Biophysics Commons^™

Structure-Function Relationships In Neurodegenerative And Infectious Diseases: Biophysical Characterization Of Rna Secondary Structures By Computational Techniques, Kendy Guarinoni

Electronic Theses and Dissertations

The research described in this dissertation focuses on the investigation of the structure and dynamics of regions of RNA implicated in two diseases: COVID-19 and amyotrophic lateral sclerosis/frontotemporal dementia (ALS/FTD). Both studies sought to create experimentally corroborated models that were used to characterize the structure and dynamics of the C9orf72 repeat expansion and the s2m region in coronaviruses, respectively and provided the foundation for future work. In our work involving the s2m region of SARS-CoV-2, the virus responsible for COVID-19, we determined that the homology modeling approach commonly used to derive atomistic structures when no coordinates are available yields a …

Modeling Accuracy Matters: Aligning Molecular Dynamics With 2d Nmr Derived Noe Restraints, Milan Patel

Honors Scholar Theses

Among structural biology techniques, Nuclear Magnetic Resonance (NMR) provides a holistic view of structure that is close to protein structure in situ. Namely, NMR imaging allows for the solution state of the protein to be observed, derived from Nuclear Overhauser Effect restraints (NOEs). NOEs are a distance range in which hydrogen pairs are observed to stay within range of, and therefore experimental data which computational models can be compared against. To that end, we investigated the effects of adding the NOE restraints as distance restraints in Molecular Dynamics (MD) simulations on the 24 residue HP24stab derived villin headpiece subdomain to …

Comparative Analysis Of Conformational Transition Pathways In Homologous Proteins, Dylan Sebastien Ogden

Graduate Theses and Dissertations

Molecular dynamics (MD) simulations are routinely used to study the dynamics of proteins. However, conventional MD limited to the sampling of local conformational changes as the functionally important conformational transitions of proteins often extend beyond the timescales of the simulations employed, for example, membrane transport proteins. We have determined the combination of multiple MD based techniques that allows for a rigorous characterization of energetics and kinetics of large-scale conformational changes in membrane proteins. The methodology is based on biased, nonequilibrium collective variable based simulations including nonequilibrium pulling, string method with swarms of trajectories, bias-exchange umbrella sampling, and rate estimation techniques. …

Developing And Applying Computational Algorithms To Reveal Health-Related Biomolecular Interactions, Yixin Xie

Open Access Theses & Dissertations

Computational biology is an interdisciplinary area that applies computational approaches in biological big data, including protein amino acid sequences, genetic sequences, etc., which is widely used to analyze protein-protein interactions, make predictions in drug discovery, develop vaccines, etc. Popular methods include mathematical modeling, molecular dynamics simulations, data science mythology, etc. With the help of computational algorithms and applications, drug development is much faster than traditional processes, as it reduces risks early on in a drug discovery process and helps researchers select target candidates that have the highest potential for success. In my doctoral research, I applied multi-scale computational approaches to …

Computational Investigations Into Binding Dynamics Of Tau Protein Antibodies: Using Machine Learning And Biophysical Models To Build A Better Reality, Katherine Lee

University Scholar Projects

Misregulation of post-translational modifications of microtubule-associated protein tau is implicated in several neurodegenerative diseases including Alzheimer’s disease. Hyperphosphorylation of tau promotes aggregation of tau monomers into filaments which are common in tau-associated pathologies. Therefore, tau is a promising target for therapeutics and diagnostics. Recently, high-affinity, high-specificity single-chain variable fragment (scFv) antibodies against pThr-231 tau were generated and the most promising variant (scFv 3.24) displayed 20-fold increased binding affinity to pThr-231 tau compared to the wild-type. The scFv 3.24 variant contained five point mutations, and intriguingly none were in the tau binding site. The increased affinity was hypothesized to occur due …

Multilevel Computational Investigation Into The Dynamics And Reaction Mechanisms Of Non-Heme Iron And 2-Oxoglutarate Dependent Enzymes, Shobhit Sanjeev Chaturvedi

Dissertations, Master's Theses and Master's Reports

Computational chemistry methods have been extensively applied to investigate biological systems. This dissertation utilizes a multilevel computational approach to explore the dynamics and reaction mechanisms of two groups of enzymes belonging to non-heme Fe(II) and 2-oxoglutarate (2OG) dependent superfamily – histone lysine demethylases from class 7 and ethylene forming enzyme (EFE). Chapter 2 uncovers the role of conformational dynamics in the substrate selectivity of histone lysine demethylases 7A and 7B. The molecular dynamics (MD) simulations of the two enzymes revealed the importance of linker flexibility and dynamics in relative orientations of the reader (PHD) and the catalytic (JmjC) domains. Chapter …

