1
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Cory MB, Li A, Hurley CM, Carman PJ, Pumroy RA, Hostetler ZM, Perez RM, Venkatesh Y, Li X, Gupta K, Petersson EJ, Kohli RM. The LexA-RecA* structure reveals a cryptic lock-and-key mechanism for SOS activation. Nat Struct Mol Biol 2024:10.1038/s41594-024-01317-3. [PMID: 38755298 DOI: 10.1038/s41594-024-01317-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2023] [Accepted: 04/15/2024] [Indexed: 05/18/2024]
Abstract
The bacterial SOS response plays a key role in adaptation to DNA damage, including genomic stress caused by antibiotics. SOS induction begins when activated RecA*, an oligomeric nucleoprotein filament that forms on single-stranded DNA, binds to and stimulates autoproteolysis of the repressor LexA. Here, we present the structure of the complete Escherichia coli SOS signal complex, constituting full-length LexA bound to RecA*. We uncover an extensive interface unexpectedly including the LexA DNA-binding domain, providing a new molecular rationale for ordered SOS gene induction. We further find that the interface involves three RecA subunits, with a single residue in the central engaged subunit acting as a molecular key, inserting into an allosteric binding pocket to induce LexA cleavage. Given the pro-mutagenic nature of SOS activation, our structural and mechanistic insights provide a foundation for developing new therapeutics to slow the evolution of antibiotic resistance.
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Affiliation(s)
- Michael B Cory
- Graduate Group in Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA, USA
| | - Allen Li
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA, USA
| | - Christina M Hurley
- Graduate Group in Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA, USA
| | - Peter J Carman
- Graduate Group in Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA, USA
| | - Ruth A Pumroy
- Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA, USA
| | | | - Ryann M Perez
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA, USA
| | - Yarra Venkatesh
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA, USA
| | - Xinning Li
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA, USA
| | - Kushol Gupta
- Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA, USA
| | - E James Petersson
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA, USA.
- Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA, USA.
| | - Rahul M Kohli
- Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA, USA.
- Department of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
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2
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Venkatesh Y, Marotta NP, Lee VMY, Petersson EJ. Highly tunable bimane-based fluorescent probes: design, synthesis, and application as a selective amyloid binding dye. Chem Sci 2024; 15:6053-6063. [PMID: 38665526 PMCID: PMC11040648 DOI: 10.1039/d4sc00024b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2024] [Accepted: 03/18/2024] [Indexed: 04/28/2024] Open
Abstract
Small molecule fluorescent probes are indispensable tools for a broad range of biological applications. Despite many probes being available, there is still a need for probes where photophysical properties and biological selectivity can be tuned as desired. Here, we report the rational design and synthesis of a palette of fluorescent probes based on the underexplored bimane scaffold. The newly developed probes with varied electronic properties show tunable absorption and emission in the visible region with large Stokes shifts. Probes featuring electron-donating groups exhibit rotor effects that are sensitive to polarity and viscosity by "intramolecular charge transfer" (ICT) and twisted intramolecular charge transfer (TICT) mechanisms, respectively. These properties enable their application as "turn-on" fluorescent probes to detect fibrillar aggregates of the α-synuclein (αS) protein that are a hallmark of Parkinson's disease (PD). One probe shows selective binding to αS fibrils relative to soluble proteins in cell lysates and amyloid fibrils of tau and amyloid-β. Finally, we demonstrate the diagnostic potential of the probe in selectively detecting αS fibrils amplified from PD with dementia (PDD) patient samples.
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Affiliation(s)
- Yarra Venkatesh
- Department of Chemistry, University of Pennsylvania 231 South 34th Street Philadelphia PA 19104 USA
| | - Nicholas P Marotta
- Department of Pathology and Laboratory Medicine, Center for Neurodegenerative Disease Research, University of Pennsylvania 3600 Spruce Street Philadelphia PA 19104 USA
| | - Virginia M-Y Lee
- Department of Pathology and Laboratory Medicine, Center for Neurodegenerative Disease Research, University of Pennsylvania 3600 Spruce Street Philadelphia PA 19104 USA
| | - E James Petersson
- Department of Chemistry, University of Pennsylvania 231 South 34th Street Philadelphia PA 19104 USA
- Graduate Group in Biochemistry and Molecular Biophysics, Perelman School of Medicine, University of Pennsylvania 421 Curie Boulevard Philadelphia PA 19104 USA
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3
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Cory MB, Jones CM, Shaffer KD, Venkatesh Y, Giannakoulias S, Perez RM, Lougee MG, Hummingbird E, Pagar VV, Hurley CM, Li A, Mach RH, Kohli RM, Petersson EJ. FRETing about the details: Case studies in the use of a genetically encoded fluorescent amino acid for distance-dependent energy transfer. Protein Sci 2023; 32:e4633. [PMID: 36974585 PMCID: PMC10108435 DOI: 10.1002/pro.4633] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2023] [Revised: 03/22/2023] [Accepted: 03/24/2023] [Indexed: 03/29/2023]
Abstract
Förster resonance energy transfer (FRET) is a valuable method for monitoring protein conformation and biomolecular interactions. Intrinsically fluorescent amino acids that can be genetically encoded, such as acridonylalanine (Acd), are particularly useful for FRET studies. However, quantitative interpretation of FRET data to derive distance information requires careful use of controls and consideration of photophysical effects. Here we present two case studies illustrating how Acd can be used in FRET experiments to study small molecule induced conformational changes and multicomponent biomolecular complexes.
