A Budding-Defective M2 Mutant Exhibits Reduced Membrane Interaction, Insensitivity To Cholesterol, And Perturbed Interdomain Coupling

Influenza A M2 is a membrane-associated protein with a C-terminal amphipathic helix that plays a cholesterol-dependent role in viral budding. An M2 mutant with alanine substitutions in the C-terminal amphipathic helix is deficient in viral scission. With the goal of providing atomic-level understanding of how the wild-type protein functions, we used a multipronged site-directed spin labeling electron paramagnetic resonance spectroscopy (SDSL-EPR) approach to characterize the conformational properties of the alanine mutant. We spin-labeled sites in the transmembrane (TM) domain and the C-terminal amphipathic helix (AH) of wild-type (WT) and mutant M2, and collected information on line shapes, relaxation rates, membrane topology, and distances within the homotetramer in membranes with and without cholesterol. Our results identify marked differences in the conformation and dynamics between the WT and the alanine mutant. Compared to WT, the dominant population of the mutant AH is more dynamic, shallower in the membrane, and has altered quaternary arrangement of the C-terminal domain. While the AH becomes more dynamic, the dominant population of the TM domain of the mutant is immobilized. The presence of cholesterol changes the conformation and dynamics of the WT protein, while the alanine mutant is insensitive to cholesterol. These findings provide new insight into how M2 may facilitate budding. We propose the AH–membrane interaction modulates the arrangement of the TM helices, effectively stabilizing a conformational state that enables M2 to facilitate viral budding. Antagonizing the properties of the AH that enable interdomain coupling within M2 may therefore present a novel strategy for anti-influenza drug design

Influence of Collision Cascade Statistics on Pattern Formation of Ion-Sputtered Surfaces

Theoretical continuum models that describe the formation of patterns on surfaces of targets undergoing ion-beam sputtering, are based on Sigmund's formula, which describes the spatial distribution of the energy deposited by the ion. For small angles of incidence and amorphous or polycrystalline materials, this description seems to be suitable, and leads to the classic BH morphological theory [R.M. Bradley and J.M.E. Harper, J. Vac. Sci. Technol. A 6, 2390 (1988)]. Here we study the sputtering of Cu crystals by means of numerical simulations under the binary-collision approximation. We observe significant deviations from Sigmund's energy distribution. In particular, the distribution that best fits our simulations has a minimum near the position where the ion penetrates the surface, and the decay of energy deposition with distance to ion trajectory is exponential rather than Gaussian. We provide a modified continuum theory which takes these effects into account and explores the implications of the modified energy distribution for the surface morphology. In marked contrast with BH's theory, the dependence of the sputtering yield with the angle of incidence is non-monotonous, with a maximum for non-grazing incidence angles.Comment: 12 pages, 13 figures, RevTe

Biochar and zeolites did not improve phosphorus uptake or crop productivity in a field trial performed in an irrigated intensive farming system

Soil conditioners, such as biochar and zeolites, may play an important role in agriculture if they increase nutrient use efficiency, in particular, that of phosphorus (P), due to the depletion of phosphate rocks from which P-fertilizers are manufactured. This study report results from a field trial, where maize was grown in summer and oats in winter, and from a pot experiment with maize. In the field, the use of biochar and zeolites, along with an untreated control in combination with various P rates (0, 50, 100 and 200 kg P2O5 ha−1), was tested. In the pot experiment, six treatments were included, biochar, zeolites and a non-amended control with and without P application. Soil conditioners did not significantly influence tissue elemental composition or the dry matter (DM) yield of maize and oats in the field trial, nor the DM yield of maize in the pots. In the field trial, average maize DM yields varied from 14.3 to 15.6 t ha−1 and 11.8 to 13.7 t ha−1 and average oats DM yields from 2.1 to 2.4 t ha−1 and 3.0 to 3.2 t ha−1, respectively, in 2018 and 2019. Biochar only significantly increased total organic carbon (C); and zeolites the levels of potassium (K) in the soil, a result of their initial composition. P application increased DM yield of maize in the second year and oats in the two years of the field trial and also the DM yield of potted maize. In the pots, P application also influenced the concentration of P and several other nutrients in plant tissues and increased the labile soil P fraction. This study showed that the biochar and zeolite soil conditioners applied may not be suitable for short-term increase of crop production in soil with high agricultural potential and under intensive irrigated farming systems.The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) and European Regional Development Fund (ERDF) under Programme PT2020 for financial support to Centro de Investigação de Montana (CIMO) (UID/AGR/00690/2015) and Centre for the Research and Technology of Agro-Environmental and Biological Sciences (CITAB) (UIDB/04033/2020).info:eu-repo/semantics/publishedVersio

