Can museum egg specimens be used for proteomic analyses?

We found that some of the expected key eggshell proteins (3 out of 11) were not present in the samples of museum quail egg. These proteins were either entirely absent from the museum eggs or the technique was unable to detect them. There was no pattern in the absent proteins in the sense of protein function or where they are located within the eggshell.We conclude it is likely that such studies on museum specimens using a proteomic approach will be limited in coverage of proteins and may, therefore, be misleading.Mass spectrometry and proteomic analyses have become powerful tools for the analysis of proteins and peptides [1]. The recent elucidation of the chicken genome has provided the opportunity to apply this technique to identify and then categorise the matrix proteome of the chicken eggshell [2,3]. The avian eggshell is a highly regulated crystalline biocomposite ceramic composed of multiple layers, predominantly the trigonal phase of calcium carbonate (CaCO3), known as calcite [3]. Eggshells provide a number of important functions such as protection against physical damage and microbial contamination, regulation of gas and water exchange during embryogenesis, and provision of calcium for embryonic development [3,4]. The general structure of the eggshell consists of the innermost membrane, a continuous calcified layer, and the outermost cuticle [2,4], and thus far, over 520 proteins have been identified from these three layers [2] by use of a proteomics approach.With few exceptions, most studies on eggshell proteins have been associated with the commercial poultry industry or other domesticated species [5,6]. For example, Panheleux et al. [6] compared the biochemical characteristics of eggshells from seven domesticated species of birds. Their study showed the presence of common matrix components in the various domestic avian species, supporting the notion of universality of their distribution across species. However, their study also demonstrated some particula