Hybrid supraparticles of carbon dots/porphyrin for multifunctional tongue-mimic sensors

Supraparticles（SPs）, such as assembly of inorganic components with organic, have made tremendous attention in biochemical analysis, which represents a novel but challenging research orientation. Herein, a single-SPs multifunctional fluorescent sensor array has been developed for high-throughput detection of heavy metal ions in biofluids, which is based on an inorganic/organic hybrid SPs consisting of carbon dots（CDs） and an easily available porphyrin [5,10,15,20-tetra（4-carboxyphenyl）porphyrin（T...     

An Elaborate Supramolecular Assembly for a Smart Nanodevice for Ratiometric Molecular Recognition and Logic Gates

Ingenious approaches to supramolecular assembly for fabricating smart nanodevices is one of the more significant topics in nanomaterials research. Herein, by using surface quaternized cationic carbon dots (CDots) as the assembly and fluorescence platform, anionic sulfonatocalix[4]arene with modifiable lower and upper rims as a connector, as well as in situ coordination of Tb³⁺ ions, we propose an elaborate supramolecular assembly strategy for the facile fabrication of a multifunctional nanodevice. The dynamic equilibrium characteristics of the supramolecular interaction can eventually endow this nanodevice with functions of fluorescent ratiometric molecular recognition and as a nano‐logic gate with two output channels.     

Chiroptical coassemblies between organic carboxylic acids and amino acid derivatives with C3-symmetry

Benzimidazole amino acid derivatives behave as supramolecular hosts to include organic acids via complementary hydrogen bonding whereby supramolecular chirality and chiroptical properties could be manipulated. Organic acids enhanced the chiral assembly that showed tunable circularly polarized luminescence with high dissymmetry g-factors at 10⁻² grade.     

meso-四(4-甲氧基-3磺酸基苯)卟啉与环糊精超分子体系的研究

采用极谱法、紫外可见光谱法及荧光光谱法研究了水溶性卟啉T(4-Mop)PS4与α-CD、-βCD、γ-CD、Hp-β-CD及SBE--βCD 5种环糊精的相互作用,结果表明T(4-Mop)PS4分别与这5种环糊精形成了T(4-Mop)PS4-CD s超分子体系。此外,本研究还采用极谱法、紫外可见光谱法及荧光光谱法测定了T(4-Mop)PS4-CD s超分子体系的包结常数和包结比,比较了T(4-Mop)PS4与5种环糊精的包结能力,并由此推测了包结机理,为T(4-Mop)PS4卟啉、环糊精的进一步应用提供了理论信息。     

Tuning thermal gelling behavior of <Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide based copolymer through introducing cucurbit[8]uril ternary complex on side-chain

Thermo-gelation polymers have attracted increasing attention over decades. However, rare facile tuning method of sol-gel transition temperature restricted the wider application. Preceding study indicated that supramolecular interactions demonstrated a powerful means to control the structure and property of polymeric materials. Here we designed an N-isopropylacrylamide (NIPAM) based thermo-sensitive copolymer with naphthyl (Np) on its side chain. Positive-charged side-chain ternary complex was formed with cucurbit[8]uril (CB[8]) and methylviologen (MV²⁺) via CB[8]-enhanced intermolecular charge-transfer (CT) interaction. Introducing the ternary complex CB[8]/MV²⁺/Np on side-chain altered microstructure of macromolecular chains and led to a strong tendency for thermo gelation. Altering content of CB[8] and MV²⁺ changed content of the positive-charged side-chain ternary complex and varied gelation temperature. Therefore, introducing supramolecular interaction endowed the hydrogel with tunable gelation property.     

