ConversionRules is an option for Cell which can be set to a list of rules specifying how the contents of the cell are to be converted to external formats.
Typical elements in the list have the form "TeX"
->
data.
Settings for ConversionRules do not affect the display of cells in the standard Mathematica notebook front end.
ConversionRules can be used to save the original form of a cell that has been converted from an external format.