The discovery of DNA by Dr Friedrich Miescher in 1869
The first person to isolate and observe it from the nuclei of cells
The first time I heard about DNA was in Biology class in high school. I remember it didn’t make much sense at the time - I couldn’t grasp what it meant for humans, or species, or biology. The next time I was hearing about DNA was at least 5 years later when I had just started my undergraduate degree. Probably one of the first things I learned about it was that Watson, Crick, and Rosalind Franklin discovered the structure of deoxyribonucleic acid in 1953. This, in my mind, occupied the spot for the discoverers of the DNA molecule, rather than the double helical structure.
It wasn’t until 9 years later, when I was writing my doctorate thesis, that I stumbled upon a paper called “Ueber die chemische Zusammensetzung der Eiterzellen” (or “On the chemical composition of pus cells”) on a website about rare science books and manuscripts. The subtitle was in English and read: “The Discovery of DNA”. The attached image was the front page of the journal where the original article was published in “Investigations in medical chemistry” issued by Dr Felix Hoppe-Seyler, from Berlin in 1871.
I was intrigued! Initially I half expected to see another paper on Watson, Crick, and Franklin and their structure discovery but it clicked that the Miescher manuscript was published at least 80 years prior to the structure discovery experiments. This was much more exciting - I realised I had missed a large part of the history of the molecule I’ve been working on for the last 4 years. I had accepted a statement for a fact without digging more into it. After I had done a bunch of working and reading for my PhD, I had started to realise there was a never ending queue of “facts” that were awaiting for me to do the digging, if I was to actually grasp the context.
After my thesis was done and dusted, I returned to Dr Miescher and his story of seeing DNA for the first time. Here’s him below as a young man, from the Ralf Dahm article on Friedrich’s life and work from 2007.
At first disheartened that maybe all the articles were going to be in German and therefore were going to remain obscure to me, I found a series of papers by Ralf Dahm and other authors who described what was known about the life and contributions of Friedrich Miescher. One particularly interesting, and slightly different approach to Dahm’s, was an article by Veigl, Harman, and Lamm from 2020 which gave a more detailed overview of the historical and scientific context. Another interesting paper was by two contemporaries of Miescher, Kingzett and Hake, from 1877, an article written in the Journal of Science in the United Kingdom - “Physiology and its chemistry at home and abroad”. I discovered this through Viegl et al, which had a variety of other relevant references - many of which were not available to me for different reasons. I highly recommend reading these if you are interested in the wider context.
“The last remaining questions concerning the development of tissues could only be solved on the basis of chemistry” Wilhelm His wrote to his nephew Friedrich Miescher encouraging him to pursue the newly established field of physiological chemistry in Tübingen, Germany, in the school of Dr Felix Hoppe-Seyler.
Johann Friedrich Miescher was born in 1844 in Basel, Switzerland in a family of scientists and medics. His father was a physician and expected his son to follow in his footsteps of medical practice. Young Miescher, however rather developed an obsession of finding out what was fundamental to all living organisms. In a letter to his father he describes his beliefs about studying the fundamentals of existence:
"It seems to me that the most immediate task of natural research to be worked on is to free humans from all the countless threads that unconsciously form the fabric of their thinking, feeling and actions in general but are intertwined with the material substance of their existence. Precisely because these relationships of dependence are not yet transparent enough to an individual, they are unable to disconnect themselves from this network to solve these problems.”
Friedrich’s uncle, Wilhelm His, was an embryologist whose work on the development of the neural crest is still respected to this day. Wilhelm His was a student of prominent figures in the field of development, Robert Remak and Rudolph Virchow. Remak was an embryologist who put forth the correct theory of cell division through binary fission in 1852.
