The semi-quantitative design method of fluorescent probe molecular structure proposed by Dalian Chemical

[ Instrument R & D of Instrumentation Network ] Recently, the team of Han Keli, a research group of the reaction kinetics of complex molecular systems at the Dalian Institute of Chemical Physics, Chinese Academy of Sciences, and the team of Park Hailong, a researcher of the functional group of biomolecules, based on the local pro Electrical index, a semi-quantitative design method for the molecular structure of glutathione sulfur transferase (GST) detection fluorescent probe is proposed.

The main function of glutathione sulfur transferase is to catalyze the coupling of electrophilic groups of certain endogenous or foreign harmful substances with the thiol groups of reduced glutathione, increasing its hydrophobicity makes it easy to cross cell membranes, and After being decomposed, it is excreted from the body to achieve the purpose of detoxification.

GST, as a phase II detoxification enzyme, can catalyze the nucleophilic attack of glutathione (GSH) thiol groups on electrophilic or hydrophobic substances to achieve its physiological function. Its multiple isoform isozymes are overexpressed in many tumor cell lines, especially anti-cancer drug-resistant cell lines, so the detection of high signal-to-noise ratio GST is of great significance for the early diagnosis and treatment of cancer. Previously reported GST fluorescent probes mostly used 2,4-dinitrobenzenesulfonyl as the recognition and reaction group. Although this group can guarantee extremely high sensitivity, it will also bring serious background noise. This is due to the considerable non-enzymatic chemical reactivity of this group towards GSH. In order to obtain a high-performance and practical GST fluorescent probe, it is necessary to reduce the background reaction noise of the recognition group. However, sensitivity and background noise are often a pair of checks and balances. Therefore, fine-tuning the reactivity is the key to finding the equilibrium point.

Fluorescent probes have characteristic fluorescence in the ultraviolet-visible-near infrared region, and their fluorescence properties (excitation and emission wavelength, intensity, lifetime, polarization, etc.) can be changed according to the nature of the environment, such as polarity, refractive index, viscosity, etc. A type of fluorescent molecule that changes sensitively.

Conceptual density functional theory (CDFT) starts from the theorem that the ground state properties of a molecule are determined by its ground state electron density, and gives the exact physical definitions and expressions of related chemical concepts, which can be used for quantitative calculation and measurement.

The classical methods of electronic structure theory, especially the Hartree-Fock method and the post-Hartree-Fock method, are based on complex multi-electron wave functions. The main goal of density functional theory is to replace the wave function with electron density as the basic quantity of research. Because the multi-electron wave function has 3N variables (N is the number of electrons, each electron contains three spatial variables), and the electron density is only a function of three variables, whether it is conceptually or practically more convenient to handle.

Although the concept of density functional theory originated from the Thomas-Fermi model, it did not have a solid theoretical basis until the Hohenberg-Kohn theorem was proposed. Hohenberg-Kohn's first theorem states that the ground state energy of a system is only a functional of electron density.

In this work, based on the above theory and the reaction mechanism of aromatic nucleophilic substitution (SNAr) of GST enzymatic reaction, the research team innovatively introduced the local electrophilic index ωk in CDFT into the design of fluorescent probes for quantification Describe the background reactivity of the probe, which facilitates targeted fine-tuning of the reactivity.

The results of the non-enzymatic reaction kinetic test show that the parameter ωk can accurately describe and predict the background reactivity of the probe molecule with GSH; the results of the enzymatic reaction kinetic test show that the value of ωk can also generally represent the strength of the sensitivity . It is worth noting that, relative to the sensitivity kcat corresponding to the enzymatic reaction, the background noise knonc corresponding to the non-enzymatic reaction is more sensitive to the value of ωk, which proves that there is a possibility to achieve noise reduction and maintain high sensitivity by fine-tuning ωk. Operating space.

In addition, in addition to the optimization of the reaction / recognition mechanism, the research team also confirmed through femtosecond transient absorption spectroscopy experiments and time-dependent density functional theory calculations that the photoinduced electron transfer (PET) process in the system has low background in the luminescence mechanism. Noise contributes. This study provides a new idea for the semi-quantitative design of fluorescent probes or drug molecules based on SNAr reaction.

Source: Encyclopedia, Dalian Institute of Chemical Physics