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Protein fluorescence measurements within electrospray droplets
S E Rodriguez-Cruz1, J T Khoury, J H Parks
1The Rowland Institute for Science, Cambridge, Massachusetts 02142, USA.
Journal of the American Society for Mass Spectrometry
|June 13, 2001
Summary
Investigating cytochrome c protein structure in electrospray droplets reveals unique conformations. Proteins in droplets show more compact structures than in bulk solution, suggesting refolding at the droplet surface.
Area of Science:
- Biophysical Chemistry
- Protein Science
- Analytical Chemistry
Background:
- Understanding protein conformation is crucial for biological function.
- Electrospray ionization is a common technique for mass spectrometry, but droplet environments remain understudied.
- Cytochrome c serves as a model protein for studying conformational changes.
Purpose of the Study:
- To investigate the conformational states of cytochrome c within electrospray droplets.
- To compare protein conformations in electrospray droplets versus bulk solution.
- To explore the influence of solvent composition and droplet environment on protein structure.
Main Methods:
- Laser-induced fluorescence spectroscopy monitoring tryptophan (Trp-59) fluorescence.
- Controlled denaturation using varying alcohol concentrations (methanol, 1-propanol).
- Comparison of fluorescence measurements in electrospray plumes and bulk solutions.
Main Results:
- Protein fluorescence intensity changes significantly with increasing alcohol concentration, indicating denaturation.
- At high alcohol concentrations, proteins appear partly or fully denatured in both droplet and solution environments.
- At intermediate alcohol concentrations, proteins in droplets exhibit more compact structures than in bulk solution, suggesting refolding.
Conclusions:
- Electrospray droplet environments can induce unique protein conformations compared to bulk solutions.
- Protein refolding at the droplet surface, influenced by the air/liquid interface, may explain observed compact structures.
- These findings represent the first reported fluorescence measurements of proteins within electrospray droplets, opening new avenues for studying protein behavior in confined environments.