Proteins are ubiquitous and play a critical role in many areas from living organisms to protein microchips. In humans, serum albumin has a prominent role in the foreign body response since it is the rst protein which will interact with e.g. an implant or stent. In this study, we focused on the inuence of salts (i.e., dierent cations (Y 3+ , La 3+ ) and anions (Cl − , I − )) on bovine serum albumin (BSA) in terms of its bulk behaviour, as well as its role of charges for the protein adsorption at the solid-liquid interface in order to understand and control the underlying molecular mechanisms and 1 interactions. This is part of our group's eort to gain a deep understanding of proteinprotein and protein-surface interactions in the presence of multivalent ions. In the bulk, we found not only multivalent cation-triggered phase transitions, but also a dependence on the anions. The induced attractive interactions were observed to increase from Cl − < NO − 3 < I − , resulting in iodide preventing re-entrant condensation and promoting liquidliquid phase separation in bulk. Using ellipsometry and a quartz-crystal microbalance with dissipation (QCM-D), we obtained insight into the growth of the protein adsorption layer thickness. Importantly, we found that phase transitions at the substrate can be triggered by certain interface properties, whether they exist in the bulk solution or not.Through the use of a hydrophilic, negatively charged surface (SiO 2 ), the direct binding of anions to the interface was prevented. Interestingly, this led to re-entrant adsorption even in the absence of re-entrant condensation in bulk. However, the overall amount of adsorbed protein was enhanced through stronger attractive protein-protein interactions in the presence of iodide salts. These ndings illustrate how carefully chosen surface properties and salts can directly steer the binding of anions and cations, which guide protein behaviour, thus paving the way for specic/triggered protein-protein, proteinsalt, and protein-surface interactions.

No abstract

No abstract