ORCID
0000-0002-6165-2497
Keywords
Actin cytoskeleton, Macromolecular crowding, Nanomaterials, Assembly kinetics, Bending stiffness, Molybdenum disulfide
Subject Categories
Biology | Cell Biology
Abstract
The actin cytoskeleton is a dynamic structure inside the cell that helps maintain the structural integrity of the cell, allows for cell division, and force generation needed for cell motility. Actin filament assembly occurs in a crowded intracellular environment packed with a variety of macromolecules, ions, and small molecules. How different types of molecules influence actin’s assembly and mechanics is not fully understood. In the first two parts of this dissertation, we investigated the effects of crowding with various macromolecules and small osmolytes on actin filament assembly dynamics and filament mechanics. We utilized total internal reflection fluorescence (TIRF) microscopy and fluorescence spectroscopy to determine the effects of crowding on filament assembly and mechanics. Our results demonstrated how different types of crowding molecules modulated actin assembly by changing solution properties, while organic osmolytes affected actin assembly kinetics and bending mechanics in a concentration dependent manner. Molecular dynamics simulations demonstrated how the different crowding agents altered monomer diffusion leading to changes in actin filament assembly.
Biomolecular interactions inside the cell can also be influenced by nanomaterials used in biomedical applications like biosensing and drug delivery. Molybdenum disulfide (MoS2) is a transition metal dichalcogenide whose unique properties have increased its use in biomedicine and thus increased its potential influence on cellular components. While its biocompatibility has been characterized, the effects of MoS2 on the actin cytoskeleton are not well understood. In the last part of this dissertation, the effects of MoS2 on individual actin filaments and NIH-3T3 fibroblast cells were explored. We demonstrated MoS2 nanoflakes at varying concentrations resulted in enhanced actin filament elongation rates, without affecting cytotoxicity and cell morphology. All together, these results reveal how macromolecular crowding, osmolytes, and nanomaterials modulate actin assembly dynamics and filament mechanics to modulate in vivo regulatory processes of the actin cytoskeleton.
Completion Date
2026
Semester
Summer
Committee Chair
Kang, Ellen
Degree
Doctor of Philosophy (Ph.D.)
College
College of Medicine
Department
Burnett School of Biomedical Sciences
Format
Document Type
Dissertation
Language
English
Release Date
8-15-2027
STARS Citation
Demosthene, Bryan, "Mechanism of Actin Assembly Dynamics and Mechanics Modulation by Macromolecular Crowding and Nanomaterials" (2026). Graduate Studies Theses and Dissertations 2026. 257.
https://stars.library.ucf.edu/gradstudies_etd_2026/257
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