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Danmaliki GI, Hwang PM. Proton TOCSY NMR relaxation rates quantitate protein side chain mobility in the Pin1 WW domain. JOURNAL OF BIOMOLECULAR NMR 2022; 76:121-135. [PMID: 35864369 PMCID: PMC9427894 DOI: 10.1007/s10858-022-00400-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2022] [Accepted: 07/03/2022] [Indexed: 06/14/2023]
Abstract
Protein side chain dynamics play a vital role in many biological processes, but differentiating mobile from rigid side chains remains a technical challenge in structural biology. Solution NMR spectroscopy is ideally suited for this but suffers from limited signal-to-noise, signal overlap, and a need for fractional 13C or 2H labeling. Here we introduce a simple strategy measuring initial 1H relaxation rates during a 1H TOCSY sequence like DIPSI-2, which can be appended to the beginning of any multi-dimensional NMR sequence that begins on 1H. The TOCSY RF field compels all 1H atoms to behave similarly under the influence of strong coupling and rotating frame cross-relaxation, so that differences in relaxation rates are due primarily to side chain mobility. We apply the scheme to a thermostable mutant Pin1 WW domain and demonstrate that the observed 1H relaxation rates correlate well with two independent NMR measures of side-chain dynamics, cross-correlated 13C relaxation rates in 13CβH2 methylene groups and maximum observable 3J couplings sensitive to the χ1 side chain dihedral angle (3JHα,Hβ, 3JN,Hβ, and 3JCO,Hβ). The most restricted side chains belong to Trp26 and Asn40, which are closely packed to constitute the folding center of the WW domain. None of the other conserved aromatic residues is as immobile as the first tryptophan side chain of the WW domain. The proposed 1H relaxation methodology should make it relatively easy to measure side chain dynamics on uniformly 15N- or 13C-labeled proteins, so long as chemical shift assignments are obtainable.
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Affiliation(s)
- Gaddafi I Danmaliki
- Department of Biochemistry, University of Alberta, Edmonton, AB, T6G 2H7, Canada
| | - Peter M Hwang
- Department of Biochemistry, University of Alberta, Edmonton, AB, T6G 2H7, Canada.
- Department of Medicine, University of Alberta, Edmonton, AB, T6G 2R3, Canada.
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2
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Paul P, Karar M, Mondal B, Roy UK, Ghosh A, Majumdar T, Mallick A. Controlled tuning of radiative-nonradiative transition via solvent perturbation: Franck-Condon emission vs. aggregation caused quenching. Phys Chem Chem Phys 2022; 24:18245-18254. [PMID: 35876115 DOI: 10.1039/d2cp02305a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Organic molecules with tunable fluorescence quantum yield are attractive for opto-electronic applications. A fluorophore with tunable fluorescence quantum yield should be a better choice for a variety of applications that demand fluorophores with different quantum yields. Here organic emitters with a continuous bell-shaped fluorescence yield profile would be promising in view of sustainability and reusability; however, fluorophores with these properties are rarely reported. A bis-indole derivative, 3,3'-bisindolyl(phenyl)methane (BIPM), was synthesised and found to undergo a unique 'rise-and-fall' profile in fluorescence yield with a compositional change of the 1,4-dioxane (DiOx)-H2O solvent system. A predominant interplay of two contrasting factors, (a) polarity and proticity induced emission enhancement and (b) aggregation caused fluorescence quenching, on either side of a crossover solvent composition (∼50% fW), resulted in a continuous bell-patterned fluorescence yield profile. Interestingly, these two factors could be observed individually or simultaneously by adjusting the H2O fraction. Detailed spectroscopic, electron microscopic and computational studies have been performed to substantiate the photophysics behind the solvent regulated modulation of fluorescence quantum yield.
