Probing the structure of water in individual living cells

TL;DR

This study uses Raman spectroscopy to reveal a small population of uniquely structured water near biomolecules inside living cells.

Contribution

The novel use of Raman micro-spectroscopy to probe intracellular water structure in living cells is introduced.

Findings

A ~3% population of non-bulk-like water with a weakened hydrogen-bonded network is found in three cell types.

Biointerfacial water is suggested to form a molecular layer around soluble proteins inside cells.

The structure of biointerfacial water remains consistent across different single cells.

Abstract

Water regulates or even governs a wide range of biological processes. Despite its fundamental importance, surprisingly little is known about the structure of intracellular water. Herein we employ a Raman micro-spectroscopy technique to uncover the composition, abundance and vibrational spectra of intracellular water in individual living cells. In three different cell types, we show a small but consistent population (~3%) of non-bulk-like water. It exhibits a weakened hydrogen-bonded network and a more disordered tetrahedral structure. We attribute this population to biointerfacial water located in the vicinity of biomolecules. Moreover, our whole-cell modeling suggests that all soluble (globular) proteins inside cells are surrounded by, on average, one full molecular layer (about 2.6 Angstrom) of biointerfacial water. Furthermore, relative invariance of biointerfacial water is observed among different single cells. Overall, our study not only opens up experimental possibilities of interrogating water structure in vivo but also provides insights into water in life.

Here the authors report a Raman scattering technique to measure vibrational spectrum of water inside living cells. A consistent population (~3%) of non-bulk-like water is seen, exhibiting a more disordered structure with a weakened hydrogen-bonded network.

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