Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2022 Apr 12;12(4):572.
doi: 10.3390/life12040572.

Hydration Dynamics of Model Peptides with Different Hydrophobic Character

Laura Lupi  1 , Brenda Bracco  2 , Paola Sassi  2 , Silvia Corezzi  3 , Assunta Morresi  2 , Daniele Fioretto  3   4 , Lucia Comez  4 , Marco Paolantoni  2
Affiliations

Hydration Dynamics of Model Peptides with Different Hydrophobic Character

Laura Lupi et al. Life (Basel). .

Abstract

The multi-scale dynamics of aqueous solutions of the hydrophilic peptide N-acetyl-glycine-methylamide (NAGMA) have been investigated through extended frequency-range depolarized light scattering (EDLS), which enables the broad-band detection of collective polarizability anisotropy fluctuations. The results have been compared to those obtained for N-acetyl-leucinemethylamide (NALMA), an amphiphilic peptide which shares with NAGMA the same polar backbone, but also contains an apolar group. Our study indicates that the two model peptides induce similar effects on the fast translational dynamics of surrounding water. Both systems slow down the mobility of solvating water molecules by a factor 6-8, with respect to the bulk. Moreover, the two peptides cause a comparable far-reaching spatial perturbation extending to more than two hydration layers in diluted conditions. The observed concentration dependence of the hydration number is explained considering the random superposition of different hydration shells, while no indication of solute aggregation phenomena has been found. The results indicate that the effect on the dynamics of water solvating the amphiphilic peptide is dominated by the hydrophilic backbone. The minor impact of the hydrophobic moiety on hydration features is consistent with structural findings derived by Fourier transform infrared (FTIR) measurements, performed in attenuated total reflectance (ATR) configuration. Additionally, we give evidence that, for both systems, the relaxation mode in the GHz frequency range probed by EDLS is related to solute rotational dynamics. The rotation of NALMA occurs at higher timescales, with respect to the rotation of NAGMA; both processes are significantly slower than the structural dynamics of hydration water, suggesting that solute and solvent motions are uncoupled. Finally, our results do not indicate the presence of super-slow water (relaxation times in the order of tens of picoseconds) around the peptides investigated.

Keywords: ATR-FTIR; depolarized Rayleigh scattering; hydration shell; protein hydration; solvation dynamics.

PubMed Disclaimer

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Graphical representation of the molecular structure of NAGMA (left) and NALMA (right).
Figure 2
Figure 2
Solvent free (SF-green line) spectrum modeled as the sum of a Debye function (red filled area), a CD function with β = 0.6, (blue filled area), and two Brownian oscillators for the vibrational modes in the THz region (orange filled area).
Figure 3
Figure 3
EDLS susceptibility data (symbols) of a representative NAGMA/water solution (50 mg/mL) at T = 20 °C. The total fitting curve and its decomposition into several contributions are indicated (see text). The small gap in the experimental data at around 7–8 GHz is due to the removal of a few spurious points arising from the leakage of the Brillouin peaks.
Figure 4
Figure 4
(a) Retardation ratio ξ = τhyd/τbulk as a function of solute molar ratio for NAGMA and NALMA [31] solutions. (b) Average hydration number Nh, calculated as described in the text, as a function of solute molar ratio for NAGMA and NALMA [31] solutions. The values obtained from the water-sharing numerical model for non-interacting molecules (see text) are also represented (solid line: h = 6.4 Å; dashed lines: h = 6.2 and 6.6 Å).
Figure 5
Figure 5
Rotational relaxation time (τD) of NAGMA (this work) and NALMA [31] as a function of the solute mole fraction.
Figure 6
Figure 6
Normalized ATR-FTIR spectra of NALMA and NAGMA solutions (75 mg/mL), and of their solvent constituted by a H2O/D2O mixture (10% w/w). The spectrum is essentially due to the OH stretching modes of HOD species.
Figure 7
Figure 7
(a) Normalized ATR-FTIR spectra of a NALMA solution (300 mg/mL) and its solvent (H2O/D2O 10% w/w), together with the resulting difference spectrum (DS). (b) Normalized ATR-FTIR spectra of a Tert-butyl alcohol (TBA) solution (300 mg/mL) and its solvent (H2O/D2O 10% w/w), together with the resulting difference spectrum (DS). In both panels, DS spectra have been multiplied by a factor of 5 for visualization purposes.
Figure 8
Figure 8
Amide I maximum peak position as a function of solute mole fraction.
See this image and copyright information in PMC

Similar articles

See all similar articles

References

    1. Pal S.K., Zewail A.H. Dynamics of Water in Biological Recognition. Chem. Rev. 2004;104:2099–2124. doi: 10.1021/cr020689l. - DOI - PubMed
    1. Bellissent-Funel M.-C., Hassanali A., Havenith M., Henchman R., Pohl P., Sterpone F., van der Spoel D., Xu Y., Garcia A.E. Water Determines the Structure and Dynamics of Proteins. Chem. Rev. 2016;116:7673–7697. doi: 10.1021/acs.chemrev.5b00664. - DOI - PMC - PubMed
    1. Laage D., Stirnermann G., Sterpone F., Rey R., Hynes J.T. Reorientation and Allied Dynamics in Water and Aqueous Solutions. Annu. Rev. Phys. Chem. 2011;62:395–416. doi: 10.1146/annurev.physchem.012809.103503. - DOI - PubMed
    1. Laage D., Elsasser T., Hynes J.T. Water Dynamics in the Hydration Shells of Biomolecules. Chem. Rev. 2017;16:10694–10725. doi: 10.1021/acs.chemrev.6b00765. - DOI - PMC - PubMed
    1. Persson F., Soderhjelm P., Halle B. The Spatial Range of Protein Hydration. J. Chem. Phys. 2018;148:215104. doi: 10.1063/1.5031005. - DOI - PubMed

LinkOut - more resources