Bacon et al. (1) “reject a 3.5 Ma assumption” for the closure of the Central American Seaway, a conclusion that echoes earlier studies that established that the “bulk [of marine ‘geminate’ or ‘transisthmian’ species on opposite sides of the Isthmus] were split at some point during the long period of...

In their PNAS article “Biological evidence supports an early and complex emergence of the Isthmus of Panama,” Bacon et al. (1) use data from molecular comparisons of terrestrial and marine organisms taken from the literature to estimate dates of rate shifts in migration. One of their conclusions is that “events...

The emergence of the Isthmus of Panama left a major imprint on the biodiversity of the Americas. The connection between South and North America facilitated dispersal of terrestrial and freshwater organisms, while separating marine species between the eastern Pacific and Caribbean seas. Recent geological data have questioned the long-standing view...

Adult cardiomyocytes—the contractile units of the heart—have little regenerative capacity, and their loss, following ischemic injury and other insults, leads to cardiac dysfunction and heart failure, a degenerative condition with a poorer prognosis than many cancers. Despite intense efforts, there are presently no effective treatments for heart failure besides heart...

CD31 is a member of the Ig gene superfamily that is present on the surface of platelets and all leukocytes (1). CD31 is also highly expressed on endothelial cells, where it represents a major constituent of the intercellular junction (1). Based on this cellular distribution and similarities in the cDNA...

Central carbon metabolism (CCM) that transforms carbon through glycolysis, gluconeogenesis, the pentose phosphate pathway, and the TCA pathway into energy is essential for the physiology of Mycobacterium tuberculosis (Mtb). In contrast to other pathogens, humans are the only known reservoir of Mtb, where it mainly resides in macrophages of the...

Over the past several decades we have witnessed record-setting wildfires across nearly every continent (1), with recent months as no exception. Widespread burning across western North America includes some of the largest wildfires on record in Washington State, with 2015 total area burned on track to exceed observations of the...

Sex and parasites are two of the most important forces in evolution, shaping everything from the appearance of organisms (sex, by favoring the evolution of ornaments and weapons) to their physiological functioning (parasites, via selection for host defenses). They have been studied both separately and together, with parasite–sex interactions similarly...

Two articles published by Pauling and Coryell in PNAS nearly 80 years ago described in detail the magnetic properties of oxy- and deoxyhemoglobin, as well as those of closely related compounds containing hemes. Their measurements revealed a large difference in magnetism between oxygenated and deoxygenated forms of the protein and,...

Adzuki bean (Vigna angularis), an important legume crop, is grown in more than 30 countries of the world. The seed of adzuki bean, as an important source of starch, digestible protein, mineral elements, and vitamins, is widely used foods for at least a billion people. Here, we generated a high-quality...

Geochemical analyses (δ11B and Sr/Ca) are reported for the coral Porites cylindrica grown within a free ocean carbon enrichment (FOCE) experiment, conducted on the Heron Island reef flat (Great Barrier Reef) for a 6-mo period from June to early December 2010. The FOCE experiment was designed to simulate the effects...

ErbB3 (HER3) is a member of the EGF receptor (EGFR) family of receptor tyrosine kinases, which, unlike the other three family members, contains a pseudo kinase in place of a tyrosine kinase domain. In cancer, ErbB3 activation is driven by a ligand-dependent mechanism through the formation of heterodimers with EGFR,...

The structure of the intact ATP synthase from the α-proteobacterium Paracoccus denitrificans, inhibited by its natural regulatory ζ-protein, has been solved by X-ray crystallography at 4.0 Å resolution. The ζ-protein is bound via its N-terminal α-helix in a catalytic interface in the F1 domain. The bacterial F1 domain is attached...

Interactions between polypeptide chains containing amino acid residues with opposite absolute configurations have long been a source of interest and speculation, but there is very little structural information for such heterochiral associations. The need to address this lacuna has grown in recent years because of increasing interest in the use...

Inflammasomes are multiprotein complexes that control the innate immune response by activating caspase-1, thus promoting the secretion of cytokines in response to invading pathogens and endogenous triggers. Assembly of inflammasomes is induced by activation of a receptor protein. Many inflammasome receptors require the adapter protein ASC [apoptosis-associated speck-like protein containing...

α-Helical antimicrobial peptides (AMPs) generally have facially amphiphilic structures that may lead to undesired peptide interactions with blood proteins and self-aggregation due to exposed hydrophobic surfaces. Here we report the design of a class of cationic, helical homo-polypeptide antimicrobials with a hydrophobic internal helical core and a charged exterior shell,...

We study the computational complexity of approximating the partition function of a q-state spin system with an external field. There are just three possible levels of computational difficulty, depending on the interaction strengths between adjacent spins: (i) efficiently exactly computable, (ii) equivalent to the ferromagnetic Ising model, and (iii) equivalent...

Wnt proteins regulate axonal outgrowth along the anterior–posterior axis, but the intracellular mechanisms that modulate the strength of Wnt signaling in axon guidance are largely unknown. Using the Caenorhabditis elegans mechanosensory PLM neurons, we found that posteriorly enriched LIN-44/Wnt acts as a repellent to promote anteriorly directed neurite outgrowth through...

The tips of the digits of some mammals, including human infants and mice, are capable of complete regeneration after injury. This process is reliant on the presence of the overlaying nail organ and is mediated by a proliferative blastema. Epithelial Wnt/β-catenin signaling has been shown to be necessary for mouse...

Heart regeneration offers a novel therapeutic strategy for heart failure. Unlike mammals, lower vertebrates such as zebrafish mount a strong regenerative response following cardiac injury. Heart regeneration in zebrafish occurs by cardiomyocyte proliferation and reactivation of a cardiac developmental program, as evidenced by induction of gata4 regulatory sequences in regenerating...