Reduction in animal abundance and oxygen availability during and after the end-Triassic mass extinction

The end-Triassic biodiversity crisis was one of the most severe mass extinctions in the history of animal life. However, the extent to which the loss of taxonomic diversity was coupled with a reduction in organismal abundance remains to be quantified. Further, the temporal relationship between organismal abundance and local marine redox conditions is lacking in carbonate sections. To address these questions, we measured skeletal grain abundance in shallow-marine limestones by point counting 293 thin sections from four stratigraphic sections across the Triassic/Jurassic boundary in the Lombardy Basin and Apennine Platform of western Tethys. Skeletal abundance decreased abruptly across the Triassic/Jurassic boundary in all stratigraphic sections. The abundance of skeletal organisms remained low throughout the lower-middle Hettangian strata and began to rebound during the late Hettangian and early Sinemurian. A two-way ANOVA indicates that sample age (p < .01, η² = 0.30) explains more of the variation in skeletal abundance than the depositional environment or paleobathymetry (p < .01, η² = 0.15). Measured I/Ca ratios, a proxy for local shallow-marine redox conditions, show this same pattern with the lowest I/Ca ratios occurring in the early Hettangian. The close correspondence between oceanic water column oxygen levels and skeletal abundance indicates a connection between redox conditions and benthic organismal abundance across the Triassic/Jurassic boundary. These findings indicate that the end-Triassic mass extinction reduced not only the biodiversity but also the carrying capacity for skeletal organisms in early Hettangian ecosystems, adding to evidence that mass extinction of species generally leads to mass rarity among survivors.     

Sultans of Spin: Syrian Sacred Music on the World Stage

This article examines how the performance of a variety of Islamic music in transnational cultural circuits helps to promote the idea of a style of sacred music within the category of world music. Taking as an example the performance of the mawlawiyya, or "Whirling Dervish," music and dance by a Syrian–based ensemble, I show how the idea of an authentic local Syrian sacred music tradition requires its performance globally. I use the concept of the "world stage" to examine how musical performance practices that are represented as authentic local traditions obtain both their authenticity and their local specificity through their staging in global contexts. I further explore how such musical styles as sacred and Sufi emerge as naturalized categories in world music discourse, and how processes of differentiation and commodification reconfigure both the "local" and "global." [Keywords: world music, globalization, style, Syria, Islam]     

Overexpression of MerT,the mercuric ion transport protein of transposon Tn501, and genetic selection of mercury hypersensitivity mutations

The small (116 amino acids) inner membrane protein MerT encoded by the transposon Tn501 has been overexpressed under the control of the bacteriophage T7 expression system. Random mutants of MerT were made and screened for loss of mercuric ion hypersensitivity. Several mutantmerT genes were selected and sequenced: Cys24Arg and Cys25Tyr mutations abolish mercury resistance, as do charge-substitution mutations in the first predicted transmembrane helix (Glyl4Arg, Glyl5Arg, Gly27Arg, Ala18Asp), and the termination mutations Trp66Ter and Cys82Ter.     

Practical applications of time-averaged restrained molecular dynamics to ligand-receptor systems: FK506 bound to the Q50R,A95H,K98I triple mutant of FKBP-13

Summary The ability of time-averaged restrained molecular dynamics (TARMD) to escape local low-energy conformations and explore conformational space is compared with conventional simulated-annealing methods. Practical suggestions are offered for performing TARMD calculations with ligand-receptor systems, and are illustrated for the complex of the immunosuppressant FK506 bound to Q50R,A95H,K98I triple mutant FKBP-13. The structure of ¹³C-labeled FK506 bound to triple-mutant FKBP-13 was determined using a set of 87 NOE distance restraints derived from HSQC-NOESY experiments. TARMD was found to be superior to conventional simulated-annealing methods, and produced structures that were conformationally similar to FK506 bound to wild-type FKBP-12. The individual and combined effects of varying the NOE restraint force constant, using an explicit model for the protein binding pocket, and starting the calculations from different ligand conformations were explored in detail.Abbreviations DG distance geometry - dmFKBP-12 double-mutant (R42K,H87V) FKBP-12 - FKBP-12 FK506-binding protein (12 kDa) - FKBP-13 FK506-binding protein (13 kDa) - HSQC heteronuclear single-quantum coherence - K_NOE force constant (penalty) for NOE-derived distance restraints - MD molecular dynamics - NOE nuclear Overhauser effect - SA simulated annealing - TARMD molecular dynamics with time-averaged restraints - tmFKBP-13 triple-mutant (Q50R,A95H,K98I) FKBP-13 - wtFKBP-12 wild-type FKBP-12     

The application of robotics and mass spectrometry to the characterisation of the Drosophila melanogaster indirect flight muscle proteome

The rapid accumulation of sequence data generated by the various genome sequencingprojects and the generation of expressed sequence tag databases has resulted in the need forthe development of fast and sensitive methods for the identification and characterisation oflarge numbers of gel electrophoretically separated proteins to translate the sequence data intobiological function. To achieve this goal it has been necessary to devise new approaches toprotein analysis: matrix-assisted laser desorption and electrospray mass spectrometry havebecome important protein analytical tools which are both fast and sensitive. When combinedwith a robotic system for the in-gel digestion of electrophoretically separated proteins, itbecomes possible to rapidly identify many proteins by searching databases with MS data. Thepower of this combination of techniques is demonstrated by an analysis of the proteins presentin the myofibrillar lattice of the indirect flight muscle of Drosophila melanogaster. Theproteins were separated by SDS-PAGE and in-gel proteolysis was performed bothautomatically and manually. All 16 major proteins could quickly be identified by massspectrometry. Although most of the protein components were known to be present in theflight muscle, two new components were also identified. The combination of methodsdescribed offers a means for the rapid identification of large numbers of gel separatedproteins.     

WEEDY ADAPTATION IN SETARIA SPP. I. ISOZYME ANALYSIS OF GENETIC DIVERSITY AND POPULATION GENETIC STRUCTURE IN SETARIA VIRIDIS

Setaria viridis is an important self-pollinating, cosmopolitan weed of temperate regions worldwide. Allozyme markers were used to investigate genetic diversity and structure in 168 accessions (including four S. italica) collected mainly from North America and Eurasia. Genetic diversity in green foxtail, and its population genetic structure, provided important clues about this weed's evolutionary history. Genetic diversity was low, with marked population differentiation: the percentage of polymorphic loci was 25% (0.95 criterion); mean number of alleles per locus was 1.86; mean panmictic heterozygosity was 0.07; and the coefficient of population genetic differentiation was 0.65. A common genotype occurred in 25 accessions distributed in six countries from both the Old World and New World, in a wide variety of ecological situations. Relatively little genetic divergence occurred between Eurasia and North America, with Nei's unbiased genetic identity between the two regions equaling 1.0. Populations from these two continents also had equivalent genetic diversity. Within North America, regional differentiation was indicated by northern and southern groups separated at 43.5° N latitude. No geographic pattern in genetic diversity was found within Eurasia. The size of the geographic range from which populations were sampled was not an accurate indicator of the extent of genetic diversity found among populations from that region. These results suggest that present patterning among green foxtail populations in North America is the consequence of multiple introductions into the New World followed by local adaptation and regional differentiation. Finally, S. italica and several green foxtail varieties did not differ isozymatically from typical forms of green foxtail. This supports the view that S. italica and S. viridis are conspecific, that the former (foxtail millet) is a domesticated form of the latter, and also questions the taxonomic validity of formally recognizing morphological varieties within green foxtail.