Regensburg 2013 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 2: Interfaces and Thin Films I (joint session with DECHEMA and VDI)

CPP 2.3: Vortrag

Montag, 11. März 2013, 10:15–10:30, H40

Protein Adsorption at the Electrified Air-Water Interface: Implications on Foam Stability — •Björn Braunschweig, Kathrin Engelhardt, and Wolfgang Peukert — University of Erlangen-Nuremberg, Institute of Particle Technology (LFG), Germany

The interfacial structure of ions, water molecules and surface active proteins as well as their tendency to form foam stabilizing networks can considerably influence and control macroscopic properties of foamy dairy products. The molecular structure and composition of adjacent electric double layers are, however, not yet fully understood on a molecular level. We have applied vibrational sum-frequency generation (SFG) as an inherently interfacial specific probe that provides information on composition and conformation of interfacial layers. In particular, we have addressed the adsorption of bovine serum albumin (BSA) at air-water interfaces and show pH depending charging and electric field-induced polar ordering of interfacial molecules such as H₂O and BSA. Varying the bulk pH of protein dilutions, changes the SFG intensity of vibrational bands due to interfacial H₂O dramatically while much weaker changes in the protein related Amide I and carboxylate R-COO⁻ bands are observed. Using the intensity of OH vibrational bands as a measure of the interfacial electric field, we have determined the isoelectric point of interfacial BSA. Based on the molecular level information from our SFG and ellipsometric measurements we can link the microscopic properties of BSA at the air-water interface with macroscopic properties such as the stability of BSA foams.