Despite the tremendous sensitivity and lower sample requirements for nanospray vs. conventional electrospray, metallized nanospray emitters have suffered from one of two problems: low mechanical stability (leading to emitter failure) or lengthy, tedious production methods. Here, we describe a simple alternative to metallized tips using polyaniline (PANI), a synthetic polymer well known for its high conductivity, anticorrosion properties, antistatic properties, and mechanical stability. A simple method for coating borosilicate emitters (1.2 mm o.d.) pulled to fine tapers (4 +/- 1 microm) with water-soluble and xylene-soluble dispersions of conductive polyaniline (which allows for electrical contact at the emitter outlet) is described. The polyaniline-coated emitters show high durability and are resistant to electrical discharge, likely because of the thick (yet optically transparent) coatings; a single emitter can be used over a period of days for multiple samples with no visible indication of the destruction of the polyaniline coating. The optical transparency of the coating also allows the user to visualize the sample plug loaded into the emitter. Examples of nanospray using coatings of the water-soluble and xylene-soluble polyaniline dispersions are given. A comparison of PANI-coated and gold-coated nanospray emitters to conventional electrospray ionization (ESI) show that PANI-coated emitters provide similar enhanced sensitivity that gold-coated emitters exhibit vs. conventional ESI.

Electrospray ionization (ESI) is a soft ionization technique that is able to transfer intact ions, as well as solution phase non-covalent complexes into the gas phase. With small molecules that have a high tendency to form hydrogen bonds, the observation of non-covalent complexes by ESI-MS can be the result of a non-specific interaction, due to the nature of the electrospray process. Special precautions and additional steps should be performed to identify the origin of the complexes observed with ESI-MS, and we have utilized solution phase hydrogen/deuterium (H/D) exchange as a method to determine the specificity of the complexes. By comparing the average number of exchanges for the monomer subunits to the average number of exchanges for the complex, one can distinguish if a specific complex is formed in solution. In this paper we have investigated non-covalent complexes of some common chemotherapy agents: paclitaxel, doxorubicin, and etoposide by ESI-MS. By using the solution phase H/D exchange, we were able to identify several specific drug-drug complexes. Thus, solution phase H/D exchange combined with ESI-MS provides for a convenient method in ascertaining the specificity of non-covalent complexes as being formed in solution or in vacuo.

Susumu Tanimura (left), Michiaki Kohno (right), and colleagues investigate how SH3P2, a downstream target of the ERK signaling pathway, inhibits cell migration. The researchers fi nd that the class I myosin Myo1E is a binding partner of SH3P2 and that ERK signaling disrupts SH3P2's association with Myo1E, allowing the myosin to relocalize from the cytosol to the tips of lamellipodial protrusions at the leading edge of the cell. There, Myo1E promotes lamellipodial extension and cell motility. In serum-starved cells (left), Myo1E (green) is largely cytosolic, but serum addition (center) prompts the myosin's translocation to lamellipodia, where it colocalizes with F-actin (magenta). This translocation is blocked by an inhibitor of the ERK signaling pathway (right). "SH3P2 functions as a cytoplasmic anchor for Myo1E… thereby negatively regulating cell motility." Study reveals that ERK signaling promotes cell migration by regulating motor protein's localization.

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