Formation, structure, and reproducibility of cerato-ulmin hydrophobin-coated bubbles

Abstract

The physical characteristics of both the submicron and micron bubble films were investigated. For the submicron bubbles, small-angle x-ray scattering (SAXS) and small-angle neutron scattering (SANS) show the bubbles are cylindrical with a ~70 nm cross-sectional diameter and film thickness of 15 nm, the equivalent of 5 CU proteins. Atomic force microscopy (AFM) of collapsed microbubbles has the same film thickness suggesting that film thickness is independent of CU bubble size. To isolate singular bubble sizes during agitation, a new experimental apparatus was designed and built to agitate the CU solutions in a controlled, reproducible method. The apparatus houses a horizontal microscope for imaging CU bubbles directly after agitation and observing their motion as they rise through the solution. Results show a positive correlation with agitation frequency and bubble size, with a steady number density for all sizes up to the maximum size at that frequency value.