Super-Temporal-Resolved Microscopy Reveals Multistep Desorption Kinetics of α-Lactalbumin from Nylon

Abstract

Insight into the mechanisms driving protein-polymer interactions is constantly improving due to advances in experimental and computational methods. In this study, we used super-temporal-resolved microscopy (STReM) to study the interfacial kinetics of a globular protein, α-lactalbumin (α-LA), adsorbing at the water-nylon 6,6 interface. The improved temporal resolution of STReM revealed that residence time distributions involve an additional step in the desorption process. Increasing the ionic strength in the bulk solution accelerated the desorption rate of α-LA, attributed to adsorption-induced conformational changes. Ensemble circular dichroism measurements were used to support a consecutive reaction mechanism. Without the improved temporal resolution of STReM, the desorption intermediate was not resolvable, highlighting both STReM's potential to uncover new kinetic mechanisms and the continuing need to push for better time and space resolution.

A mechanistic examination of salting out in protein–polymer membrane interactions

“…Membrane-based separations have garnered recent interest given the reduced mass transfer resistance, increased surface area for adsorption, and lower column costs in comparison to traditional bead-packed columns (62). Additionally, nylon is a chemically robust and optically transparent polymer stable under laser illumination (40,63) and utilized in many consumer products (64). Surface transport modes and kinetics of transferrin are quantified at the singlemolecule level and used to explain the reduction of peak broadening observed in ensemble separations.…”

“…However, atomistic details of protein surface domains and/or substrate chemistries interacting during protein physisorption is not resolved in comparison to atomistic modeling techniques (35). Heterogeneous protein surface kinetics and transport can be quantified in experimentally challenging systems (36,37) as a result of advancements in single-molecule tracking algorithms (38,39), point spread function engineering techniques (40)(41)(42)(43), and the increased sensitivity of scientific cameras (29).…”

Optical Microscopic Techniques for Synthetic Polymer Characterization

“…Recent work published by Wang et al has provided representative examples of one such method (STReM, Figure ). , In this case, the authors employed a rotating phase mask placed in the microscope detection path to encode additional temporal information in images of fluorescent beads and a dye-labeled protein adsorbing to a surface (Figure a). The orientation of the particle image for rapidly adsorbing and desorbing species represented a snapshot of the point-spread function produced when each particle adsorbed to the surface.…”

“…The surface residence time is determined from the arc length of the point spread function, shown with the blue arrows in parts B and C. The green arrows denote one camera exposure of 100 ms. For events longer than one frame, such as part D, the surface residence time is determined by cumulating its arc lengths in all consecutive frames. Reproduced from Wang, W.; Shen, H.; Moringo, N. A.; Carrejo, N. C.; Ye, F.; Robinson, J. T.; Landes, C. F. Langmuir 2018 , 34 , 6697–6702 (ref ). Copyright 2018 American Chemical Society.…”

Dissection of Interaction Kinetics through Single-Molecule Interaction Simulation

“…Scherer’s laboratory revealed the kinetics and mechanism of the physical passing of particles in an optical ring trap with an adjustable driving force . Landes’ laboratory reported the multistep desorption kinetics of α-lactalbumin from nylon, which provided insight into the mechanisms driving protein–polymer interactions …”