One hundred
microliters of a Limulus amebocyte lysate with substrate was added to the
sample. The plate was monitored at 405 nm for 40 min at 37°C in a Molecular
Devices (Sunnyvale, CA) model 384 spectrophotometer equipped with Softmax
software, version 4.7.1. The mean rate of optical density change was determined
for each well, and the BG concentration was determined by comparison to a
standard curve.