Biophysics Commons^™

Force Generation And Contraction Of Random Actomyosin Bundles., Dietmar B. Oelz

Biology and Medicine Through Mathematics Conference

No abstract provided.

Synthesis And Characterization Of Nanoparticle-Coupled Proteins In Human Serum Albumin, Kyle M. Mahoney

Honors College Theses

Recently, cancer has become an ever-growing issue and has led to many researchers attempt to unravel the mystery of the disease. This research has led to a promising field of treatment: nanotechnology-coupled pharmaceuticals. Nanoparticles act as a whole unit when in conjugation with other molecules and add to the carrier molecule, most often proteins, benefits the nanoparticles themselves possess. One such carrier protein that can be conjugated with nanoparticles is Human Serum Albumin (HSA). Albumin is of interest in cancer research for two reasons: it is native to the human vasculature so it does not elicit immunological reactions, and it …

Noninvasive Measurement Of Electrical Events Associated With A Single Chlorovirus Infection Of A Microalgal Cell, Seung-Woo Lee, Eun-Hee Lee, Gerhard Thiel, James L. Van Etten, Ravi Saraf

Department of Chemical and Biomolecular Engineering: Faculty Publications

Chlorovirus Paramecium bursaria chlorella virus 1 (PBCV-1) contains a viral-encoded K⁺ channel imbedded in its internal membrane, which triggers host plasma membrane depolarization during virus infection. This early stage of infection was monitored at high resolution by recording the cell membrane depolarization of a single Chlorella cell during infection by a single PBCV-1 particle. The measurement was achieved by depositing the cells onto a network of one-dimensional necklaces of Au nanoparticles, which spanned two electrodes 70 μm apart. The nanoparticle necklace array has been shown to behave as a single-electron device at room temperature. The resulting electrochemical field-effect transistor …

Response Of Bacterial Cells To Fluctuating Environment, Sudip Nepal

Graduate Theses and Dissertations

We have studied morphological and genomic variations occurring in a mesophilic bacterium Escherichia coli (E. coli) in a wide range of continuous and fluctuating hydrostatic pressures. For all the studies here the temperature is maintained at 37◦C, the optimal growth tem- perature of E. coli at atmospheric pressure. Cell division is inhibited at high hydrostatic pressures resulting in an increase of cell length. The increase of cell-length depends on the extent and duration of the stress applied on bacterial cells. We have studied the effect of high pressure stress in three different conditions – (i) Wild-type cells (almost no genetic …

Elucidating The Role Of Hausp Ubiquitin Like Domains In The Catalytic Function Of Usp7, Anuj Patel, Nicole Davis, Andrew Mesecar

The Summer Undergraduate Research Fellowship (SURF) Symposium

Ubiquitin specific proteases (USPs) are a class of enzymes involved in myriad cellular processes. One USP of great interest due to its oncogenic properties is USP7. In normal conditions USP7 is closely regulated due to its responsibility for destabilizing the tumor suppressor, p53, through the deubiquitination of MDM2. In multiple myeloma cases, it appears the regulation of USP7 subsides, as it is largely overexpressed, leading to the inappropriate degradation of p53. Inhibition of USP7 could, therefore, prove a viable target for cancer therapy. A greater understanding of USP7’s function and structure can lead to more insight into how this enzyme …

The Role Of Stem Cells In Adipose Tissue Remodeling., Candice Reshay Holden 1988-

Electronic Theses and Dissertations

The work presented in this dissertation outlines the role of stem cells in the remodeling of adipose tissue under conditions of nutrient excess. Obesity-induced variations in adipose tissue stem cell distribution were uncovered by analysis of the stromal vascular fraction isolated from mice fed a high fat diet for several weeks. Bone marrow cell transplantation was used to determine the derivation of progenitor cells found in adipose tissue; and supplementation of depleted progenitor cell populations achieved via direct cell transplantation, helped to determine the contribution of these progenitor cells to the remodeling process. The dissertation is presented in five chapters …

