Electrochemical spectroscopic investigations on the interaction of an ytterbium complex with DNA and their analytical applications such as biosensor

Biophysical insights on the interaction of anticoagulant drug dicoumarol with calf thymus-DNA: deciphering the binding mode and binding force with thermodynamics

The biological activity of drugs is exhibited due to their interactions with bio-receptors. Dicoumarol (DIC) is a natural hydroxycoumarin and a well-known anticoagulant. DNA is the genetic material and one of the targets of numerous drugs. The interaction of DIC with calf-thymus DNA (ct-DNA) has been studied using different biophysical techniques and docking studies. The binding constant in the order of 103 to 104 M-1 was observed from spectroscopic studies. Thermodynamic studies at 4 different temperatures revealed the spontaneity of the interaction with the entropy-driven process. Marker displacement studies with competitive markers of intercalators (ethidium bromide) and groove binders (Hoechst 33258) confirmed the groove-binding nature of DIC in DNA. The groove-binding mode of DIC was complemented by different studies like viscosity measurements, DNA melting, and the effect of KI on the binding. A minor perturbation in the DNA viscosity and no significant change in the DNA melting temperature (Tm) after binding with DIC further confirms the groove binding mode. The effect of KI on the DIC and DIC-DNA system suggested the absence of DIC intercalation. The absence of significant electrostatic force was revealed from the ionic-strength effect study. Binding-induced conformational variation in ct-DNA was absent in circular dichroism studies. Molecular docking studies suggested the position of DIC within the minor groove of ct-DNA, covering three base pairs long. The outcome of this report may help in understanding the pharmacodynamics and pharmacokinetics of dicoumarol analogs and related molecules.Communicated by Ramaswamy H. Sarma.

Binding of dicoumarol analog with DNA and its antioxidant studies: A biophysical insight by in-vitro and in-silico approaches

DNA is the major target for a number of pharmaceutical drugs. The interaction of drug molecules with DNA plays a major role in pharmacokinetics and pharmacodynamics. Bis-coumarin derivatives have diverse biological properties. Here, we have explored the antioxidant activity of 3,3'-Carbonylbis (7-diethylamino coumarin) (CDC) using DPPH, H₂O_2, and superoxide scavenging studies followed by its binding mode in calf thymus-DNA (CT-DNA) using several biophysical methods including molecular docking. CDC exhibited comparable antioxidant activity to standard ascorbic acid. The UV-Visible and fluorescence spectral variations indicate the CDC-DNA complex formation. The binding constant in the range of 10⁴ M^-1 was obtained from spectroscopic studies at room temperature. The fluorescence quenching of CDC by CT-DNA suggested a quenching constant (K_SV) of 10³ to 10⁴ M^-1 order. Thermodynamic studies at 303, 308, and 318 K revealed the observed quenching as a dynamic process besides the spontaneity of the interaction with negative free energy change. Competitive binding studies with site markers like ethidium bromide, methylene blue, and Hoechst 33258 reflect CDC's groove mode of interaction. The result was complemented by DNA melting study, viscosity measurement, and KI quenching studies. The ionic strength effect was studied to interpret the electrostatic interaction and found its insignificant role in the binding. Molecular docking studies suggested the binding location of CDC within the minor groove of CT-DNA, complementing the experimental result.

Novel approaches for rapid detection of COVID-19 during the pandemic: A review

The rapid spread of the SARS-CoV-2 virus that caused the COVID-19 disease, has highlighted our urgent need for sensitive, fast and accurate diagnostic technologies. In fact, one of the main challenges for flatting COVID-19 spread charts is the ability to accurately and rapidly identify asymptomatic cases that result in spreading the virus to close contacts. SARS-CoV-2 virus mutation is also relatively rapid, which makes the detection of COVID-19 diseases still crucial even after the vaccination. Conventional techniques, which are commercially available have focused on clinical manifestation, along with molecular and serological detection tools that can identify the SARS-CoV-2 virus however, owing to various disadvantages including low specificity and sensitivity, a quick, low cost and easy approach is needed for diagnosis of COVID-19. Scientists are now showing extensive interest in an effective portable and simple detection method to diagnose COVID-19. There are several novel methods and approaches that are considered viable advanced systems that can meet the demands. This study reviews the new approaches and sensing technologies that work on COVID-19 diagnosis for easy and successful detection of SARS-CoV-2 virus.

Ultrasound-assisted synthesis of two-dimensional layered ytterbium substituted molybdenum diselenide nanosheets with excellent electrocatalytic activity for the electrochemical detection of diphenylamine anti-scald agent in fruit extract

Metal chalcogenides with large active sites have been received great attention as an excellent catalyst due to their hierarchical structural properties. Here, we have demonstrated the synthesis of ytterbium-doped molybdenum selenide (YbMoSe₂) in the form of two-dimensional nanosheets by using a simple ultrasonic method. The formation of the crystal phase of prepared YbMoSe₂ nanosheets was studied by using the selective characterization techniques. The reported HRTEM confirmed that the introduction of heterogeneous spin of Yb with MoSe₂ creates the lattice distortion. Thus, the active sites can be increased by creating the lattice distortion on the basal plane of the metal chalcogenides nanosheets. The band gap study was carried out by using UV-visible spectrometer and demonstrated the decreasing band gap of MoSe₂ from 1.30 eV to 1.15 eV due to the Yb substitution/doping. The increasing active sites with decreasing band gap facilitate an excellent electronic conductivity and electrochemical activity. Furthermore, the electrocatalytic activity of YbMoSe₂ modified glassy carbon electrode (YbMoSe₂/GCE) toward the sensing of diphenylamine (DPA) anti-scald agent. As expected, YbMoSe₂/GCE showed a high level of electrochemical activity with a low limit of detection (0.004 µM) and excellent sensitivity (11.4 µA µM^-1 cm^-2) towards the detection of DPA. In addition, the superior selectivity, stability, and reproducibility of YbMoSe₂/GCE also were recorded. The beneficial electrochemical activity of YbMoSe₂/GCE offered the more advantages to detection of DPA in the food sample also.

Riboswitches: From living biosensors to novel targets of antibiotics

Riboswitches are generally located in 5'-UTR region of mRNAs and specifically bind small ligands. Following ligand binding, gene expression is controlled mostly by transcription termination, translation inhibition or mRNA degradation processes. More than 30 classes of known riboswitches have been identified by now. Most riboswitches consist of an aptamer domain and an expression platform. The aptamer domain of each class of riboswitch is a conserved structure and stabilizes specific structures of the expression platforms through binding to specific compounds. In this review, we are highlighting most aspects of riboswitch research including the novel riboswitch discoveries, routine methods for discovering and investigating riboswitches along with newly discovered classes and mechanistic principles of riboswitch-mediated gene expression control. Moreover, we will give an overview about the potential of riboswitches as therapeutic targets for antibiotic design and also their utilization as biosensors for molecular detection.