The heat absorbing properties of interest to us relate to the shape of certain molecules like CO2, as in this article and animation below. (skepticalscience.com)
Free radicals are atoms or groups of atoms with an odd number of electrons and can be formed when oxygen interacts with certain molecules in the body. (irwinnaturals.com)
A pancreatic cancer vaccine could be made of whole pancreatic cancer cells, treated so they can't replicate, but modified to present certain molecules on the surface of those cells. (discovermagazine.com)