Dielectric Relaxation of NaClO4Solutions in Formamide, N-Methylformamide, and N,N-Dimethylformamide

1995 ◽  
Vol 50 (1) ◽  
pp. 65-74 ◽  
Author(s):  
J. Barthel ◽  
K. Bachhuber ◽  
R. Büchner
Keyword(s):  
Average Length ◽  
Ion Pairs ◽  
Liquid Structure ◽  
Acceptor Site ◽  
Relaxation Processes ◽  
Hydrogen Bond Acceptor ◽  
Solvent Interactions ◽  
Structure And Dynamics ◽  
Relaxation Parameters ◽  
Diffusion Controlled

Complex permittivity spectra in the frequency range 0.95 ≤ v/[GHz] ≤ 89 for N,N-dimethylformamide (DMF), N-methylformamide (NMF), formamide (FA) and their solutions of NaClO4 are investigated to study the change of liquid structure and dynamics arising from the availability of one hydrogen-bond acceptor site together with no (DMF), one (NMF), or two (FA) donor sites on the same molecule. Three solvent relaxation processes are observed for NMF and two for FA and DMF. The relaxation parameters are used to determine solvation numbers. They show that ion-solvent interactions lead to a reduction of the average length of the H-bonded NMF chains but have only moderate influence on the FA structure. An additional solute relaxation process in DMF solutions is due to the diffusion-controlled formation and decomposition of solvent-shared ion pairs.

Design, Synthesis and In-Vitro Biological Activity of Some New 1,3-Thiazolidine-4-One Derivatives as Chemotherapeutic Agents Using Virtual Screening Strategies

2020 ◽  
Vol 16 ◽  
Author(s):  
Pragya Nayak ◽  
Monica Kachroo
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Virtual Screening ◽  
In Silico ◽  
Cancer Cell Line ◽  
Inhibitory Response ◽  
Chemotherapeutic Agents ◽  
Acceptor Site ◽  
Hydrogen Bond Acceptor ◽  
Screening Strategies

: A series of new heteroaryl thiazolidine-4-one derivatives were designed and subjected to in-silico prioritization using various virtual screening strategies. Two series of thiazolidinone derivatives were synthesized and screened for their in-vitro antitubercular, anticancer, antileishmanial and antibacterial (Staphylococcus aureus; Streptococcus pneumonia; Escherichia coli; Pseudomonas aeruginosa) activities. The compounds with electronegative substitutions exhibited positive antitubercular activity, the derivatives possessing a methyl substitution exhibited good inhibitory response against breast cancer cell line MCF-7 while the compounds possessing a hydrogen bond acceptor site like hydroxyl and methoxy substitution in their structures exhibited good in-vitro antileishmanial activity. Some compounds exhibited potent activity against gram positive bacteria Pseudomonas aeruginosa as compared to the standards. Altogether, the designed compounds exhibited good in-vitro anti-infective potential which was in good agreement with the in-silico predictions and they can be developed as important lead molecules for anti-infective and chemotherapeutic drug research.

scholarly journals Fluorescence Cross-Correlation Spectroscopy Yields True Affinity and Binding Kinetics of Plasmodium Lactate Transport Inhibitors

2021 ◽  
Vol 14 (8) ◽  
pp. 757
Author(s):  
Iga Jakobowska ◽  
Frank Becker ◽  
Stefano Minguzzi ◽  
Kerrin Hansen ◽  
Björn Henke ◽  
...  
Keyword(s):  
Rate Constants ◽  
Cross Correlation ◽  
Fluorescent Protein ◽  
Correlation Spectroscopy ◽  
Confocal Imaging ◽  
Binding Kinetics ◽  
Acceptor Site ◽  
Lactate Transport ◽  
Entry Site ◽  
Hydrogen Bond Acceptor

Blocking lactate export in the parasitic protozoan Plasmodium falciparum is a novel strategy to combat malaria. We discovered small drug-like molecules that inhibit the sole plasmodial lactate transporter, PfFNT, and kill parasites in culture. The pentafluoro-3-hydroxy-pent-2-en-1-one BH296 blocks PfFNT with nanomolar efficiency but an in vitro selected PfFNT G107S mutation confers resistance against the drug. We circumvented the mutation by introducing a nitrogen atom as a hydrogen bond acceptor site into the aromatic ring of the inhibitor yielding BH267.meta. The current PfFNT inhibitor efficiency values were derived from yeast-based lactate transport assays, yet direct affinity and binding kinetics data are missing. Here, we expressed PfFNT fused with a green fluorescent protein in human embryonic kidney cells and generated fluorescent derivatives of the inhibitors, BH296 and BH267.meta. Using confocal imaging, we confirmed the location of the proposed binding site at the cytosolic transporter entry site. We then carried out fluorescence cross-correlation spectroscopy measurements to assign true Ki-values, as well as kon and koff rate constants for inhibitor binding to PfFNT wildtype and the G107S mutant. BH296 and BH267.meta gave similar rate constants for binding to PfFNT wildtype. BH296 was inactive on PfFNT G107S, whereas BH267.meta bound the mutant protein albeit with weaker affinity than to PfFNT wildtype. Eventually, using a set of PfFNT inhibitor compounds, we found a robust correlation of the results from the biophysical FCCS binding assay to inhibition data of the functional transport assay.

