Computational modeling is helpful for elucidating the cellular mechanisms driving biological morphogenesis. Previous simulation studies of blood vessel growth based on the cellular Potts model proposed that elongated, adhesive or mutually attractive endothelial cells suffice for the formation of blood vessel sprouts and vascular networks. Because each mathematical representation of a model introduces potential artifacts, it is important that model results are reproduced using alternative modeling paradigms. Here, we present a lattice-free, particle-based simulation of the cell elongation model of vasculogenesis. The new, particle-based simulations confirm the results obtained from the previous cellular Potts simulations. Furthermore, our current findings suggest that the emergence of order is possible with the appli- Mathematical Institute, Leiden University, Niels Bohrweg 1, 2333 Leiden, The Netherlands cation of a high enough attractive force or, alternatively, a longer attraction radius. The methodology will be applicable to a range of problems in morphogenesis and noisy particle aggregation in which cell shape is a key determining factor.

The synthesis of three new analogues of the cyclic cationic antimicrobial peptide Gramicidin S is described. These derivatives contain a modified turn region in which the DPhe‐Pro motif has been replaced by a constrained furanoid sugar amino acid or a flexible linear aminoethoxy acetic acid moiety. Structural analysis revealed conformational changes in the modified turn region compared to GS. The biological profile of these compounds however resembles that of Gramicidin S and previously described analogues.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

In general, when performing untargeted metabolic phenotyping (metabolomics/metabonomics) studies on biological samples for example urine or food, sample preparation should be kept to a minimum. However, there are circumstances when desalting, preconcentration, or the fractionation of samples into polar and nonpolar metabolites is of value for enabling the subsequent analysis. Because of its simplicity and ease of automation SPE is well suited to such applications prior to analysis by ultra-performance LC-TOF-MS. In the present study, the properties of a range of SPE phases have been investigated with respect to the range of metabolites that can be extracted from urine. The phases include alkyl modified (C8 and, C18-OH and C18) silica and polymeric materials. The results show that the C18 phase was well suited to fractionating urine into samples suitable for separate analysis of polar and nonpolar constituents via HILIC and RPLC, respectively, while the polymeric materials were best for concentrating and desalting samples.

The cover picture shows the cationic antimicrobial peptide Gramicidin S (GS, left structure), which disrupts the bacterial membrane, however with little selectivity over the erythrocytic membrane. This mode of action is explained by the amphiphilic β‐sheet structure of GS. Three new analogues of GS were designed in which one DPhe‐Pro β‐turn motif has been replaced by different sugar amino acids (1, 2 and 3 in the right structures). The solution structures of these new analogues were assessed by 1D and 2D NMR spectroscopy, which shows a slightly altered backbone conformation. The antibacterial and hemolytic activities of all analogues were also determined in this study. Details are discussed in the article by M. Overhand et al. on p. 4231 ff.