What is a spike protein?

•A viral spike protein is like a key that “unlocks the door” to gain access to the cells of a specific host — humans, in this case.
•The researchers defined the structure of 2019-nCoV’s spike protein using a technique called cryogenic electron microscopy, or “Cryo-EM”.
•This involves cooling the protein to below -150 degree Celsius so that it crystallises and then its structure can be determined with near-atomic resolution.