3.7. Taylor Dispersion Analysis (TDA)

Taylor dispersion analysis was conducted using a Beckman P/ACE MDQ equipped with a diode array detector (Beckman-Coulter, Fullerton, CA, USA). The UV traces were recorded with the Beckman 32-Karat software 7.0 (Beckman) at a wavelength of 214 nm. A fused silica capillary (Polymicro Technologies, Phoenix, AZ, USA) with a total length of 50.2 cm (75 µm id) and 40 cm to the detection window was used for the dispersion measurements. Samples containing 2 × 10⁻⁴ M cAMP in 0.067 M phosphate buffer, pH 7.4, were introduced into the capillary by applying a pressure of 0.5 psi for 3 s into the capillary filled with the buffer, followed by a mobilization pressure of 0.7 psi to force the sample plug through the capillary with buffer (n = 7). The temperatures of the sample tray and capillary cartridge were set to 25 °C and 37 °C, respectively. The diffusion coefficient of cAMP was determined using Fida data analysis software (Fida Biosystems ApS, Søborg, Denmark).