Non-Debye segmental relaxation of poly-N-vinyl-carbazole in dilute solution

Siafarika, P.; Kouderis, C.; Kalampounias, Angelos G.

doi:10.1080/00268976.2020.1802075

Cited by 13 publications

(14 citation statements)

References 29 publications

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“…Furthermore, both f r and A fitting parameters seem to follow different trends below and above ~ 2.82 mM, which corresponds to x = 0.08 mol fraction. On the other hand, if the observed relaxation was attributed to proton-transfer reaction, the characteristic frequency and relaxation amplitude would follow a rather monotonic increase with solution concentration, as observed in the case of aqueous polyamine solutions (Siafarika et al 2021 ) and aqueous poly-vinyl-alcohol solutions (Kouderis et al 2021 ). Thus, the assignment of the present relaxation to proton-transfer reaction is questionable.…”

Section: Resultsmentioning

confidence: 91%

“…Deep understanding of the DSP self-association and its thermodynamic profile is crucial for predicting the docking properties of this molecule, which has important implications in effective drug design. Ultrasonic relaxation spectroscopy has been proved as an effective tool in studying association-dissociation mechanisms (Nishikawa et al 1991 ), proton-transfer reactions (Nishikawa et al 1973a , b , 1996 ; Nishikawa and Kamimura 2011 ; Huang et al 1999 ; Tsigoias et al 2020 a), conformational changes (Bae et al 2001 ; Bae et al 2002 ; Kalampounias 2020 ; Stogiannidis et al 2020 ), complexation (Tamm 1961 ; Petrucci 1971 ), backbone segmental motion and normal mode relaxation in polymers (Kouderis et al 2021 ; Siafarika et al 2021 ) and reaction engineering in general (Bernasconi 1976 ). Furthermore, in several cases systematic analysis of the acoustic spectra permits disentangling between different processes taking place in close time scales (Kouderis et al 2021 ).…”

Section: Introductionmentioning

confidence: 99%

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Molecular relaxation dynamics and self-association of dexamethasone sodium phosphate solutions

2021

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Detailed concentration-dependent measurements of sound absorption and velocity have been performed in dexamethasone sodium phosphate (DSP) aqueous solutions in the MHz frequency range. A single well-resolved relaxation process dominates the experimental acoustic spectra following a Debye-type distribution function. The analysis of the temperature-dependent ultrasonic relaxation data also revealed analogous effect with concentration on the relaxation spectra. All acoustic parameters were estimated by means of a fitting procedure. The behavior of the relaxation frequency and amplitude with concentration allowed us to assign the observed process to self-association mechanism. Combining the ultrasonic and electric conductivity data, the self-association scheme has been established. The thermodynamic constants and the rate of the aggregation due to hydrophobic interactions have been estimated in view of the Eyring's theory. The concentration dependence of relaxation amplitude and characteristic frequency revealed that the presence of additional relaxation processes in the spectra related to additional mechanisms, such as conformational changes and proton-transfer reaction is excluded and the self-association process considered here was found to dominate in this frequency range. The results have been discussed in view of the fair ability of DSP for hydrophobic interactions and aggregate formation in aqueous environment.

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Section: Resultsmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Molecular relaxation dynamics and self-association of dexamethasone sodium phosphate solutions

2021

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“…As shown in Figure 4, the relative contribution of S was comparable to that of O/C for most of the aromatic compounds selected, except for those with the benzenesulfonamide moiety, which shows a much higher contribution of S than that of O/C. The steric energy is a sum of energies from bond stretching, bending, torsion, Van der Waals, and electrostatic interactions within a molecule [41]. The lowest energy conformation of a molecule is most favored, and it is achieved when the steric energy is minimized [25].…”

Section: Interpretation Of the Modelmentioning

confidence: 83%

“…The coefficient of E is 1.7751, as shown in Equation ( 16), which is much larger than the other two coefficients, indicating that the change of log k SO •− As shown in Figure 5a, R 2 of log𝑘 • vs. E is 0.455, suggesting a moderate correlation between the rate constant and electron density. However, Luo et al [41] observed no clear relationship between the Gibbs free energy of SET (∆𝐺 °, which represents the reactivity of SO • toward aromatic contaminants) and the total electrostatic potential charge on the benzene ring (ESP, which represents the electron density on the benzene ring). The disparity might be due to the different ways in calculating electron density.…”