His encouraged Friedrich to pursue science, biochemistry in particular, or rather the newly established field of “physiological chemistry” as it was known at the time. Wilhelm His was very much in the contemporary conversation of cell development, inheritance, and cell division. According to E. B. Wilson in the book “The Cell in Development and Inheritance”, four scientists from that time identified the nucleus as the vehicle of inheritance in 1884-1885. Their names were Hertwig, Strasburger, Kölliker, and Weismann. However, another scientist, Haeckel expressed the view that the nucleus carries the hereditary materials from one cell to the next in 1866. Haeckel is famous for his “biogenetic law” from the same year, which is a theory of development and evolution. His law is more commonly known as “ontology recapitulates phylogeny” and was inspired by Darwin’s theory of evolution. Haeckel theorized that the stages in animal development represent forms of earlier evolutionary ancestry, supporting the theory that all organisms on Earth came from a common ancestor. This was a law that Miescher’s uncle, Wilhelm His disagreed with and considered to be overstating the similarities between organisms. His preferred the view that the obvious differences between the early stages of different species were more important in explaining development. Later attempts of scientists to recreate Haeckel’s results, which were expresed through drawings of microscope observations, including one of Wilhelm His’ students (Franz Keibel) were unsuccessful and his law became more unpopular. Instead, von Baer’s law that characters common to a taxonomic group appear before more specialised characters became popular. His conclusion was that animals are more similar at earlier stages, then diverge more and more as development progresses, which is the more accepted view from the 20th century onwards.
Wilhelm His, aware of the developments in embryology and cell theory then not only encouraged Friedrich Miescher to pursue science and biochemistry, he encouraged him to study the nucleus and how it is different to the cytoplasm, in particular. Wilhelm was a trusted friend of Friedrich, who corresponded with his uncle often throughout his life. Friedrich shared most of his discoveries and scientific ideas in letter form to his uncle and colleagues. Letters became Miescher’s form of sharing scientific ideas after receiving criticisms of his published work. Wilhelm His published these accounts after Miescher’s death and was one of his most prominent supporters.
Germany had established schools of science, one of which was Hoppe-Seyler’s school for physiological chemistry. Thus encouraged by his uncle, Miescher joined the Tübingen Castle Laboratory of Dr Felix Hoppe-Seyler in the autumn of 1868, after spending a year in Adolphe Strecker’s lab learning the organic chemistry methods he was going to employ in Tübingen. Dr Felix Hoppe-Seyler was a pioneer of biochemistry and by the time Miescher joined his lab, had published important work on proteins in the blood, naming them haemoglobins. Friedrich joined him with the intention to apply chemical principles to determine the chemical composition of human cells. Initially intending to use lymphocytes because he thought of them as “a most simple and independent cell type”, Miescher, however switched to leucocytes due to availability of materials. Leucocytes are found in pus and at the time, he could collect a large amount from bandages from the nearby hospital.
“At a time when scientists were still debating the concept of "cell," Hoppe-Seyler and his lab were isolating the molecules that made up cells.”
Initially Miescher studied whole cells, attempted to break them down into components and characterise them chemically. His analysis of the cytoplasm showed that it was comprised of lipids and proteins, but the limited methods available did not allow him to classify these compounds much further. At the time, proteins were already known substances found in cells and some of their properties were established. It was known that proteins contained carbon, hydrogen, nitrogen, oxygen, and sulfur. In his experiments, Miescher discovered an unknown substance with he could precipitate with acidic solutions and re-dissolve with alkaline solutions, and hypothesised it came from the nucleus. This was the first crude DNA extract. On February 26, 1869, he reported the discovery of this mysterious substance in a letter to Wilhelm His:
“In my experiments with low alkaline liquids, precipitates formed in the solutions after neutralization that could not be dissolved in water, acetic acid, highly diluted hydrochloric acid or in a salt solution, and therefore do not belong to any known type of protein.”
Miescher termed the unknown compound “nuclein” as he thought it belonged to the nucleus. This was his hypothesis. He had to check whether it was correct and the way of doing that was to first find a way of separating the nuclei from the cytoplasm and check if he could isolate the same substance again.
His experiments then focused on isolating the nuclei of cells which had never been done before. At the time, not many other people thought this was an interesting or important endeavour. For the acepted science, the nucleus was the “germination centre” or the “root” of the cell where it grew out from, maybe provided some nutrients, but the proteins were the important bits. No one was imagining that a single molecule could be responsible for inheritance in humans, let alone all organisms. Miescher had to come up with a method by trial and error relying on his knowledge of the chemistry extraction methods with alcohol, ether or acids. He ultimately found a way of digesting the cytoplasm with hydrochloric acid, without leaving behind smooth round nuclei. After that he shook the nuclei in water and ether which destroyed the lipid bilayer and essentially emptied the nuclei of the substances inside. This produced a precipitate of white powder, which could be dissolved again with alkaline solutions, and precipitated with acidic solutions. This had the same properties as what he had isolated from whole cell extracts. This was laborious, took weeks, and had to be done at low temperature to avoid degradation of the material. He would often work from 5am in freezing conditions. But he was on the right track - he was obtaining the same result through different methods and had shown that the novel substance originated in the nucleus.
