The Experts below are selected from a list of 258 Experts worldwide ranked by ideXlab platform
Dale L. Boger - One of the best experts on this subject based on the ideXlab platform.
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Exploration of the site-specific nature and generalizability of a Trimethylammonium salt modification on vancomycin: A-ring derivatives.
Tetrahedron, 2019Co-Authors: Dale L. BogerAbstract:Abstract Vancomycin analogues bearing an A-ring Trimethylammonium salt modification were synthesized and their antimicrobial activity against vancomycin-resistant Enterococci (VRE) was evaluated. The modification increased antimicrobial potency and provided the capability to induce bacteria cell membrane permeabilization, but both properties were weaker than that found with our earlier reported similar C-terminus modification. The results provide further insights on the additive effect and generalizability of the structural and site-specific nature of a peripheral quaternary Trimethylammonium salt modification of vancomycin.
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N-Terminus Alkylation of Vancomycin: Ligand Binding Affinity, Antimicrobial Activity, and Site-Specific Nature of Quaternary Trimethylammonium Salt Modification.
ACS infectious diseases, 2018Co-Authors: Nicholas A. Isley, Dale L. BogerAbstract:A series of vancomycin derivatives alkylated at the N-terminus amine were synthesized, including those that contain quaternary Trimethylammonium salts either directly at the terminal amine site or with an intervening three-carbon spacer. The examination of their properties provides important comparisons with a C-terminus Trimethylammonium salt modification that we recently found to improve the antimicrobial potency of vancomycin analogues through an added mechanism of action. The N-terminus modifications disclosed herein were well-tolerated, minimally altering model ligand binding affinities (d-Ala-d-Ala) and antimicrobial activity, but did not induce membrane permeabilization that was observed with a similar C-terminus modification. The results indicate that our earlier observations with the C-terminus modification are sensitive to the site as well as structure of the Trimethylammonium salt modification and are not simply the result of nonspecific effects derived from introduction of a cationic charge.
Pannuru Venkatesu - One of the best experts on this subject based on the ideXlab platform.
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Thermophysical Properties of Aqueous Solution of Ammonium-Based Ionic Liquids
The journal of physical chemistry. B, 2014Co-Authors: Reddicherla Umapathi, Pankaj Attri, Pannuru VenkatesuAbstract:Experimental densities (ρ), ultrasonic sound velocities (u), viscosities (η), and refractive indices (nD) of binary mixtures of ammonium-based ionic liquids (ILs) such as diethylammonium acetate (DEAA) [(CH3CH2)2NH][CH3COO], triethylammonium acetate (TEAA) [(CH3CH2)3NH][CH3COO], diethylammonium hydrogen sulfate (DEAS) [(CH3CH2)2NH][HSO4], triethylammonium hydrogen sulfate (TEAS) [(CH3CH2)3NH][HSO4], Trimethylammonium acetate (TMAA) [(CH3)3NH][CH3COO], and Trimethylammonium hydrogen sulfate (TMAS) [(CH3)3NH][HSO4] with water are reported over the wide composition range at 25 °C under atmospheric pressure. The excess molar volumes (VE), deviation in isentropic compressibilities (Δκs), deviation in viscosities (Δη) and deviation in refractive indices (ΔnD) are calculated from experimental values and are correlated by Redlich–Kister polynomial equations. The VE and Δκs values for the aforesaid systems are negative over the entire composition range while the Δη and ΔnD values are positive under the same experi...
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The solubility and stability of amino acids in biocompatible ionic liquids.
