Fig. 7. Cellular and nuclear accumulation of Bb-histone conjugate within the Colo-205 cells – cytoplasm and nuclei. (A) The amount of Bb-H2A present in the nuclei of cells incubated in 37°C was considered to be 100% and represents 6.4 nmol/mg protein; it was estimated to be 58% of the total added Bb-H2A. (B) Bb-H2B conjugates. ATP depletion was performed as described in Table 1 and cells were fixed (prior fixation) as described in Fig. 2. 100% represents 6.2 nmol histone/mg protein and was estimated to be 62% of the total added Bb-H2B. ^*Bb-H2B incubated in 37°C, 4°C, ATP-depleted cells or after prior fixation gave the same results as biotinylated Bb-H2B alone. Biotinylated conjugates were prepared and their accumulation within the cell cytosol and nuclei was estimated as described in Materials and Methods. , nuclei; , cytosol. The ratio given (in A and B) are in mole:mole.