Synthesis, characterization and unravelling the molecular interaction of new bioactive 4-hydroxycoumarin derivative with biopolymer: Insights from spectroscopic and theoretical aspect

Exploring the interaction of tepotinib with calf thymus DNA using molecular dynamics simulation and multispectroscopic techniques

In recent times, there has been a surge in the discovery of drugs that directly interact with DNA, influencing gene expression. As a result, understanding how biomolecules interact with DNA has become a major area of research. One such drug is Tepotinib (TPT), an FDA-approved anti-cancer medication known as a MET tyrosine kinase inhibitor, used in chemotherapy for metastatic non-small cell lung cancer (NSCLC) with MET exon 14 skipping alterations. In our study, we adopted both biophysical and in-silico methods to investigate the binding relationship of TPT and ctDNA. The absorption spectra of ctDNA exhibited a hypochromic effect when titrated with TPT and the binding constant of TPT-ctDNA complex was calculated, Ka = 9.91 × 104 M-1. By computing bimolecular enhancement constant (KB) and thermodynamic enhancement constant (KD) in fluorometric investigations, it was found that the fluorescence enhancement is a result of a static process involving the ctDNA-TPT complex formation in the ground state, as opposed to a dynamic process. The displacement assay results further supported this finding, showing that TPT exhibits a binding preference for minor groove of ct-DNA and was also demonstrated by KI quenching and CD spectroscopy. The molecular docking and molecular dynamic simulations validated TPT's groove binding nature and binding pattern with ctDNA, respectively. Thus, the results of our present investigation offer valuable insights into the interaction between TPT and ctDNA. It is evident that TPT, as an anti-cancer medication, binds to the minor groove of ctDNA.

Quantification of mirtazapine in tablets via DNA binding mechanism; development of a new HPLC method

Atypical antidepressant mirtazapine (MIR) is mostly prescribed for the management of major depressive disorder. The identification of MIR in pharmaceutical dosage forms was made possible by developing a novel, quick, sensitive high-performance liquid chromatography (HPLC) approach that was verified in accordance with ICH recommendations. In the first part of this study, HPLC investigations were optimized with regard to variables including pH, working column, mobile phase, temperature, and flow rate. The limit of detection (LOD) was 0.013 ppm, the limit of quantification (LOQ) was 0.044 ppm, and the linear range was computed as 0.5-15 ppm (R2 = 0.9998). The recovery investigation assessed the method's accuracy, which was shown to range between 98.82 and 100.97 %. In the second part, by using UV-vis spectroscopy, HPLC, thermal denaturation, and viscosity measurements, the mechanism of binding interaction of MIR with double-stranded fish sperm deoxyribonucleic acid (dsDNA) has been thoroughly studied. The DNA binding constants (Kb) were determined using UV-Vis absorption and HPLC methods. To investigate the interactions of MIR with dsDNA, molecular docking calculations and additionally, molecular dynamics simulations were performed. Results showed that MIR is located in the minor groove of dsDNA, and in addition to hydrogen bonding, electrostatic interaction is also formed between the aromatic ring of MIR and phosphate oxygen of dsDNA. Finally, a binding characterization study using MIR tablets was also conducted in order to assess the interaction mechanism of the DNA with the drug using the validated analytical procedure developed for the MIR molecule.

Fluorescence Spectroscopic Studies to Evaluate Binding Interaction between Hoechst 33258 and Bilirubin

A detailed spectroscopic study (fluorescence, absorption, and lifetime) was conducted to gain insight into the nature of the binding interaction between fluorophore Hoechst33258 (H258) and jaundice marker Bilirubin (Br). The fluorescence emission of the H258 (Ex/Em = 340-502nm) showed a conc. dependent quenching in the presence of Br (1.25[Formula: see text]M to 10[Formula: see text]M). The Stern-Volmer constant demonstrated an upward curve depicting the occurrence of both static and dynamic quenching with an acquired value of K[Formula: see text] = 3.1x 10[Formula: see text] M[Formula: see text] and biomolecular quenching rate constant K[Formula: see text] = 8.6 x 10[Formula: see text] M[Formula: see text]S[Formula: see text]. The static quenching was evaluated using the sphere of action model and a sphere radius of 0.3nm indicated the presence of a static component in the quenching. The FRET analysis with overlap integral (J) = 1.4x10[Formula: see text] M[Formula: see text]cm[Formula: see text]nm[Formula: see text] and Foster Radius(R[Formula: see text]) = 26.82 Å with 59% efficiency suggested occurrence of dynamic quenching. Further studies with the time-resolved fluorescence also indicated the presence of dynamic quenching. The lifetime values of H258 reduced from 3.9ns to 0.5ns. Molecular docking studies further support both static and dynamic components in quenching. A non-covalent interaction of H258 with Br in the presence of HSA is predominantly characterized by H-bonding with residues Lys, Asn, Glu, Gln, and Br. The H258 and Br interaction was within the distance of 3.04 Å, which is in coherence with the sphere of action model (0.3nm) and Van-der-Waals along with hydrophobic interactions, which suggested both static and dynamic quenching. Thus, H258 can serve as an efficient fluorophore to monitor binding interactions and can be further exploited as a suitable probe for investigating conformational changes and detection of Br in subsequent studies.