Protein and peptide letters, 2013Co-Authors: T. Vasantha, Pankaj Attri, Pannuru Venkatesu, Awanish Kumar, R.s. Rama DeviAbstract:In recent years, ionic liquids (ILs) represent a new class of biocompatible co-solvents for biomolecules. In this work, we report the apparent transfer free energies (ΔG'tr) for six amino acids (AA) from water to aqueous solutions of six ammonium based ILs (diethylammonium acetate (DEAA), diethylammonium sulfate (DEAS), triethyl ammonium acetate (TEAA), triethylammonium sulfate (TEAS), triethylammonium dihydrogen phosphate (TEAP), and Trimethylammonium acetate (TMAA)) through solubility measurements, as a function of IL concentration at 298.15 K under atmospheric pressure. Salting-out effect was found for AA in aqueous IL solutions with increasing IL concentrations. In addition, we observed positive values of ΔG'tr for AA from water to ILs, indicating that the interactions between ILs and AA are unfavorable. From the obtained results, we found that the selected ammonium based ILs act as stabilizers for the structure of AA.
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effect of anion variation on the thermophysical properties of triethylammonium based protic ionic liquids with polar solvent
Thermochimica Acta, 2013Co-Authors: Varadhi Govinda, Pankaj Attri, Pannuru Venkatesu, Madhusudan P Reddy, Indra Bahadur, P VenkateswarluAbstract:Abstract In this work, we explore the anion effect on the thermophysical properties of protic ionic liquids (PILs) such as triethylammonium acetate [Et3NH][CH3COO] (TEAA), triethylammonium dihydrogen phosphate [Et3NH][H2PO4] (TEAP) and triethylammonium hydrogen sulfate [Et3NH][HSO4] (TEAS) with polar solvent such as dimethylsulfoxide (DMSO). To understand the molecular interactions between DMSO with ILs, densities (ρ), ultrasonic sound velocities (u) and viscosities (η) have been measured over whole range of compositions and at three temperatures, 298.15, 303.15, and 308.15 K under atmospheric pressure. A second order empirical polynomial and Arrhenius equations were used to correlate the ρ and η as function of temperature, respectively. Sound velocity mixing rules were used on experimental values. Further, the excess molar volume (VE), the deviation in isentropic compressibility (Δκs) and deviation in viscosity (Δη) were calculated using these properties. The obtained VE, Δκs and Δη values were correlated by using the Redlich–Kister polynomial equation.
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Influence of biocompatible ammonium ionic liquids on the solubility of l-alanine and l-valine in water
Fluid Phase Equilibria, 2012Co-Authors: T. Vasantha, Pankaj Attri, Pannuru Venkatesu, Awanish Kumar, R.s. Rama DeviAbstract:Abstract Understanding the folding process of proteins or polypeptides in co-solvents is a fascinating and critical issue in biophysical chemistry. In recent years, ionic liquids (ILs) represent a versatility of the new class of co-solvents. To quantify the bimolecular interactions of amino acids (AA), such as l -alanine (Ala) and l -valine (Val) with biocompatible ILs, we report the apparent transfer free energies ( Δ G ′ t r ) for AA from water to aqueous solutions of six ammonium based ILs (diethylammonium acetate (DEAA), diethylammonium sulfate (DEAS), triethyl ammonium acetate (TEAA), triethylammonium sulfate (TEAS), triethylammonium dihydrogen phosphate (TEAP), and Trimethylammonium acetate (TMAA)) through solubility measurements, as a function of IL concentration at 298.15 K under atmospheric pressure. Salting-out effect was found for AA in aqueous IL solutions with increasing IL concentrations. In addition, we observed positive values of Δ G ′ t r for Ala and Val from water to ILs, indicating that the interactions between ILs and AA are unfavorable. From the solubility results, we envisage that the selected ammonium based-ILs provide stability to the structure of AA. Further, the stability of AA has been studied by means of the UV–vis spectroscopy.
