The invention relates to a method of identifying any protein tyrosine phosphatase that undergoes reversible modification of PTP active site invariant cysteine within a cell, such that the phosphatase is transiently protected from irreversible active site invariant cysteine-directed PTP inactivating agents. The front panel has a number of slits, two locking holes, and a through hole. This false surface allows a thin photoresist layer to be spun across the front surface. The plurality of indentations form a pocket by which the tubular element is held.