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Affiliation(s)
- Michael B. Cory
- Graduate Group in Biochemistry and BiophysicsPerelman School of Medicine, University of PennsylvaniaPhiladelphiaPennsylvania19104USA
| | - Chloe M. Jones
- Graduate Group in Biochemistry and BiophysicsPerelman School of Medicine, University of PennsylvaniaPhiladelphiaPennsylvania19104USA
| | - Kyle D. Shaffer
- Department of ChemistrySchool of Arts and Sciences, University of PennsylvaniaPhiladelphiaPennsylvania19104USA
| | - Yarra Venkatesh
- Department of ChemistrySchool of Arts and Sciences, University of PennsylvaniaPhiladelphiaPennsylvania19104USA
| | - Sam Giannakoulias
- Department of ChemistrySchool of Arts and Sciences, University of PennsylvaniaPhiladelphiaPennsylvania19104USA
| | - Ryann M. Perez
- Department of ChemistrySchool of Arts and Sciences, University of PennsylvaniaPhiladelphiaPennsylvania19104USA
| | - Marshall G. Lougee
- Department of ChemistrySchool of Arts and Sciences, University of PennsylvaniaPhiladelphiaPennsylvania19104USA
| | - Eshe Hummingbird
- Department of ChemistrySchool of Arts and Sciences, University of PennsylvaniaPhiladelphiaPennsylvania19104USA
| | - Vinayak V. Pagar
- Department of ChemistrySchool of Arts and Sciences, University of PennsylvaniaPhiladelphiaPennsylvania19104USA
| | - Christina M. Hurley
- Graduate Group in Biochemistry and BiophysicsPerelman School of Medicine, University of PennsylvaniaPhiladelphiaPennsylvania19104USA
| | - Allen Li
- Department of ChemistrySchool of Arts and Sciences, University of PennsylvaniaPhiladelphiaPennsylvania19104USA
| | - Robert H. Mach
- Department of RadiologyPerelman School of Medicine, University of PennsylvaniaPhiladelphiaPennsylvania19104USA
| | - Rahul M. Kohli
- Department of Biochemistry and BiophysicsPerelman School of Medicine, University of PennsylvaniaPhiladelphiaPennsylvania19104USA
- Department of MedicinePerelman School of Medicine, University of PennsylvaniaPhiladelphiaPennsylvania19104USA
| | - E. James Petersson
- Department of ChemistrySchool of Arts and Sciences, University of PennsylvaniaPhiladelphiaPennsylvania19104USA
- Department of Biochemistry and BiophysicsPerelman School of Medicine, University of PennsylvaniaPhiladelphiaPennsylvania19104USA
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4
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Abstract
The SOS response is a bacterial DNA damage response pathway that has been heavily implicated in bacteria's ability to evolve resistance to antibiotics. Activation of the SOS response is dependent on the interaction between two bacterial proteins, RecA and LexA. RecA acts as a DNA damage sensor by forming lengthy oligomeric filaments (RecA*) along single-stranded DNA (ssDNA) in an ATP-dependent manner. RecA* can then bind to LexA, the repressor of SOS response genes, triggering LexA degradation and leading to induction of the SOS response. Formation of the RecA*-LexA complex therefore serves as the key "SOS activation signal." Given the challenges associated with studying a complex involving multiple macromolecular interactions, the essential constituents of RecA* that allow LexA cleavage are not well defined. Here, we leverage head-to-tail linked and end-capped RecA constructs as tools to define the minimal RecA* filament that can engage LexA. In contrast to previously postulated models, we found that as few as three linked RecA units are capable of ssDNA binding, LexA binding, and LexA cleavage. We further demonstrate that RecA oligomerization alone is insufficient for LexA cleavage, with an obligate requirement for ATP and ssDNA binding to form a competent SOS activation signal with the linked constructs. Our minimal system for RecA* highlights the limitations of prior models for the SOS activation signal and offers a novel tool that can inform efforts to slow acquired antibiotic resistance by targeting the SOS response.
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Affiliation(s)
- Michael B. Cory
- Graduate Group in Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Allen Li
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Christina M. Hurley
- Graduate Group in Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Zachary M. Hostetler
- Department of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Yarra Venkatesh
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Chloe M. Jones
- Graduate Group in Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - E. James Petersson
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
- Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Rahul M. Kohli
- Department of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
- Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
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5
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Venkatesh Y, Vangala V, Mengji R, Chaudhuri A, Bhattacharya S, Datta PK, Banerjee R, Jana A, Singh NDP. One- and Two-Photon Uncaging of Carbon Monoxide (CO) with Real-Time Monitoring: On-Demand Carbazole-Based Dual CO-Releasing Platform to Test over Single and Combinatorial Approaches for the Efficient Regression of Orthotopic Murine Melanoma In Vivo. J Med Chem 2022; 65:1822-1834. [PMID: 35019659 DOI: 10.1021/acs.jmedchem.1c00750] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Herein, we report three new metal-free, photochemically active single, dual, and combinatorial CORMs (photoCORMs) based on a carbazole-fused 1,3-dioxol-2-one moiety which released one equivalent of CO, two equivalent of CO, and a combination of one equivalent of each CO and anticancer drug upon one- and two-photon excitation, respectively. The photoCORMs exhibited good cellular uptake and real-time monitoring ability of CO uncaging by a color change approach in cancerous B16F10 cells. Interestingly, the cytotoxicity assay on B16F10 cells indicated that the dual photoCORM has increased anticancer activity over the single and combinatorial photoCORMs upon irradiation. Our results also showed that CO could accelerate the effectiveness of the well-known anticancer drug (chlorambucil). Finally, the in vivo evaluation of the dual photoCORM on an established murine melanoma tumor (C57BL/6J mouse model) manifested a significant regression of tumor volume and led to significant improvement (>50%) in the overall survivability.
