Mitochondrial matrix
The cytosolic, intermembrane space, compartment has a water content of 3.8 μl/mg protein, while the mitochondrial matrix 0.8 μl/mg protein. It is not known how mitochondria maintain osmotic balance across the inner mitochondrial membrane, although the membrane contains aquaporins that are believed to be conduits for regulated water transport. Mitochondrial matrix has a pH of about 7.8. Mitochondrial DNA was discovered by Nash and Margit in 1963. One to many double stranded mainly circular DNA is present in mitochondrial matrix. Mitochondrial DNA is 1% of total DNA of a cell. It is rich in Guanine and Cytosine content. Mitochondria of mammals have 55s ribosomes.
John E. Walker
From 1969 to 1971, Walker worked at the University of Wisconsin–Madison, and from 1971–1974 in France. He met Fred Sanger in 1974 at a workshop at the University of Cambridge. This resulted in an invitation to work at the Laboratory of Molecular Biology of the Medical Research Council, which became a long-term appointment. Among the other staff was Francis Crick, who was well known for his discovery of the molecular structure of DNA. At first, he analyzed the sequences of proteins and then uncovered details of the modified genetic code in mitochondria. In 1978, he decided to apply protein chemical methods to membrane proteins. In this way, Walker characterized the subunit composition of proteins in the mitochondrial membrane and the DNA sequence of the mitochondrial genome.