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The thermal stability and dewetting effects of crystalline organic thin films on inorganic substrates have been investigated for a model system for organic epitaxy, 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) on Ag(111). The thin films deposited under a variety of growth conditions have been annealed stepwise and studied by in situ x-ray diffraction and noncontact atomic force microscopy. It has been found that comparatively smooth films deposited at temperatures T[SUBg] ≲ 350 K are metastable, while films deposited at T[SUBg] ≳ 350 K are stable against annealing on a time scale of several hours. The thermal expansion of thin PTCDA films and bulk samples has been determined. [ABSTRACT FROM AUTHOR]

We present a transmission electron microscopy (TEM)/Rutherford backscattering spectrometry (RBS)/x-ray-diffraction (XRD) study of Au evaporated on crystalline organic thin films of diindenoperylene (DIP). Cross-sectional TEM shows that the preparation conditions of the Au film (evaporation rate and substrate temperature) strongly determine the interfacial morphology. In situ XRD during annealing reveals that the organic layer is thermally stable up to about 150 °C, a temperature sufficient for most electronic applications. The x-ray measurements show that the “as-grown” Au layer exhibits a large mosaicity of around 10°. Upon annealing above approx. 120 °C the Au film starts to reorder and shows sharp (111)-diffraction features. In addition, temperature dependent RBS measurements indicate that the Au/DIP interface is thermally essentially stable against diffusion of Au in the DIP layer up to approx. 100 °C on the time scale of hours, dependent on the Au thickness. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The chemotactic migration of phagocytes to sites of infection, guided by gradients of microbial molecules, plays a key role in the first line of host defence. Bacteria are distinguished from eukaryotes by initiation of protein synthesis with formyl methionine. Synthetic formylated peptides (FPs) have been shown to be chemotactic for phagocytes, leading to the concept of FPs as pathogen-associated molecular patterns (PAMPs). However, it remains unclear whether FPs are major chemoattractants released by bacteria and whether further chemoattractants are produced. A Staphylococcus aureus mutant whose formyltransferase gene was inactivated (Δ fmt) produced no FPs and the in vitro and in vivo ability of Δ fmt culture supernatants to recruit neutrophils was considerably reduced compared with those of the parental strain. However, some chemotactic activity was retained, indicating that bacteria produce also unknown, non-FP chemoattractants. The activity of these novel PAMPs was sensitive to pertussis toxin but insensitive to the formyl peptide receptor inhibitor CHIPS. Δ fmt culture supernatants caused reduced calcium ion fluxes and reduced CD11b upregulation in neutrophils compared with wild-type supernatants. These data demonstrate an important role of FPs in innate immunity against bacterial infections and indicate that host chemotaxis receptors recognize a larger set of bacterial molecules than previously thought. [ABSTRACT FROM AUTHOR]

We present a route for the preparation of cross-sectional TEM specimens of crystalline organic thin films which minimizes the mechanical, chemical and thermal load of the organic film during preparation and allows to take TEM images with molecular resolution. A typical example of a thin film of diindenoperylene capped with a thin layer of gold is shown to demonstrate the application of the technique for the investigation of metal-organic interfaces.