Date: 31.03.2023, Time: 15:30h
The talk will be streamed online.

Prof. Khalid Salaita, Emory University

DNA-based machines that walk by converting chemical energy into controlled motion could be useful in applications such as next-generation sensors, drug-delivery platforms and biological computing. Despite their exquisite programmability, DNA-based walkers are challenging to work with because of their low fidelity and slow rates (∼1 nm min-1). It would be highly desirable to create synthetic motors that can start to approach the performance of biological motor proteins such as myosin and dynein. In this talk, I will describe the development of DNA-based machines that roll rather than walk, and consequently have a maximum speed and processivity that is three orders of magnitude greater than the maximum for conventional DNA motors. The motors are made from DNA-coated spherical particles that hybridize to a surface modified with complementary RNA; the motion is achieved through the addition of RNase H, which selectively hydrolyses the hybridized RNA but not single stranded RNA. This type of motion has been described as a burnt-bridge Brownian ratchet. The spherical motors can move in a self-avoiding manner, and anisotropic particles, such as dimerized or rod-shaped particles, can travel linearly (ballistically) without a track or external force. Motors display speeds of ~microns per minute and millimeter processivity which is starting to approach the speed and processivity of biological motors. I will highlight our recent work integrating logic gate operations into the motors to control their stop and go motion. I will also show that the motors can be used to detect SARS-CoV-2 whole virions and single nucleotide polymorphisms (SNPs) by measuring particle displacement using a smartphone camera. This type of sensing is of interest because it is far-from-equilibrium and thus provides a new conceptual approach to chemical sensing that is based on mechanotransduction. Finally, I will show that this type of motion is highly generalizable, spanning cargo that range in size from 10 nm to 10's of microns.