A modified protein assay from microgram to low nanogram levels in dilute samples.

In this article, we present a modified and improved protein assay that was previously described as "amidoschwarz assay" by Schaffner and Weissmann. Our improved protein assay is user-friendly and 30-40 times more sensitive than the earlier method. The assay was developed into three formats (macro-, micro-, and nanoassay) with trichloroacetic acid (TCA) as protein precipitating agent, measuring up to 96 samples.