Explanation of Ionic Sequences in Various Phenomena. III. Salting-in and -out of Amino Acids

Abstract

Previous developed theories were applied in explaining the mechanism for the salting-in and -out of various amino acids. Glycine is salted-in according to the cationic sequences Li⁺ > Na⁺ > K⁺ > Rb⁺ and Ca²⁺ > Ba²⁺ > Sr²⁺. The ability of a cation to increase the solubility of an amino acid therefore corresponds to the destruction of the ion-ion bond between the - CO-₂and the -NH_{+ 2}group of the amino acid by forming an insoluble ion-ion bond between the added cation and the - CO?² group. This insolubilizing effect produces a positive charge on the amino acid. If, however, the anion of the added salt forms a relatively insoluble ion-ion bond with the -NH₊₂ group of the amino acid, then the effect is minimized because now both charges on the amino acid are reduced. Consequently, the more insoluble the cation amino acid salt and the more soluble the anion amino acid salt (or vice versa), the greater will be the salting-in effect. Titration of either charged group on the amino acid zwitterion has the same effect, since now the ion-ion bond of the amino acid is again destroyed. Aliphatic and carboxylic acid groups also effect the salting-in sequence, since these groups are salted-out by addition of salt when D^± < D_H2o. These mechanisms explain how leucine is first salted-out, then salted-in (at 4 M) and finally salted-out again (at 9 M) in LiCl solutions. Urea salts-in hydrophobic amino acids by increasing the dielectric constant and salts-out polar amino acids by increasing the interaction between the two charge groups on the amino acid. Glycine reverses the salting-in effect of NaCl on asparagine by competing for the Na⁺ ion.     

The reactions of some organotin(IV) chlorides with antimony(V) chloride and boron(III) chloride

The reactions of the organotin chlorides R_nSnCl_4?n(R = Me or Ph; ? n ? 4) with the Lewis acids SbCl₅ and BCl₃ have been investigated by ¹¹⁹Sn and (where appropriate) ¹¹B NMR spectroscopy. The results show that transfer of organo-groups to antimony or boron usually takes place rather than chloride abstraction to give cationic tin(IV) species, and this process is more facile for phenyl than methyl groups. These conclusions have been confirmed in some instances by isolation of the non-volatile reaction products.     

Construction of Chemical‐Responsive Supramolecular Hydrogels from Guest‐Modified Cyclodextrins

A methodology for preparing supramolecular hydrogels from guest‐modified cyclodextrins (CDs) based on the host–guest and hydrogen‐bonding interactions of CDs is presented. Four types of modified CDs were synthesized to understand better the gelation mechanism. The 2D ROESY NMR spectrum of β‐CD‐AmTNB (Am=amino, TNB=trinitrobenzene) reveals that the TNB group was included in the β‐CD cavity. Pulsed field gradient NMR (PFG NMR) spectroscopy and AFM show that β‐CD‐AmTNB formed a supramolecular polymer in aqueous solution through head‐to‐tail stacking. Although β‐CD‐AmTNB did not produce a hydrogel due to insufficient growth of supramolecular polymers, β‐CD‐CiAmTNB (Ci=cinnamoyl) formed supramolecular fibrils through host–guest interactions. Hydrogen bonds between the cross‐linked fibrils resulted in the hydrogel, which displayed excellent chemical‐responsive properties. Gel‐to‐sol transitions occurred by adding 1‐adamantane carboxylic acid (AdCA) or urea. ¹H NMR and induced circular dichroism (ICD) spectra reveal that AdCA released the guest parts from the CD cavity and that urea acts as a denaturing agent to break the hydrogen bonds between CDs. The hydrogel was also destroyed by adding β‐CD, which acts as the competitive host to reduce the fibrils. Furthermore, the gel changed to a sol by adding methyl orange (MO) as a guest compound, but the gel reappeared upon addition of α‐CD, which is a stronger host for MO.     

Hydroxyethylammonium monosubstituted cyclodextrin as chiral selector for capillary electrophoresis

A novel cationic cyclodextrin, mono-6^A-(2-hydroxyethyl-1-ammonium)-6^A-β-cyclodextrin chloride (HEtAMCD) has been successfully synthesized and applied as chiral selector in capillary electrophoresis. The NMR study revealed this chiral selector has three recognition sites: β-CD, ammonium cation and hydroxy group in the sidearm to contribute three corresponding driving forces including inclusion complexation, electrostatic interaction and hydrogen bonding. The effect of buffer pH and HEtAMCD concentration (2.5–10 mM) on enantioselectivity, chiral resolution as well as effective mobility of analytes was investigated. This elegantly designed CD exhibits outstanding enantioselectivities toward the studied hydroxyl acids and ampholytic racemates in CE with the aid of extra hydrogen bonding. Under optimum pH 6.0, chiral resolutions over 5 can be readily obtained for hydroxy acids with CD concentration below 5 mM. The comparison study between HEtAMCD and our earlier reported ammonium CDs indicates the hydroxyethylammonium group of HEtAMCD significantly increased the enantioselective capability.     

