Question: The Oxus cobra contains what kind of ions for their venom to be active? 

full_context: Document 1: V. G. Khlopin Radium Institute: The V. G. Khlopin Radium Institute, also known as the First Radium Institute, is a research and production institution located in Saint Petersburg specializing in the fields of nuclear physics, radio- and geochemistry, and on ecological topics, associated with the problems of nuclear power engineering, radioecology, and isotope production. It is a subsidiary company of the Rosatom Russian state corporation.
Document 2: Ophionyssus natricis: Ophionyssus natricis or Reptile mite is a parasitic mite most commonly found on snakes, but also occurring on captive lizards, turtles, crocodiles and other reptiles. The parasites feed on snakes, which cause the bodies of the mites to be engorged with blood and fluids from the snake. Once the mites feed by puncturing through the snake skin, the snake usually shows symptoms of irritation and discomfort. Also this provides a point of entry where diseases from "Aeromonas spp." and Inclusion Body Disease (IBD) can be transmitted. Mites have also been shown to act as vectors for IBD. The pathology for disease transmission by the mites is still unknown. Human infestation has been reported.
Document 3: RNA modification database: This RNA modification databases are a compilation of databases and web portals and servers used for RNA modification. RNA modification occurs in all living organisms, and is one of the most evolutionarily conserved properties of RNAs. More than 100 different types of RNA modifications have been characterized across all living organisms. It can affect the activity, localization as well as stability of RNAs, and has been linked with human cancer and diseases.
Document 4: 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.
Document 5: Cemophora: Cemophora coccinea is a nonvenomous species of colubrid snake commonly known as the scarlet snake. It is the only member of its genus. They are native to the southeastern United States. There are three subspecies of "C. coccinea".
Document 6: Paranaja: Paranaja multifasciata or Naja multifasciata is a species of venomous elapid snake commonly known as the many-banded snake or burrowing cobra. The species is found in the Republic of Congo, the Democratic Republic of Congo and Cameroon in Africa.
Document 7: Nabis rugosus: Nabis rugosus is a predatory true bug. The species is found in the Palearctic.It is found in Europe from the North edge of the Mediterranean to southern Scandinavia. Further East, the distribution extends East across the Palearctic to Central Asia and Siberia. The species occurs everywhere in Central Europe and is found in the lowlands, as well as in the central uplands and in the Alps up to about 1500 meters above sea level. It is central Europe's most common species of sickle bug and it is found in many different habitats open, dry, shaded and moist but it prefers moderately moist, half shady places with dominant grass. Adjacent woodland vegetation is equally important
Document 8: Taspine: Taspine is an alkaloid which acts as a potent acetylcholinesterase inhibitor and cicatrizant. It is found in various plants including "Magnolia x soulangeana" and "Croton lechleri".
Document 9: Ribose: Ribose is a carbohydrate with the formula CHO; specifically, it is a pentose monosaccharide (simple sugar) with linear form H−(C=O)−(CHOH)−H, which has all the hydroxyl groups on the same side in the Fischer projection.
Document 10: Caspian red deer: The Caspian red deer ("Cervus elaphus maral"), is one of the easternmost subspecies of red deer that is native to areas between the Black Sea and Caspian Sea such as Crimea, Asia Minor, the Caucasus Mountains region bordering Europe and Asia, and along the Caspian Sea region in Iran. The Caspian red deer is sometimes referred to as maral, noble deer, or eastern red deer.
Document 11: Ribonuclease V1: Ribonuclease V1 (RNase V1) is a ribonuclease enzyme found in the venom of the Caspian cobra ("Naja oxiana"). It cleaves double-stranded RNA in a non-sequence-specific manner, usually requiring a substrate of at least six stacked nucleotides. Like many ribonucleases, the enzyme requires the presence of magnesium ions for activity.
Document 12: Isotopes of vanadium: Naturally occurring vanadium (V) is composed of one stable isotope V and one radioactive isotope V with a half-life of 1.5×10 years. 24 artificial radioisotopes have been characterized (in the range of mass number between 40 and 65) with the most stable being V with a half-life of 330 days, and V with a half-life of 15.9735 days. All of the remaining radioactive isotopes have half-lives shorter than an hour, the majority of them below 10 seconds, the least stable being V with a half-life shorter than 55 nanoseconds, with all of the isotopes lighter than it, and none of the heavier, have unknown half-lives. In 4 isotopes, metastable excited states were found (including 2 metastable states for V), which adds up to 5 meta states.
Document 13: Latrodectus pallidus: Latrodectus pallidus is a species of spider commonly found throughout North Africa, the Middle East, and central Asia. A common name in English is the white widow spider, and it is known in Russian as белый каракурт, or white steppe spider. It is a member of the genus "Latrodectus", which includes species known as widow spiders, which is placed in the Theridiidae family. It occurs both in the steppes of southern Russia, Kazakhstan, and other southwest Asian countries, as well as in the desert regions of the Middle East. Compared to other widow spiders in the region, the white widow spider is comparatively rare.
Document 14: Caspian tiger: The Caspian tiger ("Panthera tigris virgata") is an extinct tiger subspecies, which inhabited the sparse forests and riverine corridors west and south of the Caspian Sea, from Turkey, Mesopotamia, Iran and the Caucasus, through Central Asia to the Takla Makan desert of Xinjiang in China, until the end of the 20th century. Depending on the region, it was also called Hyrcanian tiger, Turanian tiger, Persian tiger, and "Babre Mazandaran" (Persian: ‎ ‎ , Tiger of Mazandaran). It was one of the largest big cats to have ever lived and was described as being intermediate in size between Siberian and Bengal tigers.
Document 15: Black-necked spitting cobra: The black-necked spitting cobra ("Naja nigricollis") is a species of spitting cobra found mostly in sub-Saharan Africa. They are moderately sized snakes that can grow to a length of 1.2 to in length. Their coloration and markings can vary considerably. They prey primarily on small rodents. They possess medically significant venom, although the mortality rate for untreated bites on humans is relatively low (~5–10%, in endemic regions under 1%). Like other spitting cobras, they can eject venom from their fangs when threatened (one drop over 7 m and more in perfect accuracy). The neurotoxic venom irritates the skin, causing blisters and inflammation, and can cause permanent blindness if the venom makes contact with the eyes and is not washed off.
ground_truth: magnesium