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Structural Basis for the Enhanced Stability of Protein Model Compounds and Peptide Backbone Unit in Ammonium Ionic Liquids
2012Co-Authors: T. Vasantha, Pankaj Attri, Pannuru Venkatesu, R. Rama S. DeviAbstract:Protein folding/unfolding is a fascinating study in the presence of cosolvents, which protect/disrupt the native structure of protein, respectively. The structure and stability of proteins and their functional groups may be modulated by the addition of cosolvents. Ionic liquids (ILs) are finding a vast array of applications as novel cosolvents for a wide variety of biochemical processes that include protein folding. Here, the systematic and quantitative apparent transfer free energies (ΔG′tr) of protein model compounds from water to ILs through solubility measurements as a function of IL concentration at 25 °C have been exploited to quantify and interpret biomolecular interactions between model compounds of glycine peptides (GPs) with ammonium based ILs. The investigated aqueous systems consist of zwitterionic glycine peptides: glycine (Gly), diglycine (Gly2), triglycine (Gly3), tetraglycine (Gly4), and cyclic glycylglycine (c(GG)) in the presence of six ILs such as diethylammonium acetate (DEAA), diethylammonium hydrogen sulfate (DEAS), triethylammonium acetate (TEAA), triethylammonium hydrogen sulfate (TEAS), triethylammonium dihydrogen phosphate (TEAP), and Trimethylammonium acetate (TMAA). We have observed positive values of ΔG′tr for GPs from water to ILs, indicating that interactions between ILs and GPs are unfavorable, which leads to stabilization of the structure of model protein compounds. Moreover, our experimental data ΔG′tr is used to obtain transfer free energies (Δg′tr) of the peptide backbone unit (or glycyl unit) (CH2CONH), which is the most numerous group in globular proteins, from water to IL solutions. To obtain the mechanism events of the ILs' role in enhancing the stability of the model compounds, we have further obtained m-values for GPs from solubility limits. These results explicitly elucidate that all alkyl ammonium ILs act as stabilizers for model compounds through the exclusion of ILs from model compounds of proteins and also reflect the effect of alkyl chain on the stability of protein model compounds
Pankaj Attri - One of the best experts on this subject based on the ideXlab platform.
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Thermophysical Properties of Aqueous Solution of Ammonium-Based Ionic Liquids
The journal of physical chemistry. B, 2014Co-Authors: Reddicherla Umapathi, Pankaj Attri, Pannuru VenkatesuAbstract:Experimental densities (ρ), ultrasonic sound velocities (u), viscosities (η), and refractive indices (nD) of binary mixtures of ammonium-based ionic liquids (ILs) such as diethylammonium acetate (DEAA) [(CH3CH2)2NH][CH3COO], triethylammonium acetate (TEAA) [(CH3CH2)3NH][CH3COO], diethylammonium hydrogen sulfate (DEAS) [(CH3CH2)2NH][HSO4], triethylammonium hydrogen sulfate (TEAS) [(CH3CH2)3NH][HSO4], Trimethylammonium acetate (TMAA) [(CH3)3NH][CH3COO], and Trimethylammonium hydrogen sulfate (TMAS) [(CH3)3NH][HSO4] with water are reported over the wide composition range at 25 °C under atmospheric pressure. The excess molar volumes (VE), deviation in isentropic compressibilities (Δκs), deviation in viscosities (Δη) and deviation in refractive indices (ΔnD) are calculated from experimental values and are correlated by Redlich–Kister polynomial equations. The VE and Δκs values for the aforesaid systems are negative over the entire composition range while the Δη and ΔnD values are positive under the same experi...
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The solubility and stability of amino acids in biocompatible ionic liquids.
Protein and peptide letters, 2013Co-Authors: T. Vasantha, Pankaj Attri, Pannuru Venkatesu, Awanish Kumar, R.s. Rama DeviAbstract:In recent years, ionic liquids (ILs) represent a new class of biocompatible co-solvents for biomolecules. In this work, we report the apparent transfer free energies (ΔG'tr) for six amino acids (AA) from water to aqueous solutions of six ammonium based ILs (diethylammonium acetate (DEAA), diethylammonium sulfate (DEAS), triethyl ammonium acetate (TEAA), triethylammonium sulfate (TEAS), triethylammonium dihydrogen phosphate (TEAP), and Trimethylammonium acetate (TMAA)) through solubility measurements, as a function of IL concentration at 298.15 K under atmospheric pressure. Salting-out effect was found for AA in aqueous IL solutions with increasing IL concentrations. In addition, we observed positive values of ΔG'tr for AA from water to ILs, indicating that the interactions between ILs and AA are unfavorable. From the obtained results, we found that the selected ammonium based ILs act as stabilizers for the structure of AA.
