Protein assembly at the air-water interface (AWI) occurs naturally in
many biological processes, and provides a method for creating ordered
biomaterials. However, the factors that control protein self-assembly at
the AWI are generally not well understood. Here, we describe the
behavior of a model protein, human serum albumin minimally labeled with
Texas Red dye (HSA-TR), using a new confocal microscopy technique
(Figure 1). Albumin was observed to form well-ordered, mesoscale
monolayer structures at the AWI (Figure 2), which depended on protein
concentration, ionic strength, redox state and surfactant. We are
investigating thermodynamic and kinetic details of assembly.
Figure 1. Sample chamber and imaging setup.
Figure 2. Morphology of protein assembly varied with ionic strength and addition/removal of reducing agent. Assembly
of HSA-TR (0.010 mg/mL) was investigated under four conditions:
(A) 10 mM phosphate, 30 mM NaN3, 140 mM NaCl,
(B) 10 mM phosphate, 30 mM NaN3, 500 mM NaCl,
(C) 10 mM phosphate only, and
(D) 10 mM phosphate, 30 mM dithiothreitol.
Scale bar = 20 mm