(b. Freiburg im Breisgau, Germany, 26 December 1825; d. Lake Constance, Germany, 10 August 1895)
Ernst Felix Immanuel Hoppe was the tenth child of Ernst Hoppe, a minister, and the former Friederike Nitzsch; there had been theologians and scholars on both sides of the family. Felix’s mother died when he was six years old, and his father died three years later; the boy was raised by his brother-in-law Dr. Seyler. In 1864 he was formally adopted by his guardian and changed his name to Hoppe-Seyler. He married Agnes Franziska Maria Borstein in 1858; they had a son and a daughter.
After graduation from the Gymnasium of the orphans’ home at Halle in 1846, Hoppe entered the medical school there; the following year he transferred to Leipzig, where he worked in the laboratory of the physiological chemist K. G. Lehmann and studied with the three Weber brothers, who befriended him. He completed his medical studies in 1850 at Berlin and received the M.D. in 1851, having submitted a dissertation describing a histological and chemical study of cartilage. After a year of further clinical training in Prague, he began to practice medicine in Berlin but found this uncongenial because the demands of his practice made scientific work impossible. In 1854 Hoppe became prosector in anatomy at Greifswald; because research possibilities were too limited here as well, he eagerly accepted a similar post in the new pathological institute organized in Berlin by Virchow, who made Hoppe head of the chemical laboratory and greatly encouraged his investigative efforts. There soon flowed from this laboratory a succession of papers on a variety of physiological-chemical topics. In 1860 Hoppe was appointed associate professor on the medical faculty at Berlin, and in the following year he moved to Tübingen as professor of applied chemistry at the Faculty of Medicine. After the Franco-Prussian War, Hoppe-Seyler went in 1872 to Strasbourg, then under German occupation, to become professor of physiological chemistry, the post he occupied at the time of his death.
Hoppe-Seyler’s initial researches, during the 1850’s, dealt largely with the improvement of analytical methods for the chemical study of biological fluids, such as blood and urine. These studies led to his significant researches on the substance he called hemoglobin, the absorption spectrum of which he described in 1862; in this work he introduced the new spectroscope of Bunsen and Kirchhoff into medical chemistry. During the succeeding years Hoppe-Seyler demonstrated that hemoglobin binds oxygen loosely to form oxyhemoglobin, which can give up its oxygen to the body tissues. He extended Claude Bernard’s observations on the toxic effect of carbon monoxide by showing that this gas displaced the oxygen of oxyhemoglobin. Hoppe-Seyler’s chemical and spectroscopic researches showed that treatment of hemoglobin with acid produces a material he named hemochromogen, which is readily cleaved to yield the iron-containing hematin and resembles the products formed upon the interaction of isolated hematin with various proteins. Upon treatment of hematin with strong acids, he obtained an iron-free pigment which he named hematoporphyrin. His characterization of these materials, together with the parallel work of G. G. Stokes on the reduction of oxyhemoglobin, laid the foundations of all subsequent research on the chemistry of hemoglobin and of iron-porphyrin-containing proteins, as well as on their physiological role in respiration.
Hoppe-Seyler’s studies on hemoglobin were largely completed during his stay in Tübingen, where he also conducted important work on lecithin and cholesterol. He contributed to the demonstration that these two substances are widely distributed constituents of biological systems; and his student C. Diakonow added valuable chemical data to those provided earlier by Adolph Strecker on the chemical constitution of lecithin, recognized to represent a compound formed by the union of choline, fatty acids, and glycerophosphate. Hoppe-Seyler and his students also showed that lecithin is combined with proteins to form conjugated proteins (vitellins), such as those found in egg yolk. This interest in phosphorus-containing proteins led him to urge his student Friedrich Miescher to examine more closely the chemical composition of cell nuclei; Miescher’s discovery of nuclein in 1869 marks the starting point of a development that led to the later recognition of the role of deoxyribonucleic acids (DNA) in heredity. Hoppe-Seyler himself established the presence of nuclein in yeast, and subsequent work during the 1880’s by his assistant Albrecht Kossel provided the chemical basis for the later elucidation of the structure of the nucleic acids.
Hoppe-Seyler’s personal researches at Strasbourg dealt mostly with problems relating to the nature of intracellular oxidation processes, although he continued his hemoglobin studies and also showed that the pigment of chlorophyll resembles the porphyrin of hemoglobin. During the 1870’s he participated actively in the discussions concerning the nature of biological catalysis, and he advocated the theory that the hydrogen atoms of metabolites were “activated” to react with respiratory oxygen. In connection with these discussions Hoppe-Seyler and his students conducted extensive studies on the products formed in the fermentation of various substances, notably cellulose, and in the putrefaction of proteins, especially the amino acid tyrosine.
During his years in Strasbourg, Hoppe-Seyler became the leading German protagonist of the separation of physiological chemistry from medical physiology; and in 1877 he founded the Zeitschrift für physiologische Chemie to promote the interests of bio-chemistry as an active and independent area of science. Despite the opposition of some physiologists, notably Eduard Pflüger, the influence of Hoppe-Seyler’s ideas grew, in large part because of the successes achieved by his students (especially Eugen Baumann and Kossel) and by his colleague at Heidelberg, Wilhelm Kühne. These two men, through their personal researches and those of their disciples, established German biochemistry and profoundly influenced the development of this subject in other countries, especially the United States.
I. Original Works. Hoppe-Seyler’s books include Handbuch der physiologisch and pathologisch-chemischen Analyse (Berlin, 1858; 6th ed., 1893); and Physiologische chemie, 4 pts. (Berlin, 1877–1881). Some of the research reports from his Tübingen laboratory were collected in his Medicinisch-chemische Untersuchungen (Berlin, 1866–1871). He published about 150 articles, not including the many from his laboratory, by his students and research assistants, without his name as a coauthor. Among his most important papers are “Beiträge zur Kenntnis der Constitution des Blutes,” in Medicinisch-chemische Untersuchungen, pp. 133–150, 363–385, 523–550; and “Ueber die Processe der Gährungen and ihre Beziehung zum Leben der Organismen,” in Pflüger’s Archiv für die gesamte physiologie, 12 (1876), 1–17.
II. Secondary Literature. An extensive evaluation of Hoppe-Seyler’s work, as well as a list of his publications, is given by E. Baumann and A. Kossel, in Hoppe-Seyler’s Zeitschrift für physiologische Chemie,21 (1895), i–lxi.
Joseph S. Fruton