Heavy metals elements and the more reactive of the d-block elements. They have a strong affinity for oxygen and mostly exist as relatively low density silicate minerals. Chalcophile heavy metals are mainly the less reactive d-block elements, and period 4–6 p-block metals and metalloids. They are usually found in (insoluble) sulfide minerals. Being denser than the lithophiles, hence sinking lower into the crust at the time of its solidification, the chalcophiles tend to be less abundant than the lithophiles. On the other hand, gold is a siderophile, or iron-loving element. It does not readily form compounds with either oxygen or sulfur. At
Poxvirus AX element late mRNA cis-regulatory element Poxvirus AX element late mRNA cis-regulatory element The Poxvirus AX element late mRNA family represents a "cis"-regulatory element present at the 3' end of poxvirus late ATI mRNA and is known as the AX element. The AX element is involved in directing the efficient production and orientation-dependent formation of late RNAs. It is likely that this element directs the endonucleolytic cleavage of the transcript. It has been shown that the F17R late mRNA transcript which is also cleaved is also likely to share a common factor in their mechanism despite a lack of any obvious similarity in its cis-regulatory RNA