title: GSM4308651: human_pachytene_H3K27ac_ChIP; Homo sapiens; ChIP-Seq
library_construction_protocol: Pachytene spermatocyte and round spermatid fractions were collected by StaPut (Bellve et al 1993).  Purity was assessed under phase optics and was consistently >95% for each desired cell type.  Cells were washed once in PBS and then split into two aliquots.  One aliquot (for ChIP) was fixed in 1% formaldehyde then quenched with 2.5M glycine, while the second (for RNA) was left unfixed.  Both fixed and unfixed aliquots were snap frozen in liquid nitrogen, then stored at -80C.  ChIP was performed as previously described (Lesch et al 2013). ChIP-seq libraries were prepared using a TruSeq ChIP sample prep kit (Illumina) according to the manufacturer's instructions, except that size selection was performed after instead of before PCR amplification.