California NanoSystems Institute
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December 02, 2014

Xiaojiang Chen, PhD
Professor, Molecular and Computational Biology; Chemistry; Norris Cancer Center
University of Southern California,
"The Current Structural/Functional Understanding of SV40 Large T Antigen, an Efficient Nanomachine"


Simian virus 40 large T antigen (LTag) is both a potent oncogenic protein and an efficient nanomachine in the form of a helicase that harnesses the energy from ATP binding/hydrolysis to initiate origin DNA melting and unwind replication forks. This protein with 708 amino acids has multiple folded-domains that can self-assembles into a hexamer, form a double hexamer at origin DNA, and interacts with many cellular proteins, which enable it to possess a wide range of biological functions in cell transformation, and in SV40 DNA replication in the context of mammalian cells. In fact, it’s one of the few known examples of extraordinarily versatile protein, and has been intensively investigated over the last 30 years. The advancement in the structural /biological studies of LTag, combined with cross-disciplinary approaches, such as computational, biochemical/biophysics, over recent years has provided mechanistic insights into many of its functions. Here, we will present the past and updated studies on the structural-functional understanding of this multi-functional protein, with focus on its motor functions related to DNA replication.

November 06, 2014

Laura Waller, PhD
Assistant Professor, Department of Electrical Engineering and Computer Sciences
University of California, Berkeley

“Computational illumination for high-resolution 3D phase microscopy”


This talk will describe new methods for achieving 3D and high-resolution images in a commercial microscope. Our setup involves replacing the illumination unit of the microscope with a programmable LED array for computational illumination. Using a combination of optical hardware and post-processing software, we achieve real-time darkfield, 3D and phase imaging. By rapidly coding illumination angles on the LED array, we further show that our dataset can be treated as a light field, in order to recover 3D and super-resolution results (6x better resolution than the objective allows). In addition, we benefit from long working distances and focus insensitivity, as well as embedded digital aberration correction. The result is a high-resolution gigapixel image of both phase and absorption information in 3D with fast capture times. Such computational approaches to optical microscopy add significant new capabilities to commercial microscopes without much cost or hardware modification.
October 14, 2014

Franz J. Giessibl, PhD
Professor, Department of Physics
University of Regensburg, Germany

“A Passion for the Picoscale”


Scanning probe microscopy has brought us a fascinating access to the world of single atoms. The atomic force microscope (AFM), offspring of the scanning tunneling microscope (STM), has rapidly found wider applications than the STM because it allows us to image any sample without requiring electrical conduction. However, the spatial resolution of AFM initially was inferior to the one of the STM. In the last years, the AFM’s resolution has been boosted beyond STM, e.g. when imaging organic molecules and even revealing electron clouds within single atoms. Height resolution reaches sub-picometer values, and forces below piconewtons can be measured. The origin of the forces covers chemical bonding forces, Pauli repulsion forces as well as exchange forces.

Is this the end of the development of AFM? The answer is a clear no, as there are some inspiring challenges that require great future developmental efforts.

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