Investigating the Photochemistry of Provitamin D3 as a Function of Liposome Properties by Danielle L. Sofferman A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy (Applied Physics) in The University of Michigan 2020 Doctoral Committee: Professor Roseanne J. Sension, Chair Professor Julie Biteen Professor Cagliyan Kurdak Professor Vanessa Sih Professor Sarah Veatch Danielle L. Sofferman [email protected] ORCID iD: 0000-0001-7386-4019 © Danielle L. Sofferman 2020 DEDICATION This dissertation is dedicated to all the people who have supported me throughout this journey. ii ACKNOWLEDGEMENTS Thank you, Mom, Dad, and David. Mom and Dad, you both have supported my every decision throughout my science career and were proud of my every accomplishment. Dad, thank you for working so hard to provide me with an undergraduate education at Adelphi University. Mom, thank you also for helping me pay for Adelphi as well. The opportunity that you both gave me ultimately led me to pursue and now complete a Ph.D. at the University of Michigan. Thank you, Mom, for always checking in to see if I made it home safe, and for visiting, even during the coldest times of the year. And thank you to my brother, David, for helping me move into my apartment when I first moved to Michigan. I love you guys! Thank you, Rob. Thank you for all the love and support you have given me in the short time that we have been together. Your encouragement and support has helped me complete this dissertation. Thank you for standing by myside through one of the toughest years of my Ph.D. and for reassuring me that everything will work out in the long run. Thank you, Professor Roseanne Sension. Thank you for this opportunity that allowed me to take my curiosity for science, problem solving and technical skills to a level I never imagined was possible. Thank you for challenging me to make the most compelling evidence-based arguments and pushing my creativity to come up with the next best experiment. Thank you, Professor Ken Spears for mentoring me and serving as a second advisor throughout the years. I have been very fortunate to have learned from you and have always appreciated your practical problem solving and technical skills. iii Finally, thank you to my labmates, collaborators, and friends who have helped me make my years at Michigan so memorable and making this dissertation possible. Thank you, Dr. Ted Wiley for teaching me everything about our laser system, for having patience and allowing me to make mistakes and learn from them. Thank you, Dr. Nick Miller for pushing me to make the most compelling scientific arguments during a presentation. Thank you, Dr. Orko Konar and Dr. Joseph Mastron for working with me in the Laboratory for Ultrafast Multidimensional Optical Spectroscopy (LUMOS) to obtain the most important pieces of data for this dissertation. Thank you to the Veatch Group for your expertise on sample preparation and thank you to the Kopelman Group for allowing me to use your equipment to characterize my samples. Thank you to all my friends that I have made along the way, you all have helped shape Michigan into a home. Thank you, Kurdak, Cyndi and the rest of the Applied Physics family for supporting and believing in me throughout the years. I truly wouldn’t have done this without any of you. This research was supported by the National Science Foundation grant, NSF-CHE 1464584. iv Table of Contents DEDICATION ........................................................................................................................... ii ACKNOWLEDGEMENTS ..................................................................................................... iii LIST OF FIGURES ............................................................................................................... viii LIST OF TABLES ................................................................................................................. xiv ABSTRACT ............................................................................................................................ xvi CHAPTER: 1. Introduction ....................................................................................................................... 1 Introduction to The Photochemistry of 7-Dehydrocholesterol In The Skin Membrane ............................................................................................................... 1 Time Resolved Photochemistry of DHC in Lipid Bilayers .................................. 19 Outline of Dissertation .......................................................................................... 19 2. Experimental Methods for Transient Absorption and Steady State Measurements 27 Introduction to Experimental Background............................................................ 27 Laser Instrumentation ........................................................................................... 27 Sample Preparation / Characterization .................................................................. 31 Sample Characterization ....................................................................................... 33 v Percentage of Molecules Excited .......................................................................... 37 TA Scans and Steady State Measurements ........................................................... 38 Scattering Analysis ............................................................................................... 38 Solvent Signals...................................................................................................... 45 Summary of Solvent Background Analysis .......................................................... 50 3. Excited State Dynamics of Provitamins in Solution .................................................... 54 Introduction ........................................................................................................... 54 Results ................................................................................................................... 56 Conclusion ............................................................................................................ 63 4. The Provitamin Excited State Dynamics in Lipid Bilayers ........................................ 67 Introduction ........................................................................................................... 67 Results and Discussion ......................................................................................... 68 Heterogeneity Tests .............................................................................................. 71 Sterol Interaction between The Lipid Membrane and Molecule .......................... 72 Lipid Tail Length .................................................................................................. 75 Liposome Curvature.............................................................................................. 80 Summary of Time Constants and Amplitudes ...................................................... 82 Conclusion ............................................................................................................ 87 vi 5. Photoproduct Formation from Provitamins in Solution ............................................. 90 Introduction ........................................................................................................... 90 Time Resolved Conformer Relaxation in Solution ............................................... 91 Steady State Photolysis ......................................................................................... 97 Conclusion .......................................................................................................... 107 6. Photoproduct Formation from Provitamins in Lipid Bilayers ................................. 111 Introduction ......................................................................................................... 111 Time Resolved Conformer Relaxation in DPPC Lipid Bilayers ........................ 112 Steady State Photolysis of Provitamins in Liposomes ........................................ 115 Time Resolved Data in The Excited State and Ground State ............................. 122 Discussion ........................................................................................................... 125 Conclusion .......................................................................................................... 131 7. Conclusions and Extended Ideas ................................................................................. 135 Summary of Work............................................................................................... 135 Extended Ideas .................................................................................................... 137 Conclusion .......................................................................................................... 142 vii LIST OF FIGURES Figure 1.1: Photochemical process of DHC in skin. Following absorption of UV radiation, the cyclohexadiene chromophore (red) undergoes photochemical changes to convert DHC to vitamin D3. Excess exposure of UV radiation can lead to the formation of tachysterol and lumiseterol. ... 2 Figure 1.2: Photochemistry of CHD along the reaction coordinate. After the ring opens in the excited state, the molecule undergoes conformational relaxation in the ground state to form a stable tZt species. ...........................................................................................................................