Optical Tweezers Approaches for Probing Multiscale Protein Mechanics and Assembly

Abstract

Multi-step assembly of individual protein building blocks is key to the formation of essential higher-order structures inside and outside of cells. Optical tweezers is a technique well suited to investigate the mechanics and dynamics of these structures at a variety of size scales. In this mini-review, we highlight experiments that have used optical tweezers to investigate protein assembly and mechanics, with a focus on the extracellular matrix protein collagen. These examples demonstrate how optical tweezers can be used to study mechanics across length scales, ranging from the single-molecule level to fibrils to protein networks. We discuss challenges in experimental design and interpretation, opportunities for integration with other experimental modalities, and applications of optical tweezers to current questions in protein mechanics and assembly.

Active microrheology using pulsed optical tweezers to probe viscoelasticity of Lamin A towards diagnosis of laminopathies

“…Thus, the real and imaginary components of the shear moduli, G’(ω) and G’’(ω) respectively, denote the elastic and viscous counterparts of the medium response, which elicit the same information of the medium as does force spectroscopy – with an additional component – which is its dissipative nature. This is performed by measuring the effects of the medium on the motion of a colloidal probe embedded in it – either by measuring its Brownian motion (passive microrheology [39], or its response to a drive (active microrheology [40]. However, to the best of our knowledge, active microrheology has not yet been applied to nucleoskeletal networks, but with some initial efforts to determine the amplitudes of the probe response in cytoskeletal protein keratin as described by Neckermuss et.…”

Line optical tweezers as controllable micromachines: techniques and emerging trends

“…This information could complement more active schemes of determining single-molecule unbinding kinetics under force, 60 which generally require reasonably long lifetimes, or inferring unbinding rates of transient interactions from the frequencydependent shear moduli determined via optical-tweezers microrheology. 11,24 LOT has also been used to investigate how proteins affect interactions between lipid bilayers. Kong and Parthasarathy 61,62 used LOT to measure interactions between pairs of colloidal particles coated with lipid bilayers, some of which included membrane proteins (Fig.…”

“…With the advent of optical tweezers, which use a highly focused laser beam to control positions of micron-sized dielectric particles in three dimensions, a wealth of novel measurements in the fields of biophysics and colloidal physics became possible. [1][2][3][4][5] Optical tweezers can be used to trap micron-sized particles and exert controllable forces on the order of picoNewtons; this is the typical force range to study mechanical properties of biological systems, such as the structure and dynamics of biological molecules; [6][7][8][9][10] assemblies and cells; [11][12][13][14][15][16][17] liposomes as models of cell membranes; 18 to manipulate colloidal systems; 19,20 and to study structure and interactions within solutions and gels. [21][22][23][24] Applications of optical tweezers have progressed further through the ability to direct and shape the profile of the focused laser spot(s).…”

3D magnetically controlled spatiotemporal probing and actuation of collagen networks from a single cell perspective

“…20,21 Macroscale approaches include stretch, 22 compression, 23 or shear rheology 24,25 and report bulk continuum properties of interrogated materials, yet fail to resolve local stiffness heterogeneity inherent to fiber networks. 19 On a smaller scale, atomic force microscopy, [26][27][28] traction force microscopy, 29 and both optical 30 and magnetic tweezers 31 have been used to measure mechanical properties of biomaterials with microand nanometer resolution. In particular, magnetic tweezers offer unimpeded wireless actuation and sensing capabilities within intact models of 3D ECM networks.…”