A family of single‐isomer,dicationic cyclodextrin chiral selectors for capillary electrophoresis: Mono‐6A‐ammonium‐6C‐butylimidazolium‐β‐cyclodextrin chlorides

The first member of the single‐isomer, dicationic cyclodextrin (CD) family, 6^A‐ammonium‐6^C‐butylimidazolium‐β‐cyclodextrin chlorides (AMBIMCD), has been synthesized, analytically characterized, and used to separate a variety of acidic enantiomers and amino acids by CE. Starting from mono‐6^A‐azido‐β‐cyclodextrin, the cationic imidazolium and ammonium moieties were subsequently introduced onto primary ring of β‐cyclodextrin via nucleophilic addition and Staudinger reaction. The analytically pure AC regio‐isomer CD was further obtained via column chromatography. This dicationic CD exhibited excellent enantioselectivities for selected analytes at concentration as low as 0.5 mM, which were even better than those of its mono‐imidazolium or ammonium‐substitued counterpart CDs at 10 equivalent concentrations. The effective mobilities of all studied analytes were found to decrease with the concentration of AMBIMCD. Inclusion complexation in combination with eletrostatic interactions seemed to account for the enhanced chiral discrimination process.     

Using Diphenylphosphoryl Azide (DPPA) for the Facile Synthesis of Biodegradable Antiseptic Random Copolypeptides

A facile method has been developed for the large‐scale synthesis of random copolypeptides composed of multiple (i.e., cationic, hydrophobic, and hydrophilic) amino acids and their relative ratios have been optimized for broad‐spectrum antibacterial effect. The copolypeptides obtained have measured compositions close to the design ratios in spite of the differing reactivities of the different amino acids. An optimized random copolypeptide of lysine, leucine, and serine (denoted as KLS‐3) mimicking the composition of LL‐37 host defense peptide gives broad spectrum antibacterial activity against clinically relevant Gram‐negative and Gram‐positive bacteria such as methicillin‐resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa (PAO1) with minimum inhibitory concentrations (MICs) of 32–64 μg mL⁻¹, as well as good MICs against multidrug resistant Gram‐negative bacteria of Escherichia coli EC 958 (64 μg mL⁻¹) and Klebseilla pneumoniae PTR3 (128 μg mL⁻¹). This method can be applied to the facile large‐scale copolymerization of multiple amino acids, including unnatural amino acids, to make effective antibacterial copolypeptides.

     

Effect of ionic micellar medium on kinetics and mechanism of oxidation of bovine serum albumin: A pulse radiolysis study

Effect of protein–micelle interaction on bovine serum albumin (BSA) oxidation by trichloromethyl peroxyl radical (CCl₃O₂^·) in anionic sodium dodecyl sulfate (SDS) and cationic cetyltrimethyl ammonium bromide (CTAB) micellar media has been studied using nanosecond pulse radiolysis technique. Viscosity measurement and light scattering studies have suggested that SDS and CTAB micelles produce BSA–micelle aggregates of different sizes and polydispersity. Oxidation kinetics and transients have been affected both by anionic SDS and cationic CTAB micelles but in a different manner. Tryptophanyl-CCl₃O₂^· adduct radical to tyrosyl radical transformation in BSA has been observed in anionic SDS micelles but not in cationic CTAB micelles. Similar studies have also been done with tryptophan and tyrosine amino acids, which undergo oxidation in BSA. The study suggests that Coulombic and hydrophobic interactions between micelles and protein affect the structure of the protein to shield its functional amino acids, like tryptophan and tyrosine, to neutral oxidizing radical.     

Synthesis of highly luminescent carbon dots from postconsumer waste silk cloth and investigation of its electron transfer dynamics with methyl viologen dichloride

Synthesis of luminescent carbon dots (CDs) from biological waste materials is gaining more attention in the present-day scenario. We have synthesized highly luminescent (luminescence quantum yield, φ ​= ​19.1%), water-soluble CDs from a postconsumer waste silk cloth via a facile hydrothermal synthetic method. The resulting CDs are characterized and their photophysical properties are studied in detail. The electron transfer dynamics of CDs in presence of methyl viologen dichloride hydrate (MV²⁺) is systematically investigated in this work. Knowledge of the electron transfer dynamics of CDs is essential in the structural elucidation of CDs, prediction of sensing mechanisms and utilizing the CDs in energy storage devices.     

