51
|
Shinde SV, Kulkarni M, Talukdar P. Helical supramolecular organization of a 1,2-diol appended naphthalene diimide organogelator via an extended intermolecular H-bonding network. RSC Adv 2016. [DOI: 10.1039/c6ra02729f] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Hydrogen bonded self-assembly of a 1,2-diol linked naphthalene diimide derivative features M-helical and J-type aggregation. In MCH/CHCl3, the compound exhibits intense yellow excimer and thermoreversible “sol–gel” behavior.
Collapse
|
52
|
Mukherjee A, Talukdar P, Khanra D, Ghosh P, Chakraborty A, Karak A, Samanta B, Singha S, Talukdar A, Saha M. Does non-protease inhibitor based anti-retroviral therapy modify peripheral arterial disease? A vision from eastern India. HIV & AIDS REVIEW 2016. [DOI: 10.1016/j.hivar.2016.08.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
|
53
|
Roy A, Saha T, Gening ML, Titov DV, Gerbst AG, Tsvetkov YE, Nifantiev NE, Talukdar P. Trimodal Control of Ion-Transport Activity on Cyclo-oligo-(1→6)-β-D-glucosamine-Based Artificial Ion-Transport Systems. Chemistry 2015; 21:17445-52. [PMID: 26448281 DOI: 10.1002/chem.201502656] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2015] [Indexed: 11/05/2022]
Abstract
Cyclo-oligo-(1→6)-β-D-glucosamines functionalized with hydrophobic tails are reported as a new class of transmembrane ion-transport system. These macrocycles with hydrophilic cavities were introduced as an alternative to cyclodextrins, which are supramolecular systems with hydrophobic cavities. The transport activities of these glycoconjugates were manipulated by altering the oligomericity of the macrocycles, as well as the length and number of attached tails. Hydrophobic tails of 3 different sizes were synthesized and coupled with each glucosamine scaffold through the amide linkage to obtain 18 derivatives. The ion-transport activity increased from di- to tetrameric glucosamine macrocycles, but decreased further when flexible pentameric glucosamine was introduced. The ion-transport activity also increased with increasing length of attached linkers. For a fixed length of linkers, the transport activity decreased when the number of such tails was reduced. All glycoconjugates displayed a uniform anion-selectivity sequence: Cl(-) >Br(-) >I(-) . From theoretical studies, hydrogen bonding between the macrocycle backbone and the anion bridged through water molecules was observed.
Collapse
|
54
|
Roy A, Saha T, Talukdar P. Turn-on fluorescent probe designed for fluoride ion sensing in aqueous media. Tetrahedron Lett 2015. [DOI: 10.1016/j.tetlet.2015.06.086] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
|
55
|
Saha T, Kand D, Talukdar P. Performance comparison of two cascade reaction models in fluorescence off–on detection of hydrogen sulfide. RSC Adv 2015. [DOI: 10.1039/c4ra13086c] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Comparative studies on the performances of two cascade reaction based fluorescent H2S probes are reported.
Collapse
|
56
|
Mishra PK, Saha T, Talukdar P. Hydrogen sulfide mediated cascade reaction forming an iminocoumarin: applications in fluorescent probe development and live-cell imaging. Org Biomol Chem 2015; 13:7430-6. [DOI: 10.1039/c5ob00785b] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The study on a fluorescent probe that undergoes a H2S mediated cascade reaction to form an iminocoumarin fluorophore is reported.
Collapse
|
57
|
Kand D, Saha T, Lahiri M, Talukdar P. Lysosome targeting fluorescence probe for imaging intracellular thiols. Org Biomol Chem 2015; 13:8163-8. [DOI: 10.1039/c5ob00889a] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A BODIPY-based fluorescence turn-on probe for lysosomal localization and biothiol sensing is reported.