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Affiliation(s)
- Yarra Venkatesh
- Department of Chemistry, Indian Institute of Technology Kharagpur, West Bengal 721302, India
| | - Venugopal Vangala
- Department of Applied Biology, CSIR-Indian Institute of Chemical Technology (CSIR-IICT), Hyderabad 500007, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - Rakesh Mengji
- Department of Applied Biology, CSIR-Indian Institute of Chemical Technology (CSIR-IICT), Hyderabad 500007, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - Amrita Chaudhuri
- Department of Chemistry, Indian Institute of Technology Kharagpur, West Bengal 721302, India
| | - Sayantan Bhattacharya
- Department of Physics, Indian Institute of Technology Kharagpur, West Bengal 721302, India
| | - Prasanta Kumar Datta
- Department of Physics, Indian Institute of Technology Kharagpur, West Bengal 721302, India
| | - Rajkumar Banerjee
- Department of Applied Biology, CSIR-Indian Institute of Chemical Technology (CSIR-IICT), Hyderabad 500007, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - Avijit Jana
- Department of Applied Biology, CSIR-Indian Institute of Chemical Technology (CSIR-IICT), Hyderabad 500007, India
- Department of Organic Synthesis and Process Chemistry, CSIR-Indian Institute of Chemical Technology (CSIR-IICT), Hyderabad 500007, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - N D Pradeep Singh
- Department of Chemistry, Indian Institute of Technology Kharagpur, West Bengal 721302, India
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6
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Zagotta WN, Sim BS, Nhim AK, Raza MM, Evans EG, Venkatesh Y, Jones CM, Mehl RA, Petersson EJ, Gordon SE. An improved fluorescent noncanonical amino acid for measuring conformational distributions using time-resolved transition metal ion FRET. eLife 2021; 10:e70236. [PMID: 34623258 PMCID: PMC8500717 DOI: 10.7554/elife.70236] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Accepted: 08/09/2021] [Indexed: 11/30/2022] Open
Abstract
With the recent explosion in high-resolution protein structures, one of the next frontiers in biology is elucidating the mechanisms by which conformational rearrangements in proteins are regulated to meet the needs of cells under changing conditions. Rigorously measuring protein energetics and dynamics requires the development of new methods that can resolve structural heterogeneity and conformational distributions. We have previously developed steady-state transition metal ion fluorescence resonance energy transfer (tmFRET) approaches using a fluorescent noncanonical amino acid donor (Anap) and transition metal ion acceptor to probe conformational rearrangements in soluble and membrane proteins. Here, we show that the fluorescent noncanonical amino acid Acd has superior photophysical properties that extend its utility as a donor for tmFRET. Using maltose-binding protein (MBP) expressed in mammalian cells as a model system, we show that Acd is comparable to Anap in steady-state tmFRET experiments and that its long, single-exponential lifetime is better suited for probing conformational distributions using time-resolved FRET. These experiments reveal differences in heterogeneity in the apo and holo conformational states of MBP and produce accurate quantification of the distributions among apo and holo conformational states at subsaturating maltose concentrations. Our new approach using Acd for time-resolved tmFRET sets the stage for measuring the energetics of conformational rearrangements in soluble and membrane proteins in near-native conditions.
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Affiliation(s)
- William N Zagotta
- Department of Physiology and Biophysics, University of Washington, Seattle, United States
| | - Brandon S Sim
- Department of Physiology and Biophysics, University of Washington, Seattle, United States
| | - Anthony K Nhim
- Department of Physiology and Biophysics, University of Washington, Seattle, United States
| | - Marium M Raza
- Department of Physiology and Biophysics, University of Washington, Seattle, United States
| | - Eric Gb Evans
- Department of Physiology and Biophysics, University of Washington, Seattle, United States
| | - Yarra Venkatesh
- Department of Chemistry, University of Pennsylvania, Philadelphia, United States
| | - Chloe M Jones
- Department of Chemistry, University of Pennsylvania, Philadelphia, United States
- Biochemistry and Molecular Biophysics Graduate Group, University of Pennsylvania, Philadelphia, United States
| | - Ryan A Mehl
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, United States
| | - E James Petersson
- Department of Chemistry, University of Pennsylvania, Philadelphia, United States
| | - Sharona E Gordon
- Department of Physiology and Biophysics, University of Washington, Seattle, United States
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7
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Jones CM, Robkis DM, Blizzard RJ, Munari M, Venkatesh Y, Mihaila TS, Eddins AJ, Mehl RA, Zagotta WN, Gordon SE, Petersson EJ. Genetic encoding of a highly photostable, long lifetime fluorescent amino acid for imaging in mammalian cells. Chem Sci 2021; 12:11955-11964. [PMID: 34976337 PMCID: PMC8634729 DOI: 10.1039/d1sc01914g] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Accepted: 07/18/2021] [Indexed: 01/28/2023] Open
Abstract
Acridonylalanine (Acd) is a fluorescent amino acid that is highly photostable, with a high quantum yield and long fluorescence lifetime in water. These properties make it superior to existing genetically encodable fluorescent amino acids for monitoring protein interactions and conformational changes through fluorescence polarization or lifetime experiments, including fluorescence lifetime imaging microscopy (FLIM). Here, we report the genetic incorporation of Acd using engineered pyrrolysine tRNA synthetase (RS) mutants that allow for efficient Acd incorporation in both E. coli and mammalian cells. We compare protein yields and amino acid specificity for these Acd RSs to identify an optimal construct. We also demonstrate the use of Acd in FLIM, where its long lifetime provides strong contrast compared to endogenous fluorophores and engineered fluorescent proteins, which have lifetimes less than 5 ns.
