Complex sentence: Entries in the database are organized according to chemical properties as well as biological activity against HIV in a cellular system, HIV enzymes in a cell-free system, and opportunistic pathogens associated with AIDS.
Split into simpler sentences: Entries in the database are organized according to chemical properties and biological activity. Biological activity is broken down into three categories: activity against HIV in a cellular system, activity against HIV enzymes in a cell-free system, and activity against opportunistic pathogens associated with AIDS.