Collapse
|
58
|
Deshmukh SC, Talukdar P. Stereoselective Synthesis of (2S,3R)-α-Hydroxy-β-Amino Acids (AHBAs): Valinoctin A, (2S,3R)-3-Amino-2-Hydroxydecanoic Acid, and a Fluorescent-Labeled (2S,3R)-AHBA. J Org Chem 2014; 79:11215-25. [DOI: 10.1021/jo501751u] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
|
59
|
Kand D, Mandal PS, Saha T, Talukdar P. Structural imposition on the off–on response of naphthalimide based probes for selective thiophenol sensing. RSC Adv 2014. [DOI: 10.1039/c4ra09042j] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
|
60
|
Saha T, Dasari S, Tewari D, Prathap A, Sureshan KM, Bera AK, Mukherjee A, Talukdar P. Hopping-Mediated Anion Transport through a Mannitol-Based Rosette Ion Channel. J Am Chem Soc 2014; 136:14128-35. [DOI: 10.1021/ja506278z] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
|
61
|
Roy A, Kand D, Saha T, Talukdar P. Pink fluorescence emitting fluoride ion sensor: investigation of the cascade sensing mechanism and bioimaging applications. RSC Adv 2014. [DOI: 10.1039/c4ra06933a] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
|
62
|
Saha T, Sengupta A, Hazra P, Talukdar P. In vitro sensing of Cu+through a green fluorescence rise of pyranine. Photochem Photobiol Sci 2014; 13:1427-33. [DOI: 10.1039/c4pp00097h] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
63
|
Roy A, Datar A, Kand D, Saha T, Talukdar P. A fluorescent off-on NBD-probe for F(-) sensing: theoretical validation and experimental studies. Org Biomol Chem 2014; 12:2143-9. [PMID: 24569399 DOI: 10.1039/c3ob41886c] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The design, synthesis and fluoride sensing ability of a 7-nitro-2,1,3-benzoxadiazole (NBD) based chemodosimeter is reported. Theoretical calculations were used to design a more applicable off-on response, by choosing NBD as the accurate fluorophore. Reaction of the NBD-probe with 300 equivalents of tetrabutyl ammonium fluoride (TBAF) exhibited a response time of 80 minutes and the reaction was selective to F(-) and sensing of the ion was marked by a 110-fold enhancement of green fluorescence. The off-on fluorescence characteristics of the probe enabled its application in live-cell imaging of intracellular F(-) ions.
Collapse
|
64
|
Chauhan DP, Saha T, Lahiri M, Talukdar P. BODIPY based ‘click on’ fluorogenic dyes: application in live cell imaging. Tetrahedron Lett 2014. [DOI: 10.1016/j.tetlet.2013.11.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
|
65
|
Roy A, Kand D, Saha T, Talukdar P. A cascade reaction based fluorescent probe for rapid and selective fluoride ion detection. Chem Commun (Camb) 2014; 50:5510-3. [DOI: 10.1039/c4cc01665c] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
|
66
|
Saha T, Roy A, Gening ML, Titov DV, Gerbst AG, Tsvetkov YE, Nifantiev NE, Talukdar P. Cyclo-oligo-(1 → 6)-β-d-glucosamine based artificial channels for tunable transmembrane ion transport. Chem Commun (Camb) 2014; 50:5514-6. [DOI: 10.1039/c3cc49490j] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
|
67
|
Chauhan DP, Varma SJ, Vijeta A, Banerjee P, Talukdar P. A 1,3-amino group migration route to form acrylamidines. Chem Commun (Camb) 2013; 50:323-5. [PMID: 24233059 DOI: 10.1039/c3cc47182a] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A novel 1,3-amino group migration strategy for the synthesis of acrylamidines is presented. Cu(i) catalyzed reaction of N,N-disubstituted propargylamine with tosylazide generates a highly reactive ketenimine intermediate which is trapped by a tethered amino group leading to the rearrangement reaction.
