Biophysical Society 67th Annual Meeting Program Guide

ing that the probe only interacts with the surface for only a small por tion of its oscillation, thus minimizing lateral stress while the probe is scanned across the surface. Recently, WaveMode was used to image HSV-1 virus capsids on a soft rat-liver nuclei substrate. One of the challenges for imaging this type of sample with AFM is that the capsid is expected to be stiffer than the surrounding substrate, which could cause the capsid to be pushed into the nuclei. It has been shown that the nucleus exhibits a viscoelastic stiffness response, which increases its stiffness as the AFM indentation velocity increases. Thus, imaging in WaveMode causes the nucleus to stabilize around the capsid and allows for clean images of the complex. Speaker Eugene Ogorodnik, Technical Sales and Applications, Nanosurf 4:30 PM – 6:00 PM Sutter Instrument Scientists Empowering Scientists For almost 50 years, Sutter Instrument has been collaborating with researchers. During this period, there have been many technologi cal evolutions in both imaging and patch clamp electrophysiology. Sutter has introduced many new product families, including pipette pullers, manipulators, light sources, wavelength switchers, specialized microscopes and, most recently, fully integrated patch clamp amplifier systems. At this presentation, we will teach techniques, tips and tricks for both pipette fabrication and electrophysiology, and showcase new products, such as the Lambda 721 Optical Beam Combiner and the NAN™ Open-Design Upright Microscope. Registration is available online through the Sutter Event Registration Page (https://sutter.eventbrite.com). The number of available spaces is limited, and registrations are accepted on a first-come-first-served basis. Speakers Chris Ballard, Vice President, Sutter Instrument Adair Oesterle, Support Engineer, Sutter Instrument Telly Galiatsatos, Product Manager, Patch Clamp Systems, Sutter Instrument

STELLARIS confocal platform. In particular, mfD has been implemented as a TauSense tool named TauInteraction. The advanced tools of STELLARIS confocal platform are also avail able under cryogenic conditions, enabling advanced cryo correlative (cryo-CLEM) studies. Here, new cellular mechanisms can be unraveled. Intracellular protein interactions can be further resolved by cryo elec tron microscopy (EM) down to the subnanometer scale. To increase the success rate of these types of studies, Cryo light microscopy enables the identification of specific target proteins prior to the EM imaging. LIGHTNING and TauSense provide high accuracy in identifying and targeting the desired proteins for further analysis. Speaker Giulia Ossato, Senior Product Manager, Leica Microsystems 2:30 PM – 4:00 PM Nanosurf Application of Low-Force Photothermal Off-Resonance Tapping for In Situ AFM Imaging of Soft Virus Capsids The atomic force microscope (AFM) is becoming an essential tool to image and measure the mechanical properties of biological samples in near-physiological conditions. Unlike optical or electron microscopy techniques, samples measured by AFM require very minimal prepara tion. The primary feedback mechanism in AFM is the force between the sample being measured and a probe. When working with soft bio logical samples, the force generated by the probe can often be enough to cause irreversible damage, or in some cases, physically remove the sample from the substrate if lateral stresses become too high. For this reason, imaging soft biological materials such as virus capsids on top of another soft substrate material such as cells or tissue continues to be a challenge for the AFM community. One of the most popular dynamic force AFM imaging techniques (sometimes called amplitude modulation or tapping mode) works by trying to maintain the amplitude of an oscillating probe near is reso nance frequency as it traces the contours of a surface. While it is sim ple enough to measure changes in amplitude, using this to determine how much force was applied to the surface requires complex technical modeling, which is oftentimes beyond the interest of general microsco pists. More often, it takes a skilled AFM operator to instinctively know what settings to use for any specific sample. Developing this level of expertise has a steep learning curve and it is often frustrating for those new to the technique. Photothermal off-resonance tapping mode (e.g. WaveMode) is a tech nique that combines the force selectivity of contact mode while at the same time minimizing sheer or lateral forces, which can displace loosely bound or soft materials. The benefits of a photothermally actu ated cantilever for imaging at or near the resonance of the cantilever for biological applications has been well documented. Using the same photothermal light source to drive the cantilever off-resonance is a more novel technique. First, since the measurement is done off-reso nance, the Q-factor of the cantilever is irrelevant, and thus the imaging bandwidth increases. Second, because the feedback mechanism is force-deflection via amplitude truncation and not peak-to-peak ampli tude reduction, the force that is applied to the sample can be precisely controlled down to the low pico-Newton range. Third, off-resonance tapping mode is still considered an intermittent contact mode mean

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