Detecting the quantity of a protein is one thing, knowing if its intact and functional is another. Proteins are much more difficult to work with than DNA, says Jeremy Gillespie, Ph.D., business segment manager, Invitrogen (www.invitrogen.com).
This has slowed the development of protein microarrays. But, we have begun to develop microarrays in which we can look for measures of protein function such as interactions with other proteins, DNA, signaling pathways, and with small molecules. Such microarrays may dramatically accelerate drug target identification, as well as selection and validation.
A functional microarray requires that the coated proteins maintain stability. Dr. Gillespie explains, Arrays can contain more than 3,000 different human proteins. So, the first thing we do is to express and then purify each protein. We use the baculovirus system to generate proteins.
Next we coat these onto glass slides. Weve tracked stability over time and found most proteins are stable for at least one year. Part of our processing practices involves purifying and arraying under cold temperatures followed by immediate storage in a freezer.
Dr. Gillespie believes that as functional arrays become more widely used, they will help to more fully realize the true potential of protein microarrays. There used to be a lot of pessimism about the feasibility of using protein arrays. But with new advances in protein expression, purification, and coating techniques things are looking up.
Invitrogen recently introduced its high density ProtoArray Human Protein Microarray. The functional array includes pharmaceutically relevant protein classes such as kinases, membrane-associated, cell-signaling, and metabolic proteins. The assay can be completed in less than four hours as contrasted to weeks required for similar experiments, according to the company. They also plan to launch a human proteome-wide array in 2006.