Novel aminobenzanthrone dyes for amyloid fibril detection

A Comparative Study of New Fluorescent Anthraquinone and Benzanthrone α-Aminophosphonates: Synthesis, Spectroscopy, Toxicology, X-ray Crystallography, and Microscopy of Opisthorchis felineus

In this research, we explore the synthesis of and characterize α-aminophosphonates derived from anthraquinone and benzanthrone, focusing on their fluorescence properties and potential applications in confocal laser scanning microscopy (CLSM). The synthesized compounds exhibit notable solvatochromic behavior, emitting fluorescence from green to red across various solvents. Spectroscopic analysis, including 1H-, 13C-, and 31P-NMR, FTIR, and mass spectrometry, confirms the chemical structures. The compounds' toxicity is evaluated using etiolated wheat sprouts, revealing varying degrees of impact on growth and oxidative damage. Furthermore, the study introduces these α-aminophosphonates for CLSM imaging of the parasitic flatworm Opisthorchis felineus, demonstrating their potential in visualizing biological specimens. Additionally, an X-ray crystallographic study of an anthraquinone α-aminophosphonate provides valuable structural insights.

3-(Phenylethynyl)-7H-benzo[de]anthracen-7-one

The present work describes the facile synthesis of 3-(phenylethynyl)-7H-benzo[de]anthracen-7-one via a Sonogashira coupling reaction. The structure of the synthesized benzanthrone derivative is characterized by 1H- and 13C-NMR spectroscopy and high-resolution mass spectrometry. The photophysical properties of the title compound are investigated by means of UV-Vis and fluorescence spectroscopy in various organic solvents.

Evaluation of Peptide/Protein Self-Assembly and Aggregation by Spectroscopic Methods

The self-assembly of proteins is an essential process for a variety of cellular functions including cell respiration, mobility and division. On the other hand, protein or peptide misfolding and aggregation is related to the development of Parkinson's disease and Alzheimer's disease, among other aggregopathies. As a consequence, significant research efforts are directed towards the understanding of this process. In this review, we are focused on the use of UV-Visible Absorption Spectroscopy, Fluorescence Spectroscopy and Circular Dichroism to evaluate the self-organization of proteins and peptides in solution. These spectroscopic techniques are commonly available in most chemistry and biochemistry research laboratories, and together they are a powerful approach for initial as well as routine evaluation of protein and peptide self-assembly and aggregation under different environmental stimulus. Furthermore, these spectroscopic techniques are even suitable for studying complex systems like those in the food industry or pharmaceutical formulations, providing an overall idea of the folding, self-assembly, and aggregation processes, which is challenging to obtain with high-resolution methods. Here, we compiled and discussed selected examples, together with our results and those that helped us better to understand the process of protein and peptide aggregation. We put particular emphasis on the basic description of the methods as well as on the experimental considerations needed to obtain meaningful information, to help those who are just getting into this exciting area of research. Moreover, this review is particularly useful to those out of the field who would like to improve reproducibility in their cellular and biomedical experiments, especially while working with peptide and protein systems as an external stimulus. Our final aim is to show the power of these low-resolution techniques to improve our understanding of the self-assembly of peptides and proteins and translate this fundamental knowledge in biomedical research or food applications.

Experimental and theoretical insights on the effect of solvent polarity on the photophysical properties of a benzanthrone dye

Benzanthrone derivatives show interesting solvent dependent photophysical properties. Understanding of their photophysical properties is essential for developing the fluorescence probes based on benzanthrone derivatives. The photophysical properties of 3-(N'-chlorophenyl)piperazino-7H-benzo[de]anthracen-7-one [ClPh-PBA] molecule are reported in different solvents and solvent mixtures. The change in Stokes shift, quantum yield, fluorescence life time and radiative rate constants as a function of solvent polarity shows that the Intermolecular Charge Transfer (ICT) is affected by solvent polarity and hydrogen bonding. The quantum yield and fluorescence life time values decrease and the nonradiative decay rate constant (k_nr) values are observed to be higher in polar solvents. The weak emission of ClPh-PBA in polar solvents is primarily due to the non-radiative torsional motion of the chlorophenyl group around benzanthrone moiety. The torsional motion of chlorophenyl group at the remote nitrogen around benzanthrone moiety is also evident from TDDFT calculations performed using B3LYP/6-311+ G (d, p) basis set. The ground state and excited state dipole moments, absorption and emission maxima (nm) along with other quantum chemical parameters are obtained using B3LYP/6-311+ G (d, p) basis set. The experimental and theoretical results follow the similar trends.

