TY  - JOUR
A1  - Villatoro Leal, José Andrés
A1  - Zühlke, Martin
A1  - Riebe, Daniel
A1  - Beitz, Toralf
A1  - Weber, Marcus
A1  - Löhmannsröben, Hans-Gerd
T1  - Sub-ambient pressure IR-MALDI ion mobility spectrometer for the determination of low and high field mobilities
JF  - Analytical and bioanalytical chemistry : a merger of Fresenius' journal of analytical chemistry, Analusis and Quimica analitica
N2  - A new ion mobility (IM) spectrometer, enabling mobility measurements in the pressure range between 5 and 500 mbar and in the reduced field strength range E/N of 5-90 Td, was developed and characterized. Reduced mobility (K-0) values were studied under low E/N (constant value) as well as high E/N (deviation from low field K-0) for a series of molecular ions in nitrogen. Infrared matrix-assisted laser desorption ionization (IR-MALDI) was used in two configurations: a source working at atmospheric pressure (AP) and, for the first time, an IR-MALDI source working with a liquid (aqueous) matrix at sub-ambient/reduced pressure (RP). The influence of RP on IR-MALDI was examined and new insights into the dispersion process were gained. This enabled the optimization of the IM spectrometer for best analytical performance. While ion desolvation is less efficient at RP, the transport of ions is more efficient, leading to intensity enhancement and an increased number of oligomer ions. When deciding between AP and RP IR-MALDI, a trade-off between intensity and resolving power has to be considered. Here, the low field mobility of peptide ions was first measured and compared with reference values from ESI-IM spectrometry (at AP) as well as collision cross sections obtained from molecular dynamics simulations. The second application was the determination of the reduced mobility of various substituted ammonium ions as a function of E/N in nitrogen. The mobility is constant up to a threshold at high E/N. Beyond this threshold, mobility increases were observed. This behavior can be explained by the loss of hydrated water molecules.
KW  - ion mobility spectrometry
KW  - IR-MALDI
KW  - high field mobility
KW  - dub-ambient
KW  - pressure
KW  - peptides
Y1  - 2020
U6  - https://doi.org/10.1007/s00216-020-02735-0
SN  - 1618-2642
SN  - 1618-2650
VL  - 412
IS  - 22
SP  - 5247
EP  - 5260
PB  - Springer
CY  - Heidelberg
ER  - 
TY  - JOUR
A1  - Fandrich, Artur
A1  - Buller, Jens
A1  - Memczak, Henry
A1  - Stoecklein, W.
A1  - Hinrichs, K.
A1  - Wischerhoff, E.
A1  - Schulz, B.
A1  - Laschewsky, André
A1  - Lisdat, Fred
T1  - Responsive Polymer-Electrode Interface-Study of its Thermo- and pH-Sensitivity and the Influence of Peptide Coupling
JF  - Electrochimica acta : the journal of the International Society of Electrochemistry (ISE)
N2  - This study introduces a thermally responsive, polymer-based electrode system. The key component is a surface-attached, temperature-responsive poly(oligoethylene glycol) methacrylate (poly(OEGMA)) type polymer bearing photoreactive benzophenone and carboxy groups containing side chains. The responsive behavior of the polymer in aqueous media has been investigated by turbidimetry measurements. Polymer films are formed on gold substrates by means of the photoreactive 2(dicyclohexylphosphino)benzophenone (DPBP) through photocrosslinking. The electrochemical behavior of the resulting polymer-substrate interface has been investigated in buffered [Fe(CN)6](3-)/[Fe (CN)6](4-)solutions at room temperature and under temperature variation by cyclic voltammetry (CV). The CV experiments show that with increasing temperature structural changes of the polymer layer occur, which alter the output of the electrochemical measurement. Repeated heating/cooling cycles analyzed by CV measurements and pH changes analyzed by quartz crystal microbalance with dissipation monitoring (QCM-D) reveal the reversible nature of the restructuring process. The immobilized films are further modified by covalent coupling of two small biomolecules - a hydrophobic peptide and a more hydrophilic one. These attached components influence the hydrophobicity of the layer in a different way the resulting change of the temperature-caused behavior has been studied by CV indicating a different state of the polymer after coupling of the hydrophobic peptide.
KW  - Stimuli-responsive materials
KW  - electroanalysis
KW  - modified electrode
KW  - bioreceptors
KW  - peptides
KW  - surface modification
KW  - cyclic voltammetry
KW  - IR ellipsometry
KW  - quartz crystal microbalance
Y1  - 2017
U6  - https://doi.org/10.1016/j.electacta.2017.01.080
SN  - 0013-4686
SN  - 1873-3859
VL  - 229
SP  - 325
EP  - 333
PB  - Elsevier
CY  - Oxford
ER  -