Tsvet (or Tswett), Mikhail Semenovich
TSVET (OR TSWETT), MIKHAIL SEMENOVICH
(b. Asti, Italy, 14 May 1872; d. Voronezh, Russia, 26 June 1919)
plant physiology, plant biochemistry.
Tsvet was the son of Semen Nikolaevich Tsvet, a Russian civil servant, and Maria de Dorozza, an Italian who had been raised in Russia. His parents had stopped in Asti en route to Switzerland for a cure when he was born. His mother died soon after Tsvet’s birth, and his father had to leave the infant in Lausanne with a nurse while he returned to Russia.
Tsvet’s childhood and youth were spent in Lausanne and Geneva. In 1891 he entered the department of mathematics and physics of the University of Geneva, where his special interests were chemistry, physics, and botany. While still a student, he did his first scientific work on plant anatomy, which received the Davy Prize and was published in 1894. After receiving the baccalaureate in physical and natural sciences in 1893, Tsvet continued work in the general botanical laboratory on his doctoral dissertation, ‐Études de physiologie cellylaire,” which he defended in 1896.
In the summer of 1896 Tsvet moved to Russia, and from the beginning of 1897 he continued his investigations at the laboratory of plant anatomy and physiology of the Academy of Sciences and especially at the St. Petersburg Biological Laboratory, where, however, he did not have an academic post. Not until the autumn of 1897 did he became a botany teacher in the women’s courses at the laboratory.
Since foreign scientific degrees were not legally recognized in Russia, in 1901 Tsvet passed the examination for the master’s degree in botany at Kazan University and defended his thesis, “Fiziko-khimicheskoe stroenie khlorofilnogo zerna” (“The Physicochemical Structure of the Chlorophyll Grain”). In January 1902 he became supernumerary laboratory assistant in the department of plant anatomy and physiology at Warsaw University, and in 1903 he was appointed Privatdozent. Tsvet took on the added duty of teaching botany and microbiology at the Warsaw Veterinary Institute in 1907; a year later he began teaching these subjects at Warsaw Technical University, at which time he resigned from the university. He received the doctorate in botany in 1910 after defending the dissertation on chromophils in the plant and animal kingdoms.
World War I interrupted Tsvet’s scientific work. In the summer of 1915 the Warsaw Polytechnical Institute was evacuated to Moscow and, in 1916, to Nizhni Novgorod (now Gorky). Tsvet devoted much time and effort to organizing the work of the botanical laboratory in both cities and, at Nizhni Novgorod, participated in the organization of the Society of Natural Scientists and of the advanced agricultural courses.
In March 1917 Tsvet became professor of botany and director of the botanical garden at Yuryev (now Tartu) University, and that autumn he began teaching. He worked in Yuryev for only a short time, however. On 23 February 1918 Austrian and German soldiers entered the town, and Yuryev University soon ceased to function as a Russian institution. After the signing of the Treaty of Brest-Litovsk, the university was transferred to Voronezh in August 1918. Tsvet was able to work here for less than a year. His health, uncertain since birth, was finally ruined by excessive work, the displacements, and the hardships of the war years. He died of a chronic heart ailment at the age of forty-seven.
Tsvet’s scientific legacy consists of sixty-nine publications, produced in the relatively short period from 1894 to 1916. He began research at a time when the data and methods of chemistry and physics were becoming more widely used for the discovery of the nature of the life processes. This aided the establishment of plant physiology as an independent science in the mid-nineteenth century and, toward the end of the century, contributed to the formation within plant physiology of such areas of research as cytophysiology. It was in the latter field that Tsvet saw the great possibilities for applying the results of chemical research and methods to achieve a better understanding of the nature of the plant organism. Even in his earliest works, on cytology and plant anatomy, he tried not only to describe the structures but also to discover their significance and functions, thereby creating new techniques and methods that were clearly expressed in his doctoral dissertation.
