In this dissertation the effects of anionic additives on the stability of proteins have been investigated. For this, distinct yet related issues were examined ranging from general observations to in-depth examinations. The range of topics accounted for different forms of protein stability (e.g. functional versus colloidal). The first chapter reiterates experimentally the role specific ion effects play for protein stability and outlines the limitations therewithin. In the second chapter, the balance between headgroup ionicity and tail hydrophobicity was investigated for amphiphilic, hydrotrope-type molecules. Here it was found, that a compromise between Hofmeister effects and surface activity dominates the effect of ionic additives on solubilization characteristics and protein stability. In the third chapter, a proposed hydrotropism for ATP was investigated. By performing a variety of comparative experiments, it was found that ATP does not exhibit hydrotropic properties, but influences the solubility and stability of proteins via specific ion effects and adenine-specific interactions. In the fourth chapter, phosphorylated resveratrol was investigated as a potential aggregation suppressor and was found to possess stabilizing properties for chicken egg white, amyloid beta and human insulin. Further in-vivo studies using drosophila Alzheimer´s disease models revealed signs of a neuroprotective property for the investigated compound. In the fifth chapter, the goal was to find a suitable replacement of the anti-spotting agent HEDP in automatic dishwasher formulations. Here, several experiments on the colloidal stability of suspended protein particles allowed the identification of promising alternatives. In the last chapter, the effect of ionic additives on the activity and conformational stability of functional proteins (lysozyme, proteases, phytase) was investigated. Individual trends could be recognized while a cohesive theory could not be established due to the complex nature of interconnected phenomena
