Home About us Contact
|
Home About us Contact | ||
|
|
||
Ion Selectivity (ion + selectivity)
Selected AbstractsA mutation of ion-conducting pore without effect on ion selectivity of the sodium channelACTA PHYSIOLOGICA, Issue 4 2005Matti Vornanen No abstract is available for this article. [source] Soft Metal Ion-Selective Electrodes Based on ,-Coordinate Calixarene DerivativesELECTROANALYSIS, Issue 15-16 2003Setsuko Yajima Abstract Calix[4]arene derivatives incorporating ,-unsaturated alkenyl groups or saturated alkyl groups and their monomeric analogues were used as ,-coordinate neutral carriers for ion-selective electrodes (ISEs) of soft metals [silver and thallium(I)] ions. The EMF responses were excellent for most of the ISEs, among which there was no significant difference in the response. The ion selectivities of the ISEs depend on the structure of neutral carriers employed. 1H NMR study explains the difference in the ion selectivity. In the metal-ion complexation by the ,-coordinate calixarene derivatives, thallium ion is likely to interact with the calixarene skeleton, while silver ion tends to interact with both of the calixarene skeleton and the ,-unsaturated alkenyl groups. [source] Tetrahydropyran-Amino Acids: Novel Building Blocks for Gramicidin-Hybrid Ion ChannelsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 12 2006Sabine Schröder Abstract The stereoselective synthesis of a cis -2,6-disubstituted tetrahydropyran bearing a ,-amino acid has been achieved starting from N -Boc-leucinal. The THP amino acid was incorporated into peptide sequences and the structural consequences were studied by X-ray crystallography and NMR analysis. Single-channel current measurements showed that the THP amino acid is a suitable substitute for positions 11 and 12 of the gramicidin ion channel. The resulting hybrid ion channel revealed Eisenman I ion selectivity and an ion-dependence of the channel dwell time. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Transition metal complexes of a cyclic pseudo hexapeptide: synthesis, complex formation and catalytic activities,,JOURNAL OF PEPTIDE SCIENCE, Issue 9 2008Huong Ngyen Abstract To contribute to a better understanding of metalloenzymes, we studied ion selectivity, complex formation tendencies and catalytic activities of linear and cyclic pseudopeptides. In this contribution, a linear and cyclic pseudo hexapeptide is described. The complex with transition metal ions and the sequence were designed using the programme COSMOS. Different routes of solid-phase synthesis were performed and compared using anchoring by C -terminus or a His side chain, using preformed pseudodipeptide building units or formation of N -functionalized peptide bond during stepwise assembly. The different strategies were compared regarding cyclization tendency, yield and purity. Side-chain anchoring to solid support favours the cyclization but leads to the formation of difficult to separate dioxopiperazine. Both routes require preformed building units. Complex-formation tendencies and selectivity for certain bivalent transition metal ions were experimentally estimated and compared to ones predicted theoretically. CD measurements indicate conformational changes by complex formation with different metal ions. Catalytic activities on oxidation of catechol and hydrolysis of bis-phosphate esters by some metal complexes of linear and cyclic peptide show only low catalytic activities compared to other model peptides and related metalloenzymes. The preference of the cyclic peptide for complexation of Ni2+ corresponds well to the predictions of COSMOS-NMR force field calculations. Copyright © 2008 European Peptide Society and John Wiley & Sons, Ltd. [source] MS3 using the collision cell of a tandem mass spectrometer systemRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 11 2002Lisa M. Cousins We report the feasibility of multistage fragmentation in combination with a fast background subtraction method, yielding the equivalent of MS3. The first quadrupole selects an ion of interest, and the ion is axially accelerated into Q2 to generate fragment ions. Subsequent stages of mass selection and fragmentation are obtained by quadrupolar resonant excitation within the Q2 collision cell. The fragments are analyzed downstream by either a resolving quadrupole or a time-of-flight (TOF) mass spectrometer, and multistage spectra are obtained by subtraction (MSn,,,MSn,1) for n,=,3 or 4. We discuss the characterization of this method, including product ion arrival times, fragmentation efficiencies, and ion selectivity. We report accurate TOF mass spectra of background-subtracted MS3 for protonated molecules reserpine (m/z 609), bosentan (m/z 1552), and taxol (m/z 854). Copyright © 2002 John Wiley & Sons, Ltd. [source] | ||||||||||