Understanding The Role of Reline, a Natural DES, on Temperature-Induced Conformational Changes of C-Kit G-Quadruplex DNA: A Molecular Dynamics Study

The noncanonical guanine-rich DNAs have drawn particular attention to the scientific world due to their controllable diverse and polymorphic structures. Apart from biological and medical significance, G-quadruplex DNAs are widely used in various fields such as nanotechnology, nanomachine, biosensors, and biocatalyst. So far, the applications of the G-quadruplex DNA are mainly limited in the water medium. Recently, a new generation of solvent named deep eutectic solvent (DES) has become very popular and has been widely used as a reaction medium of biocatalytic reactions and long-term storage medium for nucleic acids, even at high temperature. Hence, it is essential to understand the role of DES on temperature-induced conformational changes of a G-quadruplex DNA. In this research work, we have explored the temperature-mediated conformational dynamics of c-kit oncogene promoter G-quadruplex DNA in reline medium in the temperature range of 300-500 K, using a total of 10 μs unbiased all-atom molecular dynamics simulation. Here, from RMSD, RMSF, R_g and principal component analyses, we notice that the c-kit G-quadruplex DNA is stable up to 450 K in reline medium. However, it unfolds in water medium at 450 K. It is found that the hydrogen bonding interactions between c-kit G-quadruplex DNA and reline play a key role in the stabilization of the G-quadruplex DNA even at high temperature. Furthermore, in this work we have observed a very interesting and distinctive phenomenon of the central cation of the G-quadruplex DNA. Its position was seen to fluctuate between the two tetrad cores, that is, the region between tetrad-1 and tetrad-2 and that between tetrad-2 and tetrad-3 and vice versa at 450 and 500 K in reline medium which is absent in water medium at 450 K. Moreover, the rate of its oscillation is increased when temperature is increased.

ATP Controls the Aggregation of Aβ16-22 Peptides

The oligomerization of Aβ_16-22 peptide, which is the hydrophobic core region of full-length Aβ_1-42, causes Alzheimer's disease (AD). This progressive neurodegenerative disease affects over 44 million people worldwide. However, very few synthesized drug molecules are available to inhibit the aggregation of Aβ. Recently, experimental studies have shown that the biological ATP molecule prevents Aβ fibrillation at the millimolar scale; however, the significance of ATP molecules on Aβ fibrillation and the mechanism behind it remain elusive. We have carried out a total of 7.5 μs extensive all-atom molecular dynamics and 8.82 μs of umbrella sampling in explicit water using AMBER14SB, AMBER99SB-ILDN, and AMBER-FB15 force fields for Aβ_16-22 peptide, to investigate the role of ATP on the disruption of Aβ_16-22 prefibrils. From various analyses, such as secondary structure analysis, residue-wise contact map, SASA, and interaction energies, we have observed that, in the presence of ATP, the aggregation of Aβ_16-22 peptide is very unfavorable. Moreover, the biological molecule ATP interacts with the Aβ_16-22 peptide via hydrogen bonding, π-π stacking, and NH-π interactions which, ultimately, prevent the aggregation of Aβ_16-22 peptide. Hence, we assume that the deficiency of ATP may cause Alzheimer's disease (AD).

Does Fungicide "Dodine" Unfold Protein like Kosmo-Chaotropic Agent?

The nontargeted action of fungicides affects the structure of protein, which leads to several serious diseases such as nausea, cancer, fetus malformations, movement dysfunction, and behavioral changes in human and animals. Hence, understanding of the structural change in protein induced by fungicides is of utmost importance to decode its mode of nontargeted action. In this study, we have investigated the structural change of myoglobin by an important fungicide, namely, dodine (n-dodecylguanidinium acetate), as well as its analogues n-hexylguanidinium acetate (HGA) and guanidinium chloride (GdmCl) using spectroscopic and thermodynamic methods. The amount of dodine and HGA required for the unfolding of myoglobin is significantly less than GdmCl. GdmCl, dodine, and HGA unfold the myoglobin by decreasing the content of the helical and tertiary structures. However, the decrease in the content of tertiary structure is significantly higher than that of the secondary structure for dodine and HGA, in contrast to GdmCl, where the decrease in secondary and tertiary contents of protein is not biased. Thermodynamic and spectroscopic data depict that the unfolding of the dodine and HGA is driven by the hydrophobic interaction, whereas the hydrogen bonding of GdmCl with the amino acids of protein plays a key role in the unfolding. The long alkyl chain of dodine and HGA get accommodated at the surface of the helices of myoglobin, inducing strong hydrophobic interaction, which causes its unfolding. This study depicts that dodine unfolds protein by the chaotropic effect in which its hydrocarbon chain destabilizes the protein by the hydrophobic effect, unlike in an earlier study, where dodine was claimed to be a kosmo-chaotropic agent as its hydrocarbon group stabilizes the protein.