When nanoparticles enter a biosytem they rapidly acquire a protein corona. The nature of the outer part of this corona will determine the response of the biosystem to the foreign body. It is generally assumed that protein adsorption is irreversible and therefore that kinetics and the intial environment are dominant. However, recent experiments show that the situation is much more complex. Protein exchange, especially of smaller proteins, does occur on relevant timescales and the protein corona is then determined by a mix of kinetics, affinity and instantaneous environment. A key part in understanding this (and hence response to nanoparticles in the environment) is to determine some the kinetics of model systems. Neutron reflection is perfectly suited to the study of self exchange by the use of protonated/deuterated mixtures and we propose such a study for the protein beta2microglobin.