Table 1.

CENP-A nucleosomes have one copy of CENP-A and H2B

Chromatin	Antibody	Nucleosomes observed, N	Single 5-nm bead	Two 5-nm beads	Nm between beads*
CENP-A	CENP-A	576	576	0	> 12
CENP-A	H2B	588	588	0	> 12
Bulk	H3	632	589	43	< 9
Bulk†	H2B	114†	109	5	< 9

^*Center-to-center distances were plotted for gold beads.

^†Efficiency of detection of H2B’s C-terminal epitope was 30-fold less for bulk nucleosomes compared to CENP-A nucleosomes.