The effect of size and substitution patterns of azobenzene derivatives on the spectroscopic properties and rigidity of the smallest photoswitchable G-quadruplex.
Photoactuators and photoluminescent dyes utilize light to perform mechanical motion and undergo spontaneous radiation emission, respectively. Combining these two functionalities in a single molecule would benefit the construction of advanced molecular machines. Due to the possible detrimental interaction between the two light-dependent functional parts, the design of hybrid systems featuring both functions in parallel remains highly challenging. Here, we develop a light-driven rotary molecular motor with an efficient photoluminescent dye chemically attached to the motor, not compromising its motor function. This molecular system shows efficient rotary motion and bright photoluminescence, and these functions can be addressed by a proper choice of excitation wavelengths and solvents. The moderate interaction between the two parts generates synergistic effects, which are beneficial for lower-energy excitation and chirality transfer from the motor to the photoluminescent dye. Our results provide prospects towards photoactive multifunctional systems capable of carrying out molecular rotary motion and tracking its location in a complex environment.
In this study, we investigated the influence of a transverse electric field on the mechanical properties of carbon, boron nitride, and silicon carbide nanotubes based on density functional theory and continuum mechanics. To evaluate the Young's modulus of the nanotubes, a compressive distribution loading was implemented in the direction perpendicular to the longitudinal axis of the nanotubes in the presence and absence of an electric field. According to the obtained results from the geometry of the deformed nanotubes, an elliptical function was used to estimate the overall deformation. Based on the Green strain theory, the displacement of each particle is defined by the conversion matrix to transform the initial circular shape of the nanotubes to the final elliptical shape. The classical continuum theory was employed to estimate the relationship between strain energy and strain field of the nanotubes. An evolutionary genetic algorithm was used to achieve an accurate estimation of the fitting of the energy function versus strain based on the elasticity theory. In addition, the effect of the electric field on the electronic and mechanical properties of the nanotubes was investigated. The numerical results revealed that the nanotubes exposed to the electric field have more effective stiffness in comparison to the similar case in the off-field condition.
Stabilization of G-quadruplex structures in the c-KIT promoter with the aid of ligands has become an area of great interest in potential cancer therapeutics. Understanding the binding process between ligands and Gquadruplex is essential for a discovery of selective ligands with high binding affinity to G-quadruplex. In the present work, binding mechanisms of 4-quinazolinones to c-KIT G-quadruplex were investigated theoretically by means of molecular dynamics (MD) simulations. To explore the binding affinity of ligands, binding free energy calculations were performed using the molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) method. We demonstrate that the key interactions in G-quadruplex-ligand complexes are π-π stacking and hydrogen bond interactions. However, neither of these two interactions alone determines the stability of the Gquadruplex-ligand complexes; rather, it is the result of an intricate interplay between the two. To further examine the nature of the binding, a free energy decomposition analysis at residue level was carried out. The results clearly demonstrate the crucial roles of two hot spot residues (DG4 and DG8) for the binding of ligands to c-KIT G-quadruplex, and highlight the importance of the planar aromatic moiety of ligands in G-quadruplex stabilization via π-π stacking interactions. Our study can assist in the design of new derivatives of 4-quinazolinone with high binding affinity for c-KIT G-quadruplex.
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