Mechanisms Of Connexin-46 And -50 Intercellular Channel Function And Stability By Molecular Dynamics Simulations, Bassam George Haddad

Dissertations and Theses

Gap junctions make up a class of intercellular channels that characteristically connect the cytoplasm of directly apposed cells through large assemblies, or plaques, constituted by a multitude of intercellular channels. Gap junction mediated intercellular communication is critical for a variety of physiological functions, from coordinating electrical impulses in the heart and brain to maintaining homeostasis in most tissues. There are 21 isoforms of connexins, the constituent subunit of the gap junction, expressed in a tissue dependent manner. Gap junctions formed from different isoforms exhibit distinct biophysical properties, such as gating kinetics and sensitivity, as well as unique permeability and selectivity …

Bridging The 12-6-4 Model And The Fluctuating Charge Model, Pengfei Li

Chemistry: Faculty Publications and Other Works

Metal ions play important roles in various biological systems. Molecular dynamics (MD) using classical force field has become a popular research tool to study biological systems at the atomic level. However, meaningful MD simulations require reliable models and parameters. Previously we showed that the 12-6 Lennard-Jones nonbonded model for ions could not reproduce the experimental hydration free energy (HFE) and ion-oxygen distance (IOD) values simultaneously when ion has a charge of +2 or higher. We discussed that this deficiency arises from the overlook of the ion-induced dipole interaction in the 12-6 model, and this term is proportional to 1/r …

Understanding The Relationship Between Local Environmental Changes And The Function Of The Ph Low Insertion Peptide, Violetta Burns Casamayor

Graduate Theses, Dissertations, and Problem Reports (ETD)

Cancer is the second leading cause of death in the US with over 1.7 million new cases each year. Current cancer treatments tend to also target healthy tissues due to similarities with cancerous ones, resulting in acute side effects. Early detection is the best approach towards defeating cancer, however, modern imaging techniques require sizeable samples, often implying a late stage in the disease. One common attribute of tumors is their acidic microenvironment, which can be taken advantage of.

The pH Low Insertion Peptide (pHLIP) is a membrane-active peptide that can take advantage of the acidic microenvironment surrounding cancer cells. pHLIP …

Amyloid Proteins And Fibrils Stability, Farbod Mahmoudinobar

Dissertations

Compared to globular proteins that have a stable native structure, intrinsically disordered peptides (IDP) sample an ensemble of structures without folding into a native conformation.One example of IDP is the amyloid-beta(Abeta) protein which is the main constituent of senile plaques in the brain of Alzheimer's patients.Understanding the process by which IDPs undergo structural changes to form oligomers that eventually aggregate into senile plaques/amyloid fibrils may significantly advance the development of novel therapeutic methods to treat neurodegenerative diseases, for which there is no cure to date. This dissertation has two main objectives. The first one is to investigate and identify structural …

Structure And Thermodynamics Of Polyglutamine Peptides And Amyloid Fibrils Via Metadynamics And Molecular Dynamics Simulations, Riley Workman

Electronic Theses and Dissertations

Aggregation of polyglutamine (polyQ)-rich polypeptides in neurons is a marker for nine neurodegenerative diseases. The molecular process responsible for the formation of polyQ fibrils is not well understood and represents a growing area of study. To enable development of treatments that could interfere with aggregation of polyQ peptides, it is crucial to understand the molecular mechanisms by which polyQ peptides aggregate into fibrils. Many experimental techniques have been employed to probe polyQ aggregation, however, observations from these studies have not lead to a unified understanding of the properties of these systems, instead yielding competing, fragmented theories of polyQ aggregation. This …

Hard-Sphere-Like Dynamics In Highly Concentrated Alpha-Crystallin Suspensions, Preeti Vodnala, Laurence Lurio, Michael C. Vega, Elizabeth Gaillard

Faculty Articles, Papers, and Other Scholarship

The dynamics of concentrated suspensions of the eye-lens protein alpha crystallin have been measured using x-ray photon correlation spectroscopy. Measurements were made at wave vectors corresponding to the first peak in the hard-sphere structure factor and volume fractions close to the critical volume fraction for the glass transition. Langevin dynamics simulations were also performed in parallel to the experiments. The intermediate scattering function f(q,τ) could be fit using a stretched exponential decay for both experiments and numerical simulations. The measured relaxation times show good agreement with simulations for polydisperse hard-sphere colloids.

