Fluorescent Molecular Sensing System Based on Tri-Pyrenes-Labeled γ-Cyclodextrin at the Hetero Rim

Fluorescent active host labeled at the upper and lower rims of -cyclodextrin, namely, mono-3^A-deoxy-3^A-pyrenebutylamido-6^X,Y-O-bis-pyrenebutylate-mono-altro--cyclodextrin (-3) has been synthesized as a chemosensor for steroidal guests using fluorescence spectra change upon a guest addition. The -3 shows monomer and excimer fluorescence, which results in an increase of the intensity of monomer and decrease of excimer fluorescence with a host–guest binding in the cyclodextrin cavity. The extent of monomer and excimer fluorescence variations of -3 was used as an indication for the sensing ability for the guests examined. The guest-induced fluorescence changes were measured for 10^–7 M solutions of -3. The sensing parameters (I_ex/I⁰_ex and I_mon/I⁰_mono) were used to describe the sensing ability of -3. The values of I_ex/I⁰_ex describe that -3 shows less selectivity for guests than that of mono-3^A-deoxy-3^A-pyrenebutylamido-6^X-O-mono-pyrenebutylate-mono-altro--cyclodextrin (-2), and the values of I_mon/I⁰_mono show that -3 shows higher sensitivity and selectivity than that of -2.     

Synthesis of γ-Cyclodextrin Pyrene-Labeled at the Hetero Rim and Its Use in Fluorescent Molecular Sensing

Fluorogenic active host labeled at the upper and lower rims of -cyclodextrin, namely, mono-3^A-deoxy-3^A-pyrenebutylamido-6^X-O-mono-pyrenebutylate-mono-altro--cyclodetrin (mixture -1,X = A, B, C, D, E, F, G, or H), has been synthesized in order to investigate their host-guest complexation with steroidal compoundsusing fluorescence spectra. Monomer and excimer fluorescence was observed for mixture host. Inclusion of a guest molecule in the cyclodextrin cavity resultedin increased monomer fluorescence and decreased excimer fluorescence. The extent of monomerand excimer fluorescence variations ofmixture -1 with the guestwas used as an indication for the sensing ability. The guest inducedfluorescence changes were measured for 10^-7 M solutions of mixture -1.The values I/I ⁰ , where I ⁰ and I are fluorescence intensities in the absence and presence of a guest, respectively, and I is I ⁰ - I, were then used to describe the sensing ability.     

Molecular Recognition Study on a Supramolecular System. Part 21. Inclusion Complexation Thermodynamics of Aliphatic Alcohols by Organoselenium Modified β-Cyclodextrins

The spectrophotometric titrations have beenperformed at 25–40 °C in aqueous solution to give the complexstability constants and the thermodynamic parametersfor the stoichiometric 1 : 1 inclusion complexation ofvarious aliphatic alcohols withmono[6-(phenylseleno)-6-deoxy]--cyclodextrin (2),mono[6-(o-, m-,p-tolylseleno)-6-deoxy]--cyclodextrin (3–5),mono[6-(p-chloro-phenyl-seleno)-6-deoxy]--cyclodextrin(6), mono[6-(benzylseleno)-6-deoxy]--cyclodextrin (7) and mono[6-(naphthaleneseleno)-6-deoxy]--cyclodextrin(8). On thebasis of the present and previous results, themolecular binding abilities and selectivities forguest aliphatic alcohols of the host -cyclodextrinderivatives (2–8) are discussed comparatively and globallyfrom the thermodynamic point of view. Thethermodynamic parameters obtained are criticalfunctions of the size/shape of aliphatic alcohols, andthe position and type of the substituent introduced tothe aromatic ring of -cyclodextrin's sidearm,which are elucidatedin terms of the conformational, electrostatic,hydrogen-bonding, and hydrophobic effects.     