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Affiliation(s)
- Provakar Paul
- Department of Chemistry, University of Kalyani, Nadia, West Bengal, 741235, India
| | - Monaj Karar
- Department of Chemistry, University of Kalyani, Nadia, West Bengal, 741235, India
| | - Bibhas Mondal
- Department of Chemistry, Kazi Nazrul University, Asansol, West Bengal, 713340, India
| | - Ujjal Kanti Roy
- Department of Chemistry, Kazi Nazrul University, Asansol, West Bengal, 713340, India
| | - Ashutosh Ghosh
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER)-Kolkata, Mohanpur, West Bengal, 741246, India
| | - Tapas Majumdar
- Department of Chemistry, University of Kalyani, Nadia, West Bengal, 741235, India
| | - Arabinda Mallick
- Department of Chemistry, Kazi Nazrul University, Asansol, West Bengal, 713340, India
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3
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Indole-3-glyoxyl tyrosine: synthesis and antimalarial activity against Plasmodium falciparum. Future Med Chem 2019; 11:525-538. [PMID: 30916995 DOI: 10.4155/fmc-2018-0246] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
AIM More than 40% of the world's population, across 105 countries, live in malaria endemic areas. It is estimated that about 500 million cases of malaria and half a million deaths occur per year. RESULTS Herein, we demonstrate the biological activity of indole-3-glyoxyl tyrosine against Plasmodium falciparum, which is the causal agent of the most virulent form of malaria in humans. We developed an efficient synthesis of indole-3-glyoxyl tyrosine derivatives, which were then used as key intermediates in the synthesis of functionalized indole-3-glyoxyl biphenyl tyrosines. CONCLUSION In biological testing, the compounds exhibited a parasite growth inhibition of over 85%. A cell viability assay showed low cytotoxicity against human cells, with no significant changes in cell viability, making these compounds potential antimalarials.
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Pozharskii AF, Ozeryanskii VA, Filatova EA, Dyablo OV, Pogosova OG, Borodkin GS, Filarowski A, Steglenko DV. Neutral Pyrrole Nitrogen Atom as a π- and Mixed n,π-Donor in Hydrogen Bonding. J Org Chem 2019; 84:726-737. [PMID: 30576143 DOI: 10.1021/acs.joc.8b02562] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
9-Dimethylaminobenzo[ g]indoles 3-6 and 1-dimethylamino-8-(pyrrolyl-1)naphthalene 7 were examined as possible models for establishing the ability of the pyrrole nitrogen atom to participate in [NHN]+ hydrogen bonding as a proton acceptor. Indoles 3-5 (to a lesser extent 6) form rather stable tetrafluoroborates, with the proton mostly located on the NMe2 group but simultaneously engaged in the formation of a charged intramolecular [NHN]+ hydrogen bond (IHB) with the pyrrole N atom. The theoretically estimated energies of IHB in salts 3H+BF4--6H+BF4- vary between 7.0-10.7 and 6.2-7.0 kcal mol-1 in vapor and MeCN, respectively. The pyrrole N atom undergoes a perceptible pyramidalization but still remains involved in the 6π-electron aromatic system, suggesting that the hydrogen bonding in salts 3H+BF4--6H+BF4- represents a previously unknown mixed NH···N(n,π) interaction. Despite the favorable orientation of the N-H bond and the pyrrole ring in salt 7H+BF4-, no signs of NH···N(n) bonding in it were noticed, and the existing interaction was classified as pure NH···N(π). The results obtained may be useful in studies of secondary protein structures, especially those α-helix sections which contain tryptophan residues.