Understanding Carbohydrate Recognition Mechanisms In Non-Catalytic Proteins Through Molecular Simulations, Abhishek A. Kognole

Theses and Dissertations--Chemical and Materials Engineering

Non-catalytic protein-carbohydrate interactions are an essential element of various biological events. This dissertation presents the work on understanding carbohydrate recognition mechanisms and their physical significance in two groups of non-catalytic proteins, also called lectins, which play key roles in major applications such as cellulosic biofuel production and drug delivery pathways. A computational approach using molecular modeling, molecular dynamic simulations and free energy calculations was used to study molecular-level protein-carbohydrate and protein-protein interactions. Various microorganisms like bacteria and fungi secret multi-modular enzymes to deconstruct cellulosic biomass into fermentable sugars. The carbohydrate binding modules (CBM) are non-catalytic domains of such enzymes that …

Computational Investigation Of The Pore Formation Mechanism Of Beta-Hairpin Antimicrobial Peptides, Richard Lipkin

Dissertations, Theses, and Capstone Projects

β-hairpin antimicrobial peptides (AMPs) are small, usually cationic peptides that provide innate biological defenses against multiple agents. They have been proposed as the basis for novel antibiotics, but their pore formation has not been directly observed on a molecular level. We review previous computational studies of peptide-induced membrane pore formation and report several new molecular dynamics simulations of β-hairpin AMPs to elucidate their pore formation mechanism. We simulated β-barrels of various AMPs in anionic implicit membranes, finding that most of the AMPs’ β-barrels were not as stable as those of protegrin. We also performed an optimization study of protegrin β-barrels …

Computing Spatiotemporal Heat Maps Of Lipid Electropore Formation: A Statistical Approach, Willy Wriggers, Frederica Castellani, Julio A. Kovacs, P. Thomas Vernier

Mechanical & Aerospace Engineering Faculty Publications

We extend the multiscale spatiotemporal heat map strategies originally developed for interpreting molecular dynamics simulations of well-structured proteins to liquids such as lipid bilayers and solvents. Our analysis informs the experimental and theoretical investigation of electroporation, that is, the externally imposed breaching of the cell membrane under the influence of an electric field of sufficient magnitude. To understand the nanoscale architecture of electroporation, we transform time domain data of the coarse-grained interaction networks of lipids and solvents into spatial heat maps of the most relevant constituent molecules. The application takes advantage of our earlier graph-based activity functions by accounting for …

Modeling The Binding Of Neurotransmitter Transporter Inhibitors With Molecular Dynamics And Free Energy Calculations, Bernandie Jean

Electronic Theses and Dissertations

The monoamine transporter (MAT) proteins responsible for the reuptake of the neurotransmitter substrates, dopamine, serotonin, and norepinephrine, are drug targets for the treatment of psychiatric disorders including depression, anxiety, and attention deficit hyperactivity disorder. Small molecules that inhibit these proteins can serve as useful therapeutic agents. However, some dopamine transporter (DAT) inhibitors, such as cocaine and methamphetamine, are highly addictive and abusable. Efforts have been made to develop small molecules that will inhibit the transporters and elucidate specific binding site interactions. This work provides knowledge of molecular interactions associated with MAT inhibitors by offering an atomistic perspective that can guide …

Computational Modeling Of Allosteric Stimulation Of Nipah Virus Host Binding Protein, Priyanka Dutta

USF Tampa Graduate Theses and Dissertations

Nipah belongs to the family of paramyxoviruses that cause numerous fatal diseases in humans and farm animals. There are no FDA approved drugs for Nipah or any of the paramyxoviruses. Designing antiviral therapies that are more resistant to viral mutations require understanding of molecular details underlying infection. This dissertation focuses on obtaining molecular insights into the very first step of infection by Nipah. Such details, in fact, remain unknown for all paramyxoviruses. Infection begins with the allosteric stimulation of Nipah virus host binding protein by host cell receptors. Understanding molecular details of this stimulation process have been challenging mainly because, …

Computational Investigations Into The Molecular Underpinnings Of Eyesight Signaling Pathways, Shaan Kamal

University Scholar Projects

Phosphodiesterase 6 (PDE6) is a critical enzyme in the eyesight-signaling pathway. When activated, PDE6 hydrolyzes cGMP to GMP, which deactivates cGMP- gated ion channels, causing hyperpolarization of the cell and activating the sensory neurons responsible for vision. Within the PDE family, PDE6 is the only enzyme known to have an inhibitory subunit (PDE6-γ), which allows for the regulation of cGMP levels. When PDE6-γ is bound to PDE6, the enzyme is turned “off” and cannot catalyze cGMP. The α subunit of the G-protein transducin removes PDE6-γ and activates PDE6. PDE6 has proven problematic to isolate, making it difficult to study experimentally …

Stability Of Norwalk Virus Capsid Protein Interfaces Evaluated By In Silico Nanoindentation, Prakhar Bansal