Capillary Zone Electrophoresis Resolutions of 2,4‐Dinitrophenyl Labeled Amino Acids Enantiomers by N‐MethylatedAmino‐β‐Cyclodextrins

Abstract

Capillary zone electrophoresis resolutions of 2,4‐dinitrophenyl labeled amino acids (DNP‐AAs) enantiomers using three N‐methylated amino‐β‐cyclodextrins (CDs) [6^I‐deoxy‐6^I‐monomethylamino‐β‐CD (M‐A‐βCD), 6^I‐deoxy‐6^I‐dimethylamino‐β‐CD (diM‐A‐βCD), 6^I‐deoxy‐6^I‐trimethylammonium‐β‐cyclodextrin (triM‐A‐βCD)] as chiral selectors were investigated. These cationogenic selectors, differing in ionization and steric properties, exhibited clear differences in their enantioselectivities.

The differences in enantioresolution observed under identical acid‐base conditions (pH 5.2), providing comparable effective charges/mobilities of the CDs, e.g., excellent separations of single enantiomeric couples (triM‐A‐βCD, M‐A‐βCD), multicomponent mixtures of enantiomers (M‐A‐βCD), and mixtures of positional isomers (M‐A‐βCD, diM‐A‐βCD), indicated the importance of structural parameters (different degrees of methylation) of the studied chiral selectors in the separation mechanism.

The differences in enantioresolution observed under various acid base conditions (pH 5.2 and 9.6), providing significant differences of effective charges/mobilities of CDs, e.g., a dramatic decrease in enantioresolution as well as achiral resolution with uncharged M‐A‐βCD and preserved resolution with permanently charged triM‐A‐βCD, indicated the importance of charge of the studied chiral selectors in the separation mechanism.

The present study clearly showed that the studied CD derivatives have great potential as chiral selectors in capillary zone electrophoresis separations of DNP‐AAs and that their effective use is related to the character of the analyte (structure, hydrophobicity) as well as to working conditions (pH).     

Gold nanoparticles functionalized with supramolecular macrocycles

Cold nanoparticles(AuNPs) functionalized with supiamolecular macrocycles are versatile and diverse hybrid nanoinaterials,which combine and enhance the characteristics of the two components.In this mini-review,we summarize the recent research progress on the synthesis and assembly of AuNPs functionalized with different supramoleciilar macrocyclic compounds,i.e.,crown ethers,cyclophanes, cyclodextrins(CDs),cucurbit[n]urils(CB[n]),calix[n]arenes,and pillar[n]arenes(P[n]A).Meanwhile, applications of these supramoleciilar hybrid nanomaterials in the fields of sensors,biomedicine and plasmonic devices are also presented.     

The Effect of a Cationic Gemini Surfactant,Ethonium, on the Physicochemical Properties of Quercetin in Solutions and on the Surface of Highly Dispersed Silica

The formation of supramolecular complexes with ethonium, a cationic gemini surfactant having a broad-spectrum antimicrobial activity, is shown to significantly alter the physicochemical properties (spectral, protolytic, and adsorption properties and solubility) of a natural f lavonol, quercetin. The constant of binding between quercetin and ethonium is calculated. Apparent dissociation constants pK _a1 ^a of quercetin in solutions of this cationic surfactant are for the first time determined within a broad concentration range. A shift in the pH dependence of quercetin adsorption by 0.5 units to the alkaline region upon the transition from a premicellar ethonium solution to a micellar one correlates with an increase in pK _a1 ^a under these conditions. The value of quercetin adsorption from aqueous ethonium solutions depends on the concentration of the cationic surfactant, pH of a solution, and the pK _a1 ^a value of the f lavonol bound into the supramolecular complex.     

