FREDRICK MEISCHER

Name: Fredrick Meischer 

Born: August 1844

Education: University Of Basel

Year(s) of Major Scientific Discovery: 1869

Swiss Chemist Fredrick Meischer discovered Nuclein, a molecule that we now know today as Deoxyribonucleic acid (DNA) in the year 1869. Meischer discovered the molecule while analyzing pus-coated bandages collected from hospitals. 

Fredrick Meischer discovered Nuclein by exposing samples extracted from the used bandages and exposing them to alkaline followed by an acidic medium. This produced a precipitate. Meischer was able to differentiate the molecule he had discovered by analyzing the chemical components. He noticed that the molecule contained more than the regular carbon, nitrogen, and oxygen observed from normal organic molecules. He realized that they contained higher concentrations of phosphorous as well. These high concentrations of phosphorous are what we now recognize today as the phosphate backbone of DNA.

Furthermore, Meischer discovery pointed out a similarity between the ratios of nitrogen to phosphorous. From a modern-day point of view, we can confirm that the ratio of nitrogen to phosphate molecules makes sense since within a DNA molecule nitrogenous bases are covalently bonded to a ribose sugar and a phosphate group.

Nucleoside structure. Image 3b

FURTHER RESEARCH

Meischer, later on was able to prove he had discovered a new molecule and some of its chemical characteristics. He did this by obtaining nuclein from a secondary source, one that provided nuclein in abundance. His choice of a cell to work with was sperm (spermatozoa) specifically that of salmon. He then carried out his previous method of purifying and precipitating the samples which led him to conclude that nuclein contained: carbon, nitrogen, phosphorous and was devoid of sulfur. The fact that the molecule was devoid of sulfur enhanced the fact that Meischer had in fact discovered a new molecule and that it was not a different form of a protein molecule. 

His research using spermatozoa concluded the following: 

DNA has a high molecular weight which explained why it did not diffuse well.

DNA was acidic due to the presence of phosphoric acid/ phosphate group as a result of its negative charge associated with delocalized electrons.