Abstract
In the 310-360 mµ range, reduced pyridine nucleotide in mitochondria which are inside human liver tissue culture cells shows an absorption maximum between 335 and 330 mµ. Thus, between one-third and two-thirds of the reduced pyridine nucleotide is protein-bound. Accompanying the changes at 330 and 335 mµ, there is a decrease in absorption at 265 mµ. The decrease in 265 mµ absorption which accompanies pyridine nucleotide reduction is more than would be expected based on the increase in absorption seen at 330-340 mµ. The extra decrease in 265 mµ absorption may have its origin in adenine nucleotide loss or decreased mitochondrial light scattering. A consideration of changes in 265 mµ absorption in cultured ascites tumor cells produced by glucose and by Dicumarol has led to the proposal that the main factor responsible for the large decrease in 265 mµ absorption is adenine nucleotide loss.