ALBERT

Description: While conducting a toxicity assessment of the antidepressant paroxetine (Paxil®), in wild-derived mice ( Mus musculus ), we observed that exposed dams (P 0 ) produced female biased litters (32:68 M:F). Though numerous experimental manipulations have induced sex ratio bias in mice, none have assessed the fitness of the offspring from these litters relative to controls. Here, we retrospectively analyze experimentally derived fitness data gathered for the purpose of toxicological assessment in light of 2 leading hypothesis (Trivers–Willard hypothesis [TWH] and cost of reproduction hypothesis [CRH]), seeking to test if this facultative sex ratio adjustment fits into an adaptive framework. Control F 1 males were heavier than F 1 females, but no differences in mass were detected between exposed F 1 males and females, suggesting that exposed dams did not save energy by producing fewer males, despite producing 29.2% lighter litters relative to controls. F 1 offspring of both treatments were released into seminatural enclosures where fitness was quantified. In enclosures, the relative reproductive success of F 1 -exposed males (compared with controls) was reduced by ~20% compared with the relative reproductive success of F 1 -exposed females. Thus, exposed dams increased their fitness by adjusting litters toward females who were less negatively affected by the exposure than males. Collectively, these data provide less support that the observed sex ratio bias results in energetic savings (CRH), and more support for the TWH because fitness was increased by biasing litters toward female offspring. These mammalian data are unique in their ability to support the TWH through the use of relevant fitness data.

Description: High affinity and specificity are considered essential for affinity reagents and molecularly-targeted therapeutics, such as monoclonal antibodies. However, life's own molecular and cellular machinery consists of lower affinity, highly multivalent interactions that are metastable, but easily reversible or displaceable. With this inspiration, we have developed a DNA-based reagent platform that uses massive avidity to achieve stable, but reversible specific recognition of polyvalent targets. We have previously selected these DNA reagents, termed DeNAno, against various cells and now we demonstrate that DeNAno specific for protein targets can also be selected. DeNAno were selected against streptavidin-, rituximab- and bevacizumab-coated beads. Binding was stable for weeks and unaffected by the presence of soluble target proteins, yet readily competed by natural or synthetic ligands of the target proteins. Thus DeNAno particles are a novel biomolecular recognition agent whose orthogonal use of avidity over affinity results in uniquely stable yet reversible binding interactions.

Description: Chromatin regulates the selectivity of retroviral integration into the genome of infected cells. At the nucleosome level, both histones and DNA structure are involved in this regulation. We propose a strategy that allows to specifically study a single factor: the DNA distortion induced by the nucleosome. This strategy relies on mimicking this distortion using DNA minicircles (MCs) having a fixed rotational orientation of DNA curvature, coupled with atomic-resolution modeling. Contrasting MCs with linear DNA fragments having identical sequences enabled us to analyze the impact of DNA distortion on the efficiency and selectivity of integration. We observed a global enhancement of HIV-1 integration in MCs and an enrichment of integration sites in the outward-facing DNA major grooves. Both of these changes are favored by LEDGF/p75, revealing a new, histone-independent role of this integration cofactor. PFV integration is also enhanced in MCs, but is not associated with a periodic redistribution of integration sites, thus highlighting its distinct catalytic properties. MCs help to separate the roles of target DNA structure, histone modifications and integrase (IN) cofactors during retroviral integration and to reveal IN-specific regulation mechanisms.

Description: Author(s): M. Strebel, T.-O. Müller, B. Ruff, F. Stienkemeier, and M. Mudrich Elastic scattering cross sections are measured for lithium atoms colliding with rare-gas atoms and SF 6 molecules at tunable relative velocities down to ∼50 m/s. Our scattering apparatus combines a velocity-tunable molecular beam with a magneto-optic trap which provides an ultracold cloud of lithium ... [Phys. Rev. A 86, 062711] Published Fri Dec 21, 2012

Description: Author(s): Lucile Savary, Kate A. Ross, Bruce D. Gaulin, Jacob P. C. Ruff, and Leon Balents Here we establish the systematic existence of a U (1) degeneracy of all symmetry-allowed Hamiltonians quadratic in the spins on the pyrochlore lattice, at the mean-field level. By extracting the Hamiltonian of Er 2 Ti 2 O 7 from inelastic neutron scattering measurements, we then show that the U (1)-degener... [Phys. Rev. Lett. 109, 167201] Published Mon Oct 15, 2012

