NIH Research Festival
Water is essential in maintaining cellular activity, from mediating reactions to promoting the shuttling of macromolecules. Bulk water, made up of free-moving water molecules that can make hydrogen bonds with each other, has been very well studied, and the properties associated with the bulk are well-defined. However, intracellular water is within a very crowded and confined environment and, thus, cannot be adequately described as bulk water. Intracellular water is expected to exhibit more order or structure due to a spatially constrained milieu. Herein, we apply Raman spectral imaging to characterize water throughout a cell, generating subcellular hydration maps based on the bend-libration band of water. Because this is a label-free approach relying on intrinsic molecular vibrational signatures, we also obtained spatial-chemical information on other biomacromolecules (e.g., nucleotides, lipids, and proteins) at each location. Our results show that distinctive water structures are found in subcellular compartments, such as nucleoli and lipid droplets, based on their unique vibrational signatures. This work provides direct and conclusive spectroscopic evidence that intracellular water is chemically distinct from bulk water, emphasizing the importance of the cellular hydration environment in modulating behaviors of molecular biological systems.
Scientific Focus Area: Biomedical Engineering and Biophysics
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