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Affiliation(s)
- Alexander F Pozharskii
- Department of Organic Chemistry , Southern Federal University , Zorge str. 7 , 344090 Rostov-on-Don , Russian Federation
| | - Valery A Ozeryanskii
- Department of Organic Chemistry , Southern Federal University , Zorge str. 7 , 344090 Rostov-on-Don , Russian Federation
| | - Ekaterina A Filatova
- Department of Organic Chemistry , Southern Federal University , Zorge str. 7 , 344090 Rostov-on-Don , Russian Federation
| | - Olga V Dyablo
- Department of Organic Chemistry , Southern Federal University , Zorge str. 7 , 344090 Rostov-on-Don , Russian Federation
| | - Olga G Pogosova
- Department of Organic Chemistry , Southern Federal University , Zorge str. 7 , 344090 Rostov-on-Don , Russian Federation
| | - Gennady S Borodkin
- Institute of Physical and Organic Chemistry , Southern Federal University , Stachki Avenue 194/2 , 344090 Rostov-on-Don , Russian Federation
| | - Aleksander Filarowski
- Faculty of Chemistry , University of Wroclaw , F. Joliot-Curie 14 , 50-383 Wroclaw , Poland.,Department of Physics , Industrial University of Tyumen , Volodarskogo 38 , 625000 Tyumen , Russian Federation
| | - Dmitriy V Steglenko
- Department of Organic Chemistry , Southern Federal University , Zorge str. 7 , 344090 Rostov-on-Don , Russian Federation.,Institute of Physical and Organic Chemistry , Southern Federal University , Stachki Avenue 194/2 , 344090 Rostov-on-Don , Russian Federation
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5
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Markiewicz BN, Mukherjee D, Troxler T, Gai F. Utility of 5-Cyanotryptophan Fluorescence as a Sensitive Probe of Protein Hydration. J Phys Chem B 2016; 120:936-44. [PMID: 26783936 DOI: 10.1021/acs.jpcb.5b12233] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Tryptophan (Trp) fluorescence has been widely used to interrogate the structure, dynamics, and function of proteins. In particular, it provides a convenient and site-specific means to probe a protein's hydration status and dynamics. Herein, we show that a tryptophan analogue, 5-cyanotryptophan (TrpCN), can also be used for this purpose, but with the benefit of enhanced sensitivity to hydration. This conclusion is reached based on measurements of the static and time-resolved fluorescence properties of 5-cyanoindole, TrpCN, and TrpCN-containing peptides in different solvents, which indicate that upon dehydration the fluorescence quantum yield (QY) and lifetime (τF) of TrpCN undergo a much greater change in comparison to those of Trp. For example, in H2O the QY of TrpCN is less than 0.01, which increases to 0.11 in 1,4-dioxane. Consistently, the fluorescence decay kinetics of TrpCN in H2O are dominated by a 0.4 ns component, whereas in 1,4-dioxane the kinetics are dominated by a 6.0 ns component. The versatile utility of TrpCN as a sensitive fluorescence reporter is further demonstrated in three applications, where we used it (1) to probe the solvent property of a binary mixture consisting of dimethyl sulfoxide and H2O, (2) to monitor the binding interaction of an antimicrobial peptide with lipid membranes, and (3) to differentiate two differently hydrated environments in a folded protein.
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Affiliation(s)
- Beatrice N Markiewicz
- Department of Chemistry and ‡The Ultrafast Optical Processes Laboratory, University of Pennsylvania , Philadelphia, Pennsylvania 19104, United States
| | - Debopreeti Mukherjee
- Department of Chemistry and ‡The Ultrafast Optical Processes Laboratory, University of Pennsylvania , Philadelphia, Pennsylvania 19104, United States
| | - Thomas Troxler
- Department of Chemistry and ‡The Ultrafast Optical Processes Laboratory, University of Pennsylvania , Philadelphia, Pennsylvania 19104, United States
| | - Feng Gai
- Department of Chemistry and ‡The Ultrafast Optical Processes Laboratory, University of Pennsylvania , Philadelphia, Pennsylvania 19104, United States
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Biswal HS, Bhattacharyya S, Bhattacherjee A, Wategaonkar S. Nature and strength of sulfur-centred hydrogen bonds: laser spectroscopic investigations in the gas phase and quantum-chemical calculations. INT REV PHYS CHEM 2015. [DOI: 10.1080/0144235x.2015.1022946] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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7
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Saha TK, Mandal M, Thunga M, Chakraborty D, Ramkumar V. Imino phenoxide complexes of niobium and tantalum as catalysts for the polymerization of lactides, ε-caprolactone and ethylene. Dalton Trans 2013; 42:10304-14. [PMID: 23736066 DOI: 10.1039/c3dt50752a] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Imino phenoxide complexes of Nb and Ta show precise control towards the solvent free ring-opening polymerization of lactides (LA) and ε-caprolactone (CL). There is a close proximity between the observed number average molecular weight (M(n)) and theoretical molecular weight and the molecular weight distributions (MWDs) were found to be narrow. Analysis of low molecular weight oligomers of LA synthesized from these compounds revealed that the ligand is incorporated as one of the end terminal groups in the polymer chain. In addition, these complexes were realized to be precatalysts for the polymerization of ethylene.
