Visualizing the structure of triglyceride nanoparticles in different crystal modifications

Colloidal suspensions of triglycerides are under investigation as potential drug carrier systems. The properties of the matrix lipids are altered in the nanoparticles compared to those of the bulk material. For instance, the metastable alpha-modification of the triglycerides usually transforms into the stable beta-polymorph quite rapidly in the colloidal particles. Recently, it was observed that the alpha-modification can be preserved for a considerable period of time in tristearin nanoparticles when the particles are stabilized with a blend of saturated long-chain phospholipids and the bile salt sodium glycocholate [Bunjes, H.; Koch, M. H. J. J. Controlled Release 2005, 107, 229-243]. As triglyceride nanoparticles in the alpha-modification may offer some advantages over those in the beta-form with regard to drug delivery applications, the structure of the corresponding dispersions was investigated in more detail with differential scanning calorimetry, X-ray diffraction, and electron microscopy. The electron microscopic investigations confirmed a platelet-like, layered structure for particles in the beta-modification and revealed a spheroidal shape with concentric layers for larger particles in the alpha-form. For the first time, not only was information on the internal structure of solid triglyceride nanoparticles obtained from freeze-fracture electron micrographs but also details were observed by cryoelectron microscopy.     

Ethylene polymerization using crosslinked polystyrene as support for zirconocene dichloride/methylaluminoxane

In this paper we report on a zirconocene dichloride/methylaluminoxane catalyst system supported on a crosslinked polystyrene in order to provide ethylene polymerization catalysts for gas phase or slurry processes. Our novel approach uses the Diels‐Alder reaction of cyclopentadiene functions as the final, cross‐linking synthetic step. This provides polymer supported zirconocene catalysts with a homogeneous distribution of active sites. The catalysts were shown to be highly active and to form spherical beads as proven by scanning electron microscopy.     

Tryptammonium (2S,3S)-hydrogentartrate monohydrate [Struct Chem (2008) 19:147–154]: redetermination at 110 K and re-refinement against room temperature data

The crystal structure of the title compound was incorrectly reported as a methanol solvate [Koleva et al. in Struct Chem 19:147–154, 2008] on the basis of room temperature X-ray diffraction data. We have now established the presence of a disordered water molecule rather than the methanol molecule using a low temperature data set collected at 110 K.     

Polychloride Monoanions from [Cl3]− to [Cl9]−: A Raman Spectroscopic and Quantum Chemical Investigation

Polychloride monoanions stabilized by quaternary ammonium salts are investigated using Raman spectroscopy and state‐of‐the‐art quantum‐chemical calculations. A regular V‐shaped pentachloride is characterized for the [N(Me)₄][Cl₅] salt, whereas a hockey‐stick‐like structure is tentatively assigned for [N(Et)₄][Cl₂???Cl₃^?]. Increasing the size of the cation to the quaternary ammonium salts [NPr₄]⁺ and [NBu₄]⁺ leads to the formation of the [Cl₃]^? anion. The latter is found to be a pale yellow liquid at about 40 °C, whereas all the other compounds exist as powders. Further to these observations, the novel [Cl₉]^? anion is characterized by low‐temperature Raman spectroscopy in conjunction with quantum‐chemical calculations.     

Comparative Analysis of the Antitumor Activity of Cis- and Trans-Resveratrol in Human Cancer Cells with Different p53 Status

Resveratrol, a natural plant phytoalexin, is produced in response to fungal infection or− UV irradiation. It exists as an isomeric pair with cis- and trans-conformation. Whereas multiple physiological effects of the trans-form, including a pronounced anti-tumoral activity, are nowadays elucidated, much less knowledge exists concerning the cis-isomer. In our work, we analyzed the antiproliferative and cytotoxic properties of cis-resveratrol in four different human tumor entities in direct comparison to trans-resveratrol. We used human cell lines as tumor models for hepatocellular carcinoma (HCC; HepG2, Hep3B), colon carcinoma (HCT-116, HCT-116/p53^(−/−)), pancreatic carcinoma (Capan-2, MiaPaCa-2), and renal cell carcinoma (A498, SN12C). Increased cytotoxicity in all investigated tumor cells was observed for the trans-isomer. To verify possible effects of the tumor suppressor p53 on resveratrol-induced cell death, we used wild type and p53-deleted or -mutated cell lines for every tested tumor entity. Applying viability and cytotoxicity assays, we demonstrated a differential, dose-dependent sensitivity towards cis- or trans-resveratrol among the respective tumor types.     

An improved typology of cutting and packing problems

The number of publications in the area of Cutting and Packing (C&P) has increased considerably over the last two decades. The typology of C&P problems introduced by Dyckhoff [Dyckhoff, H., 1990. A typology of cutting and packing problems. European Journal of Operational Research 44, 145–159] initially provided an excellent instrument for the organisation and categorisation of existing and new literature. However, over the years also some deficiencies of this typology became evident, which created problems in dealing with recent developments and prevented it from being accepted more generally. In this paper, the authors present an improved typology, which is partially based on Dyckhoff’s original ideas, but introduces new categorisation criteria, which define problem categories different from those of Dyckhoff. Furthermore, a new, consistent system of names is suggested for these problem categories. Finally, the practicability of the new scheme is demonstrated by using it as a basis for a categorisation of the C&P literature from the years between 1995 and 2004.