First description of a fossil chamaeleonid from Greece and its relevance for the European biogeographic history of the group

The fossil record of Chamaeleonidae is very scarce and any new specimen is therefore considered important for our understanding of the evolutionary and biogeographic history of the group. New specimens from the early Miocene of Aliveri (Evia Island), Greece constitute the only fossils of these lizards from southeastern Europe. Skull roofing material is tentatively attributed to the Czech species Chamaeleo cf. andrusovi, revealing a range extension for this taxon, whereas tooth-bearing elements are described as indeterminate chamaeleonids. The Aliveri fossils rank well among the oldest known reptiles from Greece, provide evidence for the dispersal routes of chameleons out of Africa towards the European continent and, additionally, imply strong affinities with coeval chamaeleonids from Central Europe

Monitoring and Scoring Counter-Diffusion Protein Crystallization Experiments in Capillaries by in situ Dynamic Light Scattering

In this paper, we demonstrate the feasibility of using in situ Dynamic Light Scattering (DLS) to monitor counter-diffusion crystallization experiments in capillaries. Firstly, we have validated the quality of the DLS signal in thin capillaries, which is comparable to that obtained in standard quartz cuvettes. Then, we have carried out DLS measurements of a counter-diffusion crystallization experiment of glucose isomerase in capillaries of different diameters (0.1, 0.2 and 0.3 mm) in order to follow the temporal evolution of protein supersaturation. Finally, we have compared DLS data with optical recordings of the progression of the crystallization front and with a simulation model of counter-diffusion in 1D

Structural Properties of Polyglutamine Aggregates Investigated via Molecular Dynamics Simulations

Polyglutamine (polyQ) beta-stranded aggregates constitute the hallmark of Huntington disease. The disease is fully penetrant when Q residues are more than 36-40 ("disease threshold"). Here, based on a molecular dynamics study on polyQ helical structures of different shapes and oligomeric states, we suggest that the stability of the aggregates increases with the number of monomers, while it is rather insensitive to the number of Qs in each monomer. However, the stability of the single monomer does depend on the number of side-chain intramolecular H-bonds, and therefore oil the number of Qs. If such number is lower than that of the disease threshold, the beta-stranded monomers are unstable and hence may aggregate with lower probability, consistently with experimental findings. Our results provide a possible interpretation of the apparent polyQ length dependent-toxicity, and they do not support the so-called "structural threshold hypothesis", which supposes a transition from random coil to a beta-sheet structure only above the disease threshold

Potential of mean force treatment of salt-mediated protein crystallization.

In the initial stages of crystallization of proteins, monomers aggregate rapidly and form nuclei and large fractal clusters, as previously shown by dynamic light scattering experiments (Georgalis, Y., J. Schüler, J. Frank, D. M. Soumpasis, and W. Saenger. 1995. Protein crystallization screening through scattering techniques. Adv. Colloid Interface Sci. 58:57-86). In this communication we initiate an effort to understand the effective interactions controlling charged protein aggregation and crystallization using the potential of mean force (PMF) theory. We compute the PMFs of the system lysozyme-water-NaCl within the framework of the hypernetted chain approximation for a wide range of protein and salt concentrations. We show that the computed effective interactions can rationalize the experimentally observed aggregation behavior of lysozyme under crystallization conditions

Dynamic laser light scattering to determine size distributions of vesicles

Publisher Summary: This chapter describes dynamic laser light scattering to determine size distributions of vesicles and presents a survey of the underlying principles with regard to vesicle suspensions. From a size distribution, it can be decided whether vesicles are homogeneous in size. Its characteristics can be used for controlling the stability of a sample and for studying processes such as aggregation and fusion. The nonmicroscopic methods requiring rather homogeneous populations with a well-defined shape are most appropriately applied to small unilamellar vesicles. Electron microscopy is used for vesicles having an extended size range. Because of the remarkable sensitivity of parameters to the size distribution of vesicles based on the composition of a medium, it is important to characterize and analyze each vesicle preparation