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Affiliation(s)
- Chloe M Jones
- Department of Chemistry, University of Pennsylvania 231 South 34th Street Philadelphia PA 19104 USA
- Biochemistry and Molecular Biophysics Graduate Group, University of Pennsylvania 3700 Hamilton Walk Philadelphia PA 19104 USA
| | - D Miklos Robkis
- Department of Chemistry, University of Pennsylvania 231 South 34th Street Philadelphia PA 19104 USA
- Biochemistry and Molecular Biophysics Graduate Group, University of Pennsylvania 3700 Hamilton Walk Philadelphia PA 19104 USA
| | - Robert J Blizzard
- Department of Biochemistry and Biophysics, Oregon State University 2011 Ag Life Sciences Building Corvallis Oregon 97331 USA
| | - Mika Munari
- Department of Physiology and Biophysics, University of Washington 1705 NE Pacific St., Box 357290 Seattle WA 98195 USA
| | - Yarra Venkatesh
- Department of Chemistry, University of Pennsylvania 231 South 34th Street Philadelphia PA 19104 USA
| | - Tiberiu S Mihaila
- Department of Chemistry, University of Pennsylvania 231 South 34th Street Philadelphia PA 19104 USA
| | - Alex J Eddins
- Department of Biochemistry and Biophysics, Oregon State University 2011 Ag Life Sciences Building Corvallis Oregon 97331 USA
| | - Ryan A Mehl
- Department of Biochemistry and Biophysics, Oregon State University 2011 Ag Life Sciences Building Corvallis Oregon 97331 USA
| | - William N Zagotta
- Department of Physiology and Biophysics, University of Washington 1705 NE Pacific St., Box 357290 Seattle WA 98195 USA
| | - Sharona E Gordon
- Department of Physiology and Biophysics, University of Washington 1705 NE Pacific St., Box 357290 Seattle WA 98195 USA
| | - E James Petersson
- Biochemistry and Molecular Biophysics Graduate Group, University of Pennsylvania 3700 Hamilton Walk Philadelphia PA 19104 USA
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8
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Abstract
Site-specific protein labeling can be used to monitor protein motions and interactions in real time using Förster resonance energy transfer (FRET). While there are many fluorophores available for protein labeling, few FRET pairs are suitable for monitoring intramolecular protein motions without being disruptive to protein folding and function. Here, we describe the synthesis and use of a minimally perturbing FRET pair comprised of methoxycoumarin maleimide (Mcm-Mal) and acridonylalanine (Acd). Acd can be incorporated into a protein through unnatural amino acid mutagenesis. Mcm-Mal is fluorogenic when reacted with cysteine and can label cysteine/Acd double mutant proteins. This labeling strategy provides an easy to install FRET pair with a working range or 15-40Å, making it ideal for monitoring most intramolecular motions. Additionally, Mcm/Acd FRET can be combined with tryptophan fluorescence for monitoring multiple protein motions via three color FRET.
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Affiliation(s)
- Chloe M Jones
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA, United States; Biochemistry and Molecular Biophysics Graduate Group, University of Pennsylvania, Philadelphia, PA, United States
| | - Yarra Venkatesh
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA, United States
| | - E James Petersson
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA, United States.
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9
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Shah SS, Shee M, Venkatesh Y, Singh AK, Samanta S, Singh NDP. Organophotoredox‐Mediated Amide Synthesis by Coupling Alcohol and Amine through Aerobic Oxidation of Alcohol. Chemistry 2020; 26:3703-3708. [PMID: 31923326 DOI: 10.1002/chem.201904924] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Indexed: 12/30/2022]
Affiliation(s)
- Sk. Sheriff Shah
- Department of ChemistryIndian Institute of Technology Kharagpur Kharagpur West Bengal 721302 India
| | - Maniklal Shee
- Department of ChemistryIndian Institute of Technology Kharagpur Kharagpur West Bengal 721302 India
| | - Yarra Venkatesh
- Department of ChemistryIndian Institute of Technology Kharagpur Kharagpur West Bengal 721302 India
| | - Amit Kumar Singh
- Department of ChemistryIndian Institute of Technology Kharagpur Kharagpur West Bengal 721302 India
| | - Samya Samanta
- Department of ChemistryIndian Institute of Technology Kharagpur Kharagpur West Bengal 721302 India
| | - N. D. Pradeep Singh
- Department of ChemistryIndian Institute of Technology Kharagpur Kharagpur West Bengal 721302 India
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10
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Chaudhuri A, Venkatesh Y, Jena BC, Behara KK, Mandal M, Singh NDP. Real-time monitoring of a photoactivated hydrogen persulfide donor for biological entities. Org Biomol Chem 2020; 17:8800-8805. [PMID: 31560347 DOI: 10.1039/c9ob01982k] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Hydrogen persulfide (H2S2) plays an important role in sulfur-based redox signaling mechanisms. Herein, we developed a visible light activated ESIPT based H2S2 donor using a p-hydroxyphenacyl phototrigger. The unique feature of the designed H2S2 donor system is the ability to monitor the H2S2 release in real time through a non-invasive fluorescence color change approach, with the color changing from green to blue. Next, we demonstrated the detection and quantification of H2S2 using a fluorescein based "turn-on" fluorescent probe. Furthermore, in vitro studies of the designed H2S2 donor demonstrated the real-time monitored H2S2 release and cytoprotective ability in the highly oxidizing cellular environment of MDA-MB-468 cells.
