Fig. 1.

The SPR band shift for 50 nm gold colloid coated with S protein (at 25 °C). In order to illustrate the mixture condition, the inset picture demonstrates the color of the mixture at pH ~7 (or pH ~10) and that at pH ~3 with roughly 10 times higher concentration than was used for the SPR study. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)