Synthesis of a novel aminobenzene-containing hemicucurbituril and its fluorescence spectral properties with ions

A novel hemicucurbituril-based macrocycle, alternately consisting of amidobenzene and 2-imidazolidione moieties was designed and synthesized. Based on the fragment coupling strategy, nitrobenzene-containing hemicucurbituril was firstly prepared facilely under alkaline environment, and reduction of the nitro groups produced the desired amidobenzene-containing hemicucurbituril. As an original fluorescent chemosensor, it exhibited strong interactions with Fe3+ over other metal cations. The experimental evidence of fluorescence spectra suggested that a 1:1 complex was formed between this macrocycle and Fe3+ with an association constant up to (2.1 ± 0.3) × 104 M−1. Meanwhile, this macrocycle showed no obvious or only slight enhancement of the fluorescence intensity with selected anions.

Thermodynamic Studies of Interactions between Sertraline Hydrochloride and Randomly Methylated β-Cyclodextrin Molecules Supported by Circular Dichroism Spectroscopy and Molecular Docking Results

The interaction between sertraline hydrochloride (SRT) and randomly methylated β-cyclodextrin (RMβCD) molecules have been investigated at 298.15 K under atmospheric pressure. The method used—Isothermal Titration Calorimetry (ITC) enabled to determine values of the thermodynamic functions like the enthalpy (ΔH), the entropy (ΔS) and the Gibbs free energy (ΔG) of binding for the examined system. Moreover, the stoichiometry coefficient of binding (n) and binding/association constant (K) value have been calculated from the experimental results. The obtained outcome was compared with the data from the literature for other non-ionic βCD derivatives interacting with SRT and the enthalpy-entropy compensation were observed and interpreted. Furthermore, the connection of RMβCD with SRT was characterized by circular dichroism spectroscopy (CD) and complexes of βCD derivatives with SRT were characterized through the computational studies with the use of molecular docking (MD).

Conductometric studies of 1, 3, 5 –triazinothiocarbamide at different concentration and temperature

Conductivity plays vital role in drug diffusion. Thermodynamic parameters affected by substituents of drug. Thermodynamic parameters of 1, 3, 5 –triazinothiocarbamide (1a) have been investigated by using conductometrically carried out at different molar concentrations. This work highlights investigation of G, K and µ values. The thermodynamic parameters viz. ΔH, ΔS and ∆G for ion pair formation determine from the value of ion association constant. This technique is suitable and accurate to study of pharmokinetics and pharmodynamics parameters.

Self-assembling thermostable chimeras as new platform for arsenic biosensing

The correct immobilization and orientation of enzymes on nanosurfaces is a crucial step either for the realization of biosensors, as well as to guarantee the efficacy of the developed biomaterials. In this work we produced two versions of a chimeric protein, namely ArsC-Vmh2 and Vmh2-ArsC, which combined the self-assembling properties of Vmh2, a hydrophobin from Pleurotus ostreatus, with that of TtArsC, a thermophilic arsenate reductase from Thermus thermophilus; both chimeras were heterologously expressed in Escherichia coli and purified from inclusion bodies. They were characterized for their enzymatic capability to reduce As(V) into As(III), as well as for their immobilization properties on polystyrene and gold in comparison to the native TtArsC. The chimeric proteins immobilized on polystyrene can be reused up to three times and stored for 15 days with 50% of activity loss. Immobilization on gold electrodes showed that both chimeras follow a classic Langmuir isotherm model towards As(III) recognition, with an association constant (KAsIII) between As(III) and the immobilized enzyme, equal to 650 (± 100) L mol−1 for ArsC-Vmh2 and to 1200 (± 300) L mol−1 for Vmh2-ArsC. The results demonstrate that gold-immobilized ArsC-Vmh2 and Vmh2-ArsC can be exploited as electrochemical biosensors to detect As(III).

Insights of theoretical calculations and solubility equilibrium measurements into Ca2+-fluoride complexation and their dissociation behaviors in aqueous solutions: Implication for the association constant measured by fluoride ion selective electrodes

Although the Ca2+-F− association is of great importance for aqueous environments and industrial systems containing F−, as well as for defluorination processes, many details of the association solvation structures and...

Hydration Thermodynamics and Hydrodynamic (Stokes) Radius of the Lanthanide Ions

Many biochemical and physiological properties depend on the size of ions and the thermodynamic quantities of ion hydration. The diffusion coefficient (D) of lanthanide (III) ions (Ln+3) in solution assumed (1.558-1.618 ×10−9 m2 s−1) by Einstein–Smoluchowski relation. The association constant (KA) of Ln+3 ions was calculated (210.3-215.3 dm3 mole-1) using the Shedlovsky method, and the hydrodynamic radius calculated (1.515-1.569 ×10−10 m) by the Stokes-Einstein equation. The thermodynamic parameters (ΔGo, ΔSo) also calculated by used suitable relations, while ΔHo, values are obtained from the literature. ΔGo, for ion hydration, has negative values in the range (13.25-13.30 KJ/mole), and a negative ΔSo, results have been shown in the limit (11.016-12.506 KJ/ K. mole).

Nucleosides as organizing agents

In the present review, we discuss the results of the research we have done over the last decade on multi-porphyrinic architectures bearing a nucleotidic backbone, compare all the data, offer a novel overview, and emphasize common capabilities of nucleosides appearing in various systems, providing a new insight on the pre-organizing capabilities of nucleosidic backbones. The efficiency of nucleosides as pre-organizing agents was investigated through the synthesis and study of various bis-porphyrins bearing nucleosidic linkers, as well as through the investigation of the conformation of linear and arborescent multi-porphyrins constructed on a nucleosidic backbone. The capacity of these molecules to complex guests with a high association constant was used as a tool to evaluate their degree of pre-organization, as well as the investigation of the electronic coupling existing between their chromophores and their photo-chemical capacities. Such an overview of one decade of scientific investigations documents the fact that rigid linkers between chromophores are not necessary for their spatial pre-organization, opening new routes to the faster synthesis of flexible highly pre-organized molecular architectures avoiding the long and tedious synthesis of rigid tweezers, especially for the preparation of rigid linkers which may bring solubility and stability problems.

Experimental Sensing and DFT Mechanism of Zn(II) Complex for Highly Sensitive and Selective Detection of Acetone

In the present work, a new Zn(II) perchlorate complex with 2,2’–bipyridyl of formulation {[Zn(bipy)2(H2O)](ClO4)2} (1) was obtained and well analyzed. This chemosensor was evaluated as a selective sensor for acetone among the several different organic solvents(CH3OH, EtOH, i–PrOH, i–BuOH, CHCl3, CH2Cl2, CCl4, C6H6, C7H8, C8H10, C2H3N, C3H7NO, C4H8O2, C3H6O3) in a fluorescence turn–off response in accordance with theoretical calculations. Sensing experiments were performed at ambient temperature which shows the acetone molecule distinctly reduces transfer of energy barrier to complex 1 and hence, produces remarkable luminescent quenching. Also, the weak intermolecular hydrogen–bonding interactions thanks to the presence of various hydrogen bonding donors and acceptors, exist between ligand molecules, which were broken during fluorescence, resulting in quenching. The stoichiometry ratio and association constant were evaluated using Benesi–Hildebrand relation giving 1:1 stoichiometry between complex 1 and acetone. Additionally, DFT results can also explicate the significant response on complex 1 upon addition of acetone. This work is vital in a new loom for the detection of acetone and other ketones.