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effect of anion variation on the thermophysical properties of triethylammonium based protic ionic liquids with polar solvent
Thermochimica Acta, 2013Co-Authors: Varadhi Govinda, Pankaj Attri, Pannuru Venkatesu, Madhusudan P Reddy, Indra Bahadur, P VenkateswarluAbstract:Abstract In this work, we explore the anion effect on the thermophysical properties of protic ionic liquids (PILs) such as triethylammonium acetate [Et3NH][CH3COO] (TEAA), triethylammonium dihydrogen phosphate [Et3NH][H2PO4] (TEAP) and triethylammonium hydrogen sulfate [Et3NH][HSO4] (TEAS) with polar solvent such as dimethylsulfoxide (DMSO). To understand the molecular interactions between DMSO with ILs, densities (ρ), ultrasonic sound velocities (u) and viscosities (η) have been measured over whole range of compositions and at three temperatures, 298.15, 303.15, and 308.15 K under atmospheric pressure. A second order empirical polynomial and Arrhenius equations were used to correlate the ρ and η as function of temperature, respectively. Sound velocity mixing rules were used on experimental values. Further, the excess molar volume (VE), the deviation in isentropic compressibility (Δκs) and deviation in viscosity (Δη) were calculated using these properties. The obtained VE, Δκs and Δη values were correlated by using the Redlich–Kister polynomial equation.
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Influence of biocompatible ammonium ionic liquids on the solubility of l-alanine and l-valine in water
Fluid Phase Equilibria, 2012Co-Authors: T. Vasantha, Pankaj Attri, Pannuru Venkatesu, Awanish Kumar, R.s. Rama DeviAbstract:Abstract Understanding the folding process of proteins or polypeptides in co-solvents is a fascinating and critical issue in biophysical chemistry. In recent years, ionic liquids (ILs) represent a versatility of the new class of co-solvents. To quantify the bimolecular interactions of amino acids (AA), such as l -alanine (Ala) and l -valine (Val) with biocompatible ILs, we report the apparent transfer free energies ( Δ G ′ t r ) for AA from water to aqueous solutions of six ammonium based ILs (diethylammonium acetate (DEAA), diethylammonium sulfate (DEAS), triethyl ammonium acetate (TEAA), triethylammonium sulfate (TEAS), triethylammonium dihydrogen phosphate (TEAP), and Trimethylammonium acetate (TMAA)) through solubility measurements, as a function of IL concentration at 298.15 K under atmospheric pressure. Salting-out effect was found for AA in aqueous IL solutions with increasing IL concentrations. In addition, we observed positive values of Δ G ′ t r for Ala and Val from water to ILs, indicating that the interactions between ILs and AA are unfavorable. From the solubility results, we envisage that the selected ammonium based-ILs provide stability to the structure of AA. Further, the stability of AA has been studied by means of the UV–vis spectroscopy.