Intranuclear Strain Measured By Iterative Warping In Cells Under Mechanical And Osmotic Stress, Jonathan T Henderson

Open Access Dissertations

The nucleus is a membrane bound organelle and regulation center for gene expression in the cell. Mechanical forces transfer to the nucleus directly and indirectly through specific cellular cytoskeletal structures and pathways. There is increasing evidence that the transferred forces to the nucleus orchestrate gene expression activity. Methods to characterize nuclear mechanics typically study isolated cells or cells embedded in 3D gel matrices. Often report only aspect ratio and volume changes, measures that oversimplify the inherent complexity of internal strain patterns. This presents technical challenges to simultaneously observe small scale nuclear mechanics and gene expression levels inside the nuclei of …

Dielectric Characterization Of Coastal Cartilage Chondrocytes, Michael W. Stacey, Ahmet C. Sabuncu, Ali Beskok

Bioelectrics Publications

BACKGROUND: Chondrocytes respond to biomechanical and bioelectrochemical stimuli by secreting appropriate extracellular matrix proteins that enable the tissue to withstand the large forces it experiences. Although biomechanical aspects of cartilage are well described, little is known of the bioelectrochemical responses. The focus of this study is to identify bioelectrical characteristics of human costal cartilage cells using dielectric spectroscopy.

METHODS: Dielectric spectroscopy allows non-invasive probing of biological cells. An in house computer program is developed to extract dielectric properties of human costal cartilage cells from raw cell suspension impedance data measured by a microfluidic device. The dielectric properties of chondrocytes are …

Cellular Regulation Of Extension And Retraction Of Pseudopod-Like Blebs Produced By Nanosecond Pulsed Electric Field, Mikhail A. Rassokhin, Andrei G. Pakhomov

Bioelectrics Publications

Recently we described a new phenomenon of anodotropic pseudopod-like blebbing in U937 cells exposed to nanosecond pulsed electric field (nsPEF). In Ca²⁺ -free buffer such exposure initiates formation of pseudopod-like blebs (PLBs), protrusive cylindrical cell extensions that are distinct from apoptotic and necrotic blebs. PLBs nucleate predominantly on anode-facing cell pole and extend toward anode during nsPEF exposure. Bleb extension depends on actin polymerization and availability of actin monomers. Inhibition of intracellular Ca²⁺ , cell contractility, and RhoA produced no effect on PLB initiation. Meanwhile, inhibition of WASP by wiskostatin causes dose-dependent suppression of PLB growth. Soon after …

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 …

Partitioning The Fitness Components Of Rna Populations Evolving In Vitro, Carolina Diaz Arenas, Niles Lehman

Chemistry Faculty Publications and Presentations

All individuals in an evolving population compete for resources, and their performance is measured by a fitness metric. The performance of the individuals is relative to their abilities and to the biotic surroundings – the conditions under which they are competing – and involves many components. Molecules evolving in a test tube can also face complex environments and dynamics, and their fitnessmeasurements should reflect the complexity of various contributing factors as well. Here, the fitnesses of a set of ligase ribozymes evolved by the continuous in vitroevolution system were measured. During these evolution cycles there are three different catalytic …

Measuring And Modeling The Response Characteristics Of The Environmental Phosphate Transducer In Escherichia Coli, Chetan Sood

Open Access Dissertations

The PhoR/PhoB two-component system in Escherichia coli is a biological transducer that senses the limitation of environmental inorganic orthophosphate, the bacteria's preferred source of the essential nutrient phosphate, and transmits that information to the interior of the cell initiating a response that mitigates phosphate starvation. In the first part of this study, we present and apply a fluorescence microscopy technique to measure, in vivo, the dynamic response characteristics of the transducer with single-cell resolution. We report that the transience in the PhoR/PhoB TCS response is consistent with the transducer having a threshold sensitivity to the concentration of environmental phosphate, …