Molecular Dynamics and Multi-Spectroscopic of the Interaction Behavior between Bladder Cancer Cells and Calf Thymus DNA with Rebeccamycin: Apoptosis through the Down Regulation of PI3K/AKT Signaling Pathway

The interaction of Rebeccamycin with calf thymus (ctDNA) in the absence and presence of H1 was investigated by molecular dynamics, multi-spectroscopic, and cellular techniques. According to fluorescence and circular dichroism spectroscopies, Rebeccamycin interacted with ctDNA in the absence of H1 through intercalator or binding modes, while the presence of H1 resulted in revealing theintercalator, as the dominant role, and groove binding modes of ctDNA-Rebeccamycin complex. The binding constants, which were calculated to be 1.22 × 104 M-1 and 7.92 × 105 M-1 in the absence and presence of H1, respectively, denoted the strong binding of Rebeccamycin with ctDNA. The binding constants of Rebeccamycin with ct DNA in the absence and presence of H1 were calculated at 298, 303 and 308 K. Considering the thermodynamic parameters (ΔH0 and ΔS0), both vander waals forces and hydrogen bonds played predominant roles throughout the binding of Rebeccamycin to ctDNA in the absence and presence of H1. The outcomes of circular dichroism suggested the lack of any major conformational changes in ctDNA upon interacting with Rebeccamycin, except some perturbations in native B-DNA at local level. Additionally, the effect of NaCl and KI on ctDNA-Rebeccamycin complex provided further evidence for the reliance of their interaction modes on substituted groups. The observed increase in the relative viscosity of ctDNA caused by the enhancement of Rebeccamycin confirmed their intercalation and groove binding modes in the absence and presence of H1. Moreover, the assessments of molecular docking simulation corroborated these experimental results and also elucidated the effectiveness of Rebeccamycinin inhibiting and proliferating T24 and 5637 cells. Meanwhile, the ability of Rebeccamycin in inhibiting cell proliferation and tumor growth through the induction of apoptosis by down regulating the PI3K/AKT signaling pathway were provided.

Multi-spectroscopic, thermodynamic, and molecular docking/dynamic approaches for characterization of the binding interaction between calf thymus DNA and palbociclib

Studying the binding interaction between biological macromolecules and small molecules has formed the core of different research aspects. The interaction of palbociclib with calf thymus DNA at simulated physiological conditions (pH 7.4) was studied using different approaches, including spectrophotometry, spectrofluorimetry, FT-IR spectroscopy, viscosity measurements, ionic strength measurements, thermodynamic, molecular dynamic simulation, and docking studies. The obtained findings showed an apparent binding interaction between palbociclib and calf thymus DNA. Groove binding mode was confirmed from the findings of competitive binding studies with ethidium bromide or rhodamine B, UV–Vis spectrophotometry, and viscosity assessment. The binding constant (K_b) at 298 K calculated from the Benesi–Hildebrand equation was found to be 6.42 × 10³ M⁻¹. The enthalpy and entropy changes (∆H⁰ and ∆S⁰) were − 33.09 kJ mol⁻¹ and 61.78 J mol⁻¹ K⁻¹, respectively, showing that hydrophobic and hydrogen bonds constitute the primary binding forces. As indicated by the molecular docking results, palbociclib fits into the AT-rich region of the B-DNA minor groove with four base pairs long binding site. The dynamic performance and stability of the formed complex were also evaluated using molecular dynamic simulation studies. The in vitro study of the intermolecular binding interaction of palbociclib with calf thymus DNA could guide future clinical and pharmacological studies for the rational drug scheming with enhanced or more selective activity and greater efficacy.

Inhibition of microtubule assembly and cytotoxic effect of graphene oxide on human colorectal carcinoma cell HCT116

Nanomaterials, such as graphene oxide (GO), are increasingly being investigated for their suitability in biomedical applications. Tubulin is the key molecule for the formation of microtubules crucial for cellular function and proliferation, and as such an appealing target for developing anticancer drug. Here we employ biophysical techniques to study the effect of GO on tubulin structure and how the changes affect the tubulin/microtubule assembly. GO disrupts the structural integrity of the protein, with consequent retardation of tubulin polymerization. Investigating the anticancer potential of GO, we found that it is more toxic to human colon cancer cells (HCT116), as compared to human embryonic kidney epithelial cells (HEK293). Immunocytochemistry indicated the disruption of microtubule assembly in HCT116 cells. GO arrested cells in the S phase with increased accumulation in Sub-G1 population of cell cycle, inducing apoptosis by generating reactive oxygen species (ROS) in a dose- and time-dependent manner. GO inhibited microtubule formation by intervening into the polymerization of tubulin heterodimers both in vitro and ex vivo, resulting in growth arrest at the S phase and ROS induced apoptosis of HCT116 colorectal carcinoma cells. There was no significant harm to the HEK293 kidney epithelial cells used as control. Our report of pristine GO causing ROS-induced apoptosis of cancer cells and inhibition of tubulin-microtubule assembly can be of interest in cancer therapeutics and nanomedicine.

Anticarin β Inhibits Human Glioma Progression by Suppressing Cancer Stemness via STAT3

Glioma is the most common form of malignant brain cancer. It is very difficult to cure malignant glioma because of the presence of glioma stem cells, which are a barrier to cure, have high tumorigenesis, associated with drug resistance, and responsible for relapse by regulating stemness genes. In this study, our results demonstrated that anticarin β, a natural compound from Antiaris toxicaria, can effectively and selectively suppress proliferation and cause apoptosis in glioma cells, which has an IC₅₀ that is 100 times lower than that in mouse normal neural stem cells. Importantly, cell sphere formation assay and real time-quantitative analysis reveal that anticarin β inhibits cancer stemness by modulating related stemness gene expression. Additionally, anticarin β induces DNA damage to regulate the oncogene expression of signal transducer and activator of transcription 3 (STAT3), Akt, mitogen-activated protein kinases (MAPKs), and eventually leading to apoptosis. Furthermore, anticarin β effectively inhibits glioma growth and prolongs the lifts pan of tumor-bearing mice without systemic toxicity in the orthotopic xenograft mice model. These results suggest that anticarin β is a promising candidate inhibitor for malignant glioma.