This tendency appeared more broadly and fruitfully in Tsvet’s research at St. Petersburg. In his Geneva dissertation the central topic was the structure of chloroplasts, while in his later research the main subject was chlorophyll. In “khloroglobine” (“On Chloroglobin”) and “O prirode khloroglobina” (‐On the Natureof Chloroglobin” both 1900), Tsvet showed that the green pigment is found in the chloroplasts in the form of the chlorophyll-albumin complex, which, in analogy with hemoglobin, he called “chloroglobin,”. This term is now generally accepted: but at that time it met with sharp criticism from Tsvet’s contemporaries, who doubted the precision of his research methods.
In “Khlorofilliny i metakhlorofilliny” (“Chlorophyllins and Metachlorophyllins” 1900) Tsvet contested the widespread view that only two pigments were present in the leaf: green chlorophyll and yellow xanthophyll. Using the five existing methods of physical analysis (fractional solution, differential solution, fractional precipitation, “wet sublimation,” and diffusion) to separate the pigments with the least possible alteration, he established that in leaves there are two green pigments–chlorophyll α and β (now known as chlorophyll a and b), differing in color, fluorescence, and spectral absorption. Tsvet obtained a pure sample of the ± from of chlorophyll but not of the β. This led him to attempt to develop a method that would consider the properties of the relationships of the chloroglobin pigments by means of adsorption. Tsvet decided to make the principle of adsorption the basis of this new method that, like filter paper, would allow the extraction from a solution of pigments in unchanged form. He stated his preliminary ideas on this question in his master’s thesis, which contains, as he later recognized, the embryonic from of the method of chromatographic adsorption analysis that he soon developed.
On 30 December 1901, Tsvet presented a report to the Eleventh Congress of Russian Natural Scientists and Physicians at St. Petersburg, “Metody i zadachi fiziologicheskogo issledovania khlorofilla” (“Methods and Problems of Physiological Research on Chlorophyll”), in which he revealed his adsorption method and demonstrated its effects. He made a special, detailed report on 8 March 1903 to the biological section of the Warsaw Society of Natural Scientists, “O novoy kategorii adsorbtsionnykh yavleny i o primenenii ikh k biokhimicheskomu analizu” (“On a New Category of Adsorption Phenomena and on Its Application to Biochemical Analysis”). In it Tsvet described how he set himself the problem of creating a physical method that, in distinction from the chemical method, would, by using adsorption, allow the isolation of plant pigments and the separation of a mixture of such pigments in unchanged form. He experimentally substantiated that many substances could be adsorbed and explained the nature of this phenomenon. He also stated the theoretical bases and practical uses of the method.
In 1906, in Berichte der Deutschen botanischen Gesellschaft, Tsvet published two articles on his method and the data he had obtained with it on the pigment composition of plant leaves. In it he made the first suggestion to call the new method “chromatography” and formulated the law of adsorption replacement, giving a full description of the entire chromatographic setup, including sketches. He also provided a detailed account of the techniques of chromatographic experiments in general and in the study of chlorophyll in particular. His work on the creation of chromatography and its theoretical basis was summed up in his Russian doctoral dissertation, in which he gave a full demonstration of the difference of the chromatographic method from Friedrich Goppelsröder’s capillary analysis.
Having tried 126 different powdered adsorbents, Tsvet found that those most effective for isolating plant pigments were calcium carbonate, sugarcane, and inulin. Grinding fresh leaves in a mixture of petroleum ether and a small amount of alcohol, he obtained an extract that he shook with distilled water to remove the alcohol and then filtered through a tube filled with powdered absorbent. According to the strength of the various adsorptive capacities, the pigments were distributed into six differently colored layers in the tube. Taking the adsorbent from the tube, he obtained a column of powder that could be cut with a knife, after which each pigment could be washed from it separately. Thus Tsvet obtained in a pure form both chlorophyll a and chlorophyll b, and could separate from brown and diatomic algae the previously unknown chlorophyll c (in Tsvet’s terminology, chlorophyll γ) and a number of previously unknown forms of xanthophyll; α α’ α” and β(xanthophyll; α later became known as lutein and xanthophyll β as taraxanthin). In 1911 Tsvet discovered in the leaves of Thuja, and isolated in pure form, a red-yellow pigment that he called rodoxanthin. Having discovered many forms of xanthophyll and their chemical relationship with the yellow pigment carotene, Tsvet suggested in 1911 that they be considered as one general group and called “carotenoids”–a term that has now won general acceptance.
