Biophysics Seminar

semester, 2019


Thursday, January 24th 2019
10:10 am:
Biophysics Seminar in 120 PAN
There will be no seminar this week.

Thursday, January 31st 2019
10:10 am:
Biophysics Seminar in 120 PAN
There will be no seminar this week.

Thursday, February 7th 2019
10:10 am:
Biophysics Seminar in 120 PAN
Speaker:  Karunya Kandimalla, Associate Professor at Department of Pharmaceutics of the University of Minnesota
Subject: Nanovehicles for the Diagnosis and Treatment of Blood-Brain Barrier Dysfunction in Neurodegenerative Diseases

The blood brain barrier (BBB) performs dual functions of restricting the entry of xenobiotics into brain while serving as the major signaling and material trafficking portal between plasma and brain. Moreover, the BBB modulates cerebral blood flow to sustain neuronal activity; handles glucose as well as insulin delivery to brain; and maintains immune and inflammatory communication between periphery and brain. These critical BBB functions are disrupted in neurodegenerative disease like Alzheimer’s disease and cerebral amyloid angiopathy. We developed therapeutic nanoparticles to detect and treat BBB dysfunction in these diseases.
For successful brain delivery, a nanoparticle must withstand dominant clearance pressure from the peripheral reticuloendothelial system, marginate from the bulk blood flow to the vascular endothelium, permeate the blood-brain-barrier, and accumulate at the target site. In addition to these common challenges, the nanoparticles intended for cerebrovascular targeting must incorporate appropriate design elements to ensure their retention in the cerebral vasculature. Furthermore, a functionally optimized nanoparticle design demands synergistic amalgamation of the physicochemical properties of various components and their intended physiological effects. Strategies developed in our laboratory to surmount these barriers will be discussed in the talk.


Thursday, February 14th 2019
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Jiali Gao, Department of Chemistry, University of Minnesota
Subject: Allosteric Regulation of Biological Function of Photoreceptor proteins

Major light-harvesting complex of photosystem II (LHCII) is a photoreceptor protein that regulates energy transfer and dissipation in response to rapid fluctuations of light intensity, directly affecting the efficiency of photosynthesis. In this presentation, I will describe an investigation combining molecular dynamics simulation and temperature-jump time-resolved IR spectroscopy to understand the mechanism of energy dissipation in LHCII. I will illustrate an allosteric regulation of the global protein conformational changes induced by a local conformational transition of random coils into α-helices due to changes of external temperature and acidity. The dynamic motions induce close contacts between the associated luteins (Lut) and photoactivated chlorophyll (Chl) chromophores to facilitate fluorescence quenching. In addition, I will discuss a multistate density functional theory designed to model photochemical and charge transfer processes.


Thursday, February 21st 2019
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Gordon Smith, Assistant Professor, Department of Neuroscience, UMN
Subject: Development of large-scale networks in visual cortex.

Sensory perception requires the coordinated activity of tens of thousands of neurons, working together in large-scale networks. As developmental events define and constrain the ultimate capabilities of these networks, it is therefore essential to understand the mechanisms underlying their formation. This talk will present recent work showing that in the developing visual cortex, correlations in spontaneous neural activity define large-scale functional networks with precise local and long-range organization that span millimeters of cortical area. These early networks predict future stimulus-evoked activity well before it can be visually driven, suggesting they form a substrate for building a mature large-scale functional architecture.


Thursday, February 28th 2019
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Paul Jardine, Associate Professor, Department of Diagnostic and Biological Sciences, UMN
Subject: Using Model Systems to Drive Methods Development – The Tale of a Viral RNA

Model systems serve a critical role in the development of new research methodologies. By their nature, model systems are well defined and therefore present excellent opportunities to extend the resolution, range of application, and rigour of advanced biochemical and biophysical experimental techniques. Given that they are, by definition, some of the simplest living systems, viral model systems have been used to advance all areas of molecular biology and biophysics. Here, I will summarise the experimental history of one small component of a viral force generator nanomotor – the prohead RNA (pRNA) component of the bacteriophage phi29 DNA packaging machine – and illustrate how the study of this molecule has revealed fundamental insight into biological macromolecules. The study of pRNA has contributed to the development of experimental approaches that can be adapted to more complex systems in order to address more complex questions in biological systems.


Thursday, March 7th 2019
10:10 am:
Biophysics Seminar in 120 PAN
No speaker this week.

Thursday, March 21st 2019
10:10 am:
Biophysics Seminar in 120 PAN
Spring Break - No speaker this week.

Thursday, March 28th 2019
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Jerome C. Mertz, College of Engineering, Boston University
Subject: Fast, volumetric imaging with microscopes

Fast, volumetric imaging over large scales has been a long-standing challenge in biological microscopy. Camera-based microscopes are typically hampered by the problem of out-of-focus background which undermines image contrast. This background must be reduced, or eliminated, to achieve volumetric imaging. Alternatively, scanning techniques such as confocal and multiphoton microscopy can provide high contrast and high speed, but their generalization to volumetric imaging requires an axial scanning mechanism, which, in general, drastically reduces speed. I will describe a variety of strategies we have developed to enable fast, high-contrast, volumetric imaging over large length scales. These strategies include targeted-illumination widefield microscopy, multi-z confocal microscopy and reverberation multiphoton microscopy. I will discuss the principles of these strategies and present experimental validations.