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Affiliation(s)
- Tanmoy Kumar Saha
- Department of Chemistry, Indian Institute of Technology Madras, Chennai-600 036, Tamil Nadu, India
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8
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Density Functional Theory and Molecular Interactions: Dispersion Interactions. STRUCTURE AND BONDING 2012. [DOI: 10.1007/978-3-642-32750-6_2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/18/2023]
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9
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Bagdi K, Molnár K, Kállay M, Schön P, Vancsó JG, Pukánszky B. Quantitative estimation of the strength of specific interactions in polyurethane elastomers, and their effect on structure and properties. Eur Polym J 2012. [DOI: 10.1016/j.eurpolymj.2012.07.016] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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10
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Cabaleiro-Lago EM, Rodríguez-Otero J, Peña-Gallego Á. Computational study of the interaction of indole-like molecules with water and hydrogen sulfide. J Chem Phys 2011; 135:134310. [DOI: 10.1063/1.3643840] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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12
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Waegele MM, Gai F. Computational Modeling of the Nitrile Stretching Vibration of 5-Cyanoindole in Water. J Phys Chem Lett 2010; 1:781-786. [PMID: 20436926 PMCID: PMC2860969 DOI: 10.1021/jz900429z] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
The bandwidth of the nitrile (C≡N) stretching vibration of 5-cyanotryptophan shows a significant broadening upon hydration. Thus, it has been proposed to be a useful infrared probe of the local hydration environment of proteins. However, the molecular mechanism underlying this hydration-induced spectral broadening is not known, making interpretation of the experimental results difficult. Herein, we investigate how interactions of water with various sites of 5-cyanoindole, the sidechain of 5-cyanotryptophan, affect its C≡N stretching vibration via a combined electronic structure/molecular dynamics approach. It is found that, besides those interactions with the nitrile group, interactions of water with the indole ring also play a significant role in mediating the C≡N stretching frequency. Thus, this study provides a molecular basis for understanding how hydration affects the C≡N stretching band of 5-cyanotryptophan. In addition, an empirical model, which includes interactions of water with both the nitrile and indole groups, is developed for predicting the C≡N stretching vibrational band via molecular dynamics simulations.
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Leyva V, Corral I, Gonzalez L. Ortho-Nitrobenzaldehyde 1:1 Water Complexes. The Influence of Solute Water Interactions in the Vertical Excited Spectrum. Z PHYS CHEM 2009. [DOI: 10.1524/zpch.2008.5387] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Abstract
The intermolecular hydrogen bonding interaction of a water molecule with the caging group ortho-nitrobenzaldehyde (o-NBA) has been studied by means of quantum mechanical methods. The o-NBA chromophore presents two functional groups, NO2 and CHO, interconnected by an intramolecular hydrogen bond. Both groups compete for the interaction with the solvent molecule, leading to eleven possible stable isomers that are very close in energy. The effect of the binding water on the electronic properties of o-NBA has been analyzed in structural terms as well as using the atoms-in-molecules theory of Bader. Binding energies for all complexes are reported, and in general they range from 5 to 13 kJ/mol. Special attention has been paid to the effect of the water molecule on the vertical excitation energies of o-NBA. Upon water complexation the absorption spectrum of o-NBA shifts to higher energies and it is characterized by three bands of comparable intensities as those recently measured for o-NBA in gas phase.
