N-Acyl-l-homoserine lactones (AHLs) are small cell-to-cell signaling molecules involved in the regulation of population density and local gene expression in microbial communities. Recent evidence shows that contact of this signaling system, usually referred to as quorum sensing, to living eukaryotes results in interactions of AHL with host cells in a process termed "inter-kingdom signaling". So far details of this process and the binding site of the AHLs remain unknown; both an intracellular and a membrane-bound receptor seem possible, the first of which requires passage through the cell membrane. Here, we used sum-frequency-generation (SFG) spectroscopy to investigate the integration, conformation, orientation, and translocation of deuterated N-Acyl-L-homoserine lactones (AHL-dn) with varying chain length (8, 12, and 14 C atoms) in lipid bilayers consisting of a 1:1 mixture of POPC:POPG supported on SiO2 substrates (prepared by vesicle fusion). We found that all AHL-dn derivatives are well-ordered within the supported lipid bilayer (SLB) in a preferentially all-trans conformation of the deuterated alkyl chain and integrated into the upper leaflet of the SLB with the methyl terminal groups pointing downwards. For the bilayer system described above, no flip-flop of AHL-dn from the upper leaflet to the lower one could be observed. Spectral assignments and interpretations were further supported by Fourier transform infrared and Raman spectroscopy.

Electroreductive desorption of a highly ordered self-assembled monolayer (SAM) formed by the araliphatic thiol (4-(4-(4-pyridyl)phenyl)phenyl)methanethiol leads to a concurrent rapid hydrogen evolution reaction (HER). The desorption process and resulting interfacial structure were investigated by voltammetric techniques, in situ spectroscopic ellipsometry, and in situ vibrational sum–frequency–generation (SFG) spectroscopy. Voltammetric experiments on SAM-modified electrodes exhibit extraordinarily high peak currents, which di er between Au(111) and polycrystalline Au substrates. Association of reductive desorption with HER is shown to be the origin of the observed excess cathodic charges. The studied SAM preserves its two–dimensional order near Au surface throughout a fast voltammetric scan even when the vertex potential is set several hundred millivolt beyond the desorption potential. A model is developed for the explanation of the observed rapid HER involving ordering and pre–orientation of water present in the nanometer–sized reaction volume between desorbed SAM and the Au electrode, by the structurally extremely stable monolayer, leading to the observed catalysis of the HER.

N-Acyl-L-homoserine lactones (AHLs) are synthesized by Gram-negative bacteria. These quorum-sensing molecules play an important role in the context of bacterial infection and biofilm formation. They also allow communication between microorganisms and eukaryotic cells (inter-kingdom signalling). However, very little is known about the entire mechanism of those interactions. Precise structural studies are required to analyse the different AHL isomers as only one form is biologically most active. Theoretical studies combined with experimental infrared and Raman spectroscopic data are therefore undertaken to characterise the obtained compounds. To mimic interactions between AHL and cell membranes, we studied the insertion of AHL in supported lipid bilayers, using vibrational sum-frequency-generation spectroscopy. Deuterium-labelled AHLs were thus synthesized. Starting from readily available deuterated fatty acids, a two-step procedure towards deuterated N-acyl-L-homoserine lactones with varying chain lengths is described. This included the acylation of Meldrum's acid followed by amidation. Additionally, the detailed analytical evaluation of the products is presented herein.

Background and Aims: Gastrointestinal stromal tumors (GISTs) are rare malignancies but the most common mesenchymal tumors of the digestive tract. Recent advances in diagnostic imaging and an increasing incidence will confront us more frequently with stromal tumors. This single center study aimed to characterize GIST patients in terms of tumor location, clinical presentation, metastasis formation, as well as associated secondary malignancies. Methods: In a retrospective study, 104 patients with a histologically confirmed diagnosis of GIST, collected between 1993 and 2011, were characterized for several clinical features. Results: The most common GIST location was the stomach (67.6%) followed by the small intestine (16.2%). Gastrointestinal bleeding (55.8%) and abdominal pain (38.5%) were the most frequently reported symptoms whereas about one-third of patients remained clinically asymptomatic (31.6%); 14.4% of patients had either synchronous or metachronous metastases and there was a significant prevalence also in the low risk group. The proportion of secondary malignant associated neoplasms was 31% in our GIST cohort, among which gastrointestinal, genitourinary tumors, and breast cancer were the most prevalent. Conclusion: There was a considerable risk for metastasis formation and the development of secondary neoplasias that should encourage discussion about the appropriate surveillance strategy after surgery for GIST.

e Covalent immobilization of biomolecules has become a subject of great interest in recent years because of the expected diversity of applications, for example, biosensors in diagnosis, lab-on-chip technology, and modern cell culture focused on cell adhesion, migration, and differentiation. Our approach is to produce self-assembled monolayers (SAMs) on gold surfaces based on mixtures of a benzylguanine-terminated thiol and a thiol, carrying ethylene glycol groups. The benzylguanine head group of such SAMs acts as a substrate for the SNAP-tag system allowing for covalent attachment of any protein of interest fused to this tag. For this purpose, it is essential to determine the orientation and chemical composition of these layers. In this study, we use the strength of combining complementary surface analytical methods to achieve a comprehensive characterization. The chemical composition and the covalent binding of the thiols were proved by X-ray photoelectron spectroscopy (XPS). The orientation of the SAMs together with thickness information was achieved by nondestructive depth profiles reconstructed from parallel angle-resolved XPS data and energy-resolved photoelectron emission spectroscopy (PES). High-sensitivity low-energy ion scattering and sum-frequency-generation spectroscopy corroborate the XPS/PES results.