Zhou, Y., Bright, L. K., Shi, W., Aspinwall, C. A., & Baker, L. A. (2014). Ion channel probes for scanning ion conductance microscopy. Langmuir : the ACS journal of surfaces and colloids, 30(50), 15351-5.
The sensitivity and selectivity of ion channels provide an appealing opportunity for sensor development. Here, we describe ion channel probes (ICPs), which consist of multiple ion channels reconstituted into lipid bilayers suspended across the opening of perflourinated glass micropipets. When incorporated with a scanning ion conductance microscope (SICM), ICPs displayed a distance-dependent current response that depended on the number of ion channels in the membrane. With distance-dependent current as feedback, probes were translated laterally, to demonstrate the possibility of imaging with ICPs. The ICP platform yields several potential advantages for SICM that will enable exciting opportunities for incorporation of chemical information into imaging and for high-resolution imaging.
Gooding, J. J., Spence, D., Aspinwall, C. A., Benson, D. E., Cliffel, D. E., Culbertson, C., Desaire, H., Garcia, C. D., Garno, J., Håkansson, K., Hilder, E., Hobbs, J., Lingjun, L. i., Martin, R. S., Minteer, S. D., Nordon, A., Reid, G., Shippy, S., Stevenson, K. J., , Szunerits, S., et al. (2006). Emerging investigators special issue. Analyst, 131(2), 179-.
Shen, H., Aspinwall, C. A., & Kennedy, R. T. (1997). Dual microcolumn immunoassay applied to determination of insulin secretion from single islets of Langerhans and insulin in serum. Journal of Chromatography B: Biomedical Applications, 689(2), 295-303.
PMID: 9080314;Abstract:
A dual microcolumn immunoassay (DMIA) was developed and applied to determination of insulin in biological samples. The DMIA utilized a protein G capillary column (150 μm I.D.) with covalently attached anti-insulin to selectively capture and concentrate insulins in a sample. Insulins retained in the capillary immunoaffinity column were desorbed and injected onto a reversed-phase capillary column (150 μm I.D.) for further separation from interferences such as cross-reactive antigens and non-specifically adsorbed sample components. Bovine, porcine and rat insulin all cross-reacted with the antibody and could be determined simultaneously. Using a UV absorbance detector, the dual microcolumn system had a detection limit of 10 fmol or 20 pM for 500-μl sample volumes. The DMIA system was used to measure glucose-stimulated insulin secretion from single rat islets of Langerhans. Because of the separation in the second dimension, both rat I and rat II insulin could be independently determined. The system was also evaluated for determination of insulin in serum. Using microcolumns instead of conventional HPLC columns resulted in several advantages including use of less chromatographic material and improved mass detection limit.
Braun, K. L., Hapuarachchi, S., Fernandez, F. M., & Aspinwall, C. A. (2006). Fast Hadamard transform capillary electrophoresis for on-line, time-resolved chemical monitoring. Analytical Chemistry, 78(5), 1628-1635.
PMID: 16503616;Abstract:
We report a new approach for collecting and deconvoluting the data in Hadamard transform capillary electrophoresis, referred to as fast Hadamard transform capillary electrophoresis (fHTCE). Using fHTCE, total analysis times can be reduced by up to 48% per multiplexed separation compared to conventional Hadamard transform capillary electrophoresis (cHTCE) while providing comparable signal-to-noise ratio enhancements. In fHT-CE, the sample is injected following a pseudorandom pulsing sequence derived from the first row of a simplex matrix (S-matrix) in contrast to cHTCE, which utilizes a sequence of twice the length. In addition to the temporal savings provided by fHTCE, a 50% reduction in sample consumption is also realized due to the decreased number of sample injections. We have applied fHTCE to the analysis of mixtures of neurotransmitters and related compounds to yield improved signal-to-noise ratios with a total analysis time under 10 s. In addition, we demonstrate the capability of fHTCE to perform time-resolved monitoring of changes in the concentration of model neurochemical compounds. © 2006 American Chemical Society.
Berggren, P., Yang, S., Murakami, M., Efanov, A. M., Uhles, S., Köhler, M., Moede, T., Fernström, A., Appelskog, I. B., Aspinwall, C. A., Zaitsev, S. V., Larsson, O., Moitoso, L., Fecher-Trost, C., Weißgerber, P., Ludwig, A., Leibiger, B., Juntti-Berggren, L., Barker, C. J., , Gromada, J., et al. (2004). Removal of Ca2+ channel β3 subunit enhances Ca2+ oscillation frequency and insulin exocytosis. Cell, 119(2), 273-284.
PMID: 15479643;Abstract:
An oscillatory increase in pancreatic β cell cytoplasmic free Ca 2+ concentration, [Ca2+]i, is a key feature in glucose-induced insulin release. The role of the voltage-gated Ca2+ channel β3 subunit in the molecular regulation of these [Ca 2+]i oscillations has now been clarified by using β3 subunit-deficient β cells. β3 knockout mice showed a more efficient glucose homeostasis compared to wild-type mice due to increased glucose-stimulated insulin secretion. This resulted from an increased glucose-induced [Ca2+]i oscillation frequency in β cells lacking the β3 subunit, an effect accounted for by enhanced formation of inositol 1,4,5-trisphosphate (InsP3) and increased Ca2+ mobilization from intracellular stores. Hence, the β3 subunit negatively modulated InsP3-induced Ca 2+ release, which is not paralleled by any effect on the voltage-gated L type Ca2+ channel. Since the increase in insulin release was manifested only at high glucose concentrations, blocking the β3 subunit in the β cell may constitute the basis for a novel diabetes therapy.