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Structural Basis for the Enhanced Stability of Protein Model Compounds and Peptide Backbone Unit in Ammonium Ionic Liquids
2012Co-Authors: T. Vasantha, Pankaj Attri, Pannuru Venkatesu, R. Rama S. DeviAbstract:Protein folding/unfolding is a fascinating study in the presence of cosolvents, which protect/disrupt the native structure of protein, respectively. The structure and stability of proteins and their functional groups may be modulated by the addition of cosolvents. Ionic liquids (ILs) are finding a vast array of applications as novel cosolvents for a wide variety of biochemical processes that include protein folding. Here, the systematic and quantitative apparent transfer free energies (ΔG′tr) of protein model compounds from water to ILs through solubility measurements as a function of IL concentration at 25 °C have been exploited to quantify and interpret biomolecular interactions between model compounds of glycine peptides (GPs) with ammonium based ILs. The investigated aqueous systems consist of zwitterionic glycine peptides: glycine (Gly), diglycine (Gly2), triglycine (Gly3), tetraglycine (Gly4), and cyclic glycylglycine (c(GG)) in the presence of six ILs such as diethylammonium acetate (DEAA), diethylammonium hydrogen sulfate (DEAS), triethylammonium acetate (TEAA), triethylammonium hydrogen sulfate (TEAS), triethylammonium dihydrogen phosphate (TEAP), and Trimethylammonium acetate (TMAA). We have observed positive values of ΔG′tr for GPs from water to ILs, indicating that interactions between ILs and GPs are unfavorable, which leads to stabilization of the structure of model protein compounds. Moreover, our experimental data ΔG′tr is used to obtain transfer free energies (Δg′tr) of the peptide backbone unit (or glycyl unit) (CH2CONH), which is the most numerous group in globular proteins, from water to IL solutions. To obtain the mechanism events of the ILs' role in enhancing the stability of the model compounds, we have further obtained m-values for GPs from solubility limits. These results explicitly elucidate that all alkyl ammonium ILs act as stabilizers for model compounds through the exclusion of ILs from model compounds of proteins and also reflect the effect of alkyl chain on the stability of protein model compounds
Nicholas A. Isley - One of the best experts on this subject based on the ideXlab platform.
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N-Terminus Alkylation of Vancomycin: Ligand Binding Affinity, Antimicrobial Activity, and Site-Specific Nature of Quaternary Trimethylammonium Salt Modification.
ACS infectious diseases, 2018Co-Authors: Nicholas A. Isley, Dale L. BogerAbstract:A series of vancomycin derivatives alkylated at the N-terminus amine were synthesized, including those that contain quaternary Trimethylammonium salts either directly at the terminal amine site or with an intervening three-carbon spacer. The examination of their properties provides important comparisons with a C-terminus Trimethylammonium salt modification that we recently found to improve the antimicrobial potency of vancomycin analogues through an added mechanism of action. The N-terminus modifications disclosed herein were well-tolerated, minimally altering model ligand binding affinities (d-Ala-d-Ala) and antimicrobial activity, but did not induce membrane permeabilization that was observed with a similar C-terminus modification. The results indicate that our earlier observations with the C-terminus modification are sensitive to the site as well as structure of the Trimethylammonium salt modification and are not simply the result of nonspecific effects derived from introduction of a cationic charge.
Bryan S. Pivovar - One of the best experts on this subject based on the ideXlab platform.
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Hydroxide Degradation Pathways for Substituted Trimethylammonium Cations: A DFT Study
The Journal of Physical Chemistry C, 2012Co-Authors: Hai Long, Kwiseon Kim, Bryan S. PivovarAbstract:Substituted Trimethylammonium cations serve as small molecule analogues for tetherable cations in anion exchange membranes. In turn, these membranes serve as the basis for alkaline membrane fuel cells by allowing facile conduction of hydroxide. As these cations are susceptible to hydroxide attack, they degrade over time and greatly limit the lifetime of the fuel cell. In this research, we performed density functional theory calculations to investigate the degradation pathways of substituted Trimethylammonium cations to probe the relative durability of cation tethering strategies in alkyl and aromatic tethers. Our results show that significant changes in calculated energy barriers occur when substitution groups change. Specifically, we have found that, when available, the Hofmann elimination pathway is the most vulnerable pathway for degradation; however, this barrier is also found to depend on the carbon chain length and number of hydrogens susceptible to Hofmann elimination. S{sub N}2 barriers were also investigated for both methyl groups and substitution groups. The reported findings give important insight into potential tethering strategies for Trimethylammonium cations in anion exchange membranes.
