Protein quantification in ecological studies: A literature review and empirical comparisons of standard methodologies

Protein quantification is a routine procedure in entomological studies despite the inherent

limitations of well-acknowledged protein determination methods. We want to bridge this

knowledge gap in hopes of improving the way we quantify proteins and interpret findings.

We surveyed the literature to determine how and why researchers

quantify proteins. To determine whether different quantification methods

produce comparable results across taxa and between populations of a single

species, we estimated the protein content of eight phylogenetically diverse

taxa, and of desert isopods fed different diets, using various derived protocols

of three standard methods.

We found that many protein quantification procedures are being used, often without

reporting the crucial information needed to evaluate and repeat the study.

Our empirical work demonstrated that the three quantification methods

examined, and their derived protocols, resulted in highly divergent protein estimations

that were inconsistent in rank across taxa, preventing conversion between

methods. We also found that different quantification methods yielded different

answers to whether isopod protein content is affected by diet.

We conclude that commonly used quantification techniques yield distinct protein

estimations with varying precision. No single method is likely to be more

accurate than another across taxa which may lead to inconsistent results across

taxa and between conspecifics. Inaccurate protein quantification may explain the

observed mismatch between organismal N and protein that has plagued some recent

studies. We recommend using a single BCA protocol to reduce inconsistencies across

studies, until the promising amino acid analysis becomes more affordable, accurate and

accessible.