| Autor: |
Biesso A; Optical Spectroscopy Section, Laboratory of Molecular Biophysics, National Heart, Lung and Blood Institute, National Institutes of Health , Bethesda, Maryland 20892, United States., Xu J, Muíño PL, Callis PR, Knutson JR |
| Jazyk: |
angličtina |
| Zdroj: |
Journal of the American Chemical Society [J Am Chem Soc] 2014 Feb 19; Vol. 136 (7), pp. 2739-47. Date of Electronic Publication: 2014 Feb 06. |
| DOI: |
10.1021/ja406126a |
| Abstrakt: |
The protein-water interface is a critical determinant of protein structure and function, yet the precise nature of dynamics in this complex system remains elusive. Tryptophan fluorescence has become the probe of choice for such dynamics on the picosecond time scale (especially via fluorescence "upconversion"). In the absence of ultrafast ("quasi-static") quenching from nearby groups, the TDFSS (time-dependent fluorescence Stokes shift) for exposed Trp directly reports on dipolar relaxation near the interface (both water and polypeptide). The small protein GB1 contains a single Trp (W43) of this type, and its structure is refractory to pH above 3. Thus, it can be used to examine the dependence of dipolar relaxation upon charge reconfiguration with titration. Somewhat surprisingly, the dipolar dynamics in the 100 fs to 100 ps range were unchanged with pH, although nanosecond yield, rates, and access all changed. These results were rationalized with the help of molecular dynamics (including QM-MM) simulations that reveal a balancing, sometimes even countervailing influence of protein and water dipoles. Interestingly, these simulations also showed the dominant influence of water molecules which are associated with the protein interface for up to 30 ps yet free to rotate at approximately "bulk" water rates. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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