Description: Author(s): J. P. C. Ruff, J.-H. Chu, H.-H. Kuo, R. K. Das, H. Nojiri, I. R. Fisher, and Z. Islam In addition to unconventional high- T c superconductivity, the iron arsenides exhibit strong magnetoelastic coupling and a notable electronic anisotropy within the a - b plane. We relate these properties by studying underdoped Ba(Fe 1 - x Co x ) 2 As 2 by x-ray diffraction in pulsed magnetic fields up to 27.5 T.... [Phys. Rev. Lett. 109, 027004] Published Wed Jul 11, 2012

Description: SUMMARY Lithospheric density and thickness variations are important contributors to the state of stress of the plates. The relationship between the lithosphere's isostatic state, subcrustal structure and stress field, however, remains unresolved due to the uncertainties on its thickness, composition and rheology. To study the influence of lithospheric structure on intraplate stresses, we use a new model of global lithospheric structure (TDL) that accounts for the presence of depleted mantle to explore the effects of isostatic compensation, mantle density structure, lithospheric thickness (base depth) and mechanical coupling within the lithosphere on wavelengths 〉200 km. We compute the mean lithostatic stress (Ω) of 2°× 2° lithospheric columns and then solve for the resulting global ‘tectonic’ stress field for a homogeneous elastic lithosphere with the finite element package ABAQUS. For a 100 km base depth, a historically common value for lithospheric thickness, tectonic stress patterns are largely insensitive to mantle density structure and match patterns in the world stress map, for both isostatically compensanted and non-compensated lithospheric structure. Increasing the base depth up to 250 km to account for thick continental roots, however, leads to sharp variations in the stress field between isostatic lithospheric structure models and TDL as the mantle portion of the lithosphere dominates Ω. Decreasing the model base depths up to 25 km as a proxy for vertical strength variations due to low viscosity channels within the crust or lithosphere as a whole, strongly alters stresses in magnitude, azimuth and regime, as the influence of topography and shallow crustal structure increases. We find that restricting spatial changes in Ω to a specified region to mimic lateral variations in strength also has a large effect on the resulting stresses, which leads us to conclude that regional models may not always be adequate for modelling the stress field. Strong deviations from long-wavelength patterns on the world stress map in models with a shallow (〈〈100 km) or deep (〉〉150 km) uncompensated model base depth likely reflect that the globally averaged lithospheric thickness is close to 100 km and large deviations from this depth generate unrealistic stress patterns related to uncompensated buoyancy forces. Because the stresses are so sensitive to base depth, we conclude that using Ω to represent spatial and vertical variations in lithospheric structure is not an adequate approximation. Our results suggest that future studies must incorporate the full 3-D variations in density and rheology of the lithosphere to elucidate the source and nature of the lithospheric stress field. These studies have become possible with the advent of modern computational tools and advances in our knowledge of lithospheric structure and rheology.

Description: Author(s): S. Glawion, J. Heidler, M. W. Haverkort, L. C. Duda, T. Schmitt, V. N. Strocov, C. Monney, K. Zhou, A. Ruff, M. Sing, and R. Claessen We combine high-resolution resonant inelastic x-ray scattering with cluster calculations utilizing a recently derived effective magnetic scattering operator to analyze the polarization, excitation energy, and momentum-dependent excitation spectrum of the low-dimensional quantum magnet TiOCl in the r... [Phys. Rev. Lett. 107, 107402] Published Thu Sep 01, 2011

Description: Author(s): J. P. Carlo, J. P. Clancy, T. Aharen, Z. Yamani, J. P. C. Ruff, J. J. Wagman, G. J. Van Gastel, H. M. L. Noad, G. E. Granroth, J. E. Greedan, H. A. Dabkowska, and B. D. Gaulin The geometrically frustrated double perovskite Ba 2 YMoO 6 is characterized by quantum s =1/2 spins at the Mo 5+ sites of an undistorted fcc lattice. Previous low-temperature characterization revealed an absence of static long-range magnetic order and suggested a nonmagnetic spin-singlet ground state. We... [Phys. Rev. B 84, 100404] Published Mon Sep 19, 2011

Description: Author(s): S. Glawion, J. Heidler, M. W. Haverkort, L. C. Duda, T. Schmitt, V. N. Strocov, C. Monney, K. J. Zhou, A. Ruff, M. Sing, and R. Claessen [Phys. Rev. Lett. 107, 129902] Published Wed Sep 14, 2011