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Affiliation(s)
- Amrita Chaudhuri
- Department of Chemistry, Indian Institute of Technology Kharagpur, 721302 Kharagpur, West Bengal, India.
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11
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Chaudhuri A, Mengji R, Venkatesh Y, Jana A, Pradeep Singh ND. An improved tumor-specific therapeutic strategy by the spatio-temporally controlled in situ formation of a Cu(ii) complex, leading to prompt cell apoptosis via photoactivation of a prodrug. Chem Commun (Camb) 2020; 56:4559-4562. [DOI: 10.1039/d0cc00667j] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Biotin tagged one and two photon activable Cu chelating prodrug as a target-specific and spatio-temporal generations of Cu complex for improved cancer treatment.
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Affiliation(s)
- Amrita Chaudhuri
- Department of Chemistry
- Indian Institute of Technology Kharagpur
- 721302 Kharagpur
- India
| | - Rakesh Mengji
- Department of Applied Biology
- CSIR-Indian Institute of Chemical Technology (CSIR-IICT)
- Hyderabad 500007
- India
- Academy of Scientific and Innovative Research (AcSIR)
| | - Yarra Venkatesh
- Department of Chemistry
- Indian Institute of Technology Kharagpur
- 721302 Kharagpur
- India
| | - Avijit Jana
- Department of Applied Biology
- CSIR-Indian Institute of Chemical Technology (CSIR-IICT)
- Hyderabad 500007
- India
- Academy of Scientific and Innovative Research (AcSIR)
| | - N. D. Pradeep Singh
- Department of Chemistry
- Indian Institute of Technology Kharagpur
- 721302 Kharagpur
- India
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12
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Venkatesh Y, Chaudhuri A, Mondal S, Shah SS, Singh NDP. Wavelength-Orthogonal Photocleavable Monochromophoric Linker for Sequential Release of Two Different Substrates. Org Lett 2019; 22:295-299. [PMID: 31850765 DOI: 10.1021/acs.orglett.9b04323] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Yarra Venkatesh
- Department of Chemistry, Indian Institute of Technology Kharagpur, 721302 Kharagpur, West Bengal, India
| | - Amrita Chaudhuri
- Department of Chemistry, Indian Institute of Technology Kharagpur, 721302 Kharagpur, West Bengal, India
| | - Saugat Mondal
- Department of Chemistry, Indian Institute of Technology Kharagpur, 721302 Kharagpur, West Bengal, India
| | - Sk. Sheriff Shah
- Department of Chemistry, Indian Institute of Technology Kharagpur, 721302 Kharagpur, West Bengal, India
| | - N. D. Pradeep Singh
- Department of Chemistry, Indian Institute of Technology Kharagpur, 721302 Kharagpur, West Bengal, India
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13
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Chaudhuri A, Venkatesh Y, Das J, Gangopadhyay M, Maiti TK, Singh NDP. One- and Two-Photon-Activated Cysteine Persulfide Donors for Biological Targeting. J Org Chem 2019; 84:11441-11449. [DOI: 10.1021/acs.joc.9b01224] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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14
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Venkatesh Y, Kiran KS, Shah SS, Chaudhuri A, Dey S, Singh NDP. One- and two-photon responsive sulfur dioxide (SO2) donors: a combinatorial drug delivery for improved antibiotic therapy. Org Biomol Chem 2019; 17:2640-2645. [DOI: 10.1039/c9ob00090a] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Light-activated sulfur dioxide donors have been developed and explored their applicability for combinatorial antibiotic therapy with self-monitoring ability.
