A new genus of the subfamily Cillaeinae (Coleoptera, Nitidulidae) from the Philippines and New Guinea with notes on the taxonomy and phylogeny of the subfamily

Allenipeplus gen. nov. represented by A. philippinensis sp. nov., type species (Philippines, Luzon), A. alius sp. nov. (Philippines, Mindoro), A. harmonicus sp. nov. (Philippines, Mindanao) and A. vitellinus sp. nov. (Indonesian New Guinea), is described. This new genus combines characters with a mosaic spread among other cillaeine genera. We present a wide comparison of genera among the subfamily Cillaeinae, making it possible to elaborate a detailed diagnosis of the new genus and trace some order in character patterns and propose a hypothesis on the relationship of this genus to other groups known from the Indo-Malayan and Australian Regions. A detailed diagnosis of the new genus and key to the new species are given. The Adocimus-complex of the related genera including Allenipeplus gen. nov., Adocimus Murray, 1864, Ithyphenes Murray, 1864, Platynema Ritsema, 1885 and probably Brittonema Kirejtshuk, 2011 is defined. Some notes on the taxonomy of the genera Liparopeplus Murray, 1864 and Xanthopeplus Fairmaire, 1880, stat. nov. are given. Additionally, designation of a lectotype for Liparopeplus colastoides Murray, 1864 is made.

Deformable elastic network refinement for low-resolution macromolecular crystallography

Crystals of membrane proteins and protein complexes often diffract to low resolution owing to their intrinsic molecular flexibility, heterogeneity or the mosaic spread of micro-domains. At low resolution, the building and refinement of atomic models is a more challenging task. The deformable elastic network (DEN) refinement method developed previously has been instrumental in the determinion of several structures at low resolution. Here, DEN refinement is reviewed, recommendations for its optimal usage are provided and its limitations are discussed. Representative examples of the application of DEN refinement to challenging cases of refinement at low resolution are presented. These cases include soluble as well as membrane proteins determined at limiting resolutions ranging from 3 to 7 Å. Potential extensions of the DEN refinement technique and future perspectives for the interpretation of low-resolution crystal structures are also discussed.

In cellulostructure determination of a novel cypovirus polyhedrin

This work demonstrates that with the use of a microfocus synchrotron beam the structure of a novel viral polyhedrin could be successfully determined from microcrystals within cells, removing the preparatory step of sample isolation and maintaining a favourable biological environment. The data obtained are of high quality, comparable to that obtained from isolated crystals, and enabled a facile structure determination. A small but significant difference is observed between the unit-cell parameters and the mosaic spread ofin celluloand isolated crystals, suggesting that even these robust crystals are adversely affected by removal from the cell.

Signal to noise considerations for single crystal femtosecond time resolved crystallography of the Photoactive Yellow Protein

Femtosecond time resolved pump–probe protein X-ray crystallography requires highly accurate measurements of the photoinduced structure factor amplitude differences. In the case of femtosecond photolysis of single P63crystals of the Photoactive Yellow Protein, it is shown that photochemical dynamics place a considerable restraint on the achievable time resolution due to the requirement to stretch and add second order dispersion in order to generate threshold concentration levels in the interaction region. Here, we report on using a ‘quasi-cw’ approach to use the rotation method with monochromatic radiation and 2 eV bandwidth at 9.465 keV at the Linac Coherent Light Source operated in SASE mode. A source of significant Bragg reflection intensity noise is identified from the combination of mode structure and jitter with very small mosaic spread of the crystals and very low convergence of the XFEL source. The accuracy with which the three dimensional reflection is approximated by the ‘quasi-cw’ rotation method with the pulsed source is modelled from the experimentally collected X-ray pulse intensities together with the measured rocking curves. This model is extended to predict merging statistics for recently demonstrated self seeded mode generated pulse train with improved stability, in addition to extrapolating to single crystal experiments with increased mosaic spread. The results show that the noise level can be adequately modelled in this manner, indicating that the large intensity fluctuations dominate the merged signal-to-noise (I/σI) value. Furthermore, these results predict that using the self seeded mode together with more mosaic crystals, sufficient accuracy may be obtained in order to resolve typical photoinduced structure factor amplitude differences, as taken from representative synchrotron results.