No abstract

Nematocysts, the stinging organelles of cnidarians, have remarkable mechanical properties. Hydra nematocyst capsules undergo volume changes of 50% during their explosive exocytosis and withstand osmotic pressures of beyond 100 bar. Recently, two novel protein components building up the nematocyst capsule wall in Hydra were identified. The cnidarian proline-rich protein 1 (CPP-1) characterized by a “rigid” polyproline motif and the elastic Cnidoin possessing a silk-like domain were shown to be part of the capsule structure via short cysteine-rich domains that spontaneously crosslink the proteins via disulfide bonds. In this study, recombinant Cnidoin and CPP-1 are expressed in E. coli and the elastic modulus of spontaneously crosslinked bulk proteins is compared with that of isolated nematocysts. For the fabrication of uniform protein nanofibers by electrospinning, the preparative conditions are systematically optimized. Both fibers remain stable even after rigorous washing and immersion into bulk water owing to the simultaneous crosslinking of cysteine-rich domains. This makes our nanofibers clearly different from other protein nanofibers that are not stable without chemical crosslinkers. Following the quantitative assessment of mechanical properties, the potential of Cnidoin and CPP-1 nanofibers is examined towards the maintenance of human mesenchymal stem cells.

No abstract

Violet stimulation is a new development in optical dating which has been suggested to extend the upper age limit of optically simulated luminescence (OSL) dating of quartz. Despite the reported advantage, few validation tests and applications have been published so far. The present study investigated the violet stimulated luminescence (VSL) using a single aliquot regenerative dose (SAR) protocol and a multiple aliquot additive dose (MAAD) protocol. Sedimentary quartz samples from four archaeological sites in Europe with independent age controls spanning 40–900 ka were used, including Grotte Mandrin (France), Brooksby Quarry (UK), Cueva Negra del Estrecho del Río Quípar (Spain) and Sima de las Palomas del Cabezo Gordo (Spain). The equivalent dose of a relatively young sample (~40 ka) was successfully determined. However, significant underestimations were observed for older samples with higher doses. These findings indicate the need for further development of the measurement protocol to date high-dose natural samples.