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652 results on '"Sen, Pratik"'

11. Seismic Performance of Polynomial Friction Pendulum Isolator (PFPI) on Benchmark Cable-Stayed Bridge

Author

Sen, Pratik, Saha, Purnachandra, di Prisco, Marco, Series Editor, Chen, Sheng-Hong, Series Editor, Vayas, Ioannis, Series Editor, Kumar Shukla, Sanjay, Series Editor, Sharma, Anuj, Series Editor, Kumar, Nagesh, Series Editor, Wang, Chien Ming, Series Editor, Das, Bibhuti Bhusan, editor, Barbhuiya, Salim, editor, Gupta, Rishi, editor, and Saha, Purnachandra, editor

Published
2021
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15. Multiphase hydrogen storage in nanocontainers

Author

Shervani, Suboohi, Mukherjee, Puspal, Gupta, Anshul, Mishra, Gargi, Illath, Kavya, Ajithkumar, T. G., Sivakumar, Sri, Sen, Pratik, Balani, Kantesh, and Subramaniam, Anandh

Subjects
Condensed Matter - Materials Science
Abstract

Hydrogen can be stored in containers or in materials. In materials it can exist in molecular or atomic forms. The atomic form can further exist as multiple phases. Molecular hydrogen can be adsorbed on the surface or can be present inside the material. In the current work, we demonstrate for the first time, a methodology to store hydrogen in nearly all conceivable forms. At the heart of this strategy is the novel concept of storage of molecular hydrogen in metal Pd nanocontainers. The existence of multiple phases of hydrogen is confirmed by x ray diffraction, Raman spectroscopy, nuclear magnetic resonance and pressure-composition isotherm measurements. Enhancement in storage capacity as compared to nanocrystals of the same mass is observed (36 percent increase at 1 atm and 25C). About 18 percent of the hydrogen stored is in the molecular form and interestingly this is achieved at room temperature and 1 atm pressure.

Published
2016

19. Tracking heterogenous protein aggregation at nanoscale through fluorescence correlation spectroscopy.

Author

Halder, Bisal, Ghosh, Shreya, Khan, Tanmoy, Pal, Subhendu, Das, Nilimesh, and Sen, Pratik

Subjects
FLUORESCENCE spectroscopy, BROMELIN, PROTEINS, FLUORESCENCE microscopy, DETECTION limit
Abstract

Various biophysical techniques have been extensively employed to study protein aggregation due to its significance. Traditionally, these methods detect aggregation at micrometer length scales and micromolar concentrations. However, unlike in vitro, protein aggregation typically occurs at nanomolar concentrations in vivo. Here, using fluorescence correlation spectroscopy (FCS), we captured bromelain aggregation at concentrations as low as ~20 nM, surpassing the detection limit of traditional methods like thioflavin T fluorescence, scattering, and fluorescence microscopy by more than one order of magnitude. Moreover, using thioflavin T fluorescence‐based FCS, we have detected larger aggregates at higher bromelain concentrations, which is undetectable in FCS otherwise. Importantly, our study reveals inherent heterogeneity in bromelain aggregation, inaccessible to ensemble‐averaged techniques. The presented report may provide a platform for the characterization of premature aggregates at very low protein concentrations, which are thought to be functionally significant species in protein aggregation‐induced diseases. [ABSTRACT FROM AUTHOR]

Published
2024
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30. Role of Associated Water Dynamics on Protein Stability and Activity in Crowded Milieu

Author

Khan, Tanmoy, Halder, Bisal, Das, Nilimesh, and Sen, Pratik

Abstract

Macromolecular crowding bridges in vivoand in vitrostudies by simulating cellular complexities such as high viscosity and limited space while maintaining the experimental feasibility. Over the last two decades, the impact of macromolecular crowding on protein stability and activity has been a significant topic of study and discussion, though still lacking a thorough mechanistic understanding. This article investigates the role of associated water dynamics on protein stability and activity within crowded environments, using bromelain and Ficoll-70 as the model systems. Traditional crowding theory primarily attributes protein stability to entropic effects (excluded volume) and enthalpic interactions. However, our recent findings suggest that water structure modulation plays a crucial role in a crowded environment. In this report, we strengthen the conclusion of our previous study, i.e., rigid-associated water stabilizes proteins via entropy and destabilizes them via enthalpy, while flexible water has the opposite effect. In the process, we addressed previous shortcomings with a systematic concentration-dependent study using a single-domain protein and component analysis of solvation dynamics. More importantly, we analyze bromelain’s hydrolytic activity using the Michaelis–Menten model to understand kinetic parameters like maximum velocity (Vmax) achieved by the system and the Michaelis–Menten coefficient (KM). Results indicate that microviscosity (not the bulk viscosity) controls the enzyme–substrate (ES) complex formation, where an increase in the microviscosity makes the ES complex formation less favorable. On the other hand, flexible associated water dynamics were found to favor the rate of product formation significantly from the ES complex, while rigid associated water hinders it. This study improves our understanding of protein stability and activity in crowded environments, highlighting the critical role of associated water dynamics.

Published
2024
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31. Enhanced Photostability of the Colloidal Ruddlesden–Popper Perovskite Nanoplate through 4‑Fluorobenzylammonium Iodide-Mediated Surface Engineering for Photoluminescent Application.

Author

Sen, Arghya, Sarkar, Patralekha, and Sen, Pratik

Abstract

UV light-induced photodegradation of the organic–inorganic hybrid (OIH) Ruddlesden–Popper (RP) perovskite nanoplates (NPls) is a crucial bottleneck for optoelectronic application in the future. Continuous UV exposure triggers the deprotonation of the spacer as well as the A-site cation (CH3NH3+), ultimately leading to lattice collapse. To combat this photoinstability, we introduce a surface modification of colloidal OIH RP NPls, (OAm)2(CH3NH3PbI3)2PbI4 (n = 3) (OAm stands for oleylammonium cation) by 4-fluorobenzylammonium iodide (4FBAI). In ambient conditions, conventional NPls deteriorate within 80 min of UV exposure, whereas the 4FBAI-modified NPls exhibit remarkable endurance, maintaining structural integrity for 12 h with only a 11% reduction in the initial photoluminescence (PL). Interestingly, benzylammonium iodide (BAI) and 4-methoxybenzylammonium iodide (4OBAI)-treated NPl fail to provide similar photostability, thus signifying the importance of the fluorine atom. The fluorine atom enhances the positive charge density of the ammonium ion and facilitates faster deprotonation compared to parental ammonium ions (here, OAm+ and CH3NH3+) under UV exposure. This ensures the survival of the parent nanoplate structure. Along with the photostability enhancement, the PL quantum yield of the treated NPl also increases to 50 ± 2 from 35 ± 2%. This research not only addresses the pressing photostability issue of RP NPl stability but also illuminates the pivotal role of specific chemical modifications, such as fluorine atom incorporation, for the fabrication of UV-stable perovskite devices in the future. [ABSTRACT FROM AUTHOR]

Published
2024
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