Abstract
Herein, a novel fluorescent sensor has been developed for the detection of biothiols based on theoretical calculations of the stability constant of the complex between a Cu2+ ion and (E)-3-((2-(benzo[d]thiazol-2-yl)hydrazono)methyl)-7-(diethylamino) coumarin (BDC) as a fluorescent ligand. In this study, on the basis of density functional theory method, the Gibbs free energy of ligand-exchange reaction and the solvation model were carried out using thermodynamic cycles. The obtained results are in good agreement with the experimental data. The BDC–Cu2+ complex can be used as a fluorescent sensor for the detection of biothiols in the presence of non-thiol containing amino acids, with a detection limit for cysteine at 0.3 μM. Moreover, theoretical calculations of excited states were used to elucidate variations in the fluorescence properties. The computed results show that the excited doublet states D2 and D1 are dark doublet states, which quench the fluorescence of the complex.
Highlights
Cysteine (Cys), homocysteine (Hcy), and glutathione (GSH) are thiol biomolecules that play an important role in human biological processes
Alanine (Ala), arginine (Arg), aspartic acid (Asp), glutamic acid (Glu), glycine (Gly), histidine (His), isoleucine (Ile), leucine (Leu), lysine (Lys), methionine (Met), serine (Ser), threonine (Thr), tyrosine (Tyr), tryptophan (Trp) and valine (Val), did not cause any changes in the uorescence spectrum of the BDC– Cu2+ solution. These results indicate that the BDC–Cu2+ complex can be used as a uorescent sensor for the detection of thiol-containing amino acids in the presence of H2S and nonthiol containing amino acids in the concentration range from 0 to 10 mM
A complex exchange reaction-based uorescent chemosensor was investigated for the detection of 36272 | RSC Adv., 2020, 10, 36265–36274
Summary
Cysteine (Cys), homocysteine (Hcy), and glutathione (GSH) are thiol biomolecules that play an important role in human biological processes. Analytical methods based on uorescence technique have been widely developed due to their outstanding advantages.[8,9] This technique, in particular, can be used to detect biothiols in living cells.[10,11] A number of uorescent sensors have been reported based on various interactions with biothiols, such as Michael addition,[12,13] addition-cyclization with acrylates or aldehydes,[14,15] cleavage reactions of sulfonamide, sulfonate ester, disul des,[16,17,18] substitution reactions,[19] and disul de exchange reactions.[20] Recently, sensors for biothiols have been widely synthesized and reported; their working mechanism is based on the reactions between biothiols and complexes of uorescent ligands with metal ions.[21,22] This approach has opened a new research direction taking advantage of complexes between uorescent sensors and metal ions towards the detection of biothiols These works become more convenient if the stability constants of complexes can be determined. This problem can be effectively solved by combining theoretical calculations and empirical investigations to determine the stability constant of complexes
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