Although Tsvet’s chromotographic method was known to many of his contemporaries and was even used successfully in several laboratories to obtain pure forms of chlorophylls and carotenoids, its acceptance was very limited. The wide use of chromatography began in the 1930’s, when Richard Kuhn, L. Zechmeister, and Paul Karrer simultaneously used it to study the chemistry of carotene and vitamin A. Dozens of other previously unknown forms of carotenoids and their products also were obtained, and colorless substances were isolated and purified: vitamins, hormones, enzymes. On the basis of Tsvet’s method of chromatographic adsorption, a number of new forms of chromatography have been developed: ion-replacement, gas, distributive on paper, thin-layer, sedimentary. They have been widely used in biochemistry, analytical chemistry, biology, medicine, agriculture, and in a number of industries–chemical, pharmaceutical, food processing–where it is necessary to obtain absolutely pure substances, to separate complex mixtures, or to identify unknown compounds.
l. Original Works. Tsvet’s writings include “Études de physiologie cellulaire,” in Bulletin du Laboratoire de botanique générale de l’Université de Genéve, 1 , no. 1 (1896), 123–206, his Geneva doctoral diss.; “Fiziko-khimicheskoe stroenie khlorofilnogo zerna” (“The Physicochemical Structure of the Chlorophyll Grain”), in Trudy Kazanskogo obshchestva estestvoispytatelei, 35 , no. 3 (1901), 1–268, his master’s thesis at Kazan; “O novoy kategorii adsorbtsionnykh yavleny i o primenenii ikh k biokhimicheskomu analizu” (“On a New Category of Adsorption Phenomena and on Its Application to Biochemical Analysis”), in Trudy Varshavskago obshchestva estestvoispytatelei, Otd. biol., 14 (1903), 20–39; “Physikalisch-chemische Studien über das Chlorophyll. Die adsorptionen,” in Berichte der Deutschen botanischen gesellschaft,24 (1906), 316–323; “Adsorptionsanalyse und chromatographische Methode. Anwendung auf die Chemie des Chlorophylls,:” ibid., 384–393; Khromofilly v rastitelnom i zhivotnom mire (“Chromophils in the Plant and Animal Kingdoms” Warsaw, 1910), for which he received the doctorate in botany; and “Über das makro-und mikrochemischen Nachweis des Carotins,” in Berichte der Deutschen botanischen Gesellschaft, 29 (1911), 630–636.
II. Secondary Literature. See C. Dhéré “Michel Tswett,” in Candollea (Geneva), 10 (1943), 23–63; T. Robinson, “Michael Tswett,” in Chimia Annual Studies in the History of Chemistry, 6 (1960), 146–161; E. M. Senchenkova, Mikhail Semenovich Tsvet (Moscow, 1973), with a bibliography of works about Tsvet to 1973; “Otkrytie khromatografii i Akademia nauk” (“The Discovery of Chromatography and the Academy of Sciences,” in Prioda (1974), no. 5, 92–101; and “Michail Semenovic Tsvet und die Chromatographie,” in Schriftenreihe für Geschichte der Naturwissenschaften, Technik und Medizin12 (1975), 111–126; and R. L. M. Singe, “Tsvet, Willstätter, and the Use of Adsorption of Proteins,” in Archives of Biochemistry and Biophysics, supp. 1 (1962), 1–6.
E. M. Senchenkova