OPTICALLY MODULATED FLUORESCENT PROTEINS Copyright © Amy E. Jablonski 2014
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OPTICALLY MODULATED FLUORESCENT PROTEINS A Thesis Presented to The Academic Faculty by Amy E. Jablonski In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the School of Chemistry and Biochemistry Georgia Institute of Technology August 2014 Copyright © Amy E. Jablonski 2014 OPTICALLY MODULATED FLUORESCENT PROTEINS Approved by: Dr. Robert M. Dickson, Advisor Dr. Mostafa El-Sayed School of Chemistry and Biochemistry School of Chemistry and Biochemistry Georgia Institute of Technology Georgia Institute of Technology Dr. Laren M. Tolbert Dr. Melissa Kemp School of Chemistry and Biochemistry School of Biomolecular Engineering Georgia Institute of Technology Georgia Institute of Technology Dr. Christoph Fahrni School of Chemistry and Biochemistry Georgia Institute of Technology Date Approved: June 17, 2014 ACKNOWLEDGEMENTS I wish to thank the many individuals who I have worked with and learned from over the course of my Ph.D. First and foremost, I would like to thank my advisor, Dr. Robert Dickson for giving me the opportunity to pursue this interesting research and guiding me through this process. I am also grateful to the many group members that have been vital to my success and understanding of this project. I thank past member Nathan Hull for his guidance when I first arrived and Dr. Saugata Sarkar and Dr. Chaoyang Fan for their encouragement and words of wisdom. Additionally, I would like to thank all present members of the group, Blake Fleischer, Tzu-Hsueh Huang, Dan Mahoney, Soonkyo Jung, Aida Demissie, and Joe Richardson, for their support, especially Jung-Cheng Hsiang and Yen-Cheng Chen whom have spent a lot of time helping we work through the intricate details of my project. I also wish to thank the many collaborators that I have had the opportunity to work with over the years. Thanks to Dr. Christoph Fahrni for his insight on all things biology as well as his members Dr. Pritha Bagchi and Dr. Irina Issaeva for providing the technical expertise for protein purification and transfection and deep knowledge of mammalian systems. Additionally, I would like to thank Dr. Laren Tolbert and his members Dr. Kyril Solntsev and Dr. Russell Vegh for their support and wealth of knowledge of fluorescent proteins; I have learned so much through our discussions. Also, thanks to Dr. Andreas Bommarius and Dr. Bettina Bommarius for their speedy and outstanding assistance with blue fluorescent protein project. Without these fun and hard-working people, this project would not have been possible. iii I wish to thank my whole the committee, Dr. Christoph Fahrni, Dr. Laren Tolbert, Dr. Mostafa El-Sayed, and Dr. Melissa Kemp for their unwavering support and the enlightened discussions over the years. Additionally, I thank all Georgia Institute of Technology professors and staff that have supported me and help me nagivate this Ph.D. process. Lastly, I would like to thank all my friends and family for their patience, understanding, and encouragement. Trust me when I say, this was possible because of you guys. iv TABLE OF CONTENTS ACKNOWLEDGEMENTS ............................................................................................... iii LIST OF TABLES ............................................................................................................ xii LIST OF FIGURES ......................................................................................................... xiv LIST OF SYMBOLS AND ABBREVIATIONS ............................................................ xxi SUMMARY ................................................................................................................... xxiv CHAPTER 1 INTRODUCTION ........................................................................................ 1 1.1 Motivation ................................................................................................................. 1 1.2 Fluorescence Microscopy in Biology ....................................................................... 3 1.2.1 Fluorescence Principles ................................................................................. 3 1.2.2 Fluorescence Microscope............................................................................... 5 1.2.3 Select Fluorescence Microscopy Techniques ................................................ 6 1.2.3.1 Fluorescence Correlation Spectroscopy ...................................................... 6 1.2.3.2 Förster Resonance Energy Transfer ............................................................ 7 1.2.3.3 Total Internal Reflection Microscopy ......................................................... 7 1.2.3.4 Optical Lock-in Detection........................................................................... 8 1.3 Fluorescent Labels .................................................................................................... 8 1.3.1 Intrinsic Fluorophores .................................................................................... 9 1.3.2 Organic Dyes ............................................................................................... 10 v 1.3.3 Nanoparticles ............................................................................................... 10 1.3.4 Fluorescent Proteins ..................................................................................... 11 1.4 Fluorescent Protein Background ............................................................................. 12 1.4.1 Protein Structure .......................................................................................... 13 1.4.2 Color Palette................................................................................................. 14 1.4.3 Photophysics ................................................................................................ 15 1.5 Fluorescent Proteins in Biological Applications..................................................... 16 1.5.1 Imaging ........................................................................................................ 17 1.5.2 Sensing ......................................................................................................... 17 1.5.3 Protein-Protein Interactions ......................................................................... 18 1.5.4 Limitations ................................................................................................... 19 1.6 Optical Modulation ................................................................................................. 20 1.7 Organization of Thesis ............................................................................................ 22 CHAPTER 2 EXPERIMENTAL SECTION .................................................................... 25 2.1 Protein Preparation.................................................................................................. 25 2.2 Protein Sample Preparations ................................................................................... 26 2.2.1 Bulk Solution Measurement ........................................................................ 27 2.2.2 Bulk Immobilized Measurements ................................................................ 27 2.2.3 Buffer Exchange .......................................................................................... 30 2.2.4 Deuterium Oxide Exchange ......................................................................... 31 vi 2.2.4.1 Deuterium Oxide Purity Validation .......................................................... 31 2.2.4.2 Deuterated Buffer Preparation .................................................................. 32 2.2.4.3 Deuterated Buffer Exchange ..................................................................... 33 2.3 Bulk Characterization ............................................................................................. 33 2.3.1 Fluorescence Quantum Yield ....................................................................... 34 2.3.2 Extinction Coefficient .................................................................................. 35 2.3.3 Apparent pKa Measurements ....................................................................... 36 2.4 Fluorescence Correlation Spectroscopy .................................................................. 36 2.5 Single Molecule Measurements .............................................................................. 38 2.6 Optical Modulation ................................................................................................. 39 2.6.1 Basic Experimental Setup ............................................................................ 40 2.6.2 Analysis........................................................................................................ 45 2.6.2.1 Enhancement ............................................................................................. 45 2.6.2.2 Characteristic Frequency .......................................................................... 46 2.7 Dual Modulation ..................................................................................................... 47 2.8 Imaging Configurations .......................................................................................... 48 2.8.1 Cell Preparation ........................................................................................... 49 2.8.2 Point-by-Point Scanning .............................................................................. 50 2.8.2.1 Experimental Setup ..................................................................................