A Novel Fluorescent Probe for the Detection of Cyanide Ions in Solutions and Studies on Its Biophysical Interactions with ctDNA and Proteases.

A new cationic indolium based styryl dye (Ci) as a fluorescent probe was synthesized and its anions selectivity/sensitivity properties/molecular interactions with protease enzymes (pepsin/trypsin) and ctDNA has been studied by spectroscopic and computational methods. The fluorescence measurements at different temperatures indicated that quenching mechanism of enzymes by Ci was static. ΔH and ΔS data pointed out electrostatic/hydrophobic interactions with pepsin, and also hydrogen bonds/van der Waals forces with trypsin of Ci. According to Förster's non-radiative energy transfer, binding distances (r) were calculated as 3.53/3.27 nm for pepsin/trypsin. It was also investigated that groove binding is effective in interaction with ctDNA. The results were supported with molecular docking analyzes which have same tendency. Ci has been demonstrated hypsochromic effect with a decrease in polarity of solvents and it showed highly selective colorimetric and fluorometric sensing behavior for cyanide in organic solvent and in aqueous solution. 1H NMR titration was performed to examine the interaction mechanism between Ci and cyanide. The LOD values of cyanide ion were reported as 4.87 × 10-9 M and 9.70 × 10-7 M in DMSO and DMSO/H2O binary mixture, respectively. In addition, sensitivity of Ci as a chemosensor to cyanide was investigated in bitter almond samples.

Synthesis, crystal structure at 219†K and Hirshfeld surface analyses of 1,4,6-tri-methyl-quinoxaline-2,3(1H,4H)-dione monohydrate.

The asymmetric unit of the title compound, C11H12N2O2·H2O, contains a mol-ecule of 1,4,6-trimethyl-1,4-di-hydro-quinoxaline-2,3-dione and a solvent water mol-ecule. Four atoms of the benzene ring are disordered over two sets of sites in a 0.706 (7):0.294 (7) ratio while the N-bound methyl groups are rotationally disordered with occupancy ratios of 0.78 (4):0.22 (4) and 0.76 (5):0.24 (5). In the crystal, mol-ecules are linked by O-H⋯O and C-H⋯O hydrogen bonds into layers lying parallel to (10). The Hirshfeld surface analysis indicates that the most important contributions to the packing arrangement are due to H⋯H (51.3%) and O⋯H/H⋯O (28.6%) inter-actions. The mol-ecular structure calculated by density functional theory is compared with the experimentally determined mol-ecular structure, and the HOMO-LUMO energy gap has been calculated.

Synthesis, crystal structures and Hirshfeld surface analysis of 1,4-dibenzyl-6-methyl-1,4-di-hydro-quinoxaline-2,3-dione.

The title quinoxaline mol-ecule, C23H20N2O2, is not planar, the dihedral angle angle between the mean planes of the benzene rings being 72.54 (15)°. In the crystal, mol-ecules are connected into chains extending parallel to (10) by weak C-H⋯O hydrogen bonds. Weak C-H⋯π inter-actions link the chains, forming a three-dimensional network structure. Hirshfeld surface analysis revealed that the most important contributions for the crystal packing are from H⋯H (48.7%), H⋯C/C⋯H (32.0%), H⋯O/O⋯H (15.4%), C⋯C (1.9%), H⋯N/N⋯H (1.1%) contacts.