University Scholar Projects

Studying the mechanical properties of viral capsids can give several insights into not only the lifecycle of the virus, but also into potential drug targets to thwart the progression of viral infection. Nanoindentation using an atomic force microscope is a useful technique for determining structural properties of small molecules and particles, and is commonly used to study viral capsids. This technique utilizes the probe of the microscope to push down on the capsid and record the forces along the indentation path. We ran this experiment in silico where we simulated the nanoindentation of Norwalk virus capsids using molecular dynamics. Running …

Computational Modeling Of Rna-Small Molecule And Rna-Protein Interactions, Lu Chen

Dissertations and Theses (Open Access)

The past decade has witnessed an era of RNA biology; despite the considerable discoveries nowadays, challenges still remain when one aims to screen RNA-interacting small molecule or RNA-interacting protein. These challenges imply an immediate need for cost-efficient while predictive computational tools capable of generating insightful hypotheses to discover novel RNA-interacting small molecule or RNA-interacting protein. Thus, we implemented novel computational models in this dissertation to predict RNA-ligand interactions (Chapter 1) and RNA-protein interactions (Chapter 2).

Targeting RNA has not garnered comparable interest as protein, and is restricted by lack of computational tools for structure-based drug design. To test the potential …

The Structural Heterogeneity And Dynamics Of Base Stacking And Unstacking In Nucleic Acids, Ada Anna Sedova

Legacy Theses & Dissertations (2009 - 2024)

Base stacking provides stability to nucleic acid duplexes, and base unstacking is involved in numerous biological functions related to nucleic acids, including replication, repair, transcription, and translation. The patterns of base stacking and unstacking in available nucleic acid crystal structures were classified after separation into their individual single strand dinucleotide components and clustering using a k-means-based ensemble clustering method. The A- and B-form proximity of these dinucleotide structures were assessed to discover that RNA dinucleotides can approach B-form-like structures. Umbrella sampling molecular dynamics simulations were used to obtain the potential of mean force profiles for base unstacking at 5'-termini for …

Evaluations Of A Mechanistic Hypothesis For The Influence Of Extracellular Ions On Electroporation Due To High-Intensity, Nanosecond Pulsing, V. Sridhara, R. P. Joshi

Electrical & Computer Engineering Faculty Publications

The effect of ions present in the extracellular medium on electroporation by high-intensity, short-duration pulsing is studied through molecular dynamic simulations. Our simulation results indicate that mobile ions in the medium might play a role in creating stronger local electric fields across membranes that then reinforce and strengthen electroporation. Much faster pore formation is predicted in higher conductivity media. However, the impact of extracellular conductivity on cellular inflows, which depend on transport processes such as electrophoresis, could be different as discussed here. Our simulation results also show that interactions between cations (Na+ in this case) and the carbonyl oxygen of …

Numerical Study Of Lipid Translocation Driven By Nanoporation Due To Multiple High-Intensity, Ultrashort Electrical Pulses, Viswanadham Sridhara, Ravindra P. Joshi

Electrical & Computer Engineering Faculty Publications

The dynamical translocation of lipids from one leaflet to another due to membrane permeabilization driven by nanosecond, high-intensity (>100 kV/cm) electrical pulses has been probed. Our simulations show that lipid molecules can translocate by diffusion through water-filled nanopores which form following high voltage application. Our focus is on multiple pulsing, and such simulations are relevant to gauge the time duration over which nanopores might remain open, and facilitate continued lipid translocations and membrane transport. Our results are indicative of a N^1/2 scaling with pulse number for the pore radius. These results bode well for the use of pulse …

Tracing Beta Strands Using Strandtwister From Cryo-Em Density Maps At Medium Resolutions, Dong Si, Jing He

Computer Science Faculty Publications

Major secondary structure elements such as α helices and β sheets can be computationally detected from cryoelectron microscopy (cryo-EM) density maps with medium resolutions of 5–10 A˚ . However, a critical piece of information for modeling atomic structures is missing, because there are no tools to detect β strands from cryo-EM maps at medium resolutions. We propose a method, StrandTwister, to detect the traces of β strands through the analysis of twist, an intrinsic nature of a β sheet. StrandTwister has been tested using 100 β sheets simulated at 10 A˚ resolution and 39 β sheets computationally detected from cryo-EM …

Rescuing Acetylcholinesterase From Nerve Agent Inhibition: Protein Dynamics Driven Drug Discovery, Aiyana M. Emigh, Brian Bennion

STAR Program Research Presentations

Severe morbidity and mortality consequences result from irreversible inhibition of human acetylcholinesterase by organophosphates (OPs). Oxime-based reactivators are currently the only available treatments but lack efficacy in the central nervous system (CNS) where the most damage occurs. Computational docking and molecular dynamics (MD) simulations reveal complex structural barriers that may reduce oxime efficacy. These results may guide future drug designs of more effective countermeasures.