Table 2. Global Abundances of Histone H4 Internal Acetylation Isomers^a from Asynchronous Chlamydomonas Cultures.

unacetylated	unacetylated 52.9 ± 8%
monoacetylated	K5ac	K8ac	K12ac	K16ac
	9.0 ± 1.4%	1.1 ± 0.8%	6.8 ± 1.5%	3.6 ± 1.2%
diacetylated	K5ac + K8ac	K5*/K8ac + K12ac	K12ac + K16ac	K5*/K8ac+K16ac
	1.0 ± 0.6%	5.5 ± 1.4%	0.4 ± 0.3%	0.4 ± 0.5%
triacetylated	K5ac + K8ac + K12ac	K5ac + K8ac + K16ac	K5ac + K12ac + K16ac	K8ac + K12ac + K16ac
	1.2 ± 0.4%	0.5 ± 0.2%	1.5 ± 0.5%	0.3 ± 0.1%
tetraacetylated	K5ac + K8ac + K12ac + K16ac		K5ac + K12ac + K16ac + K20ac
	0.9 ± 0.6%		0.1 ± 0.1%
pentaacetylated	K5ac + K8ac + K12ac + K16ac + K20ac
	0.5%b

^aAll acetylated isomers in this table were also modified at Nα-ac, K79me1, and M84ox. Variances represent the standard deviation from three biological experiments.

^bOnly selected for MS/MS once among four LC–MS DDA experiments.

^*While assignment to K5 or K8 is ambiguous, the level of K5 acetylation is much greater than K8 acetylation and is identified as the predominant second acetylation site (see Figure 3 and the text).