A Force Of Nature: Molecular Mechanisms Of Mechanoperception In Plants, Gabriele B. Monshausen, Elizabeth S. Haswell

Biology Faculty Research

The ability to sense and respond to a wide variety of mechanical stimuli-gravity, touch, osmotic pressure, or the resistance of the cell wall-is a critical feature of every plant cell, whether or not it is specialized for mechanotransduction. Mechanoperceptive events are an essential part of plant life, required for normal growth and development at the cell, tissue, and whole-plant level and for the proper response to an array of biotic and abiotic stresses. One current challenge for plant mechanobiologists is to link these physiological responses to specific mechanoreceptors and signal transduction pathways. Here, we describe recent progress in the identification …

Characterizing The Effects Of Glutaraldehyde On The Ryanodine Receptor Calcium Release Channel, Joshua Dov Strauss

Legacy Theses & Dissertations (2009 - 2024)

Ryanodine receptors (RyR) are large intracellular calcium release channels, which

Nano- And Micro-Second Electrical Pulsing Of B16-F10 Mouse Melanoma Cells: Plasma Membrane And Sub-Cellular Organelle Changes, Yiling Chen

Theses and Dissertations in Biomedical Sciences

High electric field-treated cells are permeable to molecular dye through either opening of pores in the plasma membrane or other unknown processes which can disturb the membrane in an organized way. However, direct morphological evidence is lacking and responses of intracellular organelles are not clear. We used traditional chemical fixatives and biochemical techniques to capture cell membrane and organelle changes immediately after pulsing with high voltage electric field application. Different pulse durations, nanosecond (ns) and microsecond (µs), and field magnitudes, 60 kV/cm and 1.2 kV/cm, were applied to mouse melanoma B16-F10 cells. Two different ns durations (60 and 300 ns) …

Nonosecond Pulsed Electric Field Induced Changes In Dielectric Properties Of Biological Cells, Jie Zhuang

Electrical & Computer Engineering Theses & Dissertations

Nanosecond pulsed electric field induced biological effects have been a focus of research interests since the new millennium. Promising biomedical applications, e.g. tumor treatment and wound healing, are emerging based on this principle. Although the exact mechanisms behind the nanosecond pulse-cell interactions are not completely understood yet, it is generally believed that charging along the cell membranes (including intracellular membranes) and formation of membrane pores trigger subsequent biological responses, and the number and quality of pores are responsible for the cell fate. The immediate charging response of a biological cell to a nanosecond pulsed electric field exposure relies on the …

Single-Molecule Analysis Of The Microtubule Cross-Linking Protein Map65-1 Reveals A Molecular Mechanism For Contact-Angle-Dependent Microtubule Bundling, Amanda Tulin, Sheri Mcclerklin, Yue Huang, Ram Dixit

Biology Faculty Research

Bundling of microtubules (MTs) is critical for the formation of complex MT arrays. In land plants, the interphase cortical MTs form bundles specifically following shallow-angle encounters between them. To investigate how cells select particular MT contact angles for bundling, we used an in vitro reconstitution approach consisting of dynamic MTs and the MT-cross-linking protein MAP65-1. We found that MAP65-1 binds to MTs as monomers and inherently targets antiparallel MTs for bundling. Dwell-time analysis showed that the affinity of MAP65-1 for antiparallel overlapping MTs is about three times higher than its affinity for single MTs and parallel overlapping MTs. We also …

Inhibition Of Voltage-Gated Na+ Current By Nanosecond Pulsed Electric Field (Nspef) Is Not Mediated By Na+ Influx Or Ca²+ Signaling, Vasyl Nesin, Andrei G. Pakhomov

