FIGURE 2.

Optical properties of microstructured test compartments. (A) OSTR chamber with attached TC array. (B) Vertical confocal scan through TCs filled with immersion oil, 40-fold 1.0 NA objective (left) or a 4-μM aqueous solution of Alexa488-NTF2, 16-fold 0.5 NA objective (right). (C) Horizontal confocal scans of the TCs shown in B. Vertical positions of the scans as indicated. Scale bars: 30 μm. (D) Schematic drawing of arrangement in transport measurements (cf. Fig. 4). Two TCs are shown, one covered by a membrane (measuring TC), the other without membrane (reference TC). The transport substrate (triangles) is able to permeate the membrane and thus to fill both the measuring and the reference TC. The control substance (circles) cannot permeate the membrane and is therefore found only in the reference TC. The fluorescence is sampled (dashed line) at a depth of x = 30 μm (i.e., x/L = 0.6), which is optimal for measurements inside TCs.