Dr. Nanadkumar M Kamat
A doctorate in Micro-biology, is a scientist and science writer.
Deoxyribonucleic acid, a nucleic acid commonly known as DNA is unlike any other acid or chemical on Earth.
The very history of discovery of DNA as a special molecule and its structure later is a voluminous history. But the world knows more about the interesting story of the DNA structure and less about the original paper when DNA was discovered as a nuclear biochemical 150 years ago. Those were the very fresh years of beginning of the new subject of biochemistry in Europe.
There was very little understanding of the chemical basis of cells and their internal metabolism and slowly the scientists were trying to elucidate the chemical basis of life and living systems. Germany was one of the leading countries in study and research in chemistry and biochemistry in the 19th century. Ernst Felix Immanuel Hoppe-Seyler was a German physiologist and chemist, trying to develop the new field of biochemistry at the University of Tübingen, Germany. History now recognises him as the principal founder of the disciplines of biochemistry and molecular biology. He did not know that one day he would admit a Swiss student- Johann Friedrich Miescher, in his laboratory which was doing work on tissue chemistry and he would discover a new chemical which would be later called DNA.
Friedrich’s father was a physician and taught pathological anatomy. Friedrich’s uncle, Wilhelm His, was a well-known embryologist. Scientific research is full of scepticism which many times frustrates the young researchers like Miescher who was born in 1844 in Basel, Switzerland. Miescher had a hearing handicap. First, he wanted to be a priest. Due to opposition from his father; he got admission and graduated from the medical school in 1868. Then due to hearing handicap he left clinical practice and pursued a research career. After joining the laboratory of Ernst Hoppe-Seyler, Miescher began to develop an interest in the study of the white blood cells because his mentor asked him to focus researching their composition. These cells cannot be easily extracted from the lymph glands. But as the body’s cellular defenders they accumulate in large quantities in the pus from the infections. Miescher had to visit a nearby clinic, collect bandages and obtain his pus samples after washing. He experimented on the cells in the pus samples. The proximity of the clinic was useful to him to get the large quantities of the samples periodically and work on the composition of these cells.
When he began to study the nucleus of the cell, he was surprised that it contained a substance which was different from the proteins or the lipids which are the normal constituents of the cells. Since there was no previous work on the chemical identity of this substance, he named it ‘nuclein’. At that time, he was convinced that the new substance ‘nuclein’ would turn out to be as important as proteins. He discovered after analysis that the ‘nuclein’ was made up of hydrogen, oxygen, nitrogen and phosphorus. He also found a unique ratio of phosphorus to nitrogen. Then he proceeded to isolate nuclein from other cells and later used salmon sperms as samples. This discovery was reported to Ernst Hoppe-Seyler in 1869. But he was not convinced about the discovery of ‘nuclein’ as a new chemical.
Disbelieving the discovery by a young Miescher, Ernst Hoppe-Seyler began to repeat the experiments himself. But finally, he had to agree that it was a new substance. The delayed results were published in 1871. At the time of discovery Miescher was not aware about the structure of ‘nuclein’ and its role as blueprint of life. But he reported that ‘nuclein’ could be found in the sperm cells of many animals. He himself had erroneously believed that proteins were the molecules of heredity.
Miescher continued to work on nuclein for the rest of his career. Often, he spent long hours isolating ‘nuclein’. He also did research on metabolic changes that occur in salmon when they spawn. He did not enjoy his new position in 1872, as the professor of physiology at the University of Basel as he disliked teaching and preferred research. In 1899, German scientist Richard Altmann coined the term ‘nucleic acids’. Albrecht Kossel in 1910 got a Nobel Prize for his work on elucidation of ‘nuclein’ mystery. He identified and named adenine, cytosine, guanine, thymine and uracil as the five basic components of nucleic acid and founded nucleic acid research as a special branch of chemistry. Then biochemist Erwin Chargaff came on the scene and showed that in all DNA samples guanine equals cytosine and adenine equals thymine.
The interest in DNA research then picked up. On May 6, 1952, at King’s College London in England, Rosalind Franklin with her student Raymond Gosling photographed her 51st X-ray diffraction pattern of DNA. At that moment it didn’t occur to her that she was looking at a double spiral structure. But there were smarter people around who guessed it right and finally Cambridge University scientists James D Watson and Francis H C Crick solved the structural mystery of the world’s most important biomolecule DNA on the morning of February 28, 1953. The structure of 19th century nuclein and 20th century DNA was found to be a double helix.
In the past 150 years since the discovery of ‘nuclein’ the world has advanced to create synthetic life in the laboratory. But we should not forget how it all began 150 years ago.
Courtesy: The Navhind Times, Goa. www.Navhindtimes.com