=C bond of the probe led to the fluorescence enhancement. The probe HMQC could be used for the detection of HSO3− in living cells, making it to be a promising tool for delecting HSO3−. © 2023, Youke Publishing Co.,Ltd. All rights reserved.     

Characterization of the water-soluble comb–linear interpolyelectrolyte nanoaggregates by Monte Carlo simulations and fluorescence probe techniques

Insight into the microstructure of the aggregate formed by the Coulombic interaction between the cationic comb copolymer poly(acrylamide-co-[3-(methacryloylamino) propyl]trimethylammonium chloride)-graft-polyacrylamide, P(AM-co-MAPTAC)-g-PAM, and the anionic polyelectrolyte poly(sodium acrylate), NaPA, was provided by Monte Carlo simulations and the fluorescence probe technique. The computational outcome revealed a core–shell organization of the comb copolymer, with an indefinite boundary between the inner and outer region. The copolymer had a spherical shape, and its backbone moiety adopted an extended conformation. The spatial extension of the copolymer and the core region contracted when association with the oppositely charged polyelectrolyte occurred. The fluorescence probes 2-dimethylamino-6-propionylnaphthalene, PRODAN, and 1-anilinonaphthalene-8-sulfonic acid, ANS, exhibited a specific interaction with the complex. A lower polarity in the polyelectrolyte complex as compared with the water polarity was sensed by the fluorescence probes, a feature which was attributed to a certain compaction of the AM-co-MAPTAC part of comb copolymer.     

Synthesis and spectral properties of π-extended rhodamine hydrazide probe for the detection of Hg2+EI北大核心CSCD

The π-extended rhodamine derivative aminobenzopyranoxanthene ABPX was synthesized by condensation of 2-4-diethylamino-2-hydroxybenzoylbenzoic acid with resorcinol in H2 SO4 solutionthen the derivative reacted with hydrazine monohydrate to obtain ABPX-hydrazideABPX-hyand its structure was characterized by ESI-MSFT-IR and NMR spectroscopy. The UV-Vis adsorption spectra at 500-600 nm tended to increase in the presence of Hg2+ in ABPX-hy ethanol solutionand the color of the solution changed from colorless to pink and gradually deepenedenabling visual colorimetric detection of Hg2+ by naked eye. Under the coexistence of 10 common metal ionsthe recognition of Hg2+ at 533 nm showed good anti-interference sensing performance. The absorption intensity of ABPX-hy had a good exponential relationship with the addition of Hg2+. The continuous coordination of Hg2+ to the N and O binding sites of ABPX-hy formed 21 stoichiometry of the ABPX-hy-Hg2+ complex. The orbital energy and spatial distribution levels of the closed-cycle to the open-cycle form were obtained by density functional theoryDFTcalculation. © 2022, Youke Publishing Co.,Ltd. All rights reserved.     

A multifunctional probe based on the use of labeled aptamer and magnetic nanoparticles for fluorometric determination of adenosine 5’-triphosphate

A multifunctional fluorescent probe is synthesized for the determination of adenosine 5′-triphosphate (ATP). The 6-carboxyfluorescein-labeled aptamer (FAM-aptamer) was bound to the surface of magnetite nanoparticles coated with polydopamine (Fe₃O₄@PDA) by π-π stacking interaction to form the multifunctional probe. The probe has three functions including recognition, magnetic separation, and yielding a fluorescent signal. In the presence of ATP, FAM-aptamer on the surface of the probe binds to ATP and returns to the solution. Thus, the fluorescence of the supernatant is enhanced and can be related to the concentration of ATP. Fluorescence intensities were measured at excitation/emission wavelengths of 494/526 nm. Response is linear in the 0.1–100 μM ATP concentration range, and the detection limit is 89 nM. The probe was applied to the quantitation of ATP in spiked human urine and serum samples, with recoveries ranging between 94.8 and 102%.

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Graphical abstract A multifunctional fluorescent probe based on the use of FAM-aptamer and Fe₃O₄@PDA is described for the determination of ATP in spiked human urine and serum samples. FAM-aptamer: 6-carboxyfluorescein-labeled aptamer; Fe₃O₄@PDA: magnetite nanoparticles coated with polydopamine. ATP: adenosine 5′-triphosphate.

     

Studies of the dissociation and the protonation of TB-chlorosulphophenol

The dissociation constant of each step for TB-chlorosulphophenol has been determined by potentiometric method, and the thermodynamic constants, △G°, △H° and △S°, of the dissociation process have been calculated. The protonation constants were measured by the spectrophotometric method. The pH values of various forms of anions of the chromogenic reagent at their concentrations were also calculated.     

Synthesis and application of rhodamine-based fluorescent probe dyes with spacer linker arm

When rhodamine-based fluorescent probe dyes are used to track target molecules they always perturb the behavior of target molecules because of steric hindrance effect. In order to minimize potential steric problems, a kind of rhodamine-based fluorescent probe dye with spacer linker arm was designed and synthesized and its application in immunofluorescence histochemistry was investigated.     

