Under normal circumstances, the basic protein (nucleoprotein) that binds to the DNA of the sperm nucleus will undergo a natural maturation process from histone to ichthyoglobin, and this matured ichthyoglobin has a special protective effect on the sperm genes (DNA), and the process of the gradual replacement of the histone protein by the ichthyoglobin protein is called the sperm nucleoprotein histoconversion, which is of great physiological significance. Sperm nucleus carries all the genetic information from the father, these genes must be expressed after fertilization, before fertilization, sperm genes in the special protection of fischerin, tightly concentrated, without any DNA transcription, but when the nucleoprotein histotype conversion abnormalities can cause male infertility or early embryo abortion, the mechanism is: ① sperm DNA is unstable and vulnerable to damage and difficult to conceive; ② once fertilized, the sperm will be able to be used in the early stages of fertilization. Once fertilization occurs, the sperm nucleus cannot depolymerize normally due to abnormal nucleoprotein histotype, thus affecting the fusion of male and female prokaryotic nuclei; (3) the embryo cannot develop normally, resulting in the premature death of the embryo and miscarriage. Therefore, the amount of histones is an important indicator of sperm maturity.

Sperm nucleoprotein staining solution (aniline blue method) is based on the principle that under acidic conditions, aniline blue specifically combines with lysine residues rich in sperm nucleoprotein to produce violet-blue compounds, and the maturity of spermatozoa can be judged according to the depth of the coloring.