Charge switch derivatization of phosphopeptides for enhanced surface-enhanced Raman spectroscopy and mass spectrometry detection.

We report an aqueous one-pot reaction chemistry to derivatize phosphopeptides by switching the negatively charged phosphate group to a positively charged phosphonium or ammonium moiety. The phosphonium or ammonium tagged peptides then serve as peptide or protein phosphorylation signatures allowing extended and more sensitive analyses using surface-enhanced Raman spectroscopy (SERS) and mass spectrometry.

Ultrasensitive detection and characterization of posttranslational modifications using surface-enhanced Raman spectroscopy.

Posttranslational modification (PTM) of proteins is likely to be the most common mechanism of altering the expression of genetic information. It is essential to characterize PTMs to establish a complete understanding of the activities of proteins. Here, we present a sensitive detection method using surface-enhanced Raman spectroscopy (SERS) that can detect PTMs from as little as zeptomoles of peptide.

Composite organic-inorganic nanoparticles (COINs) with chemically encoded optical signatures.

To obtain a coding system for multiplex detection, we have developed a method to synthesize a new type of nanomaterial called composite organic-inorganic nanoparticles (COINs). The method allows the incorporation of a broad range of organic compounds into COINs to produce surface enhanced Raman scattering (SERS)-like spectra that are richer in variety than fluorescence-based signatures. Preliminary data suggest that COINs can be used as Raman tags for multiplex and ultrasensitive detection of biomolecules.

Microfluidic operations using deformable polymer membranes fabricated by single layer soft lithography.

We show that it is possible to use single layer soft lithography to create deformable polymer membranes within microfluidic chips for performing a variety of microfluidic operations. Single layer microfluidic chips were designed, fabricated, and characterized to demonstrate pumping, sorting, and mixing. Flow rates as high as 0.