Understanding the nature of protein translocating events through bacterial pores offers an uniqueopportunity to develop novel drug delivery systems, whilst also providing invaluable informationrelating to their biology. As part of this proposal we wish to evaluate protein translocation eventsthrough lipid nanodiscs containing protective antigen (PA), a pore forming protein produced by the bacterium Bacillus anthracis. The ability of this pore to translocate large proteins is well documented, current theory states these must unfold to allow for passage through lumen, an energy intensive process. Our hypothesis is that proteins require the PA pore to expand allowing for transit. The key objective is to determine the PA pore shape, solution structure and structural alterations that occur as a function of pH using SANS, complementing our neutron reflectometry experiment at ILL (8-03-848).