A RAPID MICROSCALE METHOD FOR THE EXTRACTION AND ANALYSIS OF PROTEIN IN MARINE SAMPLES

A micro-scale method for the extraction and analysis of proteins in pa rticulate material was developed by applying the bicinchoninic acid (B CA) assay together with a ribulose-1,5-diphosphate carboxylase (RuDPCa se) as a new standard. The BCA assay was modified for the rapid analys is of particulate protein collected on filters, and provides several a dvantages over other methods currently in use. Firstly, it is not sens itive to free amino acids or chitin which may complicate other methods . Secondly, reagent and reaction products are highly stable, allowing greater precision. As the principal algal protein and a potentially im portant component of detritus, RuDPCase is proposed as a preferred sta ndard for systems where photo-synthetically-derived carbon is the prin cipal input. The protein amino acid composition of the diatom Thalassi osira fluviatilis, the prymnesiophyte Isochrysis galbana, the cyanobac terium Synechococcus sp., suspended particulate and sediment trap mate rial showed good agreement with the RuDPCase standard, supporting its use in algal protein assays. In a comparison of the BCA and modified L owry assays, RuDPCase consistently exhibited a lower absorbance respon se than bovine serum albumin (BSA), suggesting that present field esti mates of protein to date are conservative. The combination of the modi fied BCA assay and more appropriate protein standard should allow for more quantitative estimates of protein content in marine samples.