An article for performing a reaction includes a reagent well having a side wall, a bottom wall and an open upper end. A lyophilized reagent is retained within the well by a non-integral retention feature that is inserted into the open upper end of the well and fixed to a side wall above the reagent. An opening in the retention feature is smaller than the diameter of the reagent, but is sized to permit a pipette tip to be inserted into the well. The retention feature may be a collar fixed to the side wall and may include fingers extending axially into the well. The well and the retention feature may be correspondingly tapered. A method for reconstituting a lyophilized reagent includes the steps of drawing into a pipette tip attached to an automated pipettor an amount of a diluent and dispensing the diluent into the reagent well to thereby reconstitute the lyophilized reagent.

System, apparatuses, and methods for performing automated reagent-based analysis are provided. Also provided are methods for automated attachment of a cap to a reaction receptacle, and automated removal of a cap from a capped reaction receptacle.

Methods and systems are provided for a fluid reservoir plug. In one example, a single-piece plug for a fluid reservoir includes a shaft, the shaft including a threading, a conduit, and a channel. The channel extends transversely through each thread of the threading to the conduit. Furthermore, while the threading is coupled to the fluid reservoir at an opening of the fluid reservoir, fluid exits the opening by flowing along the channel before flowing through the conduit.

A cap having a lower portion, an upper portion with an opening formed therein, and a plurality of longitudinally oriented ribs disposed on an inner surface of the cap. The inner surface of the cap is defined by the opening formed in the upper portion of the cap, and each rib is associated with a concave recess disposed directly opposite the rib on an outer surface of the upper portion of the cap. The recess extends along at least part of the length of the rib.