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Affiliation(s)
- Yarra Venkatesh
- Department of Chemistry
- Indian Institute of Technology Kharagpur
- 721302 Kharagpur
- India
| | - Kumari Shanti Kiran
- Department of Biotechnology
- Indian Institute of Technology Kharagpur
- 721302 Kharagpur
- India
| | - Sk. Sheriff Shah
- Department of Chemistry
- Indian Institute of Technology Kharagpur
- 721302 Kharagpur
- India
| | - Amrita Chaudhuri
- Department of Chemistry
- Indian Institute of Technology Kharagpur
- 721302 Kharagpur
- India
| | - Satyahari Dey
- Department of Biotechnology
- Indian Institute of Technology Kharagpur
- 721302 Kharagpur
- India
| | - N. D. Pradeep Singh
- Department of Chemistry
- Indian Institute of Technology Kharagpur
- 721302 Kharagpur
- India
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15
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Affiliation(s)
- Sk. Sheriff Shah
- Department of Chemistry, Indian Institute of Technology, Kharagpur, West Bengal 721302, India
| | - Amrita Paul
- Department of Chemistry, Indian Institute of Technology, Kharagpur, West Bengal 721302, India
| | - Manoranjan Bera
- Department of Chemistry, Indian Institute of Technology, Kharagpur, West Bengal 721302, India
| | - Yarra Venkatesh
- Department of Chemistry, Indian Institute of Technology, Kharagpur, West Bengal 721302, India
| | - N. D. Pradeep Singh
- Department of Chemistry, Indian Institute of Technology, Kharagpur, West Bengal 721302, India
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16
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Venkatesh Y, Srivastava HK, Bhattacharya S, Mehra M, Datta PK, Bandyopadhyay S, Singh NDP. One- and Two-Photon Uncaging: Carbazole Fused o-Hydroxycinnamate Platform for Dual Release of Alcohols (Same or Different) with Real-Time Monitoring. Org Lett 2018; 20:2241-2244. [PMID: 29611420 DOI: 10.1021/acs.orglett.8b00090] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A one- and two-photon activated photoremovable protecting group (PRPG) was designed based on a carbazole fused o-hydroxycinnamate platform for the dual (same or different) release of alcohols. The mechanism for the dual release proceeds through a stepwise pathway and also monitors the first and second photorelease in real time by an increase in fluorescence intensity and color change, respectively. Further, its application in staining live neurons and ex vivo imaging with two-photon excitation is shown.
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17
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Venkatesh Y, Das J, Chaudhuri A, Karmakar A, Maiti TK, Singh NDP. Light triggered uncaging of hydrogen sulfide (H 2S) with real-time monitoring. Chem Commun (Camb) 2018. [PMID: 29517102 DOI: 10.1039/c8cc01172a] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
An ESIPT based light activated hydrogen sulfide (H2S) donor using a p-hydroxyphenacyl phototrigger has been developed. The unique feature of our H2S donor system is that it provides real-time monitoring of H2S release by a non-invasive fluorescence colour change approach.
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Affiliation(s)
- Yarra Venkatesh
- Department of Chemistry, Indian Institute of Technology Kharagpur, 721302 Kharagpur, West Bengal, India.
| | - Joyjyoti Das
- Department of Biotechnology, Indian Institute of Technology Kharagpur, 721302 Kharagpur, West Bengal, India
| | - Amrita Chaudhuri
- Department of Chemistry, Indian Institute of Technology Kharagpur, 721302 Kharagpur, West Bengal, India.
| | - Anupam Karmakar
- Department of Chemistry, Indian Institute of Technology Kharagpur, 721302 Kharagpur, West Bengal, India.
| | - Tapas K Maiti
- Department of Biotechnology, Indian Institute of Technology Kharagpur, 721302 Kharagpur, West Bengal, India
| | - N D Pradeep Singh
- Department of Chemistry, Indian Institute of Technology Kharagpur, 721302 Kharagpur, West Bengal, India.
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18
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Venkatesh Y, Nandi S, Shee M, Saha B, Anoop A, Pradeep Singh ND. Bis-Acetyl Carbazole: A Photoremovable Protecting Group for Sequential Release of Two Different Functional Groups and Its Application in Therapeutic Release. European J Org Chem 2017. [DOI: 10.1002/ejoc.201701253] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Affiliation(s)
- Yarra Venkatesh
- Department of Chemistry; Indian Institute of Technology Kharagpur; 721302 Kharagpur West Bengal India
| | - Surajit Nandi
- Department of Chemistry; Indian Institute of Technology Kharagpur; 721302 Kharagpur West Bengal India
| | - Maniklal Shee
- Department of Chemistry; Indian Institute of Technology Kharagpur; 721302 Kharagpur West Bengal India
| | - Biswajit Saha
- Department of Biotechnology; Indian Institute of Technology Kharagpur; 721302 Kharagpur West Bengal India
| | - Anakuthil Anoop
- Department of Chemistry; Indian Institute of Technology Kharagpur; 721302 Kharagpur West Bengal India
| | - N. D. Pradeep Singh
- Department of Chemistry; Indian Institute of Technology Kharagpur; 721302 Kharagpur West Bengal India
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19
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Chaudhuri A, Venkatesh Y, Behara KK, Singh NDP. Bimane: A Visible Light Induced Fluorescent Photoremovable Protecting Group for the Single and Dual Release of Carboxylic and Amino Acids. Org Lett 2017; 19:1598-1601. [PMID: 28281342 DOI: 10.1021/acs.orglett.7b00416] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Amrita Chaudhuri
- Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur, 721302 West Bengal, India
| | - Yarra Venkatesh
- Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur, 721302 West Bengal, India
| | - Krishna Kalyani Behara
- Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur, 721302 West Bengal, India
| | - N. D. Pradeep Singh
- Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur, 721302 West Bengal, India
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20
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Karthik S, Jana A, Selvakumar M, Venkatesh Y, Paul A, Shah SS, Singh NDP. Coumarin polycaprolactone polymeric nanoparticles: light and tumor microenvironment activated cocktail drug delivery. J Mater Chem B 2017; 5:1734-1741. [DOI: 10.1039/c6tb02944b] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Highly sensitive hypoxia (H2O2)-activated photoresponsive polymeric nanoparticles for cocktail delivery of anticancer drugs doxorubicin (Dox) and chlorambucil (Cbl) were developed.
