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09:48
In Situ Characterization of Hydrated Proteins in Water by SALVI and ToF-SIMS
Published on: February 15, 2016
Dipolar response of hydrated proteins
1Center for Biological Physics, Arizona State University, PO Box 871504, Tempe, Arizona 85287-1504, USA. dmitrym@asu.edu
The Journal of Chemical Physics
|March 3, 2012
Summary
The study reveals that protein charge and water interactions dictate dipolar response in solution. Ubiquitin shows a negative response, repelling from electric fields, unlike charged proteins.
Area of Science:
- Biophysics
- Computational Chemistry
- Physical Chemistry
Background:
- Proteins in solution exhibit complex dipolar responses influenced by their intrinsic dipole moments and surrounding water.
- Understanding this response is crucial for various applications, including protein manipulation and spectroscopy.
Purpose of the Study:
- To develop an analytical theory and perform numerical simulations of the dipolar response of hydrated proteins.
- To investigate the factors governing the effective dielectric constant and dipolar susceptibility of proteins.
Main Methods:
- Analytical theory development for protein dipolar response.
- Numerical simulations of hydrated proteins in uniform external electric fields.
- Calculation of effective dielectric constant and cross-correlations between protein and water dipoles.
Main Results:
- Significant variation in dielectric constants observed, from 0.5 for ubiquitin to 640 for cytochrome c.
- Ubiquitin exhibits a negative dipolar response (dia-electric) and negative dielectrophoresis due to negative protein-water dipole cross-correlations.
- Charged proteins display para-electric response and positive dielectrophoresis, influenced by surface charge coupling to hydration water.
Conclusions:
- Protein surface charge strongly modulates dipolar response through coupling with hydration water.
- Protein-water dipolar cross-correlations are long-ranged (~2 nm), impacting interfacial polarization.
- High-frequency absorption of protein solutions can exceed or fall below that of water, depending on interfacial dipole orientation.
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