Abnormally glycosylated IgA leads to IgA nephropathy, the most common cause of renal failure. IgG antibody represents one-third of new drugs currently in development, and its conformational stability under various conditions is essential for biopharmaceuticals. We will unravel the solution structures of human IgA and IgG in a range of buffers. Following our earlier solution structures, we will apply our powerful constrained modelling approach based on neutron and X-ray scattering to study conformational changes in these antibodies that are crucial to disease and biotechnology. We are also investigating the solution structures of complexes formed between the major complement regulator factor H and its target C3b. Complement C3 undergo large conformational changes to form C3b, and different crystal structures reveal different domain arrangements. We will identify the C3b solution structure