Collapse
|
68
|
Kand D, Kalle AM, Talukdar P. Chromenoquinoline-based thiol probes: a study on the quencher position for controlling fluorescent Off-On characteristics. Org Biomol Chem 2013; 11:1691-701. [PMID: 23364761 DOI: 10.1039/c2ob27192c] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The design, synthesis and thiol sensing ability of chromenoquinoline-based fluorescent probes 4, 5 and 6 and are reported here. The relative position of the maleimide moiety was varied along the chromenoquinoline fluorophore to decrease the background fluorescence. Lower background fluorescence in probes 4 and 6 was rationalized by the smaller k(r)/k(nr) values compared to that of probe 5. An intramolecular charge transfer (ICT) mechanism was proposed for quenching and the extent was dependent on the position of the maleimide quencher. Fluorescent Off-On characteristics were evaluated by theoretical calculations. All probes were selective only towards thiol containing amino acids. Thiol sensing by probes 4 and 6 were much better compared to 5. Probe 4 displayed a better fluorescence response for less hindered thiol (185-, 223- and 156-fold for Hcy, Cys and GSH, respectively), while for probe 6, a higher enhancement in fluorescence was observed with more hindered thiols (180-, 205- and 245-fold for Hcy, Cys and GSH, respectively). The better response to bulkier thiol, GSH by probe 6 was attributed to the steric crowding at the C-4 position and bulkiness of the GSH group which force the succinimide unit to be in a nearly orthogonal conformation. This spatial arrangement was important in reducing the fluorescence quenching ability of the succinimide moiety. The application of probes 4, 5 and 6 was demonstrated by naked eye detection thiols using a 96-well plate system as well as by live-cell imaging.
Collapse
|
69
|
Gening ML, Tsvetkov YE, Titov DV, Gerbst AG, Yudina ON, Grachev AA, Shashkov AS, Vidal S, Imberty A, Saha T, Kand D, Talukdar P, Pier GB, Nifantiev NE. Linear and cyclic oligo-β-(1→6)-D-glucosamines: Synthesis, conformations, and applications for design of a vaccine and oligodentate glycoconjugates. PURE APPL CHEM 2013. [DOI: 10.1351/pac-con-12-09-06] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Poly-β-(1→6)-N-acetyl-D-glucosamine is an exopolysaccharide secreted by numerous pathogenic bacteria, includingStaphylococcus aureus,Escherichia coli,Yersinia pestis,Bordetella pertussis,Acinetobacter baumannii,Burkholderiaspp., and others. A convergent approach was developed for the synthesis of oligosaccharide fragments consisting of 5, 7, 9, and 11 glucosamine orN-acetylglucosamine units and for the preparation of five nona-β-(1→6)-D-glucosamines with variousN-acetylation patterns. Penta- and nona-β‑(1→6)-D-glucosamines conjugated to protein carriers through a specially developed sulfhydryl linker proved to be highly immunogenic in mice and rabbits and elicited antibodies that mediated opsonic killing of multiple strains ofS. aureus(including methicillin-resistantS. aureus, MRSA) andE. coli, and protected againstS. aureusskin abscesses and lethalE. coliandB. cenocepaciaperitonitis. These findings provide a basis for the construction of a unique semisynthetic vaccine against multiple bacterial targets. Conformational studies by means of special NMR experiments and computer modeling revealed that the oligo-β-(1→6)-D-glucosamine chain exists mostly in a helix-like conformation, where the terminal monosaccharides are arranged close to each other. Owing to this feature, oligoglucosamines consisting of 2 to 7 residues easily form products of cycloglycosylation. Cyclooligo-β-(1→6)-D-glucosamines represent a new family of functionalized cyclic oligosaccharides. Owing to their molecular architectonics, these compounds are convenient scaffolds for the design of conjugates with defined valency, symmetry, flexibility, and function.
Collapse
|
70
|
Kand D, Chauhan DP, Lahiri M, Talukdar P. δ-Unsaturated γ-amino acids: enantiodivergent synthesis and cell imaging studies. Chem Commun (Camb) 2013; 49:3591-3. [DOI: 10.1039/c3cc40824h] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
71
|
Saha T, Kand D, Talukdar P. A colorimetric and fluorometric BODIPY probe for rapid, selective detection of H2S and its application in live cell imaging. Org Biomol Chem 2013; 11:8166-70. [DOI: 10.1039/c3ob41884g] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
72
|
Kand D, Mishra PK, Saha T, Lahiri M, Talukdar P. BODIPY based colorimetric fluorescent probe for selective thiophenol detection: theoretical and experimental studies. Analyst 2012; 137:3921-4. [PMID: 22751002 DOI: 10.1039/c2an35524h] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A BODIPY-based selective thiophenol probe capable of discriminating aliphatic thiols is reported. The fluorescence off-on effect upon reaction with thiol is elucidated with theoretical calculations. The sensing of thiophenol is associated with a color change from red to yellow and 63-fold enhancement in green fluorescence. Application of the probe for selective thiophenol detection is demonstrated by live cell imaging.
