Saptarshi Mukherjee
@iiserb.ac.in
Professor at the Department of Chemistry
IISER Bhopal
RESEARCH, TEACHING, or OTHER INTERESTS
Spectroscopy, Biophysics, Physical and Theoretical Chemistry, Catalysis
Scopus Publications
Scopus Publications
Subhajit Chakraborty, Srikrishna Pramanik, Shashi Shekhar, and Saptarshi Mukherjee
AIP Publishing
Bio-templated luminescent noble metal nanoclusters (NCs) have attracted great attention for their intriguing physicochemical properties. Continuous efforts are being made to prepare NCs with high fluorescence quantum yield (QY), good biocompatibility, and tunable emission properties for their widespread practical applications as new-generation environment-friendly photoluminescent materials in materials chemistry and biological systems. Herein, we explored the unique photophysical properties of silver nanoclusters (AgNCs) templated by cytosine-rich customized hairpin DNA. Our results indicate that a 36-nucleotide containing hairpin DNA with 20 cytosine (C20) in the loop can encapsulate photostable red-emitting AgNCs with an absolute QY of ∼24%. The luminescent properties in these DNA-templated AgNCs were found to be linked to the coupling between the surface plasmon and the emitter. These AgNCs exhibited excellent thermal sensitivity and were employed to produce high-quality white light emission with an impressive color rendering index of 90 in the presence of dansyl chloride. In addition, the as-prepared luminescent AgNCs possessing excellent biocompatibility can effectively mark the nuclear region of HeLa cells and can be employed as a luminescent probe to monitor the cellular dynamics at a single molecular resolution.
Rahul Yadav, Atanu Nandy, Asim Bisoi, and Saptarshi Mukherjee
American Chemical Society (ACS)
Conformational changes play a seminal role in modulating the activity of proteins. This concept becomes all the more relevant in the context of metalloproteins, owing to the formation of specific conformation(s) induced by internal perturbations (like a change in pH, ligand binding, or receptor binding), which may carry out the binding and release of the metal ion/ions from the metal binding center of the protein. Herein, we investigated the conformational changes of an iron-binding protein, monoferric human serum transferrin (Fe-hTF), using several spectroscopic approaches. We could reversibly tune the cetyltrimethylammonium bromide (CTAB)-induced conformation of the protein, exploiting the concept of mixed micelles formed by three sequestrating agents: (3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate) hydrate (CHAPS) and two bile salts, namely, sodium cholate (NaC) and sodium deoxycholate (NaDC). The formation of mixed micelles between CTAB and these reagents (CHAPS/NaC/NaDC) results in the sequestration of CTAB molecules from the protein environment and aids the protein in reattaining its native-like structure. However, the guanidinium hydrochloride-induced denatured Fe-hTF did not acquire its native-like structure using these sequestrating agents, which substantiates the exclusive role of mixed micelles in the present study. Apart from this, we found that the conformation of transferrin (adopted in the presence of CTAB) displays pronounced esterase-like activity toward the para-nitrophenyl acetate (PNPA) substrate as compared to native transferrin. We also outlined the impact of the iron center and amino acids surrounding the iron center on the effective catalytic activity in the CTAB medium. We estimated ∼3 times higher specific catalytic efficiency for the iron-depleted Apo-hTF compared to the fully iron-saturated Fe2-hTF in the presence of CTAB.
Saurabh Rai, Srikrishna Pramanik, and Saptarshi Mukherjee
Royal Society of Chemistry (RSC)
Liquid–liquid phase separation (LLPS) exhibited by an ordered protein β-lactoglobulin (β-LG) under crowded environment prompts alterations in conformational distribution leading to emergence of new promiscuous (esterase-like) activity.
Paritosh Mahato, Koushik Mandal, Sameeksha Agrawal, Deepak Chopra, and Saptarshi Mukherjee
American Chemical Society (ACS)
The real-time monitoring of the stepwise growth process of the molecular crystal reveals a conclusive understanding of the morphological evolution, which otherwise remains elusive during the conventional crystallization processes. Herein, we report the in situ crystallization of silver nanoclusters (AgNCs) with special emphasis on their differential growth and multicolor emissive properties. A subtle variation of the methanol (MeOH) proportion in the reaction mixture induces the differential growth of these AgNCs, and thereby, a dramatic modulation in their optical properties was observed. Additionally, by increasing the temperature of the reaction (from a low temperature ice bath to 25 °C), an uncontrolled formation of AgNCs along with metallic silver nanoparticles (AgNPs) was observed, which was primarily induced by accelerating the reaction kinetics. We hope that this investigation comprehensively uncovers the serious bottlenecks of the conventional crystallization processes by showcasing systematic monitoring of structural evolution to the higher-ordered crystalline state.
