Blocked-braid Groups

We introduce and study a family of groups $\mathbf{BB}_n$, called the blocked-braid groups, which are quotients of Artin's braid groups $\mathbf{B}_n$, and have the corresponding symmetric groups $\Sigma_n$ as quotients. They are defined by adding a certain class of geometrical modifications to braids. They arise in the study of commutative Frobenius algebras and tangle algebras in braided strict monoidal categories. A fundamental equation true in $\mathbf{BB}_n$ is Dirac's Belt Trick; that torsion through $4\pi$ is equal to the identity. We show that $\mathbf{BB}_n$ is finite for $n=1,2$ and 3 but infinite for $n>3$

NSF Data Management and Public Access Initiatives

Anne Maglia, PhD, is Program Director, Division of Biological Infrastructure, National Science Foundation. She spoke about the National Science Foundation\u27s data management, data sharing, and public access policies

Artificial nanopores and uses and methods relating thereto

The invention relates to the field of nanopores and the use thereof in analyzing biopolymers, including polypeptides and polynucleotides. Provided is an artificial nanopore comprising a multimeric assembly of subunits, each subunit comprising (i) the transmembrane (TM) sequence of a β-barrel or α-helical pore forming protein fused to the amino acid sequence of (ii) a subunit of a ring-forming protein capable of controlling the transport of a polypeptide or polynucleotide across the TM region of the assembly

Biological nanopores having tunable pore diameters and uses thereof as analytical tools

The invention relates to the field of nanopores, in particular to engineered Fragaceatoxin C (FraC) nanopores and their application in analyzing biopolymers and other (biological) compounds, such as single-molecule (protein) sequencing. Provided is a system comprising oligomeric FraC nanopores comprised in a lipid bilayer, wherein the sum of the nanopore fraction in the heptameric (Type II) state and the nanopore fraction in the hexameric (Type III) state represents at least 60% of the total number of FraC nanopores

Ecosystems and Ordering: Exploring the Extent and Diversity of Ecosystem Governance

This article argues that, to grasp how global ordering will be impacted by planetary-level changes, we need to systematically attend to the question of the extent to which and how ecosystems are being governed. Our inquiry builds upon—but extends beyond—the environmental governance measures that have garnered the most scholarly attention so far. The dataset departs from the current literature on regional environmental governance by taking ecosystems themselves as the unit of analysis and then exploring whether and how they are governed, rather than taking a starting point in environmental institutions and treaties. The ecosystems researched—large-scale marine, freshwater, and terrestrial ecosystems—have been previously identified by a globe-spanning, natural science inquiry. Our findings highlight the uneven extent of ecosystem governance—both the general geographic extent and certain “types” of ecosystems seemingly lending themselves more easily to ecosystem-based cooperation. Furthermore, our data highlight that there is a wider range of governance practices anchored in ecosystems than the typical focus on environmental institutions reveals. Of particular significance is the tendency by political actors to establish multi-issue governance anchored in the ecosystems themselves and covering several different policy fields. We argue that, in light of scholarship on ecosystem-anchored cooperation and given the substantive set of cases of such cooperation identified in the dataset, these forms of ecosystem-anchored cooperation may have particularly significant ordering effects. They merit attention in the international relations scholarship that seeks to account for the diversity of global ordering practices.Ecosystems and Ordering: Exploring the Extent and Diversity of Ecosystem GovernancepublishedVersio

Single-Molecule Sampling of Dihydrofolate Reductase Shows Kinetic Pauses and an Endosteric Effect Linked to Catalysis

[Image: see text] The ability to sample multiple reactions on the same single enzyme is important to link rare intermediates with catalysis and to unravel the role of conformational changes. Despite decades of efforts, however, the single-molecule characterization of nonfluorogenic enzymes during multiple catalytic turnovers has been elusive. Here, we show that nanopore currents allow sampling the dynamic exchange between five structural intermediates during E. coli dihydrofolate reductase (DHFR) catalysis. We found that an endosteric effect promotes the binding of the substrate to the enzyme with a specific hierarchy. The chemical step then switched the enzyme from the closed to the occluded conformation, which in turn promotes the release of the reduced cofactor NADP(+). Unexpectedly, only a few reactive complexes lead to catalysis. Furthermore, second-long catalytic pauses were observed, possibly reflecting an off-path conformation generated during the reaction. Finally, the free energy from multiple cofactor binding events were required to release the product and switch DHFR back to the reactive conformer. This catalytic fueled concerted mechanism is likely to have evolved to improve the catalytic efficiency of DHFR under the high concentrations of NADP(+) in E. coli and might be a general feature for complex enzymatic reactions where the binding and release of the products must be tightly controlled