“According to known histochemical facts, I had to ascribe such material to the nuclei”
Miescher was obsessed. He knew he had isolated a new kind of substance, but he did not understand what it was, nor entirely comprehend its significance. In 1869, the idea of the nucleus carrying the genetic material was not entirely understood, at leats not in the form we know today. Nothing about DNA was known at the time.
Miescher was aware that he required pure nuclein - finding a way of completely removing all traces of proteins, if he were to determine its properties. His new task was to attempt to isolate pure nuclein, if that existed. Miescher found out from the scientific literature at the time that pepsin, a protease, could digest protein and he reasoned correctly to use it, in order to remove all of the cytoplasm and remaining proteins to attempt extracting pure nuclein. He had to isolate pepsin from pig’s stomachs himself as this was not widely available either. Using this method, initially developed by WIlhelm Kuhne, Miescher achieved degradation of cytoplasmic proteins, but also showed that nuclein was nto a protein as it remained intact.
“We are dealing with an entity sui generis not comparable to any hitherto known group”
This was the first pure sample of nuclein, and Miescher’s elemental analysis revealed that it consisted of carbon, hydrogen, nitrogen, oxygen, and traces of sulfur; but unlike proteins it contained a large amount of phosphorus. Miescher was isolating DNA in complex with histone proteins, although he did not know it at the time. The traces of sulfur suggested there was leftover protein after using pepsin, which is known today as chromatin - or DNA in association with scaffolding proteins. However, the amount of nuclein he could obtain from the cells were always small and barely enough to conduct experiments.
In the span of several months he had conducted these preliminary analyses and submitted a paper to Dr Felix Hoppe-Seyler describing his findings at the end of 1869.
“On my table lies a sealed and addressed packet. It is my manuscript, for the shipment of which I have already made all necessary arrangements. I will now send it to Hoppe-Seyler in Tubingen. So, the first step into the public is done, given that Hoppe-Seyler does not refuse it.”
Miescher wrote to his uncle in 1869 that in his preliminary observations he could isolate nuclein from liver, kidney, testicle, and nucleated erythrocytes. He further suggested its acidic nature. Hoppe-Seyler published the paper on nuclein in 1871 in the aforementioned journal, whole two years later.
”With experiments using other tissues, it seems probable to me that a whole family of such slightly varying phosphorus-containing substances will appear, as a group of nucleins, equivalen to the proteins”.
It took two years from his discovery to its initial publication because Hoppe-Seyler insisted on himself repeating the results obtained by Miescher, along with another student of his. Hope-Seyler had previously been involved in a scientific scandal with one of his students reporting and publishing results which could not be repeated by other scientists, leading to some international mistrust in Hoppe-Seyler’s laboratory. Hoppe-Seyler and two of his other students repeated Miescher’s experiments using slightly different protocols. This resulted in them obtaining the same substance altough all of their experiments yielded slightly different composition numbers. This althought contributed to the mistrust - why weren’t they obtaining the same findings?
“I think that the given analyses—as incomplete as they might be—show that we are not working with some random mixture, but … with a chemical individual or a mixture of very closely related entities.”
The existence of nuclein and the idea that it could be characteristic of the nucleus and different to protein was vigorously disputed by German, French, and English scientists. This vocal and viscious opposition seems to have discouraged Miescher from publishing papers, and he even regretted letting the scientific community know about nuclein. However, according to this letters he kept the research on nuclein going at least until 1876.
The mistrust for Hoppe-Seyler’s lab is highlighted in a paper published in the Journal of science in 1877. Kingzett nad Hake were highly skeptical of Dr Miescher’s findings and wrote:
“As we shall proceed to further demonstrate that this “nuclein” is a form of albumen, we may at once explain the absence of sulfur in most preparations by the fact that the authors heated them with caustic soda or potash, which would remove the sulfur from many forms of albumen… As for the phosphorus, we contend that its presence proves but one thing, viz., the impurity of each of the above preparations containing it… More seriously we feel that, as a result to Science, whatever might have been valuable in these researches is, for the time being, absolutely valueless".”
