Two stellar components in the halo of the Milky Way

The halo of the Milky Way provides unique elemental abundance and kinematic information on the first objects to form in the Universe, and this information can be used to tightly constrain models of galaxy formation and evolution. Although the halo was once considered a single component, evidence for its dichotomy has slowly emerged in recent years from inspection of small samples of halo objects. Here we show that the halo is indeed clearly divisible into two broadly overlapping structural components--an inner and an outer halo--that exhibit different spatial density profiles, stellar orbits and stellar metallicities (abundances of elements heavier than helium). The inner halo has a modest net prograde rotation, whereas the outer halo exhibits a net retrograde rotation and a peak metallicity one-third that of the inner halo. These properties indicate that the individual halo components probably formed in fundamentally different ways, through successive dissipational (inner) and dissipationless (outer) mergers and tidal disruption of proto-Galactic clumps.     

The biological impact of mass-spectrometry-based proteomics

In the past decade, there have been remarkable advances in proteomic technologies. Mass spectrometry has emerged as the preferred method for in-depth characterization of the protein components of biological systems. Using mass spectrometry, key insights into the composition, regulation and function of molecular complexes and pathways have been gained. From these studies, it is clear that mass-spectrometry-based proteomics is now a powerful 'hypothesis-generating engine' that, when combined with complementary molecular, cellular and pharmacological techniques, provides a framework for translating large data sets into an understanding of complex biological processes.     

The origin of protein interactions and allostery in colocalization

Two fundamental principles can account for how regulated networks of interacting proteins originated in cells. These are the law of mass action, which holds that the binding of one molecule to another increases with concentration, and the fact that the colocalization of molecules vastly increases their local concentrations. It follows that colocalization can amplify the effect on one protein of random mutations in another protein and can therefore, through natural selection, lead to interactions between proteins and to a startling variety of complex allosteric controls. It also follows that allostery is common and that homologous proteins can have different allosteric mechanisms. Thus, the regulated protein networks of organisms seem to be the inevitable consequence of natural selection operating under physical laws.     

Preserving the evolutionary potential of floras in biodiversity hotspots

One of the biggest challenges for conservation biology is to provide conservation planners with ways to prioritize effort. Much attention has been focused on biodiversity hotspots. However, the conservation of evolutionary process is now also acknowledged as a priority in the face of global change. Phylogenetic diversity (PD) is a biodiversity index that measures the length of evolutionary pathways that connect a given set of taxa. PD therefore identifies sets of taxa that maximize the accumulation of 'feature diversity'. Recent studies, however, concluded that taxon richness is a good surrogate for PD. Here we show taxon richness to be decoupled from PD, using a biome-wide phylogenetic analysis of the flora of an undisputed biodiversity hotspot--the Cape of South Africa. We demonstrate that this decoupling has real-world importance for conservation planning. Finally, using a database of medicinal and economic plant use, we demonstrate that PD protection is the best strategy for preserving feature diversity in the Cape. We should be able to use PD to identify those key regions that maximize future options, both for the continuing evolution of life on Earth and for the benefit of society.