Molecular Recognition Studies on Supramolecular Systems. 29. Anilino- and m-Toluidino-β-Cyclodextrins: Structural and Conformational Analyses and Molecular Recognition of Aliphatic Alcohols

Abstract

Mono(6-anilino-6-deoxy)-β-cyclodextrin (1) and mono[6-(m-toluidino)-6-deoxy]-β-cyclodextrin (2) were synthesized and characterized. Circular dichroism and fluorescence spectral studies and fluorescence lifetime measurements have been performed to elucidate the conformations of 1 and 2 in aqueous buffer solution. 1-D and 2-D NMR spectra of 2 have been measured in D₂O to deduce its structure and detailed conformation in solution. From the circular dichroism, fluorescence, and NMR spectroscopic studies, it was revealed that the substituents appended to 1 and 2 penetrate into the cyclodextrin cavity forming a stable self-inclusion complex in aqueous solution, and also that the short linkage between the m-toluidino and cyclodextrin moieties makes the cyclodextrin ring of 2 deformed to some extent. The complex stability constants (K _S) of 1 and 2 for a series of aliphatic alcohols have been determined by using spectropolarimetric titrations in aqueous phosphate buffer solution (pH 7.20) at 25°C to elucidate the role of introduced substituents and the weak interactions involved in inclusion complexation by the modified cyclodextrins. The results obtained indicate that the van der Waals and hydrophobic interactions mainly contribute to the formation of complexes between the cyclodextrins and aliphatic alcohols, and the inclusion complexation process involves the induced-fit mechanism. Modified β-cyclodextrin 2 can recognize not only the size, shape, and hydrophobicity of the guest molecules, but also chiral guests, affording a moderate enantioselectivity of 1.55 for (+)/(-)-borneol.     

Molecular Binding Ability and Selectivity of Natural α-, β-, γ-Cyclodextrins and Oligo(ethylenediamino) Modified β-Cyclodextrins with Chinese Traditional Medicines

The binding ability andinclusion complexation behavior of natural -, -, -cyclodextrins (1–3) and two mono[6-oligo(ethylenediamino)-6-deoxy]--cyclodextrins(4, 5) with fourChinese traditional medicines, that is, -asarone (AS), ferulic acid (FA), magnolol (MA) and honokiol (HO), have been investigated in aqueous phosphate buffer solutions(pH = 7.20). The spectral titrations have been performed at 25 °C by using fluorescence spectroscopy to calculate the complex stability constants (K_S) and Gibbs free energy changes ( G°) for the stoichiometric 1 : 1 inclusion complexation of hosts1–5 with guest medicines. The results obtained indicate that the different guest medicines fit in with hydrophobic cavities of different sizes and the appended substitutes of hosts 4 and 5 change the hydrophobic microenvironment of -cylcodextrin 2, influencing the original binding ability and molecular selectivity of host 2 consequently. The binding ability and inclusion complexation behavior of these hosts 1–5 are discussed according to the size/shape fit concept and hydrogen bonding interaction between host cyclodextrins and guest medicine molecules.     

Synthesis of Bis Dansyl-Modified β-Cyclodextrin Dimer Linked with Azobenzene and Its Fluorescent Molecular Recognition

Flexible dimeric host, 4,4'-azobenzenediamido-bis-{6-(2-dansyl-aminoethyl)6-deoxy--cyclodextrin}(beta; -1), has been synthesized in order to investigate itsfluorescent molecular sensory system transforming photoisomerization. Photoisomerizationof -1 was performed with photoirradiation by a 500W-Xelamp using a Corning 7-37 filter. Host beta; -1 showed puremonomer fluorescence, exhibiting a decrease in fluorescence intensity on accommodationof the guest, and the extent of fluorescence variation with a guest was employed to displaythe sensing ability of -1, in which the sensing parameter( I/I⁰)was used to describe the sensing ability. Host -1could detect chenodeoxycholic acid, ursodeoxycholic acid and hyodeoxycholic acid withhigh selectively. The behaviors of the appended moieties of -1during host-guest complexation were studied by induced circular dichroism (ICD) andfluorescence spectra and MM2 energy-minimized structure. The ICD and fluorescenceintensities of -1 decreased on the addition of a guest.The guest-induced variations in the ICD and fluorescence spectra, and MM2 energy-minimized structure suggested that the dansyl moieties of -1 worked as a hydrophobic cap when a host-guest complexation occurred.     

Ion Recognition and Analytical Application of a Fibroin Modified Electrode

A novel fibroin modified electrode with ion recognition was reported. The membrane with isoelectric point of pH 4.5, was modified on graphite and carbon fiber electrodes. The pH-responsive ion recognition of the modified electrode was investigated by use of some neurocompounds. The fibroin carbon fiber electrode has been used for in-vivo determination.     