Collapse
|
73
|
Kand D, Kalle AM, Varma SJ, Talukdar P. A chromenoquinoline-based fluorescent off–on thiol probe for bioimaging. Chem Commun (Camb) 2012; 48:2722-4. [DOI: 10.1039/c2cc16593g] [Citation(s) in RCA: 133] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
|
74
|
Deshmukh SC, Roy A, Talukdar P. Diastereoselective construction of syn-α-oxyamines via three-component α-oxyaldehyde–dibenzylamine–alkyne coupling reaction: application in the synthesis of (+)-β-conhydrine and its analogues. Org Biomol Chem 2012; 10:7536-44. [DOI: 10.1039/c2ob26007g] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
|
75
|
Kalle AM, Mallika A, Badiger J, Alinakhi, Talukdar P, Sachchidanand. Inhibition of SIRT1 by a small molecule induces apoptosis in breast cancer cells. Biochem Biophys Res Commun 2010; 401:13-9. [PMID: 20813094 DOI: 10.1016/j.bbrc.2010.08.118] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2010] [Accepted: 08/26/2010] [Indexed: 11/25/2022]
Abstract
Overexpression of SIRT1, a NAD+-dependent class III histone deacetylases (HDACs), is implicated in many cancers and therefore could become a promising antitumor target. Here we demonstrate a small molecule SIRT1 inhibitor, ILS-JGB-1741(JGB1741) with potent inhibitory effects on the proliferation of human metastatic breast cancer cells, MDA-MB 231. The molecule has been designed using medicinal chemistry approach based on known SIRT1 inhibitor, sirtinol. The molecule showed a significant inhibition of SIRT1 activity compared to sirtinol. Studies on the antitumor effects of JGB on three different cancer cell lines, K562, HepG2 and MDA-MB 231 showed an IC₅₀ of 1, 10 and 0.5 μM, respectively. Further studies on MDA-MB 231 cells showed a dose-dependent increase in K9 and K382 acetylation of H3 and p53, respectively. Results also demonstrated that JGB1741-induced apoptosis is associated with increase in cytochrome c release, modulation in Bax/Bcl2 ratio and cleavage of PARP. Flowcytometric analysis showed increased percentage of apoptotic cells, decrease in mitochondrial membrane potential and increase in multicaspase activation. In conclusion, the present study indicates the potent apoptotic effects of JGB1741 in MDA-MB 231 cells.
Collapse
|
76
|
Pallavi R, Roy N, Nageshan RK, Talukdar P, Pavithra SR, Reddy R, Venketesh S, Kumar R, Gupta AK, Singh RK, Yadav SC, Tatu U. Heat shock protein 90 as a drug target against protozoan infections: biochemical characterization of HSP90 from Plasmodium falciparum and Trypanosoma evansi and evaluation of its inhibitor as a candidate drug. J Biol Chem 2010; 285:37964-75. [PMID: 20837488 DOI: 10.1074/jbc.m110.155317] [Citation(s) in RCA: 130] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Using a pharmacological inhibitor of Hsp90 in cultured malarial parasite, we have previously implicated Plasmodium falciparum Hsp90 (PfHsp90) as a drug target against malaria. In this study, we have biochemically characterized PfHsp90 in terms of its ATPase activity and interaction with its inhibitor geldanamycin (GA) and evaluated its potential as a drug target in a preclinical mouse model of malaria. In addition, we have explored the potential of Hsp90 inhibitors as drugs for the treatment of Trypanosoma infection in animals. Our studies with full-length PfHsp90 showed it to have the highest ATPase activity of all known Hsp90s; its ATPase activity was 6 times higher than that of human Hsp90. Also, GA brought about more robust inhibition of PfHsp90 ATPase activity as compared with human Hsp90. Mass spectrometric analysis of PfHsp90 expressed in P. falciparum identified a site of acetylation that overlapped with Aha1 and p23 binding domain, suggesting its role in modulating Hsp90 multichaperone complex assembly. Indeed, treatment of P. falciparum cultures with a histone deacetylase inhibitor resulted in a partial dissociation of PfHsp90 complex. Furthermore, we found a well known, semisynthetic Hsp90 inhibitor, namely 17-(allylamino)-17-demethoxygeldanamycin, to be effective in attenuating parasite growth and prolonging survival in a mouse model of malaria. We also characterized GA binding to Hsp90 from another protozoan parasite, namely Trypanosoma evansi. We found 17-(allylamino)-17-demethoxygeldanamycin to potently inhibit T. evansi growth in a mouse model of trypanosomiasis. In all, our biochemical characterization, drug interaction, and animal studies supported Hsp90 as a drug target and its inhibitor as a potential drug against protozoan diseases.
