Bidirectional switches are described. The protective film is composed of at least one layer and has a total thickness of 30 to 500 nm. Preferably the head comprises flexibly linked segments and is flexibly linked to the toothbrush handle. The method of sequencing DNA can comprise contacting amplification reaction products with the composition under conditions in which excess amplification primer is degraded by the nuclease and the chemically-enhanced primer is essentially non-degraded. Finally, a lateral brake is carried by the ladder which prevents the roller carriage from moving laterally. Alternatively, metadata contained within the EndpointReference might vary depending on the recipient\u2014policy metadata contained within the EndpointReference might specify more stringent security requirements depending on the recipient.