Cation-pi interactions in aromatics of biological and medicinal interest: Electrostatic potential surfaces as a useful qualitative guide

The cation-pi interaction is an important, general force for molecular recognition in biological receptors. Through the sidechains of aromatic amino acids, novel binding sites for cationic ligands such as acetylcholine can be constructed. We report here a number of calculations on prototypical cation-pi systems, emphasizing structures of relevance to biological receptors and prototypical heterocycles of the type often of importance in medicinal chemistry. Trends in the data can be rationalized using a relatively simple model that emphasizes the electrostatic component of the cation-pi interaction. In particular, plots of the electrostatic potential surfaces of the relevant aromatics provide useful guidelines for predicting cation-pi interactions in new systems

Crossover and coexistence of quasiparticle excitations in the fractional quantum Hall regime at nu <= 1/3

New low-lying excitations are observed by inelastic light scattering at filling factors nu=p/(phip+/-1) of the fractional quantum Hall regime with phi=4. Coexisting with these modes throughout the range nuless than or equal to1/3 are phi=2 excitations seen at 1/3. Both phi=2 and phi=4 excitations have distinct behaviors with temperature and filling factor. The abrupt first appearance of the new modes in the low-energy excitation spectrum at nuless than or similar to1/3 suggests a marked change in the quantum ground state on crossing the phi=2-->phi=4 boundary at nu=1/3

Fire Department Accreditation: A New Way of Evaluating Efficiency and Effectiveness of Fire Departments

Accreditation is a way to measure the effectiveness and efficiency of a fire department by determining community risks and fire safety needs, accurately evaluating the organization’s performance, and providing a method for continuous improvement

Introduction: origins and settlement of the indigenous populations of the Aleutian Archipelago

Journal ArticleThe series of papers in this special issue of Human Biology use an interdisciplinary approach to address regional questions and to integrate disparate Aleutian data into a broad, synthetic effort. The contributors leverage decades of data on Aleut origins, biogeography, and behavior through integration of molecular analyses, linguistics, archaeology, and ethnography. This research explores the origin and colonization of the Aleutian archipelago, communication and the extent of prehistoric cultural exchange among Aleut subgroups, ethnographic information as applied to human biological variation, metric and genetic variation among Aleut groups, and prehistoric dietary reconstruction. The Aleutian archipelago, composed of eastern, central, and western islands, extends 1,800 km between the North American and Asian continents and divides the northern Pacific Ocean from the Bering Sea. Volcanic in origin and formed during the early Tertiary, the archipelago is composed of more than 200 islands divided into six groups, separated by ocean passes. The climate is maritime and is characterized by foggy and cloudy weather, frequent rain and winds, and often cold but not severe annual temperatures. The Aleutians form the southern boundary for the most biologically and commercially important region of the Pacific-the Bering Sea. Until recently, this area was a rich ecotone that supported abundant populations of large marine mammals, ocean fisheries, thick kelp forests, complex near-shore ecosystems and intertidal zones, spawning streams, and a highly diverse avian fauna pivotal to the adaptations and survival of the human groups who, in the past, peopled the islands of the archipelago. However, the Aleutians, once considered one of the richest island ecosystems in the world, have been undergoing considerable biotic turnover (Estes and Duggins 1995). Population densities of marine mammals and some economical fish have dramatically declined, and the once thick kelp forests have decreased (Committee on the Alaska Groundfish Fishery and Steller Sea Lions 2003; Trites et al. 1999). In contrast, Aleutian waters have witnessed increases in sea urchin, pollack, and shark populations, species that were historically uncommon in this ecosystem (Estes et al. 1998; Springer 1999). This biotic restructuring has occurred over a short time period and carries socioeconomic consequences and lessons for local inhabitants-and the world community, especially if rapid global warming is the cause (Estes et al. 1998)

Expression and Circular Dichroism Studies of the Extracellular Domain of the alpha Subunit of the Nicotinic Acetylcholine Receptor

To provide material suitable for structural studies of the nicotinic acetylcholine receptor, we have expressed and purified the NH2-terminal extracellular domain of the mouse muscle alpha subunit. Several constructs were initially investigated using Xenopus oocytes as a convenient small scale expression system. A fusion protein (alpha210GPI) consisting of the 210 NH2-terminal amino acids of the alpha subunit and a glycosylphosphatidylinositol anchorage sequence conferred surface alpha-bungarotoxin binding in oocytes. Coexpression of alpha210GPI with an analogous construct made from the delta subunit showed no evidence of heterodimer formation. The alpha210GPI protein was chosen for large scale expression in transfected Chinese hamster ovary cells. The alpha210GPI protein was cleaved from these cells and purified on an immunoaffinity column. Gel and column chromatography show that the purified protein is processed as expected and exists as a monomer. The purified protein also retains the two distinct, conformation-specific binding sites expected for the correctly folded alpha subunit. Circular dichroism studies of alpha210GPI suggest that this region of the receptor includes considerable beta-sheet secondary structure, with a small proportion of alpha-helix

Unangan past and present: the contrasts between observed and inferred histories

Journal ArticleAbstract Academic research focusing on the population and culture history of the Aleut (Unangan) people began in the late 19th century and continues to the present. The papers in this special issue of Human Biology summarize the latest results from archaeological, linguistic, genetic, and morphometric research approaches that bear on our current understanding of Unangan history and prehistory. Although these new analyses have provided a level of description and resolution previously unattainable, explanatory models and mechanisms for the patterned variation observed over time in the biological and cultural record of the Aleutian region remains elusive. Bringing the diverse data sets into concordance to represent an integrated synthesis of Aleut population and culture history and of Unangan origins and their relationships with other groups in the region remains a goal for future investigators