Document Type

Dissertation

Degree

Doctor of Philosophy (PhD)

Department

Physics

First Advisor's Name

Prem P. Chapagain

First Advisor's Committee Title

Co-Committee Chair

Second Advisor's Name

Bernard S. Gerstman

Second Advisor's Committee Title

Co-Committee Chair

Third Advisor's Name

Xuewen Wang

Fourth Advisor's Name

David C. Chatfield

Keywords

fluorescence, chromophore, quenching, parameterization, diffusion pathways, hydrogen bonding, chromophore planarity

Date of Defense

3-28-2013

Abstract

Fluorescent proteins (FPs) are extremely valuable biochemical markers which have found a wide range of applications in cellular and molecular biology research. The monomeric variants of red fluorescent proteins (RFPs), known as mFruits, have been especially valuable for in vivo applications in mammalian cell imaging. Fluorescent proteins consist of a chromophore caged in the beta-barrel protein scaffold. The photophysical properties of an FP is determined by its chromophore structure and its interactions with the protein barrel.

Application of hydrostatic pressure on FPs results in the modification of the chromophore environment which allows a systematic study of the role of the protein-chromophore interactions on photophysical properties of FPs. Using Molecular Dynamics (MD) computer simulations, I investigated the pressure induced structural changes in the monomeric variants mCherry, mStrawberry, and Citrine. The results explain the molecular basis for experimentally observed pressure responses among FP variants. It is found that the barrel flexibility, hydrogen bonding interactions and chromophore planarity of the FPs can be correlated to their contrasting photophysical properties at vaious pressures.

I also investigated the oxygen diffusion pathways in mOrange and mOrange2 which exhibit marked differences in oxygen sensitivities as well as photostability. Such computational identifications of structural changes and oxygen diffusion pathways are important in guiding mutagenesis efforts to design fluorescent proteins with improved photophysical properties.

Identifier

FI13042320

Included in

Physics Commons

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