We know the sequence of DNA. Proteins: can we know it all?
Modern technologies allow us to sequence the genome of nearly any living organism in the world. However, knowing only the sequence of DNA nucleotides is not nearly enough to understand how the organism works. Sofisticated software can predict the genes based on the nucleotide sequence, and even predict the proteins made on this gene matrix, but what happens to the proteins in a cell after they are produced? For specific proteins we can predict or even already know the function, but where do they go in the cell? Do they attach to the membranes or interact with other proteins? How does it affect their performance?

Tubes with Synechocystis cell culture. Left: intact cells. Center: Membrane fraction of Synechocystis is isolated from other parts of the cell and concentrated. Right: Plasma (top of the tube) and thylakoid (mid-bottom of the tube) membranes are isolated and concentrated.
My first post-doctoral work was devoted to the proper separation of different membrane fractions of cyanobacterial cell Synechocystis and identifying proteins in them. It was a fundamental research, with results that are now a reference on protein localization for other protein-related research in Synechocystis.
ADDITIONAL READING:
Pisareva T., Shumskaya M., Maddalo, G., Ilag, L., Norling B. (2007) Proteomics of Synechocystis PCC 6803: Screening of integral plasma membrane proteins. FEBS J, 274(3):791-804. Download Full Text (FEBS J 2007)