3.2. Permeation of denaturant via microchannels
Using the value of P determined in as described in Section 3.1, a
microchannel with channel height d = 500 μm, width W = 5
mm, total length Z = 40 cm was designed and fabricated. A 5 M
GdnHCl solution was fed from the feed channel inlet, pure water was fed
from the permeation channel inlet, and the GdnHCl concentrations at the
feed and permeation channel outlets were measured (Fig. 5). By changing
the flow rate of the feed side, the residence time, τ , in the
channel was changed to be 10 minutes (in a time range of 0–50 minutes),
20 minutes (in a time range of 50–150 min), or 30 minutes (in a time
range of 150–300 minutes). After switching the flow rate, the GdnHCl
concentrations converged to a constant value for both the feed and
permeate sides for each residence time. The expected GdnHCl
concentration at the feed outlet, c fZ, calculated
using eq. (3) is as shown in Table 1. The results shown in Fig. 5 are
almost identical to the values calculated using eq. (3), and confirmed
that the microchannel functioned as designed. The GdnHCl concentration
required for model protein refolding was 0.5 mol/L or less. The
concentration was attained at a residence time of 20 minutes at the feed
outlet. It therefore appears that the refolding process can be carried
out in only 20 minutes.