Disentangling proton-transfer and segmental motion relaxations in poly-vinyl-alcohol aqueous solutions by means of ultrasonic relaxation spectroscopy

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

doi:10.1016/j.polymer.2021.123479

Cited by 22 publications

(12 citation statements)

References 18 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: 90%

“…The sound velocity is estimated for all concentrations studied by determining the time required for the ultrasound to travel the fixed path length (Mpourazanis et al 2019 ; Kouderis et al 2021 ). The experimental error in velocity measurements is ± 0.01%.…”

Section: Methodsmentioning

confidence: 99%

“…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: 90%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

2021

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“…The ultrasound speed in the solutions was estimated by employing the pulse-echo overlap method with an experimental error of less than ±0.01%. Further information concerning the experimental procedures and additional details of the setup can be found in [32][33][34].…”

Section: Ultrasonic Relaxation Spectroscopymentioning

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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“…[6,7] In contrast, relaxation attenuation stems from thermal relaxation of internal degrees of freedom of polyatomic molecules. [8,9] The nonlinear relationship between relaxation attenuation and frequency makes it complex to understand attenuation effect of sound, which compels us to design an accurate acoustic attenuation prediction model. [10][11][12] Energies are stored in the translational and inner degrees of freedom at equilibrium for gas at rest.…”

Section: Introductionmentioning

confidence: 99%

Effect of viscosity on stability and accuracy of the two-component lattice Boltzmann method with a multiple-relaxation-time collision operator investigated by the acoustic attenuation model

Bai¹,

Shan²,

Yang³

et al. 2022

Chinese Phys. B

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A two-component lattice Boltzmann method (LBM) with a multiple-relaxation-time (MRT) collision operator is presented to improve the numerical stability of the single relaxation time (SRT) model. The macroscopic and the momentum conservation equations can be retrieved through the Chapman-Enskog (C-E) expansion analysis. The equilibrium moment with the diffusion term is calculated, a diffusion phenomenon is simulated by utilizing the developed model, and the numerical stability is verified. Furthermore, the binary mixture channel model is designed to simulate the sound attenuation phenomenon, and the obtained simulation results are found to be consistent with the analytical solutions. The sound attenuation model is used to study the numerical stability and calculation accuracy of the LBM model. The simulation results show the stability and accuracy of the MRT model and the SRT model under different viscosity conditions. Finally, we study the influence of the error between the macroscopic equation of the MRT model and the standard incompressible Navier–Stokes equation on the calculation accuracy of the model to demonstrate the general applicability of the conclusions drawn by the sound attenuation model in the present study.

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Disentangling proton-transfer and segmental motion relaxations in poly-vinyl-alcohol aqueous solutions by means of ultrasonic relaxation spectroscopy

Cited by 22 publications

References 18 publications

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

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

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

Effect of viscosity on stability and accuracy of the two-component lattice Boltzmann method with a multiple-relaxation-time collision operator investigated by the acoustic attenuation model

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