Proteomic analysis of individual fruit fly hemolymph.

Analysis of blood proteins holds critical promise for in depth understanding of physiological states. Protein content of hemolymph from Drosophila melanogaster is of particular analytical interest because the insect open circulatory system involves chemical signaling through the hemolymph. The challenge of working with this sample, however, is the nanoliter volumes of solution available for analysis. In this study, we developed a novel hyphenated Agilent nano-HPLC chip column-MS method to obtain proteomic information from individual fruit fly hemolymph, using a low-volume sample collection technique established previously. The total amount of individual Drosophila hemolymph protein is determined around 0.798 ± 0.251 μg/100 nL based upon a Bradford assay with BSA. Hemolymph samples around 50 nL were collected from single flies and digested using a customized micro-scale digestion protocol. Mass spectral analysis shows a total of 19 proteins were identified from the hemolymph of individual flies. Of these findings, 6 novel proteins have been identified for the first time with evidence at the translation level. Detection of 13 proteins well-known in the literature speaks to the method's validity and demonstrates the ability to reproducibly analyze volume-limited samples from individual fruit flies for protein content. This nano-scale analysis method will facilitate future study of Drosophila and lead to a more complete understanding of the physiology of the fly model system.