The annual flu epidemics caused by influenza viruses, especially the influenza A virus, affect about 10–20% of the world’s population each season. This highly contagious illness can trigger serious complications and lead at times to death. A team of scientists led by Bill DeGrado from UC San Francisco have been studying the M2 proton channel from the influenza A virus, which is one of nature’s smallest proton-selective channels and a drug target for this virus. Protein crystallography performed at the Advanced Light Source (ALS) Beamline 8.3.1 helped scientists understand the M2 proton-channel structure and function, and will aid the design of better anti-influenza medications. Read the ALS Science Brief.