Collapse
|
77
|
Mehta G, Talukdar P, Pullepu V, Sen S. Conformationally Restricted Nucleocyclitols: a Study into their Conformational Preferences and Supramolecular Architecture in the Solid State. European J Org Chem 2009. [DOI: 10.1002/ejoc.200900611] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
|
78
|
Bhosale S, Sisson AL, Talukdar P, Fürstenberg A, Banerji N, Vauthey E, Bollot G, Mareda J, Röger C, Würthner F, Sakai N, Matile S. Photoproduction of Proton Gradients with π-Stacked Fluorophore Scaffolds in Lipid Bilayers. Science 2006; 313:84-6. [PMID: 16825567 DOI: 10.1126/science.1126524] [Citation(s) in RCA: 350] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Rigid p-octiphenyl rods were used to create helical tetrameric pi-stacks of blue, red-fluorescent naphthalene diimides that can span lipid bilayer membranes. In lipid vesicles containing quinone as electron acceptors and surrounded by ethylenediaminetetraacetic acid as hole acceptors, transmembrane proton gradients arose through quinone reduction upon excitation with visible light. Quantitative ultrafast and relatively long-lived charge separation was confirmed as the origin of photosynthetic activity by femtosecond fluorescence and transient absorption spectroscopy. Supramolecular self-organization was essential in that photoactivity was lost upon rod shortening (from p-octiphenyl to biphenyl) and chromophore expansion (from naphthalene diimide to perylene diimide). Ligand intercalation transformed the photoactive scaffolds into ion channels.
Collapse
|
79
|
Abstract
Supramolecular pi-stack architecture is fundamental in DNA chemistry but absent in biological and synthetic ion channels and pores. Here, a novel rigid-rod pi-stack architecture is introduced to create synthetic ion channels with characteristics that are at the forefront of rational design, that is, ligand gating by a conformational change of the functional supramolecule. Namely, the intercalation of electron-rich aromatics is designed to untwist inactive electron-poor helical pi-stacks without internal space into open barrel-stave ion channels. Conductance experiments in planar lipid bilayers corroborate results from spherical bilayers and molecular modeling: Highly cooperative and highly selective ligand gating produces small, long-lived, weakly anion selective, ohmic ion channels. Structural studies conducted under conditions relevant for function provide experimental support for helix-barrel transition as origin of ligand gating. Control experiments demonstrate that minor structural changes leading to internal decrowding suffice to cleanly annihilate chiral self-organization and function.
Collapse
|
80
|
Talukdar P, Bollot G, Mareda J, Sakai N, Matile S. Synthetic Ion Channels with Rigid-Rod π-Stack Architecture that Open in Response to Charge-Transfer Complex Formation. J Am Chem Soc 2005; 127:6528-9. [PMID: 15869262 DOI: 10.1021/ja051260p] [Citation(s) in RCA: 141] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We describe the design, synthesis, and evaluation of synthetic ion channels with a new rigid-rod pi-stack architecture that open in response to guest binding by aromatic electron donor-acceptor interactions. Highly cooperative and highly selective ligand gating is shown to yield anion selective, small ion channels that have the characteristic plum color of the charge-transfer complexes formed between the dialkoxynaphthalene ligands and the stacked naphthalenediimide acceptors of the channel.