Section: Interpretation Of the Modelmentioning

confidence: 99%

Prediction of Second-Order Rate Constants of Sulfate Radical with Aromatic Contaminants Using Quantitative Structure-Activity Relationship Model

Ding

2022

Water

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Predicting the second-order rate constants between aromatic contaminants and a sulfate radical (kSO4•−) is vital for the screening of pollutants resistant to sulfate radical-based advanced oxidation processes. In this study, a quantitative structure-activity relationship (QSAR) model was developed to predict the values for aromatic contaminants. The relationship between logkSO4•− and three molecular descriptors (electron density, steric energy, and ratio between oxygen atoms and carbon atoms) was built through multiple linear regression. The goodness-of-fit, robustness, and predictive ability of the model were characterized statistically with indicators showing that the model was reliable and applicable. Electron density was found to be the most influential descriptor that contributed the most to logkSO4•−. All data points fell within the applicability domain, and no outliers existed in the training set. The comparison with other models indicates that the QSAR model performs well in elucidating the mechanism of the reaction between aromatic compounds and sulfate radicals.

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“…It is important to achieve progress on the comprehensive understanding of Nisin behaviour at the molecular level in the solution state, where several structural and dynamic processes may take place, such as self-association, cooperative conformational transitions and protolytic reactions. The combined use of vibrational and acoustic relaxation spectroscopy and theoretical calculations provides important insights into microstructural interactions and dynamical phenomena in the liquid state [6][7][8]. Furthermore, the results of molecular docking studies can be used as a starting model of the molecular interactions among ligand and receptor molecules.…”

Section: Introductionmentioning

confidence: 99%

Evidence of Self-Association and Conformational Change in Nisin Antimicrobial Polypeptide Solutions: A Combined Raman and Ultrasonic Relaxation Spectroscopic and Theoretical Study

et al. 2023

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The polypeptide Nisin is characterized by antibacterial properties, making it a compound with many applications, mainly in the food industry. As a result, a deeper understanding of its behaviour, especially after its dissolution in water, is of the utmost importance. This could be possible through the study of aqueous solutions of Nisin by combining vibrational and acoustic spectroscopic techniques. The velocity and attenuation of ultrasonic waves propagating in aqueous solutions of the polypeptide Nisin were measured as a function of concentration and temperature. The computational investigation of the molecular docking between Nisin monomeric units revealed the formation of dimeric units. The main chemical changes occurring in Nisin structure in the aqueous environment were tracked using Raman spectroscopy, and special spectral markers were used to establish the underlying structural mechanism. Spectral changes evidenced the presence of the dimerization reaction between Nisin monomeric species. The UV/Vis absorption spectra were dominated by the presence of π → π* transitions in the peptide bonds attributed to secondary structural elements such as α-helix, β-sheets and random coils. The analysis of the acoustic spectra revealed that the processes primarily responsible for the observed chemical relaxations are probably the conformational change between possible conformers of Nisin and its self-aggregation mechanism, namely, the dimerization reaction. The activation enthalpy and the enthalpy difference between the two isomeric forms were estimated to be equal to ΔH1* = 0.354 ± 0.028 kcal/mol and ΔH10 = 3.008 ± 0.367 kcal/mol, respectively. The corresponding thermodynamic parameters of the self-aggregation mechanism were found to be ΔH2* = 0.261 ± 0.004 kcal/mol and ΔH20 = 3.340 ± 0.364 kcal/mol. The effect of frequency on the excess sound absorption of Nisin solutions enabled us to estimate the rate constants of the self-aggregation mechanism and evaluate the isentropic and isothermal volume changes associated with the relaxation processes occurring in this system. The results are discussed in relation to theoretical and experimental findings.

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Non-Debye segmental relaxation of poly-N-vinyl-carbazole in dilute solution

Cited by 13 publications

References 29 publications

Molecular relaxation dynamics and self-association of dexamethasone sodium phosphate solutions

Molecular relaxation dynamics and self-association of dexamethasone sodium phosphate solutions

Prediction of Second-Order Rate Constants of Sulfate Radical with Aromatic Contaminants Using Quantitative Structure-Activity Relationship Model

Evidence of Self-Association and Conformational Change in Nisin Antimicrobial Polypeptide Solutions: A Combined Raman and Ultrasonic Relaxation Spectroscopic and Theoretical Study

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