The Oxus cobra contains what kind of ions for their venom to be active? 
Ribonuclease V1:  Like many ribonucleases, the enzyme requires the presence of magnesium ions for activity. Caspian cobra: The Caspian cobra ("Naja oxiana"), also called the Central Asian cobra, Oxus cobra or Russian cobra, a member of the family Elapidae found in Central Asia.
magnesium