Development of Enantioselective Fluorescent Sensors for Chiral Recognition

Novel chiral compounds have been synthesized for the enantioselective fluorescent recognition of alpha-hydroxycarboxylic acids and amino acids. By introducing dendritic branches to the chiral receptor units, the fluorescence signals of the receptors are significantly amplified because of the light-harvesting effect of the dendritic structure. This has greatly increased the sensitivity of the sensors in the fluorescent recognition. Highly enantioselective fluorescent responses have also been ac…     

Complexation of the Non-steroidal Anti-inflammatory Drug Loxoprofen with Modified and Unmodified β-Cyclodextrins

The inclusion complex of the anti-inflammatory drug, loxoprofen, with -cyclodextrin-(CD), sulfated -CD, and glycerol ether -CD was studied by UV-VIS absorption and ¹H-NMR spectroscopy in solution. The inclusion complex of loxoprofen with -CDs was prepared by freeze-drying, and then characterized in the solid state by thermal analysis, X-ray diffraction, FT-IR and FT-Raman spectroscopy, and scanning electron microscopy (SEM). Furthermore, a physical mixture of loxoprofen/-CD (1/1, mol-%) in the solid state was also characterized. The solubility of the loxoprofen increased on addition of -CDs. The solubility enhancement of the loxoprofen with -CDs is in the following order: glycerol ether -CD > sulfated -CD > -CD.     

Molecular Recognition and Cooperative Binding Ability of Fluorescent Dyes by Bridged Bisβ-cyclodextrin)s Tethered with Aromatic Diamine

A novel bridged bis(β-cyclodextrin),m-phenylenediimino-bridged bis(6-imino-6-deoxy-β-cyclodextrin) (2), was synthesized by the reaction of m-phenylenediamine and 6-deoxy-6-formyl-β-cyclodextrin. The inclusion complexation behavior of the novel bridged bis(β-cyclodextrin) 2,as well as native β-cyclodextrin (1),p-phenylenediamino-bridged bis(6-amino-6-deoxy-β-cyclodextrin) (3) and 4,4'-bianilino-bridged bis(6-amino-6-deoxy-β-cyclodextrin) (4) with representative fluorescent dye molecules, i.e., acridine red (AR), neutral red (NR), Rhodamine B (RhB), ammonium 8-anilino-1-naphthalenesulfonate (ANS) and sodium 6-toluidino-2-naphthalenesulfonate (TNS), was investigated at 25 °C in aqueous phosphate buffer solution (pH 7.20) by means of fluorescence, and circular dichroism, as well as 2D NMR spectrometry. The spectrofluorometric titrations have been performed to calculate the complex stability constants (K_S) and Gibbs free energy changes (Δ G°) for the stoichiometric 1 : 1 inclusion complexation of 1–4 with fluorescent dye molecules. The results obtained demonstrated that bis(β-cyclodextrin)s 2–4 showed much higher affinities toward these guest dyesthan native β-cyclodextrin 1. Typically, dimer 2 displayed the highest binding ability upon inclusion complexation with ANS, affording 35 times higher K_S value than native β-cyclodextrin. The significantlyenhanced binding abilities of these bis(β-cyclodextrin)s are discussed from thebinding mode and viewpoints of size/shape-fit concept and multiple recognition mechanism.     

Correlation between Thermodynamic Behavior and Structure in the Complexation of Modified β-Cyclodextrins and Bile Salts

Complex stability constants (K _S), standard molar enthalpy changes (ΔH ⁰) and entropy changes (ΔS ⁰) for the inclusion complexation of two cyclodextrin dimers, 6,6′-{2,2′-diselenobis[2-(benzoylamino)ethylamino]}-bridged bis(β-cyclodextrin) (1) and o-phenylenediseleno bridged bis(β-cyclodextrin)s (3), and their monomer analogs, 6-deoxy-6-{[2-(2,3-dihydro-3-oxo-1,2-benzisoselenazol-2-yl)ethyl]amino}-β-cyclodextrin (2) and mono[6-(phenylseleno)-6-deoxy]-β-cyclodextrin (4), with two bile salt guests, sodium cholate (CA) and sodium deoxycholate (DCA), were determined at 25°C in Tris buffer solutions (pH 7.4) at 298.15?K by means of isothermal titration microcalorimetry (ITC). The interactions and binding modes between the host cyclodextrins and the guest bile salts were further studied by ROESY spectroscopy. The thermodynamic parameters obtained, together with the ROESY spectra, were used to examine the correlations between thermodynamic behavior and binding modes of the host–guest complexation. The results indicate that the length, structure and conformation of the tethers linked to the cyclodextrins determine the binding modes and the binding abilities between hosts and guests to a great extent, leading to a reversion in binding ability when comparing the corresponding dimer and its monomer analog.     