Bioelectrics Publications

In earlier studies, we found that permeabilization of mammalian cells with nsPEF was accompanied by prolonged inhibition of voltage-gated (VG) currents through the plasma membrane. This study explored if the inhibition of VG Na⁺ current (I_Na) resulted from (i) reduction of the transmembrane Na⁺ gradient due to its influx via nsPEF-opened pores, and/or (ii) downregulation of the VG channels by a Ca²⁺ -dependent mechanism. We found that a single 300?ns electric pulse at 1.65.3?kV/cm triggered sustained Na⁺ influx in exposed NG108 cells and in primary chromaffin cells, as detected by increased fluorescence of a …

Protein Folding By 'Levels Of Separation': A Hypothesis, Lesley H. Greene, Terri M. Grant

Chemistry & Biochemistry Faculty Publications

The protein folding process has been studied both computationally and experimentally for over 30 years. To date there is no detailed mechanism to explain the formation of long-range interactions between the transition and native states. Long-range interactions are the principle determinants of the tertiary structure. We present a theoretical model which proposes a mechanism for the acquisition of these interactions as they form in a modified version of ‘degrees of separation’, that we term ‘levels of separation’. It is based on the integration of network science and biochemistry. (C) 2012 Federation of European Biochemical Societies.

Mechanical Forces And Tumor Cells: Insight Into The Biophysical Aspects Of Cancer Progression, Indrajyoti Indra

Wayne State University Dissertations

Mechanical forces play an important role in the regulation of cellular behavior and physiological processes including adhesion, migration, proliferation, tissue repair, embryogenesis and development. In addition, a number of diseases including cancer, have been linked to changes in cellular and extracellular mechanical properties. However, whether a correlation exists between the progression of cancer towards metastasis and mechanical factors has not been clearly defined. Additionally, how a cell responds to changes in extracellular mechanical cues as it gains metastatic abilities is poorly understood. To address these questions, we have utilized a panel of murine breast cancer cell lines with progressive metastatic. …

Analysis Of The Phosphorylated Forms Of Protein Kinase R, Christine Quartararo

Honors Scholar Theses

Protein Kinase R (PKR) is induced by interferon and activated by dsRNA. Subsequent autophosphorylation and phosphorylation of eIF2alpha inhibits viral replication. In the latent state PKR exists as an unphosphorylated monomer. Work in the Cole laboratory has shown two additional states, a phosphorylated monomeric state (pPKRm) and a phosphorylated dimeric state (pPKRd). RNA serves as a scaffold bringing two PKRs together allowing dimerization and autophosphorylation to occur. The contribution of each state to the function of PKR remains unclear. Western blots were performed to examine the phosphorylation states of the essential residues,

T446 and T451. Activity assays have shown activation …

Nanosecond Pulsed Electric Fields Induce A Mitochondria-Independent Apoptosis In B16f10 Melanoma Cells In Vitro, Wentia Elissa Ford

Theses and Dissertations in Biomedical Sciences

Nanosecond pulsed electric fields (nsPEFs) are ultra-short pulses that induce direct electric field and biological effects that initiate apoptosis. Here the application of ten 300ns pulses ranging in electric fields from 12kV/cm-60kV/cm was administered to determine the effects on B16F10 melanoma cells evaluated by in vitro studies. Initial application of nsPEFs demonstrated apoptosis induction in an electric field- and pulse number-dependent manner measured by caspase activation that correlated with decrease in cell viability 24hr post pulse. In addition caspase activity was shown to be independent of calcium mobilization though ions may play a part in other aspects of apoptosis. The …

Selective Field Effects On Intracellular Vacuoles And Vesicle Membranes With Nanosecond Electric Pulses, Ephrem Tekle, Hammou Oubrahim, Sergey M. Dzekunov, Juergen F. Kolb, Karl H. Schoenbach

