A number of phosphoproteins and glycoproteins are found in bone. Some Sp100 variants contain a domain similar to two interferon-inducible nuclear phosphoproteins, suppressin and DEAF1. Other materials (such as lipids, phosphoproteins, and phospholipids) are also secreted. Phosphorus-32 is widely used for labeling nucleic acids and phosphoproteins. The nucleocapsid core is composed of the genomic RNA, nucleocapsid proteins, phosphoproteins and polymerase proteins. It is in the class of phosphoproteins and generally occurs in mammalian milk. Synapsins encode neuronal phosphoproteins which associate with the cytoplasmic surface of synaptic vesicles. Synapsin I phosphoproteins make up approximately 6% of the total protein in synaptic vesicles. Phosphoproteins have been proposed as biomarkers for breast cancer. Phosphoproteins could be cancer markers useful to cancer diagnostics and therapeutics.