Paritosh Mahato, Shashi Shekhar, Rahul Yadav, and Saptarshi Mukherjee
Royal Society of Chemistry (RSC)
The present work conclusively delineates the role of the core and the electrostatic surface of metal nanoclusters involved in the catalytic reduction reaction. The electrostatic surface dramatically modulates the reactivity of metal nanoclusters.
Saptarshi Mukherjee, Sobhan Sen, and Anindya Datta
Springer Science and Business Media LLC
Rahul Yadav, Bijan Kumar Paul, and Saptarshi Mukherjee
MDPI AG
The binding of drugs to nucleic acids, proteins, lipids, amino acids, and other biological receptors is necessary for the transportation of drugs. However, various side effects may also originate if the bound drug molecules are not dissociated from the carrier, especially with the aid of non-toxic agents. The sequestration of small drug molecules bound to biomolecules is thus central to counter issues related to drug overdose and drug detoxification. In this article, we aim to present several methods used for the dissociation of small drug molecules bound to different biological and biomimicking assemblies under in vitro experimental conditions. To this effect, the application of various molecular assemblies, like micelles, mixed micelles, molecular containers, like β-cyclodextrin, cucurbit[7]uril hydrate, etc., has been discussed. Herein, we also try to shed light on the driving forces underlying such sequestration processes through spectroscopic and calorimetric techniques.
Shashi Shekhar, Raibat Sarker, Paritosh Mahato, Sameeksha Agrawal, and Saptarshi Mukherjee
Royal Society of Chemistry (RSC)
Inter-cluster conversion through the strategic tuning of external stimuli and thereby modulation of the optical properties of metal nanoclusters (MNCs) is an emerging domain for exploration.
Paritosh Mahato, Amar S Thomas, Rahul Yadav, Saurabh Rai, Shashi Shekhar, and Saptarshi Mukherjee
Wiley
AbstractThe solvent plays an influential role in controlling the nucleation process of metal nanoclusters (MNCs) and thereby significantly modulates their optical signatures. Herein, we have demonstrated the solvent‐induced modulation in the optical properties of copper nanoclusters (CuNCs), primarily governed by the solvent polarity. During the preparation of para‐mercaptobenzoic acid (p‐MBA)‐templated CuNCs, the simultaneous formation of blue‐emitting CuNCs (B‐CuNCs) and red‐emitting CuNCs (R‐CuNCs) were observed up to 7 h of reaction time, reflected from the systematic increment in the photoluminescence (PL) intensity at 420 nm and 615 nm, respectively. However, after 7 h of reaction time, the exclusive formation of B‐CuNCs was observed. Such simultaneous growth and depletion dynamics of CuNCs result in a significant modulation in their optical properties. The variation of the solvent from water to less polar solvents such as DMSO and DMF restricts this inter‐cluster dynamics by stabilizing both the CuNCs (B‐CuNCs and R‐CuNCs). Thereby, a single‐component White Light Emission (WLE) was realized in DMSO with CIE coordinates (0.37, 0.36). The isomeric effect of the templates has also been investigated which extensively controls the optical and catalytic properties of the CuNCs.
Srikrishna Pramanik, Sree Chithra, Saurabh Rai, Sameeksha Agrawal, Debanggana Shil, and Saptarshi Mukherjee
American Chemical Society (ACS)
The understanding of interactions between organic chromophores and biocompatible luminescent noble metal nanoclusters (NCs) leading to an energy transfer process that has applications in light-harvesting materials is still in its nascent stage. This work describes a photoluminescent supramolecular assembly, made in two stages, employing an energy transfer process between silver (Ag) NCs as the donor and a host-guest system as the acceptor that can find potential applications in diverse fields. Initially, we explored the host-guest chemistry between a cationic guest ethidium bromide and cucurbit[8]uril host to modulate the fluorescence property of the acceptor. The host-guest interactions were characterized by using UV-vis absorption, steady-state and time-resolved spectroscopy, molecular docking, proton 1H nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry, and isothermal calorimetry studies. Next, we prepared a series of blue-emitting AgNCs using different templates such as proteins and peptides. We have found that these AgNCs can be employed as a donor in the energy transfer process upon mixing with the above acceptor for emission color tuning. Our in-depth studies also revealed that surface ligands could play a key role in modulating the energy transfer efficiency. Overall, by employing a noncovalent strategy, we have tried to develop Förster resonance energy transfer (FRET) pairs using blue-emitting NCs and a host-guest complex that could find potential applications in constructing advanced sustainable light-harvesting, white light-emitting, and anti-counterfeiting materials.
