A new cationic indolium based styryl dye as a fluorescent probe, (E)-2-(4-(dibutylamino)styryl)-1,3,3trimethyl-3H-indol-1-ium iodide (Ci), 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. H and S 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 solvent polarity and it showed highly selective colorimetric and fluorometric sensing behavior for cyanide ions in organic solvent and aqueous solution. 1 H NMR titration was performed to examine the interaction mechanism between Ci and cyanide ions. The LOD values of cyanide ion were reported as 4.87x10 -9 M and 9.70x10 -7 M in DMSO and DMSO/H2O binary mixture, respectively. In addition, sensitivity of Ci as a chemosensor to cyanide ions was investigated in bitter almond samples.

A new cationic indolium based styryl dye as a fluorescent probe, (E)-2-(4-(dibutylamino)styryl)-1,3,3-trimethyl-3H-indol-1-ium iodide (Ci), 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 solvent polarity and it showed highly selective colorimetric and fluorometric sensing behavior for cyanide ions in organic solvent and aqueous solution. 1H NMR titration was performed to examine the interaction mechanism between Ci and cyanide ions. The LOD values of cyanide ion were reported as 4.87x10− 9 M and 9.70x10− 7 M in DMSO and DMSO/H2O binary mixture, respectively. In addition, sensitivity of Ci as a chemosensor to cyanide ions was investigated in bitter almond samples.

A novel carbazole compound, named 1-(9-ethyl-9H-carbazol-3-yl)-3-phenylurea (Cpu) was synthesized and its binding properties with protease enzymes (pepsin and trypsin) has been examined by steady-state fluorescence measurements, UV/vis absorption, infrared (FT-IR) and circular dicroism (CD) spectroscopies and also computational methods. The fluorescence experimental results indicated that the quenching mechanism of enzyme by Cpu is static process. The thermodynamic parameters (both negative ΔH/ΔS) and molecular docking results suggested that the binding of Cpu to pepsin/trypsin were driven by hydrogen bonds and van der Waals forces. Based on Förster’s theory, the binding distance (r) between pepsin/trypsin and Cpu was calculated to be 3.072/2.784 nm, which implies that non-radiative energy transfer occurs from enzyme to Cpu. Furthermore, absorption, CD, and FT-IR spectral analysis provided an evidence that the presence of Cpu induced notable changes in the secondary structures and microenvironmental of both pepsin and trypsin, supporting its significant influence on these enzymes.