Wald (Wald), George( American biochemist and Nobel Prize in Physiology or Medicine, 1967)
Comments for Wald (Wald), George
Biography Wald (Wald), George
genus. November 18, 1906
The American biochemist George Wald was born in New York in the family of Isaac Wald, tailor, sewing factory, and Ernestine (Rozenman) Wald, immigrant from Germany. U. received his primary and secondary education in public schools in Brooklyn (New York). After assignment to the degree of Bachelor of Science in 1927. in the name of Washington College at New York University, he enrolled at Columbia University, where in 1928. he was awarded the degree of Master of Science, and in 1932. - Doctor of Philosophy.
At Columbia University have. studied vision led Selig Hecht, an outstanding, world-renowned biophysics. Hecht completed numerous studies on the physiology of the eye, but mainly interested in clarifying the biochemistry of. In 1877, Mr.. Franz Boll found that when light excised retina (the inner membrane of the eye) frog weak light was pink, with a strong light its color turns white. Complementing the work of Ball, William Kyuhn showed that the retina contains a visual pigment that is now known under the name 'rhodopsin', which absorbs the light falls on the magenta, yellow and white fractions and synthesized in the dark again. Human retina consists of a set of light-sensitive rod and cone cells. Kyuhn found, . that rhodopsin is present only in rod cells, . that, . is known, . provide twilight, . black and white vision, . but do not perceive colors; cone cells, . are elements of color vision, . much less sensitive and thus are active only when illuminated.,
. Based on the study Kyuhna, . Hatch suggested, . that the primary event in vision occurs in the decay of rhodopsin to other products under the influence of light, . one of which is electrical stimulation of the optic nerve, . and thus there is a receptor potential,
. In parallel with the phototransformation of visual pigments has been characterized by their permanent rehabilitation.
'I left the lab Hecht, - said William, - with a great desire to do the molecules'. National Research Society on the distribution of scholarships in biology provided him in 1932. opportunity to continue work on the vision under the leadership of Otto Warburg at the Kaiser Wilhelm Institute in Berlin. In the laboratory Warburg Y. identified rhodopsin and its decay products, one of which (protein), he called opsin. The second product was aldehyde of vitamin A. Although, . as subsequently admitted U., . 'good reason' to investigate vitamin A in the retina (eg, . knew, . that night blindness is a symptom of deficiency of this vitamin), . 'it is difficult even to imagine, . that vitamins are directly involved in physiological processes'.,
. Knowing that the Swiss chemist Paul Karrer recently established structure of vitamin A, Y
. went to his laboratory in Zurich to complete the identification of vitamin A in the rhodopsin. Subsequent studies he completed in 1933. with Otto Meyerhof in Heidelberg University, after which he returned to the United States, where during the year was a scholar of the University of Chicago. In 1934, Mr.. He became a professor of biochemistry, in the next year - teacher of biology at Harvard University. In 1944, Mr.. He was appointed Associate professoom, and in 1948. - A full professor.
In the late 30's and 40-ies. U. investigated the chemical properties of rhodopsin and its decay products under the influence of various modes of illumination in different species. Based on his experiments he concluded that 'all the visual pigments, which are known to have been built on a unified plan: composed of retinal (vitamin A aldehyde), associated with ... opsin '.
By 1950, Mr.. U. already had enough information about the rhodopsin to try to synthesize a substance. Together with his graduate student Ruth Hubbard spent his first experience with the use of vitamin A in the form of fish oil. As they expected, the reaction formed rhodopsin, which fade and then rebuilt with different modes of illumination in the same way as the natural rhodopsin. To confirm these results have. Hubbard and repeated the experiment using pure crystalline vitamin A. However, in this case, rhodopsin is not synthesized.
Soon the experimenters realized that they had not failed, and faced with the mechanism of action of rhodopsin. Retinal is the molecule with a long 'arm' of carbon atoms, which may be located in several different ways, each location leads to the existence of so-called isomer. The most stable trans-isomer, formed of crystalline vitamin A, in which carbon atoms are arranged in one plane. Further investigation revealed the existence of other forms are not exposed to light retinal (11-cis-isomer), exactly corresponding protein molecule opsin. 'This deviation from the plane - explained U., - seemed to make such an unstable molecule that can be difficult to detect its. However, it became clear that the resultant 11-cis-isomeric form of retinal moderately stable, but only under condition of preservation of darkness'. Since the direct trans-isomer does not match the binding sites on the molecule, opsin, illuminated rhodopsin dissociates into retinal (vitamin A aldehyde) and opsin.
Y. explained that "the only action of light in the visual process is the isomerization of the chromophore (atomic group, causing a color) the visual pigment 11-cis-isomeric form in the trans-isomeric. What is ... represents the consequences of this single light reaction '. In an interview with 'New Worker' Y. presented his idea more simply: 'The molecule of vitamin A, as is known, can change its isomeric forms ... The role of light in the visual process is the straightening of the molecule of vitamin A in its natural form. All other processes in the eye, may occur in the dark '.
In the late 50-ies. U. began studying the cones of the retina, the receptors of light effect. During the ten years before Ragnar Granit has shown that the human eye contains three types of cone cells, each sensitive to different colors of the spectrum. U. with Paul K. Brown, other colleagues received a biochemical rationale for studies of granite, having determined that each cone contains one of the three pigments: blue, green or red. All pigments contain the same chromophore, 11-cis-retinal form, the differences between them are due to different proteins (opsin). Violations of color vision occur in the absence of certain human genes, which carry out the synthesis of one or more specialized opsin.
W., Granite and X. Keffer Hartlayn in 1967. shared the Nobel Prize in Physiology or Medicine "for discoveries concerning the primary physiological and chemical processes visual '. Presenting the award, Carl Gustaf Bernhard of the Karolinska Institute Congratulates Y. and noted its 'ability to penetrate deeply into biological processes and high efficiency of biological methods used by them' in the identification of visual pigments and their precursors. 'As an additional result you are able to determine the absorption spectra of different types of cones, which serve to color vision, - continued Bernhard. - Your most important discovery of the primary molecular reaction to light in the retina represents significant progress in the field of view, t. to. she plays the role of photoreceptors trigger all living animals'.
Between 1968 and 1980. U. was a professor of biology at Harvard. For many years he followed his own commandments, . that the teacher should 'be the same student, . but having a more extensive knowledge, . than others, . strive to create a creative atmosphere and live the student life as, . to become a part of it '.,
. In free time I
. participated in the political and social actions. He strongly supported the student movement 60's and 70-ies. and became an active participant in the mass rallies against the Vietnam War, the construction of nuclear power plants and the accumulation of weapons.
In 1931, Mr.. U. married Frances Kingsley, they had two sons. They separated in 1957,. A year later. married Ruth Hubbard; they have a son and a daughter.
Among the honorary awards have. - Albert Lasker Award of the National Association of Health (1953), . Rumford Medal of the American Academy of Arts and Sciences (1959), . Frederic Ives Medal Ophthalmologic Society of America (1966), . Memorial Prize Daketta Jones Fund, Helen Hay Whitney (1967) and the Paul Karrer Medal of Chemistry, University of Zurich, . which he was awarded jointly with his wife (1967),
. He - a member of the National Academy of Sciences, American Philosophical Society, the American Academy of Arts and Sciences and Ophthalmologic Society of America.