Direct Synthesis of Amphiphilic α-, β-, and γ-Cyclodextrins

ABSTRACT

The clean one step synthesis of the amphiphilic α-, β-, and γ-cyclodextrins starting from per-(6-bromo-6-deoxy)-α-, -β-, and -γ-cyclodextrins is described. The role of the lipophilic tail is played by various aryl groups (phenyl, p-bromophenyl, p-O-butoxyphenyl, p-pentylphenyl, and o-, m-, and p-nitrophenyl) linked by a thioether bridge to the position C-6 of each glucopyranose unit. The yields of the S-alkylation reactions were very high (85-95%).     

Recognition of ClO－ and Cellular Imaging with Xanthene-based Fluorescent Probes北大核心CSCD

Selective recognition of hypochlorite ion（ClO－）in intracellular biological environment is important for research and application in cellular physiology and pathology. A novel fluorescent molecule, 6-bis （dimethylamino）-9-（1-（3-methyl-benzothiazole）-trimethyl）-xanthene（R-1）,is designed and synthesized with a combination of dimethylamino-substituted xanthene and benzothiazole segments through continuous carbon-carbon double bonds. In the presence of ClO－ ,the fluorescence emission of R-1 at 600 nm is significantly enhanced（the quantum yield is as high as 20. 3%）,and other reactive oxygen species do not affect the recognition of ClO－. Fluorescence imaging experiments demonstrate that probe R-1 can detect ClO－ in human lung adenocarinoma （A549）cells and emit red fluorescence,indicating the potential application of R-1 in ClO－ biological imaging. © 2022, Science Press (China). All rights reserved.     

Novel Mixed LB Films of Porphyrin and Phthalocyanine Based on Molecular Recognition

Phthalocyaninesaresyntheticsubstancesrelatedtothenaturallyoccurringporphyrins.Itsthermalandchemicalstabilitymakesitveryusefulinmolecularelectronicsl.TheLBfilmsofphthalocyaninehavebeenwidelystudiedinthepastdecade.ButfewreportsonthemixedLBfilmsofphthalocyanineandporphyrinhavebeenpublished"'HerewereportanovelmixedLBfilmfabricatedbydepositingporphyrinandphthalocyaineinonelayerbasedonmolecularrecognition.Figure1.ThestructureofcompoundAandBAsymmetricallysubstitutedphthalocyanineAandporphyrinBa…     

Effects of Modified β-Cyclodextrins on the Hydrolysis Reaction of p-Nitrophenyl α-Methoxyphenylacetate

Effects of -cyclodextrin (-CD) 1and its derivatives 2–7 on the deacylationreaction of p-nitrophenyl (R or S)--methoxyphenylacetatewere studied. The-CD derivatives used were6--D-glucosyl--CD 2, sulfated-CD (7–11 sulfate groups/CD ring) 3,dimethylated -CD 4, carboxymethylated-CD (3.5 carboxymethyl groups/CD ring) 5,2-tri(2-hydroxypropyl)--CD 6, and-CD appended on poly(allylamine) 7. Therate constant (k ^CD) of thesubstrate/-CD complexes and the formationconstants (K) of the complexes were determinedfrom the dependence of the pseudo-first order rateconstants of the deacylation reaction on theconcentration of -CDs. The order ofk ^CD for the R-enantiomer at pH8.0 is 45H₂O3 6 1 2 7, whilethat for the S-enantiomer is 4 5 6H₂O 1 2 3 7: H₂O denotes the rate in theabsence of -CDs. The order of K values is3 7 6 2 1 4 5. This work indicates that, though thesecondary hydroxyl groups of -CD play criticalroles in the deacylation reactions of the esterscomplexed with -CDs, the reactivity of theester/-CD complexes depends highly on thenature of the substituents at the secondary face of-CD. It also suggests that the substratesinserted from the secondary side as well as theprimary side of -CD of poly(allylamine)-bound-CD undergo the reaction by attack of aminogroups on the polymer chain.     