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Affiliation(s)
- S. Karthik
- Department of Chemistry
- Indian Institute of Technology Kharagpur
- India
| | - Avijit Jana
- Biomaterials Group
- Division of Natural Product Chemistry
- Academy of Scientific & Innovative Research (AcSIR)
- CSIR-Indian Institute of Chemical Technology Hyderabad
- Hyderabad 500007
| | - M. Selvakumar
- Rubber Technology Centre
- Indian Institute of Technology Kharagpur
- India
| | - Yarra Venkatesh
- Department of Chemistry
- Indian Institute of Technology Kharagpur
- India
| | - Amrita Paul
- Department of Chemistry
- Indian Institute of Technology Kharagpur
- India
| | - Sk. Sheriff Shah
- Department of Chemistry
- Indian Institute of Technology Kharagpur
- India
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21
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Gangopadhyay M, Mengji R, Paul A, Venkatesh Y, Vangala V, Jana A, Singh NDP. Redox-responsive xanthene–coumarin–chlorambucil-based FRET-guided theranostics for “activatable” combination therapy with real-time monitoring. Chem Commun (Camb) 2017; 53:9109-9112. [DOI: 10.1039/c7cc03241b] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
A FRET-based theranostic agent, xanthene–coumarin–chlorambucil, exhibited redox-responsive “activatable” synergic treatment involving PDT and chemotherapy with fluorescence-change from green to blue.
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Affiliation(s)
| | - Rakesh Mengji
- Division of Chemical Biology
- CSIR-Indian Institute of Chemical Technology Hyderabad
- Hyderabad 500007
- India
| | - Amrita Paul
- Department of Chemistry
- Indian Institute of Technology
- Kharagpur 721302
- India
| | - Yarra Venkatesh
- Department of Chemistry
- Indian Institute of Technology
- Kharagpur 721302
- India
| | - Venugopal Vangala
- Division of Chemical Biology
- CSIR-Indian Institute of Chemical Technology Hyderabad
- Hyderabad 500007
- India
- Academy of Scientific and Innovative Research (AcSIR)
| | - Avijit Jana
- Division of Chemical Biology
- CSIR-Indian Institute of Chemical Technology Hyderabad
- Hyderabad 500007
- India
- Academy of Scientific and Innovative Research (AcSIR)
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22
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Behara KK, Rajesh Y, Venkatesh Y, Pinninti BR, Mandal M, Singh NDP. Cascade photocaging of diazeniumdiolate: a novel strategy for one and two photon triggered uncaging with real time reporting. Chem Commun (Camb) 2017; 53:9470-9473. [DOI: 10.1039/c7cc04635a] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We report a new strategy, viz. cascade photocaging, for protecting diethylamine diazeniumdiolate (O2-position), a light sensitive molecule.
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Affiliation(s)
| | - Y. Rajesh
- School of Medical Science and Technology
- Indian Institute of Technology (IIT) Kharagpur
- Kharagpur-721302
- India
| | - Yarra Venkatesh
- Department of Chemistry
- Indian Institute of Technology Kharagpur
- Kharagpur-721302
- India
| | - Bhaskar Rao Pinninti
- Department of Chemistry
- Indian Institute of Technology Kharagpur
- Kharagpur-721302
- India
| | - Mahitosh Mandal
- School of Medical Science and Technology
- Indian Institute of Technology (IIT) Kharagpur
- Kharagpur-721302
- India
| | - N. D. Pradeep Singh
- Department of Chemistry
- Indian Institute of Technology Kharagpur
- Kharagpur-721302
- India
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23
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Venkatesh Y, Karthik S, Rajesh Y, Mandal M, Jana A, Singh NDP. Three-Arm, Biotin-Tagged Carbazole-Dicyanovinyl-Chlorambucil Conjugate: Simultaneous Tumor Targeting, Sensing, and Photoresponsive Anticancer Drug Delivery. Chem Asian J 2016; 11:3482-3486. [PMID: 27706928 DOI: 10.1002/asia.201601264] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2016] [Indexed: 01/13/2023]
Affiliation(s)
- Yarra Venkatesh
- Department of Chemistry; Indian Institute of Technology Kharagpur; 721302 West Bengal India
| | - S. Karthik
- Department of Chemistry; Indian Institute of Technology Kharagpur; 721302 West Bengal India
| | - Y. Rajesh
- School of Medical Science and Technology; Indian Institute of Technology Kharagpur; 721302 West Bengal India
| | - Mahitosh Mandal
- School of Medical Science and Technology; Indian Institute of Technology Kharagpur; 721302 West Bengal India
| | - Avijit Jana
- Biomaterials Group; Division of Natural Products Chemistry; CSIR-Indian Institute of Chemical Technology; Hyderabad 500007 India
| | - N. D. Pradeep Singh
- Department of Chemistry; Indian Institute of Technology Kharagpur; 721302 West Bengal India
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24
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Venkatesh Y, Rajesh Y, Karthik S, Chetan AC, Mandal M, Jana A, Singh NDP. Photocaging of Single and Dual (Similar or Different) Carboxylic and Amino Acids by Acetyl Carbazole and its Application as Dual Drug Delivery in Cancer Therapy. J Org Chem 2016; 81:11168-11175. [PMID: 27754672 DOI: 10.1021/acs.joc.6b02152] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
A new fluorescent photoremovable protecting group (FPRPG) based on acetylcarbazole framework has been explored for the first time release of single and dual (similar or different) substrates from single chromophore. Mechanistic studies of the photorelease process revealed that photorelease of two (similar or different) substrates from acetyl carbazole proceeds via a stepwise pathway. Further, we constructed photoresponsive dual drug delivery system (DDS) to release two different anticancer drugs (caffeic acid and chlorambucil, 1 equiv each). In vitro study reveals that our DDS exhibit excellent properties like biocompatibility, cellular uptake, and photoregulated dual drug release.