Supramolecular Chemistry of Cyclodextrins in Cuba

Cyclodextrins (CDs) are a class of cyclic oligosaccharides composed of α(1→4)-linked D-glucopyranose units in the ⁴ C ¹ chair conformation. The overall form of the molecules is a truncated cone with an essentially hydrophobic cavity. Such a structure allows them to form stable inclusion complexes with a wide variety of guests. That is the reason for which CDs constitute an indivisible part of supramolecular chemistry, a field of chemistry in constant growth and development all around the world.

Here we present a survey of the different types of supramolecular compound that CDs and their derivatives can form and the applications we are targeting in Cuba. This consists mainly of the following. ? Pharmaceutical formulations of copper(II) complexes insoluble in water, solubilized by their inclusion in βCD and in one of its dimers.

? Cu,Zn-SOD enzyme mimetics based on copper(II) complexes of CD derivatives with ammonium salts included in the CD cavity.

? Enzymes conjugated, by both chemical and enzymatic methods, to CDs with increased thermostability and catalytic activity.

? Sensors based on the self-assembly of CD derivatives on metal electrodes and nanoparticles, which permit selective differentiation between species with very similar electrochemical properties.

     

The First Use of a ReX5 Synthon to Modulate FeIII Spin Crossover via Supramolecular Halogen⋅⋅⋅Halogen Interactions

We have added the {Re^IVX₅}⁻ (X=Br, Cl) synthon to a pocket-based ligand to provide supramolecular design using halogen⋅⋅⋅halogen interactions within an Fe^III system that has the potential to undergo spin crossover (SCO). By removing the solvent from the crystal lattice, we “switch on” halogen⋅⋅⋅halogen interactions between neighboring molecules, providing a supramolecular cooperative pathway for SCO. Furthermore, changes to the halogen-based interaction allow us to modify the temperature and nature of the SCO event.     

Synergistic Porosity and Charge Effects in a Supramolecular Porphyrin Cage Promote Efficient Photocatalytic CO2 Reduction**

We present a supramolecular approach to catalyzing photochemical CO₂ reduction through second-sphere porosity and charge effects. An iron porphyrin box ( PB ) bearing 24 cationic groups, FePB-2(P) , was made via post-synthetic modification of an alkyne-functionalized supramolecular synthon. FePB-2(P) promotes the photochemical CO₂ reduction reaction (CO₂RR) with 97 % selectivity for CO product, achieving turnover numbers (TON) exceeding 7000 and initial turnover frequencies (TOF_max) reaching 1400 min⁻¹. The cooperativity between porosity and charge results in a 41-fold increase in activity relative to the parent Fe tetraphenylporphyrin ( FeTPP ) catalyst, which is far greater than analogs that augment catalysis through porosity ( FePB-3(N ), 4-fold increase) or charge (Fe p-tetramethylanilinium porphyrin ( Fe-p-TMA ), 6-fold increase) alone. This work establishes that synergistic pendants in the secondary coordination sphere can be leveraged as a design element to augment catalysis at primary active sites within confined spaces.     

Electrospray ionization mass spectrometric study of encapsulation of amino acids by cyclodextrins

Electrospray ionization (ESI) mass spectrometry has been used to study inclusion (host-guest) complexes of cyclodextrins (CDs) with amino acids. Host-guest complexes formed in solution are stable for characterization by ESI mass spectrometry: The relative abundances and the stoichiometry of the complexes formed in solution can, thus, be determined in the gas phase. The studies verified that β- and γ-cyclodextrin better accommodate protonated amino acids than α-cyclodextrin, and that chemically modified cyclodextrins such as heptakis(2,6-di-O-methyl)-β-cyclodextrin (DM-β-CD) may show profound improvement in complexation. The preferential formation of DM-β-CD-aromatic amino acid over DM-β-CD-aliphatic amino acid complexes is confirmed by the experiments, and the relative gas-phase stabilities determined by repeller-collimator collision-induced dissociation show an identical trend to the complexation in solution. Although molecular mechanics studies also may predict the encapsulation preference of protonated amino acids by cyclodextrins, only small differences in the total complexation energies are obtained because of the inability of the calculations to consider hydrophobic interactions. An experimental approach based on ESI mass spectrometry is, therefore, more reliable in predicting host-guest interactions that involve cyclodextrins and amino acids than the theoretical calculations that employ molecular mechanics models.