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).

Interaction of 9-Methoxyluminarine with Different G-Quadruplex Topologies: Fluorescence and Circular Dichroism Studies

The interactions of G–quadruplexes of different topologies with highly fluorescent 9-methoxyluminarine ligand 9-MeLM were investigated by fluorescence and circular dichroism spectroscopy. The results showed that 9-methoxyluminarine was able to interact and did not destabilize any investigated molecular targets. The studied compound was selectively quenched by parallel c-MYC G-quadruplex DNA, whereas hybrid and antiparallel G4 topology caused only a negligible decrease in the fluorescence of the ligand. A high decrease of fluorescence of the ligand after binding with c-MYC G-quadruplex suggests that this molecule can be used as a selective probe for parallel G-quadruplexes.

Evaluation of the secondary structure of poly-γ-glutamic acid produced by Bacillus subtilis EGP5QL12 by circular dichroism spectroscopy method

An extracellular polymer was isolated from the culture liquid of Bacillus subtilis EGP5QL12 with the yield of 5,6 g/L. On the basis of the data of thin layer chromatography, colorimetric analyses and FTIR spectroscopy, it was established that the polymer is poly-γ- glutamic acid (PGA). PGA is widely used in medicine, cosmetology and the food industry due to its ability to bind water and metal ions. To assess the biotechnological potential of the isolated polymer and predict the possibilities of its application in various fields of the national economy, it is necessary to analyze the characteristic spectral features that make it possible to establish its secondary structure. The isolated PGA preparation was analyzed by circular dichroism spectroscopy at various pH values. According to the results of this study, it was found that the polymer forms predominantly β-structures with a low proportion of irregular structures and α-helices, which gives it a high potential for creating hydrogels and composite materials.