After completing his university studies, Kossel returned to the University of Strassburg as research assistant to Felix Hoppe-Seyler. At the time, Hoppe-Seyler was intensely interested in research concerning an acidic substance that had first been chemically isolated from pus cells by one of his former students, Friedrich Miescher, in 1869. Unlike protein, the substance contained considerable amounts of phosphorus, but with its high acidity, it was unlike any cellular substance that had yet been observed.

In 1872, Kossel attended the University of Strassburg to study medicine. He studied under Felix Hoppe-Seyler, who was head of the department of biochemistry, the only such institution in Germany at the time. He attended lectures by Anton de Bary, Waldeyer, August Kundt, and Baeyer. He completed his studies at University of Rostock, and passed his German medical license exam in 1877.

Kossel contributed to early issues of the Zeitschrift für Physiologische Chemie (Journal of Physiological Chemistry). This publication was founded by his professor and mentor, Felix Hoppe-Seyler, in 1877, the same year that Kossel started work as his research assistant. After Hoppe-Seyler’s death in 1895, Kossel took over editorship of the Zeitschrift and continued in that role until his own death in 1927.

In 1883, Kossel left Strassburg to become Director of the Chemistry Division of the Physiological Institute at the University of Berlin. In this post, he succeeded Eugen Baumann and worked under the supervision of Emil du Bois-Reymond.

In 1886, Kossel married Luise Holtzman, daughter of Adolf Holtzmann. Holtzmann was Professor at the University of Heidelberg, lecturing in German literature as well as Sanskrit. He was also a noted philologist of his day. The couple had three children, two of whom survived to maturity: Walther, born in 1888, and daughter Gertrude, born in 1889.

In 1895, Kossel was professor of physiology as well as director of the Physiological Institute at the University of Marburg. Around this time, he began investigations into the chemical composition of proteins, the alterations in proteins during transformation into peptone, the peptide components of cells, and other investigations.

In 1896, Kossel discovered histidine, then worked out the classical method for the quantitative separation of the “hexone bases” (the alpha-amino acids arginine, histidine, and lysine). He was also the first to isolate theophylline, a therapeutic drug found naturally in tea and cocoa beans. Kossel determined its structure and its relation to caffeine.

Kossel was awarded the Nobel Prize in Physiology or Medicine in 1910 for his research in cell biology, the chemical composition of the cell nucleus, and for his work in isolating and describing nucleic acids. The award was presented on 10 December 1910.

Luise Kossel died in 1913 of acute pancreatitis. Kossel died quietly on 5 July 1927, after a recurring attack of angina pectoris. He is buried in Heidelberg, Germany.

Albrecht Kossel was apparently not greatly interested in politics, but in 1914 he did not sign the propaganda Pronunciamento of German professors at the start of the war. He suffered under the lies which filled the world in war time. In 1917 Kossel was summoned by the government to pronounce that the allotted food provisions were sufficient. He refused this demand, would never declare untruths as truths

In 1923, Kossel was honored by being named Germany’s representative to the Eleventh Physiological Congress in Edinburgh, Scotland. When he appeared before the assembled scientists, they gave him an ovation that lasted several minutes. At the congress, he was conferred an honorary degree by the University of Edinburgh.

In 1924, Kossel became professor emeritus, but continued to lecture at Heidelberg University. In April 1927, he attended the Lister Centenary Celebration held in England.

Albrecht Kossel is considered one of the great scientists of biochemistry and genetics. By isolating and defining nucleic acid and the nucleobases, he provided the necessary precursors that led to the double-helix model of DNA, devised by James D. Watson and Francis Crick in 1953.