Parallel sequential reactor

A reactor for sequentially modifying a molecule attached to a solid phase support, comprising

• a plurality of substrate carriers, each substrate carrier capable of carrying a solid phase support to which a molecule to be modified can be attached,
• a plurality of reagent chambers, each capable of comprising a reagent for effecting a modification of said molecule, and
• means for individually bringing each of a plurality of chosen substrate carriers into a reagent-contact mode and a reagent-non-contact mode with each of a plurality of reagent chambers comprising means for individually positioning each of a plurality of chosen substrate carriers in a reagent-contact mode and in a reagent-non-contact mode, and means for positioning each of a plurality of chosen reagent chambers relative to a chosen substrate carrier such that when said chosen substrate carrier is in said reagent-contact mode said chosen substrate carrier is in contact with the contents of a chosen reagent chamber and when said chosen substrate carrier is in said reagent-non-contact mode said chosen substrate carrier is not in contact with said contents of said chosen reagent chamber and wherein said individual positioning means is positioned such that a first substrate carrier and a second substrate carrier can be simultaneously placed in the reagent-contact mode with respect to a first chosen reagent chamber,
• each of a plurality of said substrate carriers being capable of sequential contact with the contents of a plurality of said reagent chambers said sequential contact being capable of resulting in the sequential modification of molecules attached to said solid phase supports on said plurality of substrate carriers.