Tapasi Chand, Laxmikanta Khamari, Saptarshi Mukherjee, and Manmohan Kapur
American Chemical Society (ACS)
The direct formation of a C-N bond at the ortho-position of naphthalene monoimides (NMI) and perylene monoimides (PMI) is reported herein using dioxazolones as the amide source. This method affords direct access to ortho-amino NMI and PMI through an amidation and deprotection sequence. One-pot telescopic bay-bromination of ortho-amino PMIs was also achieved. The ortho-amidated NMIs and PMIs, accessed by the current methodology, show significant red shifts in their absorption and fluorescence spectra compared with the NMI and PMI alone. An improvement in the quantum yield and fluorescence lifetime was observed by the incorporation of pivalamide groups at the ortho-positions of NMI and PMI.
Iman Zare, Daniel M. Chevrier, Anna Cifuentes-Rius, Nasrin Moradi, Yunlei Xianyu, Subhadip Ghosh, Laura Trapiella-Alfonso, Ye Tian, Alireza Shourangiz-Haghighi, Saptarshi Mukherjee,et al.
Elsevier BV
Prasun Acharya, Arun Kuila, Ushasi Pramanik, Venkatesha R. Hathwar, Paula Brandao, Saptarshi Mukherjee, Swapan Maity, Tithi Maity, Ribhu Maity, and Bidhan Chandra Samanta
Royal Society of Chemistry (RSC)
Combined theoretical and experimental insights on DNA and BSA binding interactions of Cu(ii) and Ni(ii) complexes along with DPPH method of antioxidant assay and cytotoxicity studies.
Shashi Shekhar, Shivam Shrivastava, Adhil Kabeer Kurukkan, Preeti Sagarika, Srikrishna Pramanik, Chandan Sahi, and Saptarshi Mukherjee
Elsevier BV
Khadeeja Mubashira, Ushasi Pramanik, Laxmikanta Khamari, and Saptarshi Mukherjee
Springer Science and Business Media LLC
Minakshi Maity, Ushasi Pramanik, Venkatesha R. Hathwar, Paula Brandao, Saptarshi Mukherjee, Swapan Maity, Ribhu Maity, Tithi Maity, and Bidhan Chandra Samanta
Elsevier BV
Ushasi Pramanik, Atanu Nandy, Laxmikanta Khamari, and Saptarshi Mukherjee
American Chemical Society (ACS)
Intrinsically disordered proteins (IDPs) are a class of proteins that do not follow the unanimated perspective of the structure-function paradigm. IDPs enunciate the dynamics of motions which are often difficult to characterize by a particular experimental or theoretical approach. The chameleon nature of the IDPs is a result of an alteration or transition in their conformation upon binding with ligands. Experimental investigations via ensemble-average approaches to probe this randomness are often difficult to synchronize. Thus, to sense the substates of different conformational ensembles of IDPs, researchers have often targeted approaches based on single-molecule measurements. In this Perspective, we will discuss various single-molecule approaches to explore the conformational transitions of IDPs in different scenarios, the outcome, challenges, and future prospects.
Laxmikanta Khamari and Saptarshi Mukherjee
American Chemical Society (ACS)
Intercalated-motif (i-motif) DNA formed by cytosine (C)-rich sequences has been considered a novel target in anticancer research. Interestingly, this type of noncanonical DNA structure is highly dynamic and can display several conformational polymorphisms based on the immediate surrounding environment. However, studies regarding the folding pathway of i-motifs having disease-specific sequences under a confined environment at physiological pH are relatively scarce. This thereby warrants more explorations that will decipher their structural and functional properties inside constrained media. Herein, using the single-molecule Förster Resonance Energy Transfer (smFRET) studies, for the first time, we have illustrated the conformational dynamics of c-MYC promoter-based i-motif structures at physiological pH inside microemulsions of different dimensions. We concluded that the folding of such motifs under confined space is not a direct transition between the random coil and i-motif conformations; rather it occurs through a partially folded intermediate, depending on the confined dimension.
