Comparing the accuracy of protein measures for arthropods

Data on the protein content of arthropods can be useful for addressing a variety of ecological, behavioral, and physiological hypotheses. Yet, the most accurate method for measuring protein content (i.e., amino acid analysis) is expensive and the accuracy of less expensive measures of protein is unclear. We analyzed a diversity of ar-thropods to test for relationships between digestible protein content as measured by amino acid analysis and several common protein measures: crude protein, Bradford assay, BCA assay, and Lowry assay. In the full dataset, the closest relationship to the amino acid data was found for the Lowry assay and the average of the Bradford and Lowry assays. However, one species, Blattella germanica, appeared to be an outlier in some analyses. When the data were analyzed without B. germanica, the closest relationships to the amino acid data were found for the Lowry assay. Our results suggest that not all protein measures are equal in their ability to estimate amino acid content. Some arthropod species can also contain chemicals that interfere with the accuracy of protein assays. Given that it is unclear how often interfering compounds are found in invertebrates, it may be best to conduct multiple assays when analyzing the protein content of arthropods, especially the Bradford and Lowry assays.

Automated summary

Data on arthropod protein content is valuable for ecological, behavioral, and physiological studies. However, the accuracy of affordable protein measures is uncertain compared to amino acid analysis. By analyzing various arthropods, it was found that the Lowry assay and the average of the Bradford and Lowry assays showed the closest relationship to amino acid data. However, the species Blattella germanica appeared as an outlier in some analyses. When excluding B. germanica, the closest relationships to amino acid data were found with the Lowry assay. This suggests that not all protein measures are equally accurate and some arthropod species may contain interfering compounds.