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14
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Cabaleiro-Lago EM, Carrazana-García JA, Rodríguez-Otero J. Study of the interaction between water and hydrogen sulfide with polycyclic aromatic hydrocarbons. J Chem Phys 2009; 130:234307. [PMID: 19548727 DOI: 10.1063/1.3152577] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
A computational study has been carried out for determining the characteristics of the interaction between one water and hydrogen sulfide molecule with a series of polycyclic aromatic hydrocarbons of increasing size, namely, benzene, anthracene, triphenylene, coronene, circumcoronene, and dicircumcoronene. Potential energy curves were calculated for structures where H(2)X (X=O,S) molecule is located over the central six-membered ring with its hydrogen atoms pointing toward to (mode A) or away from (mode B) the hydrocarbon. The accuracy of different methods has been tested against the results of coupled cluster calculations extrapolated to basis set limit for the smaller hydrocarbons. The spin component scaled MP2 (SCS-MP2) method and a density functional theory method empirically corrected for dispersion (DFT-D) reproduce fairly well the results of high level calculations and therefore were employed for studying the larger systems, though DFT-D seems to underestimate the interaction in hydrogen sulfide clusters. Water complexes in mode A have interaction energies that hardly change with the size of the hydrocarbon due to compensation between the increase in the correlation contribution to the interaction energy and the increase in the repulsive character of the Hartree-Fock energy. For all the other clusters studied, there is a continuous increase in the intensity of the interaction as the size of the hydrocarbon increases, suggesting already converged values for circumcoronene. The interaction energy for water clusters extrapolated to an infinite number of carbon atoms amounts to -13.0 and -15.8 kJ/mol with SCS-MP2 and DFT-D, respectively. Hydrogen sulfide interacts more strongly than water with the hydrocarbons studied, leading to a limiting value of -21.7 kJ/mol with the SCS-MP2 method. Also, complexes in mode B are less stable than the corresponding A structures, with interaction energies amounting to -8.2 and -18.2 kJ/mol for water and hydrogen sulfide, respectively. The DFT-D calculations give values of -16.2 and -9.3 kJ/mol for hydrogen sulfide complexes in modes A and B, less negative than those predicted by the SCS-MP2 method, probably indicating problems with sulfur dispersion parameters.
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Affiliation(s)
- Enrique M Cabaleiro-Lago
- Departamento de Química Física, Facultade de Ciencias, Universidade de Santiago de Compostela, Campus de Lugo, Avda. Alfonso X El Sabio s/n, 27002 Lugo, Galicia, Spain.
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15
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Biswal HS, Shirhatti PR, Wategaonkar S. O−H···O versus O−H···S Hydrogen Bonding I: Experimental and Computational Studies on the p-Cresol·H2O and p-Cresol·H2S Complexes. J Phys Chem A 2009; 113:5633-43. [DOI: 10.1021/jp9009355] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Himansu S. Biswal
- Department of Chemical Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400 005, India
| | - Pranav R. Shirhatti
- Department of Chemical Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400 005, India
| | - Sanjay Wategaonkar
- Department of Chemical Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400 005, India
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Ramachandran C, Fazio DD, Sathyamurthy N, Aquilanti V. Guest species trapped inside carbon nanotubes. Chem Phys Lett 2009. [DOI: 10.1016/j.cplett.2009.03.068] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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17
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Rutledge LR, Wetmore SD. Remarkably Strong T-Shaped Interactions between Aromatic Amino Acids and Adenine: Their Increase upon Nucleobase Methylation and a Comparison to Stacking. J Chem Theory Comput 2008; 4:1768-80. [DOI: 10.1021/ct8002332] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Lesley R. Rutledge
- Department of Chemistry and Biochemistry, University of Lethbridge, 4401 University Drive, Lethbridge, Alberta, Canada T1K 3M4
| | - Stacey D. Wetmore
- Department of Chemistry and Biochemistry, University of Lethbridge, 4401 University Drive, Lethbridge, Alberta, Canada T1K 3M4
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Cabaleiro-Lago EM, Rodríguez-Otero J, Peña-Gallego Á. Characteristics of the interaction of azulene with water and hydrogen sulfide: A computational study. J Chem Phys 2008; 129:084305. [DOI: 10.1063/1.2973632] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
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19
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Cabaleiro-Lago EM, Rodríguez-Otero J, Peña-Gallego Á. Computational Study on the Characteristics of the Interaction in Naphthalene···(H2X)n=1,2 (X = O, S) Clusters. J Phys Chem A 2008; 112:6344-50. [DOI: 10.1021/jp8021979] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Enrique M. Cabaleiro-Lago
