Nanoscience Colloquia

2021 Spring term

Nanoscience colloquia are on Thursdays at 15:15 (unless otherwise stated). This term, colloquia will be held in Zoom and the meeting link will be sent to all NanoLundians shortly before the start. In case you are not on our "All at NanoLund"-mailing list and would like to receive the meeting link, please send an e-mail to webmaster [at] nano [dot] lu [dot] se

June 10^th 15:15

Brain-inspired Computing using Phase Change Memory Devices

Dr. Abu Sebastian, IBM Research, Zurich

Host: Mattias Borg

Talk abstract

There is a significant need to build efficient non-von Neumann computing systems for highly data-centric artificial intelligence related applications. Brain-inspired computing is one such approach that shows significant promise. Memory is expected to play a key role in this form of computing and in particular, phase-change memory (PCM), arguably the most advanced emerging non-volatile memory technology. Brain-inspired computing is likely to be realized in multiple levels of inspiration given a lack of comprehensive understanding of the working principles of the brain. As the first level of inspiration, one could build computing units where memory and processing co-exist in some form. Computational memory is an example where the physical attributes and state dynamics of memory devices are exploited to perform certain computational tasks in place with very high areal and energy efficiency. In a second level of brain-inspired computing using PCM devices, one could design a co-processor comprising multiple cross-bar arrays of PCM devices to accelerate inference and training of deep neural networks. PCM technology could also play a key role in the space of specialized computing substrates for spiking neural networks and this can be viewed as the third level of brain-inspired computing using these devices.

February 11^th 15:15

Nanofluidics for Single Particle Catalysis and Single Molecule Detection flavoured with a little bit of Entrepreneurship

Prof. Christoph Langhammer, Department of Physics, Chalmers University of Technology,
Göteborg

Host: Jonas Tegenfeldt

Talk abstract

Nanofluidics have been developed as a means to control the transport of fluids at the nanoscale and to investigate molecules, such as DNA, in nanoconfinement. In this talk, I will outline the key findings of our research that aims at combining the concept of nanofluidics with optical nanospectroscopy and imaging using visible light, in the context of plasmonics, heterogeneous catalysis and label-free single molecule detection. More specifically, I will tell the story of how realizing the seemingly simple idea of placing a single nanoparticle inside a nanofluidic channel, has enabled us to study catalytic reactions in an entirely new way and to for example visualize that, just like in real life, having good neighbors actually is important. Then I will demonstrate how a light scattering effect highly unwanted in these catalysis experiments, upon a second careful look, opened the door to a groundbreaking new microscopy method. This “Nanofluidic Scattering Microscopy”, which now is the core technology of our startup Envue Technologies AB, makes it possible to image individual biomolecules in free motion inside a nanofluidic structure, and to determine both their mass and hydrodynamic radius, without the need for any labels or surface attachment.

January 21^st 15:15

Virus diffusion at the cell surface: from cell-surface mimics to live cell microscopy

Dr. Marta Bally, Department of Clinical Microbiology & Wallenberg Centre for Molecular Medicine,
Umeå University, e-mail: Marta [dot] bally [at] umu [dot] se

Host: Christelle Prinz

Abstract

Viruses are small pathogenic particle that rely on hijacking a cellular host to replicate and spread. The initial recruitment of a virus particle to the cell surface is a complex dynamic multistep process that requires diffusion of the virus particle through the glycocalyx, the sugar coat covering cells, to reach the cell membrane where it may further diffuse laterally in search of a suitable point of entry. Many viruses, including herpes simplex virus (HSV), initiate their recruitment on the host cell by binding to carbohydrates found on the cell surface and in the glycocalyx, in particular sulfated glycosaminoglycans (GAGs), heparan sulfate for example. This initial recognition is crucial in the viruses’ life cycle as it leads to infection. Equally important is however, the capability of the virus to overcome these interactions upon egress to ensure virus propagation. A tight regulation of such interactions is also essential in the context of virus transport at the cell surface since binding a high amount of receptors with high affinity might trap the virion at the cell surface before it meets entry receptors, while a too weak binding may not be enough for attachment of the particle or to ensure sufficient residence time for entry.

In our work, we study the molecular mechanisms modulating HSV binding, release and diffusion at the cell surface. To do so, our experimental approach is based on probing interactions between individual virus particles and the cell surface using a combination of minimal cell-surface mimics and live cell microscopy. A minimal model of the cell’s carbohydrate coat based on the end-on immobilization of GAG chains makes it possible to study the details of virus-GAG interactions. [1-3] These findings can be further correlated with the behavior of the virus on live cells, where single particle investigation provide fine details on the different steps leading to viral entry. [4]
Taken together, our research contributes to a better understanding of the mechanisms regulating the interaction between a virus and the surface of its host. Such insights will without doubt facilitate the design of more efficient antiviral drugs or vaccines.
 
[1] Altgarde, N., et al., Mucin-like Region of Herpes Simplex Virus Type 1 Attachment Protein Glycoprotein C (gC) Modulates the Virus-Glycosaminoglycan Interaction. Journal of Biological Chemistry, 2015. 290(35): p. 21473-21485.
 
[2]. Peerboom, N., et al., Binding Kinetics and Lateral Mobility of HSV-1 on End-Grafted Sulfated Glycosaminoglycans. Biophysical Journal, 2017. 113(6): p. 1223-1234.
 
[3] Delguste et al. Regulatory Mechanisms of the Mucin-Like Region on Herpes Simplex Virus during Cellular Attachment. ACS Chemical Biology, 2019, 14, 3, 534–542
 
[4] Abidine, Y., et al., Cellular glycosaminoglycans and viral carbohydrates regulate diffusion of herpesvirus simplex virus 1 in the glycocalyx. Submitted.