Using Dendrimer to Selective Extract and Concentrate Peptides for Analysis by MALDI-TOF MS
Figure 1. Second generation amphiphilic dendrimer forms reverse micelles that have negatively charged interior when it is assembled in toluene.
Very selective and highly sensitive ways to detect peptides or proteins of interest remain important goals in proteomics applications. Amphiphilic dendrimers that self-assemble in apolar solvents can be used in a liquid-liquid extraction methodology to selectively extract and concentrate peptides from aqueous solutions (Figure 1). After extraction the dendrimer-peptide mixtures are amenable to direct analysis by mass spectrometry (MS) using matrix-assisted laser desorption/ionization (MALDI). The dendrimers that self-assemble in apolar solvents have charged interiors that allow oppositely-charged peptides to readily migrate into the aggregate’s core, while similarly-charged peptides do not (Figure 2).Studying the factors such as pH, ionic strength, hydrophobicity, dendrimer generation, which influence the uptake of peptides by these materials, will help optimize this method of peptide extraction. In addition, a better understanding of the extraction mechanism and how these materials potentially improve the MALDI analysis of peptides will pave the way for a faster and more reliable way to protein identification.
Figure 2. A Schematic representation of the extraction protocol. Dendrimeric reverse micelles are capable to selectively extract complementary peptides from the aqueous solution
Once peptide extractions with the dendrimers are optimized and better understood, these dendrimers will be used as part of a new approach for protein identification. This approach will involve a two-step process in which samples are first fractionated by pI and then extracted based on the amino acids present in each pI fraction. Such fractionations will constrain database searches sufficiently to allow for faster and more accurate protein identification in the context of the peptide mass fingerprinting approach.