Diffusion Phenomena of the Oxygen and Nitrogen in Niobium by Mechanical Spectroscopy

2010 ◽  
Vol 297-301 ◽  
pp. 1346-1353
Author(s):  
Odila Florêncio ◽  
Paulo Sergio Silva ◽  
Carlos Roberto Grandini
Keyword(s):  
Diffusion Coefficients ◽  
Short Range ◽  
Annealed Sample ◽  
Relaxation Processes ◽  
Torsion Pendulum ◽  
Mechanical Spectroscopy ◽  
Interstitial Diffusion ◽  
Relaxation Parameters ◽  
Low Concentrations ◽  
Diffusion Phenomena

The short-range diffusion phenomenon (Snoek Effect) was investigated by mechanical spectroscopy measurements between 300 K and 650 K, in a polycrystalline niobium sample, containing oxygen and nitrogen, using a torsion pendulum. Experimental spectra of anelastic relaxation were obtained under three conditions: as-received sample; annealed sample and subsequently annealed in an oxygen atmosphere for three hours at 1170 K in partial pressure of 5x10-5mbar. The experimental spectra obtained were decomposed in elementary Debye peaks and the anelastic relaxation processes were identified. With anelastic relaxation parameters and the lattice parameters, the interstitial diffusion coefficients of the oxygen and nitrogen in niobium were calculated for each kind of preferential occupation (octahedral and tetrahedral). The results were compared with the literature data, and confirmed that the best adjustment is for the preferential occupation octahedral model for low concentrations of interstitial solutes, but at higher concentration of oxygen were observed deviations of experimental data for the interstitial diffusion coefficients of oxygen in niobium when compared with the literature data, this could be related to the possible occurrence of a double occupation of interstitial sites in the niobium lattice by oxygen interstitials.

scholarly journals Investigation of Microscopic Structure and Ion Dynamics in Liquid Li(Na, K)EutecticCl Systems by Molecular Dynamics Simulation

2018 ◽  
Vol 8 (10) ◽  
pp. 1874 ◽  
Author(s):  
Jie Wu ◽  
Jia Wang ◽  
Haiou Ni ◽  
Guimin Lu ◽  
Jianguo Yu
Keyword(s):  
Molecular Dynamics ◽  
Ionic Conductivity ◽  
Shear Viscosity ◽  
Ion Pairs ◽  
Liquid Structure ◽  
Distribution Functions ◽  
Dynamics Simulation ◽  
Molten Chloride ◽  
Ion Clusters ◽  
Self Diffusion

Molten chloride salts are the main components in liquid metal batteries, high-temperature heat storage materials, heat transfer mediums, and metal electrolytes. In this paper, interest is centered on the influence of the LiCl component and temperature on the local structure and transport properties of the molten LiCl-NaCl-KCl system over the temperature range of 900 K to 1200 K. The liquid structure and properties have been studied across the full composition range by molecular dynamics (MD) simulation of a sufficient length to collect reliable values, such as the partial radial distribution function, angular distribution functions, coordination numbers distribution, density, self-diffusion coefficient, ionic conductivity, and shear viscosity. Densities obtained from simulations were underestimated by an average 5.7% of the experimental values. Shear viscosities and ionic conductivity were in good agreement with the experimental data. The association of all ion pairs (except for Li-Li and Cl-Cl) was weakened by an increasing LiCl concentration. Ion clusters were formed in liquids with increasing temperatures. The self-diffusion coefficients and ionic conductivity showed positive dependences on both LiCl concentration and temperature, however, the shear viscosity was the opposite. By analyzing the hydrodynamic radii of each ion and the coordination stability of cation-anion pairs, it was speculated that ion clusters could be the cation-anion coordinated structure and affected the macro properties.

