Using deuterated cellular lysate obtained from living cells, we will to establish a natural crowding environment for protonated "tracer" or"target" proteins. We will systematically investigate the influence of this natural crowding environment on both the conformation and interaction of of the target proteins using SANS. We have previously tested the feasibility of thisexperiment, and we have been allocated the required preparation of the lysate by the ILL deuteration laboratory through a successfulpeer-reviewed D-lab proposal.