TY  - JOUR
A1  - Sagu Tchewonpi, Sorel
A1  - Huschek, Gerd
A1  - Homann, Thomas
A1  - Rawel, Harshadrai Manilal
T1  - Effect of sample preparation on the detection and quantification of selected nuts allergenic proteins by LC-MS/MS
JF  - Molecules : a journal of synthetic chemistry and natural product chemistry / Molecular Diversity Preservation International
N2  - The detection and quantification of nut allergens remains a major challenge. The liquid chroma-tography tandem mass spectrometry (LC-MS/MS) is emerging as one of the most widely used methods, but sample preparation prior to the analysis is still a key issue. The objective of this work was to establish optimized protocols for extraction, tryptic digestion and LC-MS analysis of almond, cashew, hazelnut, peanut, pistachio and walnut samples. Ammonium bicar-bonate/urea extraction (Ambi/urea), SDS buffer extraction (SDS), polyvinylpolypyrroli-done (PVPP) extraction, trichloroacetic acid/acetone extraction (TCA/acetone) and chloro-form/methanol/sodium chloride precipitation (CM/NaCl) as well as the performances of con-ventional tryptic digestion and microwave-assisted breakdown were investigated. Overall, the protein extraction yields ranged from 14.9 ± 0.5 (almond extract from CM/NaCl) to 76.5 ± 1.3% (hazelnut extract from Ambi/urea). Electrophoretic profiling showed that the SDS extraction method clearly presented a high amount of extracted proteins in the range of 0–15 kDa, 15–35 kDa, 35–70 kDa and 70–250 kDa compared to the other methods. The linearity of the LC-MS methods in the range of 0 to 0.4 µg equivalent defatted nut flour was assessed and recovery of internal standards GWGG and DPLNV(d8)LKPR ranged from 80 to 120%. The identified bi-omarkers peptides were used to relatively quantifier selected allergenic protein form the inves-tigated nut samples. Considering the overall results, it can be concluded that SDS buffer allows a better protein extraction from almond, peanut and walnut samples while PVPP buffer is more appropriate for cashew, pistachio and hazelnut samples. It was also found that conventional overnight digestion is indicated for cashew, pistachio and hazelnut samples, while microwave assisted tryptic digestion is recommended for almond, hazelnut and peanut extracts.
KW  - nut allergenic proteins
KW  - protein extraction
KW  - sample preparation
KW  - tryptic digestion
KW  - microwave assisted digestion
KW  - SDS PAGE
KW  - LC-MS/MS
Y1  - 2021
U6  - https://doi.org/10.3390/molecules26154698
SN  - 1420-3049
VL  - 26
IS  - 15
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Draude, F.
A1  - Pelster, A.
A1  - Koersgen, M.
A1  - Kassenboehmer, R.
A1  - Schwerdtle, Tanja
A1  - Muething, J.
A1  - Arlinghaus, H. F.
T1  - ToF-SIMS imaging of plasma membrane lipids with sub-micrometer resolution
JF  - Surface and interface analysis : an international journal devoted to the development and application of techniques for the analysis surfaces, interfaces and thin films
N2  - Time-of-flight secondary ion mass spectrometry (ToF-SIMS) was used for label-free analyses of the molecular lateral distribution of two different epithelial cell membranes (PANC-1 and UROtsa). The goal of the research was to enhance the ion yield of specific membrane molecules for improving the membrane imaging capability of ToF-SIMS on the nanoscale lateral dimension. For this task, a special silicon wafer sandwich preparation technique was optimized using different wafer materials, spacers, and washing procedures. Under optimized preparation conditions, the yield could be significantly enhanced, allowing imaging of the inhomogeneous distribution of phosphocholine (common head group for phosphatidylcholine and sphingomyelin) of a PANC-1 cell membrane's outer lipid layer with a lateral resolution of less than 200nm. Copyright (c) 2014 John Wiley & Sons, Ltd.
KW  - ToF-SIMS
KW  - high-resolution imaging
KW  - membrane analysis
KW  - lipid analysis
KW  - yield enhancement
KW  - sample preparation
Y1  - 2014
U6  - https://doi.org/10.1002/sia.5576
SN  - 0142-2421
SN  - 1096-9918
VL  - 46
SP  - 127
EP  - 130
PB  - Wiley-Blackwell
CY  - Hoboken
ER  -