Thematic minireview series: metals in biology.

Metals have important roles in biochemistry ranging from essential to toxic. This prologue introduces the second of the Thematic Minireview Series on Metals in Biology, which includes minireviews on five metals: iron, zinc, nickel, vanadium, and arsenic. Three of the minireviews are focused on the roles of the metals in enzymes (iron, nickel, and vanadium). Zinc deficiency is discussed in another, and the arsenic minireview deals with the toxic and some potentially useful applications of the biological effects.