A Pseudorotaxane System Containing γ-Cyclodextrin Formed via Chiral Recognition with an AuI6AgI3CuII3 Molecular Cap

Solvent-mediated crystal-to-crystal transformations of [Au₆Ag₃Cu₃(H₂O)₃(d -pen)₆(tdme)₂]³⁺ (d -[ 1 (H₂O)₃]³⁺; pen²⁻= penicillaminate, tdme=1,1,1-tris(diphenylphosphinomethyl)ethane) to form unique supramolecular species are reported. Soaking crystals of d -[ 1 (H₂O)₃]³⁺ in aqueous Na₂bdc (bdc²⁻=1,4-benzenedicarboxylate) yielded crystals containing d -[ 1 (bdc)(H₂O)₂]⁺ due to the replacement of a terminal aqua ligand in d -[ 1 (H₂O)₃]³⁺ by a monodentate bdc²⁻ ligand. When γ-cyclodextrin (γ-CD) was added to aqueous Na₂bdc, d -[ 1 (H₂O)₃]³⁺ was transformed to d -[ 1 (bdc@γ-CD)(H₂O)₂]⁺, where a γ-CD ring was threaded by a bdc²⁻ molecule to construct a pseudorotaxane structure. While the use of dicarboxylates with an aliphatic carbon chain instead of bdc²⁻ afforded analogous pseudorotaxanes, such pseudorotaxane species were not formed when crystals of [Au₆Ag₃Cu₃(H₂O)₃(l -pen)₆(tdme)₂]³⁺ (l -[ 1 (H₂O)₃]³⁺) enantiomeric to d -[ 1 (H₂O)₃]³⁺ were soaked in aqueous Na₂bdc and γ-CD, affording only crystals containing l -[ 1 (bdc)(H₂O)₂]⁺.     

Binding of Acridinedione Dyes with α, β and γ-Cyclodextrins: Fluorescence Quenching and Estimation of Thermodynamic Parameters

Using absorption and fluorescence spectroscopy, acridinedione (ACD) was found to be included into the -cyclodextrin (-CD) cavity to form a 1 : 1 inclusion complex. As a consequence of inclusion, the fluorescence of ACD is strongly quenched. Lifetime data confirm that the quenching is purely static. The association constant for the formation of the complex was calculated using linear and non-linear equations. H and S values obtained from the temperature dependent association constants of the -CD/ACD(B) system are reported. It was also observed that these dyes complexed very weakly with and -CD.     

Guest-Binding and Catalytic Properties of Immobilized β-Cyclodextrins

Abstract

Cyclodextrins¹(CyDs), cyclic oligomers of 6–8 glucose units, form inclusion complexes with guest compounds and have been used as catalyst for the selective syntheses.² Previously, immobilization of CyD with epichlorohydrin as crosslinking agent have been described.^3-4 Here, we report the first successful immobilization of β-CyD using various crosslinking agents. The guest binding abilities and the catalytic abilities of these immobilized β-CyDs are shown.     

Post-Assembly Modification of Homochiral Titanium–Organic Cages for Recognition and Separation of Molecular Isomers

A chiral metal–organic cage (MOC) was extended and fixed into a porous framework using a post-assembly modification strategy, which made it easier to study the host–guest chemistry of the solid-state MOC using a single-crystal diffraction technique. Anionic Ti₄L₆ (L=embonate) cage can be used as a 4-connecting crystal engineering tecton, and its optical resolution was achieved, thus homochiral ΔΔΔΔ- and ΛΛΛΛ-[Ti₄L₆] cages were obtained. Accordingly, a pair of homochiral cage-based microporous frameworks ( PTC-236(Δ) and PTC-236(Λ) ) were easily prepared by a post-assembly reaction. PTC-236 has rich recognition sites provided by the Ti₄L₆ moieties, chiral channels and high framework stability, affording a single-crystal-to-single-crystal transformation for guest structure analyses. Thus it was successfully utilized for the recognition and separation of isomeric molecules. This study provides a new approach for the orderly combination of well-defined MOCs into functional porous frameworks.