Collapse
|
81
|
Sakai N, Talukdar P, Matile S. Use of the exciton chirality method in the investigation of ligand-gated synthetic ion channels. Chirality 2005; 18:91-4. [PMID: 16385620 DOI: 10.1002/chir.20221] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The objective of this brief highlight is to point out the central role of the exciton chirality method to gain insights on the structural basis of the recently achieved ligand gating of synthetic ion channels. This unprecedented ligand gating was achieved with an equally unprecedented transmembrane rigid-rod pi-stack architecture that is designed to adopt a closed conformation with helically stacked naphthalenediimide (NDI) acceptors. The intercalation of the complementary electron-rich dialkoxynaphthalene ligands then stimulates the untwisting of the closed pi-helices into hollow barrel-stave supramolecules. During this helix-barrel transition, the angle between the transition moments of the exciton-coupled NDI chromophores decreases toward zero. The corresponding disappearance of the split CD provides, according to the exciton chirality method, the otherwise elusive experimental support that ligand-gated ion channel formation really occurs by this rationally designed helix-barrel transition.
Collapse
|
82
|
Talukdar P, Sakai N, Sordé N, Gerard D, Cardona VMF, Matile S. Outer surface modification of synthetic multifunctional pores. Bioorg Med Chem 2004; 12:1325-36. [PMID: 15018904 DOI: 10.1016/j.bmc.2003.06.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2002] [Revised: 06/09/2003] [Accepted: 06/10/2003] [Indexed: 10/26/2022]
Abstract
The characteristics of pores formed by p-octiphenyl beta-barrels with LWV triads at the outer surface are reported in comparison with the conventional rigid-rod beta-barrels with all-L outer surface. Maintained multifunctionality of tetrameric pores with external LWV triads (inversion of ion selectivity, molecular recognition and transformation) is implicative for intact barrel interior. Increased pore activity supports dominance of high bilayer affinity for W over low affinity for V. Transmembrane p-octiphenyl orientation (from fluorescence depth quenching) supports barrel-stave (rather than toroidal) pores and dominance of transmembrane preference of rigid rods over interfacial preference of W. Destabilization of beta-barrel pores in membranes (from short single-channel lifetimes) and in the media (from 4th-power dependence on monomer concentration) by LWV triads supports dominance of low beta-propensity for W over high beta-propensity for V. The relation between the stability of supramolecular (pre)pores and dependence of activity on monomer concentration is discussed in a more general context.
Collapse
|
83
|
Som A, Talukdar P, Baumeister B, Matile S. Catalytic Rigid-Rod ?-Barrels with Hydrazide Cofactors to Convert Poor Substrates as Hydrazone Conjugates. Chimia (Aarau) 2003. [DOI: 10.2533/000942903777679541] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The usefulness of pyrene-1,3,6-trisulfonates as cofactors for p-octiphenyl ?-barrel ion channels to mediate recognition and conversion of otherwise inaccessible benzaldehyde substrates is described.
Collapse
|
84
|
Baudry Y, Baumeister B, Das G, Gerard D, Matile S, Sakai N, Som A, Sordé N, Talukdar P. Bioorganic Chemistry of Rigid-Rod Molecules: Adventures with p-Oligophenyls. Chimia (Aarau) 2002. [DOI: 10.2533/000942902777679948] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
|
85
|
Das G, Talukdar P, Matile S. Fluorometric detection of enzyme activity with synthetic supramolecular pores. Science 2002; 298:1600-2. [PMID: 12446904 DOI: 10.1126/science.1077353] [Citation(s) in RCA: 142] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The reversible blockage of synthetic pores formed by rigid-rod beta barrels, either by substrates or products, was used to sense a variety of enzymatic reactions in high-throughput format with "naked-eye" fluorescent detection. Improvement of sensor sensitivity beyond three orders of magnitude by straightforward internal mutations underscores the functional plasticity of rigid-rod beta barrels. Such detectors of enzyme activity with the aforementioned characteristics are needed in areas as diverse as proteomics and environmentally benign organic synthesis.
Collapse
|
86
|
Mehta G, Lakshminath S, Talukdar P. A norbornyl route to aminocyclohexitols: syntheses of diverse aminocarbasugars and ‘confused’ aminocarbasugars. Tetrahedron Lett 2002. [DOI: 10.1016/s0040-4039(01)02125-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
|
87
|
Mehta G, Talukdar P, Mohal N. A general norbornyl based synthetic approach to carbasugars and ‘confused’ carbasugars. Tetrahedron Lett 2001. [DOI: 10.1016/s0040-4039(01)01454-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|