Atom scattering studies of liquid structure and dynamics: Collisions of Xe with a model of squalane

1994 ◽  
Vol 100 (11) ◽  
pp. 8408-8417 ◽  
Author(s):  
N. Lipkin ◽  
R. B. Gerber ◽  
N. Moiseyev ◽  
G. M. Nathanson
Keyword(s):  
Liquid Structure ◽  
Structure And Dynamics ◽  
Atom Scattering

Pressure and Temperature Tuning of Gas-Expanded Liquid Structure and Dynamics

2019 ◽  
Vol 123 (13) ◽  
pp. 2915-2924 ◽  
Author(s):  
J. Pablo Palafox-Hernandez ◽  
Camina H. Mendis ◽  
Ward H. Thompson ◽  
Brian B. Laird
Keyword(s):  
Liquid Structure ◽  
Structure And Dynamics ◽  
Temperature Tuning

Relaxation mapping analysis with an hyperbolic heating rate

2002 ◽  
Vol 754 ◽  
Author(s):  
C. J. Dias
Keyword(s):  
Activation Parameters ◽  
Activation Entropy ◽  
Relaxation Processes ◽  
Complex Materials ◽  
Cooperative Phenomena ◽  
Relaxation Parameters ◽  
A Value ◽  
Polarization Temperature ◽  
Free Activation Energy ◽  
Map Analysis

ABSTRACTThermally stimulated discharge currents (TSDC) together with the Relaxation Map Analysis (RMA) method is a convenient method to study relaxation processes in complex materials. In the RMA technique, one performs repeated TSDC runs while selecting polarization states through the use of a fixed polarization time schedule and a sucessively higher polarization temperature. Each peak has an associated polarization strength and a pair of activation parameters which can be the Gibbs free activation energy and the activation entropy. In the present paper we propose a different approach to RMA. It consists of a global heating of the sample in an hyperbolic manner to determine the activation parameters as a function of temperature. This determination is done by first selecting a value for the activation entropy for each temperature and then calculating the implied activation enthalpy or Gibbs free energy.We have reasoned that normal relaxation processes usually proceed with a null or close to zero activation entropy and that only relaxations associated to the glass transitionand/or cooperative phenomena involve large values of the activation entropy. In those cases and based on the curvature of the TSDC curve one can select a minimum activation entropy value which will fit the TSDC curve at a particular temperature. Using this data one determines the polarization strength associated to each pair of activation parameters. Results for the TSDC relaxation parameters spectra of a liquid crystal polymer will be presented together with comparisons between the thermal sampling method and the proposed method.

Physical and Chemical Stress Relaxation of Elastomers

1977 ◽  
Vol 50 (5) ◽  
pp. 895-905 ◽  
Author(s):  
J. G. Curro ◽  
E. A. Salazar
Keyword(s):  
Stress Relaxation ◽  
Relaxation Modulus ◽  
Kinetic Mechanism ◽  
Chemical Kinetic ◽  
Relaxation Processes ◽  
Temperature Range ◽  
Kinetic Information ◽  
Relaxation Parameters ◽  
Chemically Reacting ◽  
Physical And Chemical

Abstract In this paper we have developed a method whereby physical and chemical relaxation processes can be distinguished, using stress relaxation experiments as a function of temperature. We assumed that there exists some temperature range above the glass transition temperature over which the chemical effects can be neglected for the time scale of the experiments. The data in this low temperature range were then used to determine the WLF constants and other physical relaxation parameters. The physical component of the stress relaxation could then be subtracted from high temperature experiments in order to extract chemical kinetic information. Based on certain reasonable assumptions, an equation was developed for the relaxation modulus of a chemically reacting system. This equation could be used to determine the time dependence of the crosslink density, or conversely could be used to predict the long-term relaxation modulus from an assumed kinetic mechanism. These calculations were demonstrated for ethylene-propylene and butyl elastomers.

Ion-ion-solvent interactions in solution. I. Solutions of LiClO4 in acetone

1982 ◽  
Vol 35 (9) ◽  
pp. 1775 ◽  
Author(s):  
DW James ◽  
RE Mayes
Keyword(s):  
Raman Band ◽  
Ion Pairs ◽  
Ion Association ◽  
Solvent Interactions ◽  
Solvation Numbers ◽  
Solvated Ions ◽  
Component Band ◽  
Li Ion ◽  
Contact Ion Pairs ◽  
Association Equilibrium

Vibrational spectra and 7Li, 13C and 35Cl n.m.r. spectra have been obtained for solutions of LiClO4 in acetone for salt concentrations from 0.05 to 6 M. Infrared spectra give qualitative indications of ion association. Analysis of the Raman band due to C-C stretching in acetone yields solvation numbers for the Li+ ion of the order of 3. Component band analysis of the ClO4- symmetric stretching vibrational band and the various n.m.r. spectra lead to the identification of solvent-separated ion pairs, contact ion pairs and ion aggregates, in addition to free solvated ions. The dependence on salt concentration of all four species has been determined. The association quotient for the association equilibrium (Li+)s(ClO4)- ↔ [Li+(acetone)ClO4-)s was determined to be 1.4 � 0.3 dm3 mol-1.

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