Computer Simulation of a Surface Charge Nanobiosensor with Internal Signal Integration.

The ionized states of molecular analytes located on solid surfaces require profound investigation and better understanding for applications in the basic sciences in general, and in the design of nanobiosensors, in particular. Such ionized states are induced by the interactions of molecules between them in the analyzed substance and with the target surface. Here, computer simulations using COMSOL Multiphysics software show the effect of surface charge density and distribution on the output generation in a dynamic PIN diode with gate control.

Narrow Aperture Detection Electrodes ICR Cell with Quadrupolar Ion Detection for FT-ICR MS at the Cyclotron Frequency.

Ion signal detection at the true (unperturbed) cyclotron frequency instead of the conventional reduced cyclotron frequency has remained a formidable challenge since the inception of Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Recently, routine FT-ICR MS at the true cyclotron frequency has become a reality with the implementation of ICR cells with narrow aperture detection electrodes (NADEL). Here, we describe the development and implementation of the next generation of these cells, namely, a 2xNADEL ICR cell, which comprises four flat detect and four ∼45° cylindrical excite electrodes, enabling independent ion excitation and quadrupolar ion detection.

Periodic sequence distribution of product ion abundances in electron capture dissociation of amphipathic peptides and proteins.

The rules for product ion formation in electron capture dissociation (ECD) mass spectrometry of peptides and proteins remain unclear. Random backbone cleavage probability and the nonspecific nature of ECD toward amino acid sequence have been reported, contrary to preferential channels of fragmentation in slow heating-based tandem mass spectrometry. Here we demonstrate that for amphipathic peptides and proteins, modulation of ECD product ion abundance (PIA) along the sequence is pronounced.

Electron capture dissociation implementation progress in Fourier transform ion cyclotron resonance mass spectrometry.

Successful electron capture dissociation (ECD) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) applications to peptide and protein structural analysis have been enabled by constant progress in implementation of improved electron injection techniques. The rate of ECD product ion formation has been increased to match the liquid chromatography and capillary electrophoresis timescales, and ECD has been combined with infrared multiphoton dissociation in a single experimental configuration to provide simultaneous irradiation, fast switching between the two techniques, and good spatial overlap between ion, photon, and electron beams. Here we begin by describing advantages and disadvantages of the various existing electron injection techniques for ECD in FT-ICR MS.