04-06-2012, 12:14 PM
ORIGIN IN THE SALT MARSHES
Interest in Bacteriorhodopsin dates back to the early 1970’s
when Walther Stocknius of the University of California at San
Francisco and Dieter Oesterhelt discovered that the protein
exhibited unusual properties when it was exposed to light.
Bacteriorhodopsin is the light harvesting protein in the
purple membrane of a micro organism called Halobacterium
Halobium. This bacterium grows in salt marshes where the salt
concentration is roughly six times that of seawater. It grows the
purple membrane when the oxygen concentration is too low to
sustain respiration. The protein upon the absorption of light
pumps a proton across the membrane generating a chemical
and osmotic potential that serves as an alternative source of
energy. Thus Halobacterium Halobium can switch from
respiration to photosynthesis when the need arises, a unique
capability among organisms.
Survival in harsh environment of a salt marsh where
temperatures can exceed 150(0) F for extended periods of time
requires a robust protein that resist thermal and photochemical
damage. The protein’s cyclicity exceeds 10(6), a value higher
than that of the most synthetic photochromic materials. Thus
the common perception that the biological materials are too
fragile for use in computing devices does not apply to
Bacteriorhodopsin.
101seminartopics.com
Both rhodospin and Bacteriorhodopsin are complex
proteins that include a light absorbing component known as a
“chromophore”. The chromophore absorbs energy from light,
triggering a complex series of internal motions that result in the
dramatic changes in the structure of the larger proteins optical
and electrical characteristics. For example , when rhodopsin
absorbs light in the human eye, the change in structure
releases energy that serves as electrical signals, able to convey
visual information to the brain.