Dielectric spectroscopy on aqueous solutions of some zwitterionic amino acids

Kaatze, U.; Bieler, H.; Pottel, R.

doi:10.1016/0167-7322(85)80007-6

Cited by 24 publications

(23 citation statements)

References 11 publications

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“…This interpretation rationalizes, for example, the low-frequency process in solutions of some amino acids. [13][14][15][39][40][41] Such a mechanism was also suspected by us in the initial stages of the present work. A more detailed analysis does not confirm this speculation.…”

Section: Data Evaluationmentioning

confidence: 87%

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Hydration Dynamics of Water near an Amphiphilic Model Peptide at Low Hydration Levels: A Dielectric Relaxation Study

Padmanabhan¹,

Weingärtner²

2008

ChemPhysChem

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A dielectric relaxation study of aqueous solutions of the amphiphilic model peptide N-acetyl-leucine amide (NALA) at 298 K over a wide range of hydration levels is presented. The experiments range from states where water builds up several hydration layers to states where single water molecules or small water clusters are shared by several NALA molecules. The dielectric spectra reveal two modes on the 10 and 100 ps timescales. These are largely broadened with regard to the Lorentzian shape caused by simple Debye-type relaxation, and are well described by the Kohlrausch-Williams-Watts stretched exponential function. The fast mode is assigned to water reorientation comprising bulk water as well as hydration water. Even when all water molecules are in contact with the solute, this fast component is dominant, and its mean relaxation time is retarded by less than a factor of two relative to neat water. The amplitude of the slow process is far higher than expected for the dipolar reorientation of the solute. The observations are consistent with results from molecular dynamics simulations for a similar model peptide reported in the literature. They suggest that the slow relaxation mode is mainly founded in peptide-water dipolar couplings, with some additional contribution from slowly reorienting hydration water molecules. The results are discussed with regard to the hydration dynamics of proteins and the interpretation of dielectric spectra of protein solutions.

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Section: Data Evaluationmentioning

confidence: 87%

“…This dipole moment largely contrasts to values of the order of 10-20 D for zwitterionic amino acids, [13][14][15][39][40][41] because model peptides such as NALA cannot form zwitterions. The literature offers several dielectric models for calculating the resulting relaxation amplitudes S…”

Section: Data Evaluationmentioning

confidence: 97%

Hydration Dynamics of Water near an Amphiphilic Model Peptide at Low Hydration Levels: A Dielectric Relaxation Study

Padmanabhan¹,

Weingärtner²

2008

ChemPhysChem

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“…As the number of possible conformations of a polymethylene chain undergoing gauche-trans isomerizations grow as 3 n, a linear growth of the dipole moment with n is completely unrealistic. Dipole moment measurements on non amphiphilic zwitterionic molecules in water have shown this important feature [35,36]. The electrostatic attraction between the two opposite charges of the flexible dipole may also make folded conformations more probable.…”

Section: Fig 4 the Two N-dependent Contributions To The Free Energymentioning

confidence: 97%

Micellar properties of zwitterionic phosphobetaine amphiphiles in aqueous solution: Influence of the intercharge distance

Chevalier

Germanaud

Perchec

1988

Colloid & Polymer Sci

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Zwitterionic amphiphiles of the general formula H(CH2)y +N(CH3)2(CH2)n PO2C6H~-, where the number of intercharge methylenes n is varied, were studied in dilute aqueous solution. Their critical micellar concentrations show a peculiar variation with n, first increasing as n varies from 1 to 4 and then slowly decreasing as methylenes are added up to 10. This behavior is interpreted as being the consequence of two opposite contributions. The first is the classical CMC lowering due to the increase of hydrophobic character with the total number of methylene groups in the surfactant molecule. The second contribution is the increase in the dipole moment of the zwitterionic headgroup with n, leading to stronger dipole-dipole repulsions between headgroups at the micellar surface. Experimental results suggest that the dipole moment does not increase linearly with n because of the polymethylene chain flexibility. This is supported by 13C NMR relaxation experiments.

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“…Previous experiments on water find two Debye relaxation modes in the THz frequency range [14,19]. The lower-frequency mode describes the dynamics associated with the reestablishment of this network [20,21], and the higherfrequency mode represents rotational relaxation of the molecular dipoles within the network [22]. We expect that the parameters of this model will change as the dynamics are altered by the hydration of DNA molecules in solution.…”

Section: Analysis Based On the Debye Modelmentioning

confidence: 99%

“…It is well known that highly viscous solutions can exhibit non-linear behavior with respect to dielectric relaxation times [34]; there are regimes where relaxation time is independent of bulk viscosity [35], which is the case with our DNA solutions. Both the main relaxation time that is associated with the reestablishment of the hydrogen bond network [20,21] and the secondary relaxation time that describes the free rotational relaxation time of the molecular dipoles within the network [22] are slowed at high concentrations and high viscosities. The secondary relaxation time seems to be more sharply altered than the main relaxation time.…”

Section: Analysis Based On the Debye Modelmentioning

confidence: 99%

Concentration-dependent effects on fully hydrated DNA at terahertz frequencies

Glancy

2015

J Biol Phys

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Using terahertz time-domain spectroscopy (THz-TDS), the frequency-dependent dielectric constant of deoxyribonucleic acid (DNA) in solution was measured. The response of the buffer solution is dominated by two Debye modes in this frequency range, and, from an analysis of the concentration dependence, the presence of the DNA increases the main relaxation time and dielectric constant. This reflects the fact that the water in the hydration layer is more tightly bound under the influence of the DNA molecule in comparison to bulk water. This dynamical slowing down with increasing DNA concentration is similar to what is observed with purine nucleotides, but opposite to the behavior of pyrimidine nucleotides. In addition, a suspension model was used with the concentration-dependent data to isolate the dielectric response of the hydrated DNA molecule. The data for the hydrated DNA molecule is still dominated by a Debye response. It is also possible to determine the thickness of the hydration layer, and the DNA molecule influences the surrounding water out to 16 or 17 Å, which corresponds to about six effective hydration layers.

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Dielectric spectroscopy on aqueous solutions of some zwitterionic amino acids

Cited by 24 publications

References 11 publications

Hydration Dynamics of Water near an Amphiphilic Model Peptide at Low Hydration Levels: A Dielectric Relaxation Study

Hydration Dynamics of Water near an Amphiphilic Model Peptide at Low Hydration Levels: A Dielectric Relaxation Study

Micellar properties of zwitterionic phosphobetaine amphiphiles in aqueous solution: Influence of the intercharge distance

Concentration-dependent effects on fully hydrated DNA at terahertz frequencies

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