Ushasi Pramanik, Laxmikanta Khamari, Saurabh Rai, Paritosh Mahato, Atanu Nandy, Rahul Yadav, Sameeksha Agrawal, and Saptarshi Mukherjee
Wiley
AbstractTrypsin, the most abundant pancreatic protein, aids in protein digestion by hydrolysis and exhibits aggregation propensity in presence of alcohol, which can further lead to pancreatitis and eventually pancreatic cancer. Herein, by several experimental and theoretical approaches, we unearth the inhibition of alcohol‐induced aggregation of Trypsin by macrocyclic cavitand, β‐cyclodextrin (β‐CD). β‐CD interacts with the native protein and shows inhibitory effect in a dose dependent manner. Moreover, the secondary structures and morphologies of Trypsin in presence of β‐CD also clearly emphasize the inhibition of fibril formation. From Fluorescence Correlation Spectroscopy, we observed an enhancement in diffusion time of Nile Red with ∼2.5 times increase in hydrodynamic radius, substantiating the presence of fibrillar structure. Trypsin also shows reduction in its functional activity due to alcohol‐induced aggregation. Our simulation data reports the probable residues responsible for fibril formation, which was validated by molecular docking studies.
Tapasi Chand, Laxmikanta Khamari, Deepak Chopra, Saptarshi Mukherjee, and Manmohan Kapur
Wiley
AbstractA one‐step Rh‐catalyzed site‐selective ortho‐C−H alkynylation of perylene as well as naphthalene mono‐ and diimides is reported. A single step regioselective access to ortho‐C−H alkynylated derivatives of these ryleneimides not only increases the step economy of the ortho‐functionalization on these dyes but also provides a quick access route towards highly functionalized dyes that have potential optoelectronic applications. Increased solubility of tetra(triisopropylsilyl)acetylenyl PDIs in organic solvents greatly enhances their utility for further derivatization.
Atanu Nandy and Saptarshi Mukherjee
American Chemical Society (ACS)
Nature has beautifully assembled its light harvesting pigments within protein scaffolds, which ensures a very high energy transfer. Designing a highly efficient artificial bioinspired light harvesting system (LHS) thus requires the nanoscale spatial orientation and electronic control of the associated chromophores. Although DNA has been used as a scaffold to organize chromophores, proteins or polypeptides, however, are very rarely explored. Here, we have developed a highly efficient, artificial, bioinspired LHS using polypeptide (poly-d-lysine, PDL) nanostructures making use of their β-sheet structure in an aqueous alkaline medium. The chromophores used herein are compatible for an energy transfer process and are nonfluorescent in an aqueous medium but exhibit high fluorescence intensity when bound to the nanostructure of PDL. The close proximity of the chromophores results in an energy transfer efficiency of ∼92% besides generating white light emission at a particular molar ratio between the chromophores.
Saptarshi Mukherjee
Elsevier BV
Paritosh Mahato, Shashi Shekhar, Sameeksha Agrawal, Srikrishna Pramanik, and Saptarshi Mukherjee
American Chemical Society (ACS)
Srikrishna Pramanik, Paritosh Mahato, Ushasi Pramanik, Atanu Nandy, Laxmikanta Khamari, Shivam Shrivastava, Saurabh Rai, and Saptarshi Mukherjee
American Chemical Society (ACS)
This work delineates an integrative approach combining spectroscopic and computational studies to decipher the association-induced fluorescence properties of a fluorescent molecular rotor, viz., auramine O (AuO), after interacting with 20-mer duplex DNA having diverse well-matched base pairs. While exploring the scarcely explored sequence-dependent interaction mechanism of AuO and DNA, we observed that DNA could act as a conducive scaffold to the formation of AuO dimer through noncovalent interactions at lower molecular density. The photophysical properties of AuO depend on the nucleotide compositions as described from sequence-dependent shifting in the emission and absorption maxima. Furthermore, we explored such DNA base pair-dependent fluorescence spectral characteristics of AuO toward discriminating the thermodynamically most stable single nucleotide mismatch in a 20-mer sequence. Our results are interesting and could be useful in developing analogues with further enhanced emission properties toward mismatched DNA sequences.
Nandkishor Prakash Khot, Paritosh Mahato, Sajeev T. K., Saptarshi Mukherjee, and Manmohan Kapur
American Chemical Society (ACS)
Reported herein is a sustainable approach for a regioselective, Rh(III)-catalyzed C(7)-H alkylation of 8-aminoquinolines via metal carbene migratory insertion. This transformation displays a high functional group tolerance and exquisite site selectivity to afford the C-7 alkylated products. These products are derivatized to afford π-extended angular pyrroloquinolines, one of which (4h) shows white-light emission (WLE) with CIE coordinates (0.26, 0.34). An excellent cell viability and in vivo cellular imaging substantiate the nontoxic nature of these compounds.