2,034 research outputs found
Spectral Evolution of the X-Ray Remnant of SN 1987A: A High-resolution Chandra HETG Study
Get PDFBased on observations with the Chandra X-ray Observatory, we present the latest spectral evolution of the X-ray remnant of SN 1987A (SNR 1987A). We present a high-resolution spectroscopic analysis using our new deep (∼312 ks) Chandra HETG observation taken in 2018 March as well as archival Chandra grating spectroscopic data taken in 2004, 2007, and 2011 with similarly deep exposures (∼170-350 ks). We perform detailed spectral model fits to quantify changing plasma conditions over the last 14 yr. Recent changes in electron temperatures and volume-emission measures suggest that the shocks moving through the inner ring have started interacting with less dense circumstellar material, probably beyond the inner ring. We find significant changes in the X-ray line-flux ratios (among H- and He-like Si and Mg ions) in 2018, consistent with changes in the thermal conditions of the X-ray-emitting plasma that we infer based on the broadband spectral analysis. Post-shock electron temperatures suggested by line-flux ratios are in the range ∼0.8-2.5 keV as of 2018. We do not yet observe any evidence of substantial abundance enhancement, suggesting that the X-ray emission component from the reverse-shocked metal-rich ejecta is not yet significant in the observed X-ray spectrum
Physical properties of high performance fluoride ion conductor BaSnF4 thin films by pulsed laser deposition
No full textThis article presents the results on the growth and characterization of BaSnF4 thin films on glass substrates prepared by pulsed laser deposition technique. The structural results of BaSnF4 thin film carried out by glancing angle X-ray diffraction technique indicates the formation of the film with similar structure (tetragonal, P-4/nmm) to the bulk target material. The absorption coefficient and band gap of the film is determined by suitable analysis of the transmittance spectra. The transport properties of the thin films are studied using impedance spectroscopy in the temperature range of 323-573 K. The frequency-dependent imaginary part of impedance plot shows that the conductivity relaxation is non-Debye in nature. The scaling behavior of the imaginary part of impedance at various frequencies indicates temperature-independent relaxation behavior
Chandra Shekhar : the last icon of ideological politics
No full textChandra Shekhar : the last icon of ideological politic
Genomics and Proteomics Using Computational Biology
No full textCurrent functional genomics relies on known and characterised genes, but despite significant efforts in the field of genome annotation, accurate identification and elucidation of protein coding gene structures remains challenging. Methods are limited to computational predictions and transcript-level experimental evidence; hence translation cannot be verified. Proteomic mass spectrometry is a method that enables sequencing of gene product fragments, enabling the validation and refinement of existing gene annotation as well as the elucidation of novel protein coding regions. However, the application of proteomics data to genome annotation is hindered by the lack of suitable tools and methods to achieve automatic data processing and genome mapping at high accuracy and throughput
Molecular Dynamics Simulation Approach to Investigate Dynamic Behaviour of System Through the Application of Newtonian Mechanics
No full textMolecular dynamics simulations have been successfully incorporated and evolved into a mature technique within a variety of pharmaceutical research programs to study the complex biological and chemical systems. Broadly used in modern drug design, molecular docking methods can be used effectively to understand the macromolecular structure-to-function relationships and ligand conformations adopted within the binding sites of macromolecular targets. Information gathered about the dynamic properties of ligand–receptor binding such as free energy by evaluating critical phenomena involved in the intermolecular recognition process. These results can be employed to shift the usual paradigm of structural bioinformatics from studying single structures to analyse conformational ensembles. Today, as a variety of docking algorithms are available, an understanding of advantages and limitations of each method is of fundamental importance in the development of effective strategies and the generation of relevant results. The purpose of this chapter is to examine the current molecular docking strategies used in drug discovery and medicinal chemistry, exploring the advancements in the field and role played by integration of structure-and ligand-based methods
Ligand-Based Approach for In-silico Drug Designing
No full textIn this chapter, a brief introduction to ligand-based methodologies employed for designing of drug has been described. Generally, ligand-based approach for drug designing (LB-CADD) technique is employed when biological target structure is not known and hence, this technique is considered as an ancillary approach for the drug designing. The theoretical basis of ligand-based approach involves quantitative structure–activity relationships (QSAR) and biomolecular docking studies. Like molecular descriptors, molecular fingerprint, similarity searches, similarity networks and off-target predictions. Finally, a brief description of the present work is given
Receptor Thermodynamics of Ligand–Receptor or Ligand–Enzyme Association
No full textExperimental techniques that directly assess the thermodynamics of ligand–receptor or ligand–enzyme association, such as isothermal titration calorimetry, have been improved in recent years and can provide thermodynamic details of the binding process. Parallel to the continuous increase in computational power, several classes of computational methods have been developed that can be used to get a more detail insight into the mode and affinity of compounds (drug) to their target (off). Such methods are affiliated with a qualitative and/or quantitative assessment of binding free energies, and differently trade off speed versus physical accuracy. With the current wealth of available three-dimensional structures of proteins and their complexes with ligands, structure-based drug design studies can be used to identify the key ligand interactions and free energy calculations, and can quantify the thermodynamics of binding between ligand and the target of interest
Thermodynamic Cycles and Their Application in Protein Targets
No full textA key part of drug design and development is the optimization of molecular interactions between an engineered drug candidate and its binding target. Thermodynamic characterization provides information about the balance of energetic forces driving binding interactions and is essential for understanding and optimizing molecular interactions. Comprehensive thermodynamic evaluation is vital in the drug development process to speed drug development towards an optimal energetic interaction profile while retaining good pharmacological properties. Practical thermodynamic approaches, such as enthalpic optimization, thermodynamic optimization plots and the enthalpic efficiency index, have now been developed to provide proven utility in design process. Improved throughput in calorimetric methods remains essential for even greater integration of thermodynamics into drug design
Structure-Based Approach for In-silico Drug Designing
No full textIn recent years, research area of structure-based drug design is a rising field that has been used to achieve many successes. Structure-based computer-aided drug design (SB-CADD) depends on the ability to determine and analyse the 3D structures of the target of interest. In other words, a prerequisite for the SB-CADD approach can be defined based on molecule’s ability to interrelate with a specific ligand, that can be a chemical species or biomolecule such as protein, and a desired biological activity based on its ability to favourably interact at a binding site on the selected target. This purposed that the molecules sharing those favourable interactions will reflect the similar biological effects. Therefore, novel ligands can be predicted and concluded by careful analysis of a protein’s binding site. Also, structure-based approach for drug designing allows a rapid selection of potential ligands from different and large compound libraries that can be later validated through modelling/simulation and visualization techniques
Three-Dimensional (3D) Pharmacophore Modelling-Based Drug Designing by Computational Technique
No full textThree-dimensional (3D) pharmacophore modelling is a modern approach used to elucidate the intermolecular interaction of ligands with the target of interest. In the past few years, pharmacophore models have been developed with chemical features and are intuitively understandable and broadly employed successfully in computational drug discovery by the researchers. The concert and utility of pharmacophore modelling are demarcated by the two major factors; (i) definition and placement of pharmacophoric features and (ii) the arrangement approaches used to overlay the 3D pharmacophore models and small molecules. This chapter provides a brief account of the recent technologies and developed model used in pharmacophores-based drug design
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