Influence of Hydration and Dehydration on the Viscoelastic Properties of Snail Mucus by Brillouin Spectroscopy

TL;DR

This study uses Brillouin spectroscopy to investigate how hydration and dehydration affect the GHz-frequency viscoelastic properties of snail mucus, revealing water's influence and three molecular transitions.

Contribution

It provides new insights into the molecular transitions and viscoelastic behavior of snail mucus under hydration changes using GHz-frequency spectroscopy.

Findings

Identification of two peaks in diluted mucus spectra, with one related to ice.

Observation of a single peak in dehydrated mucus spectra.

Discovery of three molecular transitions during dehydration.

Abstract

Brillouin spectroscopy was used to probe the viscoelastic properties of diluted snail mucus at GHz frequencies over the range -11 $^\circ$C $\leq T \leq$ 52 $^\circ$C and of dehydrated mucus as a function of time. Two peaks were observed in the spectra for diluted mucus: the longitudinal acoustic mode of the liquid mucus peak varies with dilution but fluctuates around the typical value of 8.0 GHz. A second peak due to ice remained unchanged with varying dilution and was seen at 18.0 GHz and appeared below the dilutions "freezing" point depression. Only a single peak was found in all the dehydrated mucus spectra and was also attributed to the longitudinal acoustic mode of liquid mucus. Anomalous changes in the protein concentration dependence of the frequency shift, linewidth, and ``freezing" point depression and consequently, hypersound velocity, compressibility, and apparent viscosity suggest that the viscoelastic properties of this system is influenced by the presence of water. Furthermore, this research uncovered three unique transitions within the molecular structure. These transitions included the first stage of glycoprotein cross-linking, followed by the steady depletion of free water in the system, and eventually resulted in the creation of a gel-like state when all remaining free water was evaporated.