Biochemical and ultrastructural characterizations of nucleoprotamine in human sperm heads treated with micrococcal nuclease and salt

Preparation of human sperm heads containing mainly nucleoprotamines as their chromatin constituent was described. Acrosome‐depleted human sperm heads were treated with micrococcal nuclease followed with 2 M NaCl. The treatment specifically removed nucleohistone as small chromatin fragments from the human sperm heads. The nuclease‐NaCl‐treated sperm head pellets primarily contained nuclease‐resistant nucleoprotamine as their chromatin. Transmission electron microscopic study showed that there were two populations of the nuclease‐NaCl‐treated human sperm head pellets. One population had thick nucleoprotamine cords of ˜650–1,200 Å in diameter, and the other had thin nucleoprotamine cords of ˜330–420 Å.