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Affiliation(s)
- Yarra Venkatesh
- Department of Chemistry, ‡School of Medical Science and Technology, Indian Institute of Technology Kharagpur , 721302 West Bengal, India.,Biomaterials Group, ⊥Division of Natural Products Chemistry, CSIR-Indian Institute of Chemical Technology , Hyderabad 500007, India
| | - Y Rajesh
- Department of Chemistry, ‡School of Medical Science and Technology, Indian Institute of Technology Kharagpur , 721302 West Bengal, India.,Biomaterials Group, ⊥Division of Natural Products Chemistry, CSIR-Indian Institute of Chemical Technology , Hyderabad 500007, India
| | - S Karthik
- Department of Chemistry, ‡School of Medical Science and Technology, Indian Institute of Technology Kharagpur , 721302 West Bengal, India.,Biomaterials Group, ⊥Division of Natural Products Chemistry, CSIR-Indian Institute of Chemical Technology , Hyderabad 500007, India
| | - A C Chetan
- Department of Chemistry, ‡School of Medical Science and Technology, Indian Institute of Technology Kharagpur , 721302 West Bengal, India.,Biomaterials Group, ⊥Division of Natural Products Chemistry, CSIR-Indian Institute of Chemical Technology , Hyderabad 500007, India
| | - Mahitosh Mandal
- Department of Chemistry, ‡School of Medical Science and Technology, Indian Institute of Technology Kharagpur , 721302 West Bengal, India.,Biomaterials Group, ⊥Division of Natural Products Chemistry, CSIR-Indian Institute of Chemical Technology , Hyderabad 500007, India
| | - Avijit Jana
- Department of Chemistry, ‡School of Medical Science and Technology, Indian Institute of Technology Kharagpur , 721302 West Bengal, India.,Biomaterials Group, ⊥Division of Natural Products Chemistry, CSIR-Indian Institute of Chemical Technology , Hyderabad 500007, India
| | - N D Pradeep Singh
- Department of Chemistry, ‡School of Medical Science and Technology, Indian Institute of Technology Kharagpur , 721302 West Bengal, India.,Biomaterials Group, ⊥Division of Natural Products Chemistry, CSIR-Indian Institute of Chemical Technology , Hyderabad 500007, India
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25
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Kabade S, Venkatesh Y, Karthik S, Kumar V. Comparative study of granisetron versus pethidine for the prevention of perioperative shivering under spinal Anesthesia. ACTA ACUST UNITED AC 2016. [DOI: 10.4103/2394-6954.190769] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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26
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Kumar PH, Venkatesh Y, Prashanthi S, Siva D, Ramakrishna B, Bangal PR. Diffusive and non-diffusive photo-induced proton coupled electron transfer from hydrogen bonded phenols to meso-tetrakis-5,10,15,20-pentafluorophenyl porphyrin. Phys Chem Chem Phys 2015; 16:23173-81. [PMID: 25253044 DOI: 10.1039/c4cp02505a] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Enhanced reductive fluorescence quenching of meso-tetrakis-5,10,15,20-pentafluorophenyl porphyrin (H2F20TPP) by two different phenols, 4-methoxy phenol (4-MeOPhOH) and 2,6-dimethoxy phenol (2,6-DiMeOPhOH) in the presence of various pyridine bases in dichloromethane solution is studied using steady state and time resolved fluorescence spectroscopic methods by employing time correlated single photon counting (TCSPC) and fluorescence up-conversion techniques. An enhanced quenching behaviour of H2F20TPP is observed when phenols are hydrogen bonded to various pyridine bases. Quenching observed in the steady state and time resolved studies in the nanosecond time domain follows second order kinetics and generates quenching rate constants and hydrogen bond equilibrium constants, the latter of which agree quite closely with those obtained from independent spectroscopic measurements. A significant kinetic deuterium isotope effect is observed, indicating the importance of proton movement in the quenching processes. This quenching effect is attributed to be due to a tri-molecular transition state involving H2F20TPP and a hydrogen bonded phenol complex, in which electron transfer from phenol to excited H2F20TPP is concerted with proton movement from the phenol to hydrogen bonded base. Observed quenching behaviours are rationalized by invoking diffusion controlled proton coupled electron transfer. Fluorescence up-conversion studies in the 100 ps time domain confirm ultrafast PCET for 4-MeOPhOH and base pairs which fall in a non-diffusive regime.
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Affiliation(s)
- P Hemant Kumar
- Inorganic and Physical Chemistry Division, CSIR - Indian Institute of Chemical Technology, Uppal Road, Tarnaka, 500007 Hyderabad, India.
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Osorio Flores M, Venkatesh Y. Natural vs. Drug-Modified Cholesterol Levels and the Incidence of Ischemic Stroke (P06.228). Neurology 2012. [DOI: 10.1212/wnl.78.1_meetingabstracts.p06.228] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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28
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Nair S, Venkatesh Y. Angiographic Patterns in Patients with HIV at Hahnemann University Hospital (P06.244). Neurology 2012. [DOI: 10.1212/wnl.78.1_meetingabstracts.p06.244] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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