Anti-polyubiquitin antibodies and methods of use

An isolated antibody that specifically binds a first polyubiquitin comprising a K11 lysine linkage, wherein:

• a) the antibody does not specifically bind a second polyubiquitin comprising a second lysine linkage, or
• b) wherein the antibody binds a second polyubiquitin comprising a second lysine linkage with a substantially reduced binding affinity as compared to the binding affinity of the antibody for the first polyubiquitin,
• wherein the second lysine linkage differs from a K11 lysine linkage.