Bioelectrics Publications

Electric pulses across intact vesicles and cells can lead to transient increase in permeability of their membranes. We studied the integrity of these membranes in response to external electric pulses of high amplitude and submicrosecond duration with a primary aim of achieving selective permeabilization. These effects were examined in two separate model systems comprising of 1), a mixed population of 1,2-di-oleoyl-sn-glycero-3-phosphocholine phospholipid vesicles and in 2), single COS-7 cells, in which large endosomal membrane vacuoles were induced by stimulated endocytosis. It has been shown that large and rapidly varying external electric fields, with pulses shorter than the charging time of …

Theoretical Predictions Of Electromechanical Deformation Of Cells Subjected To High Voltages For Membrane Electroporation, R. P. Joshi, Q. Hu, K. H. Schoenbach, H. P. Hjalmarson

Bioelectrics Publications

An electromechanical analysis based on thin-shell theory is presented to analyze cell shape changes in response to external electric fields. This approach can be extended to include osmotic-pressure changes. Our calculations demonstrate that at large fields, the spherical cell geometry can be significantly modified, and even ellipsoidal forms would be inappropriate to account for the deformation. Values of the surface forces obtained from our calculations are in very good agreement with the 1–10 mN/m range for membrane rupture reported in the literature. The results, in keeping with reports in the literature, demonstrate that the final shape depends on membrane thickness. …

Mechanism For Membrane Electroporation Irreversibility Under High-Intensity, Ultrashort Electrical Pulse Conditions, R. P. Joshi, K. H. Schoenbach

Bioelectrics Publications

An improved electroporation model is used to address membrane irreversibility under ultrashort electric pulse conditions. It is shown that membranes can survive a strong electric pulse and recover provided the pore distribution has a relatively large spread. If, however, the population consists predominantly of larger radii pores, then irreversibility can result. Physically, such a distribution could arise if pores at adjacent sites coalesce. The requirement of close proximity among the pore sites is more easily satisfied in smaller organelles than in outer cell membranes. Model predictions are in keeping with recent observations of cell damage to intracellular organelles (e.g., mitochondria), …

Unusual Structure Of A Human Middle Repetitive Dna, Duminda D. Ratnasinghe

Electronic Theses and Dissertations

The L2Hs sequences are a polymorphic, interspersed, middle repetitive DNA family unique to human genomes. Genomic fingerprinting indicates that these DNAs vary from one individual to another and between tissues of the same individual. Sequence analysis reveals that they are AT-rich (76%) and contain many unusual sequence arrangements (palindromes, inverted and direct repeats). These sequence properties confer on the L2Hs elements the potential to fold into non-B-form structures, a characteristic of recombination hot spots. To test this hypothesis carbodiimide, osmium tetroxide and S$\sb1$ nuclease were used as single-strand specific probes to study a recombinant plasmid, pN6.4.39, containing a single L2Hs …

Characterization Of Two Temperature-Sensitive Mutants Of Escherichia Coli Exhibiting An Altered L22 Ribosomal Protein, Bonnie A. Burnette-Vick

Electronic Theses and Dissertations

Analysis of E. coli strains SK1047 and SK1048 have shown them to be temperature-sensitive, protein-synthesis deficient. An alteration in ribosomal protein L22 was detected in both strains using two dimensional gel electrophoresis. Protein L22 was purified from both strains by reversed phase high performance liquid chromatography and from two dimensional electrophoretic gels. Purified ribosomal protein L22 was labeled by reductive methylation and used in 23S RNA binding assays with and without ribosomal protein L4. At the permissive temperature, protein L22 from SK1047 bound less efficiently than the control while protein L22 from SK1048 bound as efficiently as the control. At …

Rapid Electroosmosis Measurements, James O. Wear

Journal of the Arkansas Academy of Science

A cell has been designed and built that allows for rapid measurement of volume moved in a definite time by electroosmosis. The cell is simple to use and is not very elaborate. Using a water jacket, the cell temperature can be controlled to ± 0.1° C. Measurements are presented for acetonitrile, dimethylformamide, and nitrobenzene at 25° C for applied voltages of 25, 50, 75, and 100 volts.