Experimental and theoretical study on structure and spectroscopic properties of 2-bromo-3-N-(N',N'-dimethylformamidino) benzanthrone

The goal of present research is a theoretical and experimental investigation of geometrical structure, electronic properties, absorption and fluorescence spectra prediction for 2-bromo-3-N-(N',N'-dimethylformamidino)benzanthrone. As a result of conformational analysis, two rotamers have been found with a rotational barrier of 5.45 kcal/mol. Absorption and fluorescence spectra maxima in the solvent (ethanol) have been calculated using the concepts of the Jablonsky diagram. The obtained values of the absorption and fluorescence maxima (437 and 679 nm, respectively) correspond to the experimental values (447 and 659 nm). The abnormally large Stokes shift is associated with the redistribution of electron density, as well as flattening of the structure of the molecule in the excited state. According to the frontal molecular orbital analysis data, the peak in the long-wave part of the absorption spectra is created by an electron transition from the highest occupied molecular orbital (HOMO) to the lowest occupied molecular orbital (LUMO) (π→π*). Substitute group does not participate in the formation of absorption and fluorescence spectra.

Photophysical properties of benzanthrone derivatives: effect of substituent, solvent polarity and hydrogen bonding

Benzanthrone derivatives are potential fluorescent probes for various chemical and biological environments. A mechanistic understanding of their photophysical properties is pivotal for designing an efficient fluorescence sensor based on the benzanthrone framework. In this study, we report on the effect of chemical substitution on the photophysical properties of two benzanthrone derivatives, namely, 3-(N'-methyl)-piperazino-7H-benzo[de]anthracen-7-one [Me-PBA] and 3-(N'-phenyl)-piperazino-7H-benzo[de]anthracen-7-one [Ph-PBA] in different solvents and solvent mixtures of varying polarities and proticities. Both benzanthrone derivatives show interesting solvent-dependent photophysical properties. Although both derivatives exhibit strong intramolecular charge transfer (ICT) characteristics in the excited state, the extent of the charge transfer is significantly influenced by the nature of the chemical substitution. Modulation of photophysical parameters as a function of solvent properties led us to propose that ICT is affected by solvent polarity and hydrogen bonding. From the viscosity effect, it is revealed that the weaker emission of Ph-PBA compared to Me-PBA in polar solvents is primarily due to the non-radiative torsional motion of the phenyl group in the former derivative. In protic solvents, intermolecular hydrogen bonding imparts strong non-radiative deactivation to both derivatives, thus rendering a weak fluorescence yield.

Novel benzanthrone probes for membrane and protein studies

The applicability of a series of novel benzanthrone dyes to monitoring the changes in physicochemical properties of lipid bilayer and to differentiating between the native and aggregated protein states has been evaluated. Based on the quantitative parameters of the dye-membrane and dye-protein binding derived from the fluorimetric titration data, the most prospective membrane probes and amyloid tracers have been selected from the group of examined compounds. Analysis of the red edge excitation shifts of the membrane- and amyloid-bound dyes provided information on the properties of benzanthrone binding sites within the lipid and protein matrixes. To understand how amyloid specificity of benzanthrones correlates with their structure, quantitative structure activity relationship (QSAR) analysis was performed involving a range of quantum chemical molecular descriptors. A statistically significant model was obtained for predicting the sensitivity of novel benzanthrone dyes to amyloid fibrils.