Gallium

Metals that are good semiconductors for computers are found to have anti-tumor activity.

Med Hypotheses 1988 Aug;26(4):239-49
Carcinogenesis as the result of the deficiency of some essential trace elements.
Marczynski B
Department of Biochemistry, Silesian University, Katowice, Poland.
"Energetic" biological trace elements:

• gallium (III)
• germanium (IV)
• silicon (silica)
• arsenic (V)
• selenium (IV)

occurring in DNA of eukaryotic cells may improve the semiconductor properties of DNA and may influence the mechanisms that control genetic expression at the electronic level. Their roles are postulated as follows: (i) to maintain the level and direction of free sliding electrons in DNA, (ii) to modulate the electron conductivity and hole conductivity of DNA. This specific electronic nature of DNA take the form of magnetic pigeonholes in which an electric pulse is (0), or is not (1) stored as an area of local magnetisation. These types of conductivity occurring in different parts of DNA of different cells could participate in the switch on and switch off of genetic information in gene expression. This model may help to elucidate the mechanism of action of these naturally occurring antitumor agents and may help in understanding the role of trace elements in charge transport of DNA and in carcinogenesis.