Faculty Host: Jochen Mueller

Thursday, April 11th 2019
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Mark Sanders, Program Director, University of Minnesota Imaging Centers
Subject: Frontiers in Imaging Technologies and Strategies for Researchers at University Imaging Centers

Core facilities are an essential resource in research institutes.The University Imaging Centers (UIC) has instrumentation, staffing expertise available for teaching, training and outreach in the imaging pipeline from experimental design through analysis. The UICs instrumentation list ranges from nano to mesoscales and includes electron microscopy; super-resolution; single and multi-photon confocal microscope systems; and high-content screening (HCS) systems. We have added tissue clearing, light sheet imaging and, coming soon, a mass spectrometry-based imaging platform in mid-2019. At the mesoscale, the UIC is equipped for in vivo small animal imaging providing investigators with bioluminescence, fluorescence, x-ray, µCT, µPET and ultrasound. How the UIC can help you would be our goal.


Thursday, April 18th 2019
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Erin Sheets, Associate Professor, University of Minnesota, Duluth, Department of Chemistry and Biochemistry
PLEASE NOTE THAT THE SEMINAR FOR THIS WEEK IS CANCELLED
Faculty Host: Elias Puchner

Thursday, April 25th 2019
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Siddarth Karuka, PhD student in Jochen Mueller’s lab, School of Physics and Astronomy
Subject:  Progress Report: Axial Super-Resolution with Two-Photon Microscopy

The Nuclear Envelope (NE) is a ~40 nm space enclosed by the Outer and Inner Nuclear Membrane (ONM and INM), that separates the nucleus from the cytoplasm. Although recent research has identified the NE as a critical signaling hub for a cell, it remains difficult to study with current fluorescence microscopy techniques that are limited to 50 nm axial resolution. To study systems like these, we have developed the dual color z-scan (DC Z-Scan) technique that can achieve axial resolution on the order of a nanometer. We first demonstrate the technique on a supported lipid bilayer, and then use it to measure the thickness of NE, distinguish proteins that reside on the ONM vs INM and study the translocation kinetics of these proteins.


Thursday, May 2nd 2019
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Prof. Louis M. Mansky, Director, Institute for Molecular Virology, University of Minnesota
Subject: "Biophysical and Molecular Studies of Human Retroviral Assembly"

An underexplored aspect of human retrovirus replication are the steps involved in virus particle assembly. In particular the behavior of Gag movement to the plasma membrane, the engagement of particle budding sites, the molecular Gag-Gag interactions that create the immature Gag lattice, and subsequent particle biogenesis and morphogenesis remain poorly understood. Detailed comparative analysis of close relatives can be highly informative for gaining new insight into these steps in virus replication. Our interdisciplinary collaborative research team has made key observations regarding the differences in the pathways for Gag nucleation leading to punctum formation, as well as the nature of particle biogenesis also remain poorly understood aspects of the retrovirus assembly pathway, particularly among human immunodeficiency virus type 1 and its close relatives – i.e., human immunodeficiency virus type 2 (HIV-2) and human T-cell leukemia virus type 1 (HTLV-1). This lecture will discuss ongoing collaborative studies regarding 1) a comparative analysis of immature and mature virus particles and 2) an investigation of the nature of human retrovirus particle biogenesis. To date, our observations provide new insights into a highly significant and poorly understood aspect of the human retroviral life cycle, which has utility in informing intervention strategies.


Thursday, May 9th 2019
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Angel Mancebo, University of Minnesota
Subject: Mitigating phototoxicity in (super-resolution) fluorescence microscopy using precisely calibrated feedback illumination

Fluorescence microscopy is a powerful method for measuring spatial and dynamic information of specifically-labeled proteins in living cells. With the development of superresolution fluorescence microscopy methods diffraction-limited structures can be resolved and quantitative measurements of the spatio-temporal organization of proteins can be made. Because single-molecule localization-based superresolution microscopy methods rely on a spatio-temporally sparse distribution of fluorescent labels, long data acquisition times and high excitation powers are needed to localize a high fraction of molecules. Satisfying these two requirements results in a large amount of energy delivered to the cells by the lasers which is detrimental to cell health. The unfavorable implications are two-fold: unintended cell stress may compromise an experiment; and dying cells become autofluorescent making it impossible to detect single molecules. We developed a technique which makes use of a digital mirror array for accurately and precisely patterning the short-wavelength activation laser. This technique can be applied to any conventional or superresolution fluorescence microscopy experiment that requires spatial patterning as well as optogenetic experiments. We demonstrate this technique on budding yeast for confining the activation laser to only the plasma membrane where proteins with the plextrin homology domain are labeled with the photoactivatable protein mEos2. Patterned photoactivation mitigates cell death which improves single-molecule statistics by enabling longer acquisition times and an increase in the number of single-molecule localizations.


Thursday, May 16th 2019
10:10 am:
Biophysics Seminar in 120 PAN
There will be no seminar this week.

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