Biographical Memoirs Volume 57 (1987) / Chapter Skim
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Bessel Kok
Bessel Kok
Pages 124-149
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From page 125... ...
~ was for almost thirty years a distant colleague, a sometime confidant, a scientific admirer, anct a friend all of which accounts for the highly personal tone of this ac125
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From page 126... ...
Bessel Kok was born November 7, HIS, in the village of Hardinxveld, The Netherlands. His father, Tohannes Evert Kok, was the principal of a local school; he is remembered as a talented man who cast himself in the image of a professor, a puritan Calvinist who lived at the hand of the Bible.
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From page 127... ...
One clifficulty was that the subject itself, which had been hot in the early 1940s, was only smoldering in 1948. A second difficulty was that a quantum yield, usually expressed as the reciprocal or quantum number (quanta absorbed per oxygen molecules evolved)
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From page 128... ...
Hence quanta absorbed from a monochromatic light beam couIcl be counted simply as incident quanta. The second feature was an assumption that oxygen evolution of photosynthesis was properly evaluated from pressure changes observed in short light periods minus those observed in alternating short dark periods.
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From page 129... ...
, Bessel discovered a related phenomenon. The curve for the oxygen rate versus the quantum rate hac!
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From page 130... ...
With sufficient turbulence in a dense culture, individual algal cells move rapidly into and out of the illuminated front surface and thereby receive high light only in flashes. It was well known that short flashes could be used with higher efficiency, but the time parameters of the effect were not known.
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From page 131... ...
Now he couIct choose a very small reaction vessel (<5 mm diameter coupled to a volumeter arrangement that measured oxygen evolution with high sensitivity. The broacl scope of the experiments proviclect an unequivocal answer to a twenty-year controversy about the reality of the "photosynthetic unit." The oxygen yield from short flashes confirmed the earlier fincting of R
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From page 132... ...
M Duysens, "In Memory of Bessel Kok," in Proceedings, Fifth International Congress on Photosynthesis, ed.
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From page 133... ...
, then each flash restored absorption of the "700 pigment." Here were reciprocal effects of recI and far-red light like those clescribec! by Robert Emerson for the quantum yield of oxygen evolution.
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From page 134... ...
By that time important publications from the laboratories of Lou Duysens anct Robin Hill had derivecl indepenclently the two-light-reaction hypothesis from other (lata. And the Hill-Benclall mocle!
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From page 135... ...
After several minutes of darkness there was a clelay in oxygen evolution cluring the first seconds of light. Now he observed the oxygen yields from short elec~n sequence after a clerk periocl.
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From page 136... ...
With a characteristic touch, Bessel called his mode} the "oxygen clock." In retrospect it appears that rather small technical improvements lecl Bessel to a mocle} that was simpler and apparently more nearly correct than that which Pierre hacI clerivecI. The history of research on photosynthesis records some acrimonious debates and personal animosities that arose uncler less stressful conditions.
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From page 137... ...
Also surviving is a daughter, now Cornelie Angeline Forbush; two sons, ~ohannes AlIart Bessel and Allart Alexander Bessel; and three grandchildren. Among Bessel's scientific family of colleagues and friends there are many memories.
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From page 138... ...
And I am grateful to many others of the Kok circle who shared their thoughts and recollections, notably, Welcome Bender, Leonard Bongers, George Cheniae, Lou Duysens, George Hoch, Andre Jagendorf, Anne and Pierre Toliot, Olga Owens, and Pete Zill.
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From page 139... ...
Tissues of prismatic celloidin cells containing biocolloids.
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From page 140... ...
The efficiency of light-energy conversion in Chlorella cultures as compared with higher plants. In: Algal Culture from Laboratory to Pilot Plant, ed.
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From page 141... ...
Tijdschr., 70:334-43. 1959 Light induced absorption changes in photosynthetic organisms.
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From page 142... ...
Hoch. The light induced electron paramagnetic resonance signal of photocatalyst P700.
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From page 143... ...
Relationship between light induced EPR signal and pigment P700. In: Photosynthetic Mechanisms in Green Plants.
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From page 144... ...
Extraterrestrial life detection based on oxygen isotope exchange reactions. Science, 155: 1 1 10-12.
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From page 145... ...
Photosynthetic electron transport induced by flashing light in the purple photosynthetic bacterium Rhodospirallum rubrum. Biochim.
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From page 146... ...
Electron transport in photosystem II. In: Proceedings of the Third International Congress on Photosynthes~s Research, ed.
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From page 147... ...
Plastocyanin as the possible site of photosynthetic electron transport inhibition by glutaraldehyde. Plant Physiol., 60:225-29.
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From page 148... ...
Photosynthetic oxygen evolution from hydrogen peroxide. Biochim.
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