news of the week COURTESY O F REU T ABRAMOVICH & ALYSSA CO BB (BOT H)
AUGUST 23, 20 10 EDITED BY WILLIAM G. SCHULZ & KENNETH J. MOORE
UNCOVERING A NEW CHLOROPHYLL NATURAL PRODUCTS CHEMISTRY:
Researchers find a fifth type of the ubiquitous pigment in coastal Australia
F
OR THE FIRST TIME in more than 60 years, re-
searchers have found a new kind of chlorophyll, the pigment used by both plants and bacteria to catch sunlight and convert it into energy by means of photosynthesis (Science, DOI: 10.1126/science.1191127). The newly christened chlorophyll f was found in cyanobacteria living in rocky outcroppings off the west coast of Australia. It absorbs redder wavelengths of light— stepping beyond the visible to the infrared whose structure they elucidated using nurange—than its four chlorophyll siblings clear magnetic resonance spectroscopy. and thus widens the spectrum of light Chlorophyll f differs only slightly from known to be harvested by photosynthetic chlorophylls a, b, and d. Its uniqueness organisms. The finding might be exploited primarily involves placement of a formyl by those aiming to use biotechnology to group on carbon-2 of the pigment molproduce renewable energy from light. ecule, whereas the same formyl group reThe discovery of this fifth chlorophyll sides on C-3 of chlorophyll d, for example. pigment was “totally unexpected,” says Min Chen, a This minor chemical modification “changes the specbiochemist at the University of Sydney, who led the tral properties dramatically,” allowing chlorophyll f study. The last time a chlorophyll pigment was discovto absorb wavelengths of light to about 760 nm, some ered was in 1943. For decades, most researchers thought 20 nm deeper into the infrared than chlorophyll d, this chlorophyll d was actually a laboratory artifact beChen says. Chlorophyll-f-producing cyanobacteria cause it could not be reproducibly found in nature. Then living in stromatolites have an advantage because they in 1996, Japanese researchers finally discovered a cycan absorb the longer wavelengths of light that percoanobacterium that carries out photosynthesis primarily late deep within the rocky formations, she adds. with chlorophyll d, which also absorbs in the infrared. “This is a very important new development,” says Chen and her colleagues were Robert Blankenship, who studies looking for microorganisms that photosynthetic reactions at WashR´ R´´ produce chlorophyll d in an Ausington University in St. Louis. The tralian coastal area called Hamelin finding “could have biotechnologiR Pool when they unsuspectingly cal implications because it permits N N collected bacteria that produce use of a wider range of the solar Mg chlorophyll f. In the shallow waspectrum and could possibly conN N ters of Hamelin Pool, biofilms of tribute to improving the efficiency cyanobacteria form hard, rocky of photosynthesis,” for example, in structures called stromatolites. biofuel production. O O The researchers picked up some Next up, Chen and her colOCH O 3 of the stromatolites, ground them leagues are planning to further OC20H39 up, and cultured in red light the cystudy the function of chlorophyll Chlorophyll a: R = CH3, R´= CHCH2, R´´ = CH3 anobacteria growing inside them, f in photosynthesis and narrow b: R = CH3, R´= CHCH2, R´´ = CHO only to discover that they were prodown the exact species of cyd: R = CH3, R´= CHO, R´´ = CH3 ducing chlorophyll d as well as an anobacteria that produces the new f: R = CHO, R´= CHCH2, R´´ = CH3 unknown pigment, chlorophyll f, pigment.—SARAH EVERTS WWW.CEN-ONLINE.ORG
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Chlorophyll f was discovered in cyanobacteria living in rocky stromatolites (inset) on the west coast of Australia.
