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DNA functions only in aqueous environments and adopts different conformations depending on the hydration level. The dynamics of hydration water and hydrated DNA leads to rotating and oscillating dipoles that, in turn, give rise to a strong megahertz to terahertz absorption. Investigating the impact of hydration on DNA dynamics and the spectral features of water molecules influenced by DNA, however, is extremely challenging because of the strong absorption of water in the megahertz to terahertz frequency range. In response, we have employed a high-precision megahertz to terahertz dielectric spectrometer, assisted by molecular dynamics simulations, to investigate the dynamics of water molecules within the hydration shells of DNA as well as the collective vibrational motions of hydrated DNA, which are vital to DNA conformation and functionality. Our results reveal that the dynamics of water molecules in a DNA solution is heterogeneous, exhibiting a hierarchy of four distinct relaxation times ranging from ~8 ps to 1 ns, and the hydration structure of a DNA chain can extend to as far as ~18 A from its surface. The low-frequency collective vibrational modes of hydrated DNA have been identified and found to be sensitive to environmental conditions including temperature and hydration level. The results reveal critical information on hydrated DNA dynamics and DNA-water interfaces, which impact the biochemical functions and reactivity of DNA.
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Investigating hydration dynamics and protein collective motions by high-precision dielectric spectroscopy
Biological processes often take place at surfaces of proteins, where the dynamic and structural properties of aqueous solvents are modified. Information about solvent properties including hydration dynamics and structure, and protein collective motions can be obtained by measuring directly the dielectric response in the megahertz to terahertz frequencies of aqueous protein solutions. Due to the strong absorption of water in this frequency range, the experiment is challenging. Our home built dielectric spectrometer using a vector network analyzer together with frequency extenders allows us to perform the experiment in a wide range of frequency from megahertz to terahertz with a high dynamical range up to 120 dB. A detailed investigation of the dielectric response has revealed the hydration structure including the tightly, loosely bound layers and the number of water molecules in each hydration layer. These water molecules relax with different time constants at different temperatures. As a result, the dynamics of hydrated protein is also probed at different temperatures. Understanding the hydration structure and dynamics of lysozyme in biological conditions can explain the enzymatic activities of biomolecules.
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- Award ID(s):
- 1665157
- PAR ID:
- 10284927
- Date Published:
- Journal Name:
- Proceedings of SPIE
- Volume:
- 11499
- ISSN:
- 1996-756X
- Page Range / eLocation ID:
- 114990O
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Conference Paper:
- https://doi.org/10.1117/12.2567857
