Nematic field transfer in a two-dimensional protein fibril assembly

Area of Science:

• Biophysics
• Materials Science
• Polymer Science

Background:

• Understanding interactions in complex biopolymer systems is crucial for fields like biomaterials and drug delivery.
• Beta-lactoglobulin (β-lactoglobulin) can form both long fibrils and short linear aggregates, creating bimodal systems.
• The behavior of such bimodal systems at interfaces, particularly their self-assembly and ordering, remains an active research area.

Purpose of the Study:

• To investigate the spatial organization and orientational behavior of a bimodal solution of β-lactoglobulin fibrils and aggregates at an air-water interface.
• To elucidate the mechanisms driving the observed ordering, specifically the role of aggregate stretching in proximity to fibrils.
• To contribute to the understanding of anisotropic interactions in two-dimensional nematic fields of biopolymers.

Main Methods:

• Atomic Force Microscopy (AFM) was employed to visualize and analyze the structure of the biopolymer assemblies at the air-water interface.
• Numerical simulations were conducted to model the interactions and predict the behavior of the bimodal system.
• Analysis focused on the distribution and orientation of short aggregates relative to long fibrils at varying distances.

Main Results:

• Short, flexible β-lactoglobulin aggregates exhibited distinct orientational preferences relative to long, semiflexible fibrils.
• Perpendicular orientation was observed at very short distances, transitioning to parallel alignment at intermediate distances.
• An isotropic distribution was noted at larger separations, with parallel ordering correlating with aggregate stretching to approach fibrils.

Conclusions:

• Aggregate stretching is a key mechanism enabling short β-lactoglobulin aggregates to achieve close proximity and parallel alignment with fibrils.
• These findings highlight the complex interplay of shape, flexibility, and anisotropic interactions in governing the self-assembly of bimodal biopolymer systems.
• The study provides insights into the transfer of anisotropic interactions within two-dimensional nematic fields at liquid interfaces.