The scientific community was sceptical of their findings and highlighted the differences in the results obtained by Miescher, Hoppe-Seyler, and the students. However, the findings were broadly the same - they had all recovered a substance which could be precipitated with acids, dissolved in alkaline, and contained phosphorus.
After 1869 Miescher had relocated to his new position in Basel, where he continued to attempt to characterise nuclein, however his working conditions had worsened.
“During the last two years, I have feverishly yearned to be back at the meat pots of the Tubingen castle laboratory. I do not really have a laboratory to speak of here, I am just tolerated in a small corner of the chemistry lab where I can hardy twitch, as it is already overly stuffed with students and on top of that, the professor of chemistry does his research here too… You can surely imagine what it is like to be hindered by appalling external circumstances from energetically pursuing things that may never again be placed so conveniently beneath my fingertips….”
His day job was focused on other experiments related to salmon and the development of sperm cells. Basel’s location on the river Rhine where the salmon migrate provided Miescher with access to freshly caught fish. During this research he realised that salmon sperm cells are largely comprised of nuclei and therefore were an ideal source for obtaining purer nuclein in large quantities. By the time his paper was actually published in the autumn of 1871, he had started using salmon sperm as his source material for nuclein. This lead him to develop new, increasingly sophisticated protocols, which remained in use for many years.
His dedication is evidenced by getting up in the middle of the night to catch salmon and then carrying out his nuclein isolations in the winter with the windows wide open to maintain the freezing temperatures, which his work required. One of his students recollected that Miescher was late for his own wedding and instead was found working in the lab. His efforts paid off - Miescher was able to isolate copious amounts of pure nuclein. Now he was able to perform the comprehensive analyses he couldn’t complete in Tübingen. He thus confrimed his earlier results and accurately determined the phosphorus content, which he published in 1874 in a paper on the occurence of nuclein in salmon and the sperm of other vertebrates. At the time when scientists were looking to explain heredity, Miescher suggested in his paper:
“If one wants to hypothesize that a single substance specifically is the cause of fertilization in any way, then-without a doubt-one would have to think primarily about nuclein.”
He did not however believe that nuclein could explain the inheritance because he could not imagine how a single molecule with limited diversity could be responsible for the vast differences between species. He was a proponent of an idea that mechanical stimuli of the sperm movement are somehow are responsible for the feritlization. Nevertheless he speculated that information might be encoded in the arrangement of carbon atoms within molecules. He speculated that like “an alphabet of 26 letters is sufficient to express all words and concepts in a variety of different languages, molecules could be made up of different stereoisomers, or specific geometric arrangements of the constituent atoms. The vast numbers of asymmetric carbon atoms in large organic molecules, such as proteins, would allow an enormous number of stereoisomers.” He further proposed that errors in molecules can be prevented from manifesting by the fusion of two germ cells during fertilization. This view is remarkably close to the modern understanding that wild-type alleles can compensate for recessive alleles.
“If in the germinal cell there is an absence of a member of the series of factors which determines normal cellular activity ... the spermatozoon reintroduces that part and restores cellular activity. Like muscle after a nerve stimulus, the egg, when it received the sperm stimulus, becomes chemically and physically different”.
In these experiments, Miescher isolated pure nuclein from salmon sperm and separated the nuclein from the protein which he called “protamine”, which is specific for sperm cells. Note that the name protamine is still used today. He was aware that he had identified two compounds as evidenced by his letters he refers to a “nucleinsaures Protamin” (nuclein-acidic protamine). He had managed to determine the acidic qualities of nuclein and used protamine to precipitate nuclein from any cells. During 1871 to 1873 he isolated nuclein from the sperm of frog, carp, and bull and showed it was also found in the nuclei of their spermatozoa.
His name and the associated with DNA remained forgotten - the molecule he discovered bore a different name, he lacked students to keep pursuing his scientific ideas, he was introvert and prefered to be on his own, insecure and a perfectionist which lead him to delay publications. He witnessed how other researchers became associated with nuclein, the molecule he discovered.
