Radiation damage to cryocooled protein crystals during x-ray structure determination has become an inherent part of macromolecular diffraction data collection at third-generation synchrotrons. Generally, radiation damage is an undesirable component of the experiment and can result in erroneous structural detail in the final model. The characterization of radiation damage thus has become an important area for structural biologists. The calculated dose limit of 2 × 10 ⁷ Gy for the diffracting power of cryocooled protein crystals to drop by half has been experimentally evaluated at a third-generation synchrotron source. Successive data sets were collected from four holoferritin and three apoferritin crystals. The absorbed dose for each crystal was calculated by using the program raddose after measurement of the incident photon flux and determination of the elemental crystal composition by micro-particle-induced x-ray emission. Degradation in diffraction quality and specific structural changes induced by synchrotron radiation then could be compared directly with absorbed dose for different dose/dose rate regimes: a 10% lifetime decrease for a 10-fold dose rate increase was observed. Remarkable agreement both between different crystals of the same type and between apoferritin and holoferritin was observed for the dose required to reduce the diffracted intensity by half ( D _1/2 ). From these measurements, a dose limit of D _1/2 = 4.3 (±0.3) ×10 ⁷ Gy was obtained. However, by considering other data quality indicators, an intensity reduction to I _ln2 = ln2 × I ₀ , corresponding to an absorbed dose of 3.0 × 10 ⁷ Gy, is recommended as an appropriate dose limit for typical macromolecular crystallography experiments.

We present a new transcriptome assembly of the Pacific whiteleg shrimp (Litopenaeus vannamei), the species most farmed for human consumption. Its functional annotation, a substantial improvement over previous ones, is provided freely. RNA-Seq with Illumina HiSeq technology was used to analyze samples extracted from shrimp abdominal muscle, hepatopancreas, gills and pleopods. We used the Trinity and Trinotate software suites for transcriptome assembly and annotation, respectively. The quality of this assembly and the affiliated targeted homology searches greatly enrich the curated transcripts currently available in public databases for this species. Comparison with the model arthropod Daphnia allows some insights into defining characteristics of decapod crustaceans. This large-scale gene discovery gives the broadest depth yet to the annotated transcriptome of this important species and should be of value to ongoing genomics and immunogenetic resistance studies in this shrimp of paramount global economic importance.

Staphylococcus aureus can adhere to and invade endothelial cells by binding to the human protein fibronectin (Fn). FnBPA and FnBPB, cell wall-attached proteins from S. aureus , have multiple, intrinsically disordered, high-affinity binding repeats (FnBRs) for Fn. Here, 30 years after the first report of S. aureus /Fn interactions, we present four crystal structures that together comprise the structures of two complete FnBRs, each in complex with four of the N-terminal modules of Fn. Each ≈40-residue FnBR forms antiparallel strands along the triple-stranded β-sheets of four sequential F1 modules ( ^2–5 F1) with each FnBR/ ^2–5 F1 interface burying a total surface area of ≈4,300 Å ² . The structures reveal the roles of residues conserved between S. aureus and Streptococcus pyogenes FnBRs and show that there are few linker residues between FnBRs. The ability to form large intermolecular interfaces with relatively few residues has been proposed to be a feature of disordered proteins, and S. aureus /Fn interactions provide an unusual illustration of this efficiency.