Abstract
Osmolytes are small organic compounds that can affect the stability of proteins in living cells. The mechanism of osmolytes’ protective effects on protein structure and dynamics has not been fully explained, but in general, two possibilities have been suggested and examined: a direct interaction of osmolytes with proteins (water replacement hypothesis), and an indirect interaction (vitrification hypothesis). Here, to investigate these two possible mechanisms, we studied myoglobin-osmolyte systems using FTIR, UV-vis, CD, and femtosecond IR pump-probe spectroscopy. Interestingly, noticeable changes are observed in both the lifetime of the CO stretch of CO-bound myoglobin and the spectra of UV-vis, CD, and FTIR upon addition of the osmolytes. In addition, the temperature-dependent CD studies reveal that the protein’s thermal stability depends on molecular structure, hydrogen-bonding ability, and size of osmolytes. We anticipate that the present experimental results provide important clues about the complicated and intricate mechanism of osmolyte effects on protein structure and dynamics in a crowded cellular environment.
Highlights
A detailed knowledge of protein structure and dynamics and the relation between them is essential for a thorough understanding of protein function
The fact that sorbitol and trehalose induce a notable change in the vibrational lifetime is important, 20.5 ± 0.5 ps, in glycine betaine 3.0 M solution 20.1 ± 0.6 ps, and in sorbitol 3.0 M solution 20.4 ± 0.6 as it provides a clue about osmolyte effects on protein structure and function in this particular case
We have studied the effects of five different osmolytes on the structure and dynamics of myoglobin, using a variety of spectroscopic methods, e.g., UV-vis, circular dichroism (CD), FTIR and IR pump-probe spectroscopy
Summary
A detailed knowledge of protein structure and dynamics and the relation between them is essential for a thorough understanding of protein function. [15,16], even spectroscopic techniques with sufficiently high time resolution, which are capable of probing ultrafast dynamics, still cannot provide atomic scale information on structural dynamics. COMb is an excellent model system for such time-resolved spectroscopic studies because of its high chemical stability in solution, almost unitary quantum efficiency for photolysis, and ultrafast (
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