UNDERSTANDING THE TRANSITION FROM NON-LIVING TO LIVING: CHARACTERIZATION OF PROTOCELL SYSTEMS BASED ON AQUEOUS PHASE COEXISTENCE
Open Access
- Author:
- Pir Cakmak, Fatma
- Graduate Program:
- Chemistry
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- March 06, 2020
- Committee Members:
- Christine Dolan Keating, Dissertation Advisor/Co-Advisor
Christine Dolan Keating, Committee Chair/Co-Chair
Philip C Bevilacqua, Committee Member
Paul S Cremer, Committee Member
Peter J Butler, Outside Member
Philip C Bevilacqua, Program Head/Chair - Keywords:
- phase separation
coacervate
protocell
artificial cell models - Abstract:
- Understanding how life might started requires prebiotically relevant protocell models capable of concentrating genetic material that could be subject to Darwinian evolution. I have studied liquid- liquid phase separation as a way of compartmentalization for extant and prebiotic cells. The liquid- liquid phase separated systems described here shed light to how to control physicochemical properties of liquid-liquid phase separated compartments for protocell and artificial cells models. Chapter 1 provides a general background of liquid-liquid phase separation, followed by a discussion of physical properties and function of the compartments presented. Chapter 2 describes how natural clay particles could act as a catalyst in phase separated PEG/dextran systems. Different types of clay particles show different wetting properties and can stabilize PEG-rich or dextran-rich phase. Combining catalytic natural mineral particles with phase separated compartments could provide primitive microreactors, which might be relevant to prebiotic chemistry on the early Earth. In Chapter 3, prebiotically more relevant compartments than PEG/dextran formed through complex coacervation was investigated. We explored how peptides and nucleotides at low concentration could phase separate and form compartments. These phase separated compartments formed with short peptides were quite resistant at different salt conditions. Besides, these compartments provide rather different physicochemical properties than bulk water. Properties of the compartments depend on the type of the molecules used to form coacervate droplets. For instance, compartments formed with shorter length peptides were better at preserving double stranded RNA compared to coacervate compartments formed with longer peptides. This means that simpler compartments might provide an advantage to protecting secondary structure of genetic material. Chapter 4 looks at the combinations of different compartmentalization methods. I combined type of vesicles with polymers with variable charge ratio. This study provides insights into how properties of coacervate and liposome affect assembly of both systems. We established a guideline that is useful to understand governing interactions liposome assembly at the interface. In Chapter 5, we present a simple method to create lipid membrane templated with coacervates. Instead of complicated microfluidic devices, we can use simple vesicle hydration to create a membrane. Finally, Chapter 6 offers some general conclusions from this work, along with the future perspective of phase separated models.