Seeing a carbon-monoxide molecule escaping from the clutches of the Myoglobin protein
In a stunning tour-de-force
the ejection of carbon dioxide (CO) from a molecule of myoglobin is
directly measured using time-resolved X-ray crystallogaphy.
Myoglobin, also known as the hydrogen
of protein structures, normally binds and transports oxygen molecules
(O) around blood-stream. The actual binding to O is done by a heme group
trapped in the heart of the myoglobin structure. One of the remarkable
things is that by itself, a heme molecule will prefer to bind to CO
rather than O. But when the heme is trapped in myoglobin, the myoglobin
structure ejects the CO from the heme if it happens to bind.
This following movie is a direct measurement of the ejection of CO from
the heme in a molecule of myoglobin. Incredibly sensitive – the movie
occurs in 0.00000316 s of real time – time-resolved X-ray
crystallography is used to directly observe changes in the electron
density of the CO, the heme and myoglobin: