LINDERSTRøM-LANG, KAJ ULRIK

(b. Frederiksberg, Copenhagen, Denmark, 29 November 1896; d. Copenhagen, 25 May 1959)

biochemistry, protein chemistry.

Linderstrøm-Lang was a leader in protein chemistry, both theoretical and experimental. His power of mathematical analysis and his grasp of modern physical chemistry enabled him to develop new approaches to the chemistry of proteins. He was also a highly skilled and imaginative experimentalist who developed new microchemical techniques that permitted studies on the metabolism of individual living cells and tissues. These talents, and Lang’s remarkable personal qualities, made the chemical department of the Carlsberg Laboratory in Copenhagen, under his directorship, one of the greatest centers in the world for research in protein chemistry and related fields; it attracted gifted investigators from many parts of the world. Although Lang traveled widely and spent a year in the United States, his life was centered at the Carlsberg Laboratory from the time he received his university degree until his death.

His father, Carl Frederik Linderstrøm-Lang, a teacher of German and Latin at the Frederiksberg Gymnasium, was the son of the cantor at Vemmetofte, a home for unmarried ladies of rank. The cantor’s second wife (Lang’s grandmother), Johanna Ulrica Linderstrøm, was the daughter of a cavalry officer and lighthouse inspector; from her the family acquired the name Linderstrøm. Teaching had long been a vocation in the Lang family and was part of the atmosphere in which young Lang grew up. His mother, born Ellen Hedvig Bach, was the daughter of P. J. Bach, a banker in Svendborg. Most of the men of the family had been fishermen, and it was primarily because of a leg injury that P. J. Bach became a banker instead. Ellen Linderstrøm–Lang was musical and artistic and had wanted to be a music teacher; her brother was an architect. Lang considered that his strong artistic bent was inherited from his mother, to whom he was always close. Lang was the youngest child; he had two sisters, both of whom became schoolteachers.

The friends of the family were largely in academic circles. At dinner parties there were lively discussions of cultural and artistic subjects; humorous afterdinner speeches, verses, and recitals played an important part on these occasions. Such diversions were later characteristic of Lang’s own social gatherings; as a host he was memorable for his liveliness and charm.

As a boy he drew, painted, modeled, played the violin, wrote poetry, and was a good carpenter. In spite of his diverse talents, he was self-conscious and considered himself to be hopelessly ugly. The family situation suffered a change after his father died of cancer when Lang was fifteen. Their house had to be sold, and their way of life was altered. Nine years later his mother died of tongue cancer, for which she had had an operation some ten years earlier.

At the age of seventeen Lang began the study of chemistry at the Technical University in Copenhagen. His fellow students held him in high esteem for his talents as a playwright in their annual the atricals and for his other gifts, but his academic work in chemistry was not distinguished. His major interests were artistic and literary; he was bold enough to send one of his plays to the eminent critic Georg Brandes, who replied that the play was “not boring” but that Lang would have to decide whether he really had the necessary talent to continue. He found no publishers for his writings and experienced what was apparently a rather serious emotional crisis. However, he graduated in 1919 from the university with a respectable record.

Soon afterward an event occurred that was decisive for his future career. Lang had obtained a temporary job at the National Research Institute on Animal Husbandry in Copenhagen. His supervisor, A. C. Andersen, who had previously worked at the Carlsberg Laboratory, recognized the young man’s talents and recommended him to Søren P. L. Sørensen, the great protein chemist who was head of the chemical department at Carlsberg. Lang applied for a job as assistant there and was appointed in August 1919.

Sørensen was then at the height of his career, but there was a grave shortage of chemicals and supplies, which had been cut off during the war. He set Lang to preparative and analytical work, demanding high purity in the products and accuracy in the analyses. Lang performed thousands of Kjeldahl nitrogen analyses during this period. This discipline, under the guidance of a demanding but kindly master deeply devoted to science, was a turning point in Lang’s life. He wrote later in his obituary of Sørensen: “Science and its employment in the service of mankind was his only passion; it was the principle on which he built his life. I never came across any scientific question that did not interest him and which he was not willing to hear about, however busy he might be. Therefore he was the most encouraging chief imaginable.”¹ Soon Lang was Sørensen’s most trusted assistant, and he became dedicated to science without losing his keen interest in art, music, and literature.

In March 1922 Lang married Gerda Kyndby, a schoolteacher who was a close friend of his sister’s. They had two daughters and a son. She kept her interest in teaching while her life became increasingly busy with the activities of the laboratory and its numerous visitors. When Lang succeeded Sørensen as director in 1939, the family moved into the director’s quarters in the laboratory building, so that their home life was closely interwoven with that of the laboratory.

Lang went deeply into the study of what were then frontiers of physical chemistry. With much help from personal discussions with Niels Bjerrum and Jens A. Christiansen, he mastered the work of Willard Gibbs and others, as well as the newer knowledge of electrolyte solutions, molecular structure, and intermolecular and interionic forces. His first independent paper (1924), on the “salting out” of polar and nonpolar molecules by electrolytes in water, was an extensive experimental study combined with a thoughtful theoretical discussion of intermolecular forces in solution.

In “On the lonization of Proteins” (1924) Lang applied the interionic attraction theory of Debye and Hückel—published the previous year—to the analysis of the influence of electrostatic forces on acid-base equilibria in proteins. All proteins contain many acid and basic groups, so that the net charge, Ζ (in proton units), on a proteins molecule can assume a wide range of values, both positive and negative, as the pH is varied by adding acids or bases. As Ζ increases in either direction, electrostatic repulsion makes the addition of more charges of the same sign increasingly difficult. However, the addition of neutral salts, which in water are completely ionized, diminishes this repulsion, since the electrostatic field around the protein ion is partly counterbalanced by a preferential clustering of small ions of opposite charge in its neighborhood, as explained in detail by the Debye-Hückel theory.

As a model for the protein Lang chose a sphere of radius b, and the net charge Ζ was assumed to be spread uniformly over its surface. This was the simplest working assumption available at the time, and it worked well when applied to experimental data. The ionic strength I = 1/2 Σ c_iz_i², where c_i is the molar concentration of the i’th ion of the salt, and z_i is its valence. The electrical free energy (Gibbs energy) of the protein ion is:

where ε is the proton charge, D is the dielectric constant of the solvent, k is Boltzmann’s constant, and κ is the reciprocal mean distance of the ion atmosphere around the central protein ion in the Debye-Hückel theory. In water near 25°C, The first term in parentheses gives the G_e value for the protein ion at zero ionic strength; the second term, which increases with the square root of the ionic strength, partly counter balances the first. The distance a represents the distance of closest approach between the centers of the protein ion and the small ions; approximately a = b + 2 (values in Angstrom units). The parameter w, as defined here, was introduced by Linderstroslash;m Lang. It is a measure of the shift in the form of the titration curve that arises from electrostatic repulsions. It decreases as the square root of the ionic strength increases but is always positive, since a > b. If one is titrating a protein (or other macromolecule) containing a set of n equivalent acid or basic groups, the slope of the titration curve dZ̄/dpH at the midpoint, when half the groups have been titrated, is given by

Here Z̄ is the mean value of Z, averaged over all protein molecules in the system.

Actually the slope, as defined by this equation, remains essentially constant for a considerable distance on either side of the midpoint. R. K. Cannan² showed later that the data for a set of equivalent acid groups, all with the same intrinsic pK value, reduce to a simplified form of Lang’s equations:

Here α represents the fraction of the groups in the set from which protons have been removed.

Lang recognized from the beginning that the distribution of charges in such an assembly of macromolecules must be statistical. At a given moment a particular molecule may carry a net charge Ζ but all the molecules are constantly exchanging protons with the solvent, and the value of Ζ for any individual molecule is constantly fluctuating. Hence the charge as measured from the titration curve is a mean value, Z̄, averaged over all the molecules in the system. Later Lang showed, in his Dunham lectures at Harvard Medical School (1939), that the steepness deviation of Z̄ is directly related to the steepness of the titration curve, which gives Z̄ as a function of pH at any point:

This simple and elegant relation is applicable to any system involving the binding of ligands, in which the binding can be defined by a sequence of dissociation (or association) constants. Such as the combination of oxygen molecules with the four heme groups of hemoglobin.

In 1926 Lang applied the analysis developed in this 1924 paper to the titration of egg albumin at various ionic strengths previously carried out by Sørensen and Ellen Lund. The form of the curves accorded well with the predictions of the theory, and it was possible, from the observed values of w, to calculate the radius b of the protein molecule, taking a = b+ 2 (values in Ångströms). Which is a reasonable estimate for the closest distance of approach of the small ions to the protein surface. The resulting value of b was 22 Å, in close agreement with that derived from the molecular weight deduced by Sorensen from osmotic pressure measurements.

Lang never lost interest in these electrostatic interactions of macromolecules. In a much later paper (1953) he calculated the activity coefficients of large multipolarions of various shapes and charge dis tributions, taking account of and extending the studies in this field by John G. Kirkwood and others.

In the same paper of 1926 Lang also introduced an important distinction, for proteins and other am pholytes, between two quantities, which he termed the isoelectric point and the isoionic point. The isoelectric point may be defined as the pH value at which the mean net charge of the protein, arising from all bound ions, including H⁺ and OH^- is zero. To define the isoionic point, consider a protein in its state of maximum positive charge Z_max when all potential cationic groups in the molecule are charged, and then remove Z_max protons per molecule by addition of hydroxyl ion. The resulting protein is then isoionic by definition. If the protein combines only with H⁺ and OH^-, the isoelectric and isoionic points coincide; but if it combines with other ions as well, the two may be significantly different. To determine the isoionic point, one needs isoionic protein, which may be prepared by electrodialysis or (better) by treatment with a mixed-bed ion exchange resin.

Lang proposed that either procedure removes essentially all small ions, other than H⁺ or OH^- from the system, Two experimental methods for determination of the isoionic point were proposed: according to one, it is the pH of the protein solution that does not change on the addition of more isoionic protein; according to the other, it is the pH of a solution of the isoionic protein in water, or in a solution of another solute that does not produce H⁺ or OH^- ions when dissolved in water alone. These definitions are based on a much later discussion in one of Lang’s last papers, written with Sigurd O. Nielsen (1959), in which he gave the most mature formulation of his concepts in this field; it appeared in Electrophoresis, edited by Milan Bier.

Lang’s doctoral dissertation (1929), on the fractionation of the milk protein casein, reflected Sørensen’s concerns with the purification and separation of proteins from the complex mixtures found in nature. He demonstrated clearly, by laborious frac tionations, that casein, then widely supposed to be a pure protein, was actually a mixture of several closely related constituents—a conclusion later fully confirmed by the simpler and more powerful tech niques that had become available in the meantime. He did not pursue further studies in this area but turned in other directions.

Lang worked in the United States from 1931 to 1932 as a Rockefeller research fellow at the California Institute of Technology. He broadened his primarily chemical background by studying general biology with Thomas Hunt Morgan and worked on biochemical problems with Linus Pauling and Henry Borsook. This year was important in his life, and he established close and lasting relations with many American friends.

Lang had early developed a strong interest in enzymes, especially proteolytic enzymes, and in 1926 he spent two months in the laboratory of Richard Willstätter in Munich, which was then the most famous center of enzyme chemistry. He was not, however, converted to Willstätter’s view that en zymes were not proteins and pursued his independent path upon returning to Copenhagen. He concentrated his investigations on the peptidases, enzymes that hydroyzed rather small peptides. He showed in the period 1929 to 1930 that two dipeptides, leucylglycine and alanylglycine, were attacked by two different enzymes from the mucous membrane of the intestine; one of them could break down longer peptide chains, provided they contained a terminal leucine. Some members of Willstätter’s school sharply criticized these conclusions, and it was several years before it was definitely established that Lang’s views were correct.

A major influence on Lang’s research was the arrival in 1930 of a young Austrian. Heinz Holter, in the laboratory. Holter was eager to trace the biological role of enzymes by relating their activity to the structure of the cells and tissues in which they occur. Lang pointed out that it was essential to work quantitatively and to be able to measure extremely small amounts of material in a well-defined region of a tissue—ideally, to work with individual cells. This required the development of micro methods of a totally new sort. These studies on enzymatic histochemistry lasted for twenty years. Lang and Holter developed a wide array of sensitive and precise ultramicro methods for the study of the distribution of a great variety of enzymes and other constituents of cells and tissues; the work was widely influential in other laboratories. Lang’s remarkable versatility was evident in his ability to apply physical principles to new analytical methods. The use of the Cartesian diver for the measurement of oxygen consumption or of specific enzyme activity, in single microscopic sections of tissue or even in individual cells, is an outstanding example. Lang not only developed the experimental technique but also treated the theory of the method in great detail, considering all sources of error and the means of correcting them. Another major contribution was the use of mixtures of components of different densities in such a way as to form a density gradient column. This could be used to determine the density of very small droplets by determining the position at which they came to rest in the column. For this it was essential that the material in the droplets be insoluble in the column.

Holter stayed at the Carlsberg Laboratory for the rest of his career. In 1942 he became head of the new subdepartment of cytochemistry within the chemical department. In 1956 he became head of the physiological department of the Carlsberg Lab oratory, as successor to Øjvind Winge.

Though his work with Holter on cytochemistry absorbed much of Lang’s time and energy during the 1930’s, he continued to work on protein chemistry. There was much debate over the nature of native proteins, partly inspired by the cyclol theory of Dorothy Wrinch, which for a few years aroused much interest. For a time Lang considered it possible that native proteins might not contain peptide bonds, and that these bonds might appear, by an intra molecular rearrangement, only after the protein had become denatured. He pictured the attack of proteolytic enzymes on the protein as involving a process that, in its simplest form, could be written as

If the native and denatured proteins were in a re versible equilibrium, the attack of the enzyme on the latter would constantly shift the equilibrium to the right, and hydrolysis would proceed.

In pursuing this problem, Lang, with C. F. Jacobsen (1941), studied the volume changes accom panying the enzymatic breakdown of proteins. For simple peptides, the breakage of a peptide linkage in neutral solution is accompanied by a volume decrease, of the order of 15–22 cm³ per mole. Denoting a peptide by the simplified formula R·NH·CO·R, the process may be written thus:

This shrinkage in volume is due primarily to electrostriction; the electric field around the ions pro duced by the hydrolysis causes the surrounding polar water molecules to become oriented around the ions and to pack more tightly together. Using dilatometers, Lang and Jacobsen followed the volume change that occurred with β-lactoglobulin hydrolyzed by trypsin or chymotrypsin, correlating the volume change with the number of bonds broken by the enzyme. In the early stages of hydrolysis the volume change, ΔV, was –50 cm³/mol of bonds broken, far higher than for simple peptides. As hydrolysis proceeded, the bonds broken at a later stage gave lower ΔV values, like those of simple peptides. Lac toglobulin is a compact globular protein molecule that readily forms excellent crystals. They found that another protein, the histone clupein, with a more open flexible structure, behaved much like simple peptides; ΔV was near –15 cm³/mole throughout the course of its hydrolysis. Lang and Jacobsen inferred that the native lactoglobulin, with its highly folded structure, was initially undergoing a partial collapse of the native structure, involving volume changes that could not be explained simply in terms of breakage of peptide linkages.

Nearly a decade later, in his Lane lectures at Stanford University (published in 1952). Lang elab orated these ideas into a more general picture of the structure of native proteins. By that time Fred erick Sanger’s work on insulin at Cambridge had provided decisive evidence that amino acid residues in proteins are indeed linked by peptide bonds. Lang pictured the structure of native proteins as being describable in terms of three levels of order: (1) primary structure, defined by the sequence of amino acid residues in the peptide chain; (2) secondary structure, consisting of segments of the pep tide chain that are arranged in a definite repeating spatial order, such as the α-helix or the pleated sheets described by Linus Pauling; (3) tertiary structure, involving the additional folds and turns that completed the formation of the structure of the native protein. Lang’s conceptual scheme and his terminology have found general acceptance among biochemists as a convenient basis for describing the structures of native globular proteins, consisting of a single peptide chain or subunits of proteins containing several such chains. J. D. Bernal later extended the scheme for globular proteins composed of several peptide chains by the concept of “qua ternary structure,” which involves the packing to gether of the individual folded chains to form a compact structure of higher order.

Lang’s researches on the action of proteolytic enzymes became directed, especially after 1945, to the use of such enzymes as tools for exploring the secondary and tertiary structure of proteins by following changes in volume, optical rotation, and other properties, and correlating them with the number of peptide bonds broken as hydrolysis proceeded. The addition of denaturing agents, such as urea, could be used to shift the balance between native and reversibly denatured protein to probe further the effects of breaking peptide bonds that were im portant for maintaining the native structure. L. Korsgaard Christensen (1952) studied in great detail the enzymatic hydrolysis of β–lactoglobulin, with some additional important experiments on egg al bumin. As in many other cases, Lang’s name does not appear on this long paper, but his thinking is apparent throughout. A year later (1953) Lang gave a detailed exposition of his ideas on the modes of degradation of proteins by enzymes, and their im plications for protein structure, at the Ninth Solvay Congress. His discussion was inevitably tentative; the direct evidence from X–ray diffraction for the three–dimensional structures of proteins did not be come available until several years later, but the general picture, as he envisaged it, was to be borne out by later developments.

Also in his Lane lectures, Lang considered the problem of protein biosynthesis, about which little was then known. His thinking was in several respects ahead of his time. He emphasized the thermodynamic considerations that must impose constraints on any biosynthetic scheme and pointed out the likelihood that the phosphorylation of amino acids, probably by adenosine triphosphate (ATP), could, in the presence of suitable catalysts, provide a higher level of free energy that could be expended in the for mation of peptide bonds. It seemed to him highly unlikely that the biosynthesis of proteins could be brought about by the same enzymes that hydrolyzed them, acting in reverse; rather, it seemed necessary that a different set of enzymes must be involved, drawing upon the free energy reserves provided by ATP (or some other free energy source) to make the process go. To a significant extent his thinking foreshadowed the extraordinary advances in this field that began a few years later. Indeed, Paul C. Zamecnik, who became one of the leaders in those developments, had worked earlier in Lang’s labo ratory (1939), although on different problems.

Lang’s last major line of research introduced a new and powerful approach to the study of the forces responsible for maintaining secondary and tertiary structure. This was the study of hydrogen deuterium exchange between proteins and the water around them. By infrared spectroscopy H. Lenor mant and E. R. Blout (1953) had shown that proteins contained at least two different kinds of peptide linkages; one kind was easily deuterated with D₂O at room temperature, whereas the others exchanged H for D only at high temperature or at high or low pH. Lang decided to study such exchanges by mea suring the rate of change in the density of the water surrounding the protein, since the mass of deuterium (D) is twice that of hydrogen (H). The density gradient systems that he had developed much earlier permitted rapid and accurate density determinations on very small drops of water in the gradient tubes. Hydrogen bound to carbon was essentially nonex changeable, but in small molecules, including simple peptides, H–D exchange was generally very rapid for hydrogens attached to oxygen, nitrogen, or sulfur. For proteins, however—Lang studied insulin, pancreatic ribonuclease, and β–lactoglobulin—there was a wide range of exchange rates from virtually in stantaneous to extremely slow. Indeed, at temper atures near 0°C some peptide hydrogens showed virtually no exchange over several days. Rise of temperature to 38°C or above greatly increased the rates for some of these peptides, as did change of pH to more acid or more alkaline values, or the addition of denaturing agents, such as urea or guan idinium chloride.

Lang proposed models to interpret the data, but these were necessarily tentative; it was only later that detailed structural data became available for correlation. He had, however, opened up a new and powerful approach to the dynamics of protein structures that could reveal the character and frequency of fluctuations in the native structure that would permit exchange of hydrogens as portions of the native structure opened up momentarily and exposed normally buried hydrogens to contact with the solvent. Lang led the way in introducing these methods. His death in 1959, preceded by a year of illness, cut off the further progress of his work. Other workers, using a variety of techniques—nuclear magnetic resonance, tritium-hydrogen exchange followed by radioactivity measurements, and neutron diffraction studies on protein crystals, among other methods—have carried such studies much further; but Lang was certainly the pioneer in this field.

During World War II, Denmark had been largely cut off from the outside world, especially during the long German occupation. Lang was active in the resistance movement and aided many Jews and other refugees to escape to Sweden. As the country recovered from the war, the Carlsberg Laboratory became a great center of attraction, especially to protein chemists, from foreign lands. Among them were Christian B. Anfinsen, William F. Harrington, Frederic M. Richards. John A. Schellman, and Har old A. Scheraga from the United States, and Sidney J. Leach from Australia, along with many others. These visitors worked largely as independent in vestigators, although they published joint papers with Lang on some occasions; there was constant free discussion and interchange of ideas. The en thusiasm and intellectual stimulus that Lang provided were pervasive, and his influence was far more than intellectual.

The range of Lang’s talents was immense: He was a painter of considerable talent, a gifted writer, a musician, a delightful conversationalist and raconteur. There was a strong element of gaiety in his nature, together with sensitiveness to human difficulties and suffering. His scientific gifts, great as they were, do not fully account for the remarkable flowering of the Carlsberg Laboratory under his directorship. He traveled widely to scientific meetings and other events and took a deep interest in the international relations of science. In addition to many other honors, he was elected president of the In ternational Union of Biochemistry, succeeding Marcel Florkin, in 1958. He never took office, how ever; he had suffered for some years from a mild diabetes that became greatly exacerbated after the removal of a benign intestinal tumor in 1958. He spent the last year of his life mostly in the hospital and died in 1959 at the age of sixty-two.

NOTES

1. K. Linderstrøm-Lang, “S. P. L. Sørensen 1868–1939,” in Comptes rendus des travaux du Laboratoire Carlsberg, série chimique, 23 (1939), i–xxi; see xi.

2. For later developments in this field, derived from Linderstrøm Lang’s work, see R. Keith Cannan. “The Acid–Base Titration of Proteins,” in Chemical Reviews, 30 (1942), 395–412; and Charles Tanford, “The Interpretation of Hydrogen Ion Titration Curves of Proteins,” in Advances in Protein Chemistry, 17 (1962), 69–165. As the three-dimensional structure of many proteins has become known in detail, correspondingly elaborate calculations of electrostatic forces around protein ions have been developed, notably by F. R. N. Gurd and his associates.

BIBLIOGRAPHY

I. Original Works. Listings of Linderstrøm–Lang’s works are in Poggendorff, VI, 1535, and VIIb, 2283–2287. Most of his papers appeared (in English) in Comptes rendus des travaux du Laboratoire Carlsberg, série chi mique (CRLC); others were in diverse journals, conference proceedings, and treatises. He never published a book. The biographical article by Heinz Holter (see below) lists 154 publications to which his name is attached, but many other papers from the laboratory reflect his influence. A very useful collection is Kai Linderstrøm-Lang; Selected Papers, Heinz Holter, Hans Neurath, and Martin Ottesen, eds. (Copenhagen, New York, and London, 1962); the twenty-five papers in this volume include the complete texts of his Lane Medical Lectures at Stanford, which originally appeared as Proteins and Enzymes. Stanford University Publications, University Series. Medical Sci ences, 6 (1952).

His writings include “On the Salting–out Effect,” in CRLC, 15 , no. 4 (1924); “On the Ionization of Proteins.” ibid., 15 , no. 7 (1924); “On Peptide Bonds in Globular Proteins,” in Nature, 142 (1938), 996, with R. D. Hotchkiss and G. Johansen; “The Contraction Accompanying Enzymatic Breakdown of Proteins,” in CRLC, 24 , no. 1 (1941), 1–48, with C. F. Jacobsen; “On the Cartesian Diver Microrespirometer,” ibid., 24 , no. 17 (1943), 333– 398; “Degradation of Proteins by Enzymes,” in Rapport et discussion …Institute International Chimique Solvay, 9 Congrès (1953), 247–296; and “Deuterium Exchange Between Peptides and Water,” in Special Publications of the Chemical Society (London), no. 2 (1955), 1–20. The Selected Papers also contains a jeu d’esprit “The Thermodynamic Activity of the Male Housefly,” with the imaginary F. Fizz–Loony. Two important reviews, written near the end of his life, are “Acid–Base Equilibria in Proteins,” in Milan Bier, ed., Electrophoresis, I (New York, 1959), 35–89, with Sigurd O. Nielsen; and “Protein Structure and Enzyme Activity,” in Paul D. Boyer, Henry Lardy, and Karl Myrbäck, eds., The Enzymes, 2nd ed., rev. (New York, 1959), 443–510, with John A. Schellman. These are more than reviews; they contain original ideas not previously discussed elsewhere.

II. Secondary Literature. The most important biographical article on Lang is Heinz Holter, “K. U. Linderstrøm–Lang, 1896–1959,” in CRLC, 32 (1960/1962), i–xxxiii, including a portrait and a bibliography. This is reprinted, without the bibliography but with several ad ditional photographs and illustrations of apparatus, in Heinz Holter and K. Max Møller, eds., The Carlsberg Laboratory, 1876–1976 (Copenhagen, 1976), 88–117. Other articles in this book provide important background, especially Lang’s article on Sørensen, 63–81.

Other useful articles on Lang include K. Bailey, in Proceedings of the Chemical Society (London) (1960), 92–93; F. Duspiva, in Ergebnissen der Physiologie51 (1961), 1–20; John T. Edsall, in Advances in Protein Chemistry, 14 (1959), xiii–xxiii, with portrait; Herman M. Kalckar, “Kaj Ulrik Linderstrøm–Lang. Scientist, Man. Artist,” in Science, 131 (1960), 1420–1425; Hans Neurath, in Archives of Biochemistry and Biophysics, 86 (1960), i–iv; Martin Ottesen, in American Philosophical Society: Year Book 1959 (1960), 133–138 and A. Tiselius, in Biographical Memoirs of Fellows of the Royal Society, 6 (1960), 157–168.

John T. Edsall