- Departamento de Química Física, Facultade de Ciencias, Universidade de Santiago de Compostela, Campus de Lugo, Avda. Alfonso X El Sabio s/n 27002 Lugo, Galicia, Spain, and Departamento de Química Física, Facultade de Química, Universidade de Santiago de Compostela, Avda. das Ciencias, s/n 15706 Santiago de Compostela, Galicia, Spain
| | - Jesús Rodríguez-Otero
- Departamento de Química Física, Facultade de Ciencias, Universidade de Santiago de Compostela, Campus de Lugo, Avda. Alfonso X El Sabio s/n 27002 Lugo, Galicia, Spain, and Departamento de Química Física, Facultade de Química, Universidade de Santiago de Compostela, Avda. das Ciencias, s/n 15706 Santiago de Compostela, Galicia, Spain
| | - Ángeles Peña-Gallego
- Departamento de Química Física, Facultade de Ciencias, Universidade de Santiago de Compostela, Campus de Lugo, Avda. Alfonso X El Sabio s/n 27002 Lugo, Galicia, Spain, and Departamento de Química Física, Facultade de Química, Universidade de Santiago de Compostela, Avda. das Ciencias, s/n 15706 Santiago de Compostela, Galicia, Spain
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20
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Pál K, Kállay M, Köhler G, Zhang H, Bitter I, Kubinyi M, Vidóczy T, Grabner G. Efficient singlet-state deactivation of cyano-substituted indolines in protic solvents via CN--HO hydrogen bonds. Chemphyschem 2008; 8:2627-35. [PMID: 18058777 DOI: 10.1002/cphc.200700479] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The photophysical properties of indoline (I) and three of its derivatives, namely, N-methylindoline (MI), 5-cyanoindoline (CI), and 5-cyano-N-methylindoline (CMI), are studied in H-donating solvents of varying polarity. Based on measurements of fluorescence yield and lifetime, and of triplet yield and hydrated-electron formation, two distinct mechanisms of solvent-induced fluorescence quenching are evidenced. The first mechanism involves the cyano substituent and leads to an increase in the rate constant of internal conversion of one order of magnitude in ethanolic solution and of more than two orders of magnitude in water, as compared to solutions in n-hexane or acetonitrile. A similar trend had previously been observed in the case of 4-N,N-dimethylaminobenzonitrile (DMABN). The second mechanism reduces the fluorescence lifetimes of the non-cyanated derivatives in aqueous solution by one order of magnitude and is related to the formation of hydrated electrons. Neither of these mechanisms is influenced by methylation at the ring nitrogen. Quantum chemical calculations are performed on the ground and excited states of the hydrogen-bonded complexes between protic solvents and MI as well as CMI. Stable hydrogen-bonded configurations involving the CN substituent and a solvent OH group are found; these configurations are stable both in the ground and the first excited singlet states, whereas the corresponding complex at the ring amino nitrogen is stable in the ground state only. The CN--HO configuration is therefore a prime candidate for a mechanistic explanation of the observed quenching by the first mechanism. These findings may have useful applications for the design of fluorescence probes for water in biological systems.
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Affiliation(s)
- Krisztina Pál
- Vidóczy, Institute of Structural Chemistry, Chemical Research Center, Hungarian Academy of Sciences, P.O. Box 17, 1525 Budapest, Hungary
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Zhao Y, Tishchenko O, Truhlar DG. How well can density functional methods describe hydrogen bonds to pi acceptors? J Phys Chem B 2007; 109:19046-51. [PMID: 16853454 DOI: 10.1021/jp0534434] [Citation(s) in RCA: 159] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We employed four newly developed density functional theory (DFT) methods for the calculation of five pi hydrogen bonding systems, namely, H2O-C6H6, NH3-C6H6, HCl-C6H6, H2O-indole, and H2O-methylindole. We report new coupled cluster calculations for HCl-C6H6 that support the experimental results of Gotch and Zwier. Using the best available theoretical and experimental results for all five systems, our calculations show that the recently proposed MPW1B95, MPWB1K, PW6B95, and PWB6K methods give accurate energetic and geometrical predictions for pi hydrogen bonding interactions, for which B3LYP fails and PW91 is less accurate. We recommend the most recent DFT method, PWB6K, for investigating larger pi hydrogen bonded systems, such as those that occur in molecular recognition, protein folding, and crystal packing.
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Muñoz MA, Carmona C, Balón M. FTIR and fluorescence studies on the ground and excited state hydrogen-bonding interactions between 1-methylindole and water in water–triethylamine mixtures. Chem Phys 2007. [DOI: 10.1016/j.chemphys.2007.01.018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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23
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Alagona G, Ghio C. Protonated serotonin conformational landscape in vacuo and in aqueous solution (IEF-PCM): Role of correlation effects and monohydration. ACTA ACUST UNITED AC 2006. [DOI: 10.1016/j.theochem.2005.12.039] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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