TY - JOUR A1 - Dietrich, Paul M. A1 - Streeck, Cornelia A1 - Glamsch, Stephan A1 - Ehlert, Christopher A1 - Lippitz, Andreas A1 - Nutsch, Andreas A1 - Kulak, Nora A1 - Beckhoff, Burkhard A1 - Unger, W. E. S. T1 - Quantification of Silane Molecules on Oxidized Silicon: Are there Options for a Traceable and Absolute Determination? JF - Analytical chemistry N2 - Organosilanes are used routinely to functionalize various support materials for further modifications. Nevertheless, reliable quantitative information about surface functional group densities after layer formation is rarely available. Here, we present the analysis of thin organic nanolayers made from nitrogen containing silane molecules on naturally oxidized silicon wafers with reference-free total reflection X-ray fluorescence (TXR.F) and X-ray photoelectron spectroscopy (XPS). An areic density of 2-4 silane molecules per nm(2) was calculated from the layer's nitrogen mass deposition per area unit obtained by reference-free TXRF. Complementary energy and angle-resolved XPS (ER/AR-XPS) in the Si 2p core-level region was used to analyze the outermost surface region of the organic (silane layer)-inorganic (silicon wafer) interface. Different coexisting silicon species as silicon, native silicon oxide, and silane were identified and quantified. As a result of the presented proof-of-concept, absolute and traceable values for the areic density of silanes containing nitrogen as intrinsic marker are obtained by calibration of the XPS methods with reference-free TXRF. Furthermore, ER/AR-XPS is shown to facilitate the determination of areic densities in (mono)layers made from silanes having no heteroatomic marker other than silicon. After calibration with reference-free TXRF, these areic densities of silane molecules can be determined when using the XPS component intensity of the silane's silicon atom. Y1 - 2015 U6 - https://doi.org/10.1021/acs.analchem.5b02846 SN - 0003-2700 SN - 1520-6882 VL - 87 IS - 19 SP - 10117 EP - 10124 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Hornemann, Andrea A1 - Eichert, Diane Madeleine A1 - Hoehl, Arne A1 - Tiersch, Brigitte A1 - Ulm, Gerhard A1 - Ryadnov, Maxim G. A1 - Beckhoff, Burkhard T1 - Investigating Membrane-Mediated Antimicrobial Peptide Interactions with Synchrotron Radiation Far-Infrared Spectroscopy JF - ChemPhysChem : a European journal of chemical physics and physical chemistry N2 - Synchrotron radiation-based Fourier transform infrared spectroscopy enables access to vibrational information from mid over far infrared to even terahertz domains. This information may prove critical for the elucidation of fundamental bio-molecular phenomena including folding-mediated innate host defence mechanisms. Antimicrobial peptides (AMPs) represent one of such phenomena. These are major effector molecules of the innate immune system, which favour attack on microbial membranes. AMPs recognise and bind to the membranes whereupon they assemble into pores or channels destabilising the membranes leading to cell death. However, specific molecular interactions responsible for antimicrobial activities have yet to be fully understood. Herein we probe such interactions by assessing molecular specific variations in the near-THz 400-40 cm(-1) range for defined helical AMP templates in reconstituted phospholipid membranes. In particular, we show that a temperature-dependent spectroscopic analysis, supported by 2D correlative tools, provides direct evidence for the membrane-induced and folding-mediated activity of AMPs. The far-FTIR study offers a direct and information-rich probe of membrane-related antimicrobial interactions. KW - antimicrobial peptides KW - electrostatic interactions KW - IR spectroscopy KW - phospholipid membranes KW - protein folding Y1 - 2022 U6 - https://doi.org/10.1002/cphc.202100815 SN - 1439-4235 SN - 1439-7641 VL - 23 IS - 4 PB - Wiley-VCH CY - Weinheim ER -