In 1889, another scientist, Altmann isolated nuclein with a slightly modified protocol of adding another precipitation step. This allowed him to also separate nuclein from protein. He then suggested that nuclein be renamed “nucleic acid” because of its properties. Miescher hadn’t formally reported his results and acidic nuclein preparations in a paper - to the scientific community it didn’t count. Altmann introduced a confusion that Miescher’s nuclein was nuclein+protamine; however Miescher has made distinction between nuclein and protamine and isolated pure nuclein, which he himself provided to Altmann for comparison. That confusion brought Miescher’s work one step closer to being forgotten.
Miescher unfortunately died at only 51 years of age from ill health in 1895. Even though he didn’t publsh any more research papers on nuclein, Miescher left behind numerous letters, laboratory notes and manuscripts. Some letters were compiled by Wilhelm His after his death, the rest by some of his friends and published in 1896. His uncle wrote:
“The appreciation of Miescher and his works will not diminish with time, instead it will grow, and the facts he has found and the ideas he has postulated are seeds which will bear fruit in the future.”
Even as late as 1895 Miescher was thinking about nuclein and proposed that sperm could be suppliying a missing component to the egg nucleus perhaps by contact or through molecular movement. He however potentially missed interacting with the whole field of cytology, in which researchers were staining cells’ nuclei and had observed an association between nuclein and the chromosomes. One of the cytologists, Hertwig even suggested that nuclein was the fertilization substance, but these opinions remained obscured for Miescher.
The following 50 years of DNA research were not extremely fruitful as scientists could not explain how one molecule could encode all the required information for the diversity of life. It wasn’t until the 1940s when Avery, MacLeod, and McCarty demonstrated that DNA carries geentic infromation in their experiments with bacteria. In 1952 the Hershey and Chase experiments showed that genes were indeed made of DNA. Finally, in 1953, Rosalind Franklin, Maurice Wilkins, Francis Crick, and James Watson solved the double-helical structure of the molecule. It could finally be explained how DNA might function and how it can be replicated every time from one cell to another. The genetic code was solved almost a century after Miescher’s initial observations and by then there have been some historical articles and mentions of Miescher, however his work was largely forgotten, even thought the exptraction protocols remained fairly similar to his original methods.
"As grievous as it may be to be so sick, to you remains the consolation of having performed imperishable acts. You have made accessible a substantial analysis of the centre of all organic life, and as often during the next centuries as the cell and your work is scrutinized and exposed, the grateful descendant will remember you as a research pioneer."
Carl Ludwig to Miescher when he was ill
Miescher’s findings initiated the research into nuclein or nucleic acid, even though his findings were initially largely regarded as contaminations or “bad” science. The scientific community of his time and in the following 50 years did not consider DNA as a satisfactory explanation of heredity. His work on the mysteryous nuclein that he at least at one time considered might be the fertilization substance, persisted to his early death. His obsession lead him to ask questions, improve the extraction techniques, support his findings through other lines of investigation. His isolation methods remained the standard procedures for years after his death. Knowingly or not, he did discover DNA in the early days when no one could understand its significance - he had the appropriate interests, approach, and persistence at the time. He was researching the composition of cells, but grasped the opportunity to make the serendipous discovery of something much more anomalous and enigmatic at the time. His mind was ready to consider the possibility despite the unexpectedness of his findings.
All great reads and resources I used -
Anguera de Sojo, Á., Ares, J., Martínez, M.A. et al. Serendipity and the Discovery of DNA. Found Sci 19, 387–401 (2014). https://doi.org/10.1007/s10699-014-9348-0
Dahm, R. Discovering DNA: Friedrich Miescher and the early years of nucleic acid research. Hum Genet 122, 565–581 (2008). https://doi.org/10.1007/s00439-007-0433-0
Hall K, Sankaran N. DNA translated: Friedrich Miescher's discovery of nuclein in its original context. Br J Hist Sci. 2021 Mar;54(1):99-107. doi: 10.1017/S000708742000062X. PMID: 33602346.
Veigl, S.J., Harman, O. & Lamm, E. Friedrich Miescher’s Discovery in the Historiography of Genetics: From Contamination to Confusion, from Nuclein to DNA. J Hist Biol 53, 451–484 (2020). https://doi.org/10.1007/s10739-020-09608-3
Wilson, E.B. (1896) The Cell in Development and Inheritance. Macmillan (Columbia University biological series: Columbia University). Available at: https://books.google.co.uk/books?id=WRNysv0lfesC.