The synthesis and study of the fluorescent probe for sensing Cu2＋ based on a novel coumarin Schiff-base

A novel, fluorescent probe was synthesized from 2,4-dihydroxybenzaldehyde and 8-hydroxyquinoline for sensing Cu2+by the naked eye. The structure was confirmed by IR, MS,1H NMR,13 C NMR and the spectral properties of the probe were investigated. It exhibited strong fluorescence responses toward Cu2+and high selectivity over other metal ions. The binding constant between the probe and Cu2+was calculated using Benesi–Hildebrand equation.     

A reversible fluorescent INHIBIT logic gate for determination of silver and iodide based on the use of graphene oxide and a silver–selective probe DNA

We describe a reversible fluorescent DNA–based INHIBIT logic gate for the determination of silver(I) and iodide ions using graphene oxide (GO) as a signal transducer and Ag(I) and iodide as mechanical activators. The basic performance, optimized conditions, sensitivity and selectivity of the logic gate were investigated and revealed that the method is highly sensitive and selective over potentially interfering ions. The limits of detection for Ag(I) and iodide are 10 nM and 50 nM, respectively. This logic gate was successfully applied to the determination of Ag(I) and iodide in (spiked) tap water and river water. It was also used for the determination of iodide in human urine samples with satisfactory results. Compared to other methods, this INHIBIT logic gate is simple in design and has small background interference.

A simple and reversible fluorescent DNA-based INHIBIT logic gate is designed by using graphene oxide as a signal transducer and silver ions and iodide as mechanical activators.

     

Sensitive and selective DNA probe based on “turn-on” photoluminescence of C-dots@RGO

In this study, highly hydrophilic and photoluminescent sheets of reduced graphene oxide decorated with carbon dots (C-dots@RGO), methylene blue (MB), and a probe DNA have been used for the detection of DNA. The photoluminescence of C-dots@RGO is quenched by MB, which is restored in the presence of a target DNA. The combination of the C-dots@RGO, MB, and a DNA probe is selective for perfectly matched DNA over mismatched DNA, mainly because relative to single-stranded DNA, double-stranded DNA intercalates more strongly with MB, but interacts more weakly with RGO. In the presence of a target DNA, MB intercalates with the as-formed double-stranded DNA and is released from the surface of C-dots@RGO, leading to “turn-on” photoluminescence. The practicality of this assay has been validated by the determination of tumor suppressor gene BRCA1, with linearity over the concentration range from 25 to 250 nM and a limit of detection (LOD, at a signal-to-noise ratio of 3) of 14.6 nM. The C-dots@RGO probe provides higher specificity towards target DNA than towards common salts, carbohydrates, amino acids, and proteins found in real samples. Having the advantages of simplicity, cost-effectiveness, selectivity, and sensitivity, the DNA-P/C-dots@RGO–MB probe on microwells has been successfully employed for the detection of DNA, suggesting its potential for multiple analyses of DNA targets when various DNA probes are employed.     

Inclusion complex of charge transfer probe 4-amino-3-methyl benzoic acid methyl ester (AMBME) with β-CD in aqueous and non-aqueous medium: medium dependent stoichiometry of the complex and orientation of probe molecule inside β-CD nanocavity

The absorption and emission characteristics of donor?acceptor charge transfer system 4-amino-3-methyl benzoic acid methyl ester (AMBME), capable of dual emission, i.e., local emission (LE) and charge transfer (CT) emission, have been investigated inside the β-cyclodextrin (β-CD) nanocavity in the aqueous and non-aqueous dimethylsulphoxide (DMSO) medium. Large enhancement of both LE and CT band in aqueous β-CD medium is due to decrease in non-radiative processes in less polar and restricted environment. Whereas in non-aqueous DMSO medium the CT process is hindered as a result CT intensity decreases with enhancement of LE band. These spectral differences indicate that in aqueous medium the donor –NH₂ group sticking in the hydrophilic region of β-CD cavity whereas in non-aqueous DMSO medium it exists in the hydrophobic part of the cavity. Spectral characteristics indicate that different stoichiometry of host–guest inclusion complexes are formed in aqueous and non-aqueous β-CD medium.     

A novel resorufin based fluorescent “turn-on” probe for the selective detection of hydrazine and application in living cells

In this study, a resorufin derivative RTP-1, which is a novel fluorescent ‘‘turn-on' probe for sensitive detection of hydrazine within 30 min, is designed and synthesized. The selective deprotection of the ester group of the probe by hydrazine led to a prominent enhancement of fluorescent intensity, as well as a remarkable color change from colorless to pink, which could be distinguished by naked eye. The fluorescence enhancement showed decent linear relationship with hydrazine concentration ranging from 0 to 50 mmol/L, with a detection limit of 0.84 mmol/L. The specificity of RTP-1 for hydrazine to a number of metal ions, anions and amines is satisfactory. The sensing mechanism of RTP-1 and hydrazine was evaluated by HPLC, ESI mass spectrometry and density functional theory(DFT).Moreover, we have utilized this fluorescent probe for imaging hydrazine in living cells, and the fluorescence was clearly observed when the cells were incubated with hydrazine(100 mmol/L) for 30 min.     

