[MOS] MOS 12/6/05

[Zina Queen]

Seminar on
Modern Optics and Spectroscopy

Joel Parks,
Rowland Institute at Harvard

Probing the dynamics of trapped gas-phase proteins with photons

December 6, 2005
12:00 - 1:00 p.m.
34-401

Abstract:

Characterization of the structure and dynamics of biopolymers is of 
paramount importance to understanding life processes at the molecular 
level. Measurements of these molecules in the absence of a solvent or 
surface are useful for elucidating the effects of the solvent 
environment on the native structure and dynamics. We have been 
applying fluorescence spectroscopy to unsolvated biomolecule ions to 
take advantage of the unique ability of this technique to directly 
probe the local molecular environment surrounding the fluorophore. 
This talk will discuss the first fluorescence measurements of protein 
unfolding in the gas phase. Trp-cage is an actively studied 20 amino 
acid protein that folds cooperatively in 4 ms and presents a 
tractable size for calculations. The native structure includes a 
Tryptophan amino acid "caged" by three Proline amino acids, a feature 
that makes this protein especially suitable for the detection of 
unfolding in the gas phase by intramolecular fluorescence quenching. 
As the protein is heated to induce conformational change, the Trp 
will be released from its cage and become more exposed to 
intramolecular collisions with a covalently attached fluorescent dye, 
BODIPY TMR. Such collisions quench the dye fluorescence so that 
conformational changes will be directly correlated with the 
fluorescence intensity. The talk will describe these new methods and 
present results of their application to Trp-cage, and polypeptides.
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