Density functional theory (DFT) and ab initio investigations of the electronic and molecular structures of the monomer and the dimer of trimethylaluminium

The electronic and molecular structures of the monomer and dimer of trimethylalu-minium have been studied using density functional theory and ab initio MP2 method. The optimized geometry of the monomer Al(CH3)3 is of C3h symmetry, whereas that of the dimer [A1(CH3)3]2 contains a carbon-bridged four-membered ring structure with C2h symmetry. The hydrogen-bridged six-membered ring structure is found to be unstable. The calculated dimerization energy for the four-membered ring structure is 78 kJ/mol, in close proximity to the experimental value of 85.27 kJ/mol.     

Correlation Analysis of the Runoff of the Rivers and the Seisms in China

In recent hundred years the annual discharge variations of the Changjiang River (represented by the Yichang station) and the Huanghe River (represented by Shanxian and Tangnaihe, respectively) have closely related to the geographical distribution of the earthquakes coming about in China in the same year, Both the occurrence of the destructive seism or seismic swarm in the river basins and the disappearance of the shocks in the east and south of the basins are the conditions that the Changjiang and Huanghe Rivers are the high flow while that the strong earthquake of magnitude 7 or more occurred in North China is the condition for the Changjiang low flow year and that of 6 or more in the Qilian Mountains area is for the Huanghe River. In the latter part of this paper, a 2-year sample is given to explain that the conditions of the 2 rivers being high flow years are that the north-south seismic belt is active and in the meanwhile no seism occurred in South China, and those of the low flow year are that the     

Analysis of the hyperfine structures and

From the theories of the nuclear hyperfine structure (HFS) and Λ doubling of diatomic molecules, several brief algebraic equations for interpretation of HFS and Λ doubling of transitions of diatomic molecule have been developed. A few important parameters of HFS and Λ doubling of¹⁵N¹⁶O have been efficiently and accurately obtained from the analysis of the high resolution spectra of¹⁵N¹⁶O (X²∏) observed in our experiments with these equations. This method can provide an effective approach to obtain important hyperfine parameters of novel radicals from their high resolution laser magnetic resonance spectra. Liu Yu-yan, Guo Yuan-qing, Assignments of FIR-LMR spectra of CF X²∏(υ= 1) and MIR-LMR spectra of NO X²∏ (υ =1←0), Spectroscopy and Spectral Analysis (in press).     

Effect of the Charge and the Nature of Both Cations and Anions on the Solubility of Zwitterionic Amino Acids,Measurements and Modeling

The effect of the charge and the nature of both the cations and the anions of some electrolytic salts: sodium fluoride (NaF), potassium fluoride (KF), sodium bromide (NaBr), potassium bromide (KBr), sodium iodide (NaI), potassium iodide (KI), sodium sulfate (Na₂SO₄), potassium sulfate (K₂SO₄), calcium chloride (CaCl₂), and barium chloride (BaCl₂), on the solubility of zwitterionic amino acids (glycine, DL-alanine, DL-valine, and DL-serine) in aqueous solutions at 298.15 K are studied and discussed. A salting-in effect is observed for all amino acids under investigation with all electrolytes used in the present study, except for DL-alanine and DL-valine in aqueous solutions containing sodium fluoride where a salting-out effect was observed. The orders of the effect of the nature and the charge of both the anions and the cations are: F^- < Cl^- < Br^- < I^- < NO₃^- < SO₄^2-\mathrm{F}^{-}<{}\mathrm{Cl}^{-}<{}\mathrm{Br}^{-}<{}\mathrm{I}^{-}<\mathrm{NO}_{3}^{-}<{}\mathrm{SO}_{4}^{2-} with both sodium and potassium cations; Na⁺<K⁺<Ca²⁺<Ba²⁺ with chloride anion.     

A ‘clicked’ macrocyclic probe incorporating Binol as the signalling unit for the chiroptical sensing of anions

We describe a macrocyclic chiroptical sensor for the detection of halide anions, with the Binol moiety acting as the CD signalling unit. The macrocycle is conveniently synthesized using CuAAC ‘click’ reactions in the cyclization step; this methodology installs 1,2,3-triazole moieties within the macrocyclic backbone, able to directionally bind anions by means of CH?X^– hydrogen bonds. ¹H NMR complexation studies in CDCl₃ reveal weak binding to halide and aliphatic carboxylate anions. Halide anions, however, when held into the macrocyclic cavity, are able to trigger a large chiroptical response originating from the steric interaction with the Binol moiety, which changes its dihedral angle, thus modulating its characteristic CD signature.     

Studies on the Syntheses of the Side Chains of Brassinolide and Dolicholide

(4R,5S)-2,2-Dimethyl-4-(1',2'-dimethylpropyl)-5-(1'-bromoethyl)--1,3-dioxolane(15) with the side chain of brassinolide and (4R, 5S)--2, 2-dimethyl-4-(l'-methylene-2'-methylpropyl)-5-(1'-bromoethyl) 1,3-dioxolane(14) with the side chain of dolicholide were first synthesized through 11 and 10 stepes from D-mannitol respectively. All of the intermediates 7-13 were first synthesized too.