Optimization of the Kinematic Chain of the Thumb for a Hand Prosthesis Based on the Kapandji Opposition Test

Ponènica presentada a International Symposium on Computer Methods in Biomechanics and Biomedical Engineering - CMBBE 2019The thumb plays a key role in the performance of the hand for grasp-ing and manipulating objects. In artificial hands the complex thumb’s kinematic chain (TKC) is simplified and its five degrees of freedom are reduced to only one or two with the consequent loss of dexterity of the hand. The Kapandji op-position test (KOT) has been clinically used in pathological human hands for evaluating the thumb opposition and it has also been employed in some previ-ous studies as reference for the design of the TKC in artificial hands, but with-out a clearly stated methodology. Based on this approaches, in this study we present a computational method to optimize the whole TKC (base placement, link lengths and joint orientation angles) of an artificial hand based on its per-formance in the KOT. The cost function defined for the optimization (MPE) is a weighted mean position error when trying to reproduce the KOT postures and can be used also as a metric to quantify thumb opposition in the hand. As a case study, the method was applied to the improvement of the TKC of an artificial hand developed by the authors and the MPE was reduced to near one third of that of the original design, increasing significantly the number of reachable po-sitions in the KOT. The metric proposed based on the KOT can be used directly or in combination with other to improve the kinematic chain of artificial hands

A unification in the theory of linearization of second order nonlinear ordinary differential equations

In this letter, we introduce a new generalized linearizing transformation (GLT) for second order nonlinear ordinary differential equations (SNODEs). The well known invertible point (IPT) and non-point transformations (NPT) can be derived as sub-cases of the GLT. A wider class of nonlinear ODEs that cannot be linearized through NPT and IPT can be linearized by this GLT. We also illustrate how to construct GLTs and to identify the form of the linearizable equations and propose a procedure to derive the general solution from this GLT for the SNODEs. We demonstrate the theory with two examples which are of contemporary interest.Comment: 8 page

Long-time discrete particle effects versus kinetic theory in the self-consistent single-wave model

The influence of the finite number N of particles coupled to a monochromatic wave in a collisionless plasma is investigated. For growth as well as damping of the wave, discrete particle numerical simulations show an N-dependent long time behavior resulting from the dynamics of individual particles. This behavior differs from the one due to the numerical errors incurred by Vlasov approaches. Trapping oscillations are crucial to long time dynamics, as the wave oscillations are controlled by the particle distribution inhomogeneities and the pulsating separatrix crossings drive the relaxation towards thermal equilibrium.Comment: 11 pages incl. 13 figs. Phys. Rev. E, in pres

The 6dF Galaxy Survey: bulk flows on 50-70 h

We measure the bulk flow of the local Universe using the 6dF Galaxy Survey peculiar velocity sample (6dFGSv), the largest and most homogeneous peculiar velocity sample to date. 6dFGSv is a Fundamental Plane sample of ∼104 peculiar velocities covering the whole Southern hemisphere for galactic latitude |b| > 10°, out to redshift z = 0.0537. We apply the ‘minimum variance’ bulk flow weighting method, which allows us to make a robust measurement of the bulk flow on scales of 50 and 70 h−1 Mpc. We investigate and correct for potential bias due to the lognormal velocity uncertainties, and verify our method by constructing Λ cold dark matter (ΛCDM) 6dFGSv mock catalogues incorporating the survey selection function. For a hemisphere of radius 50 h−1 Mpc we find a bulk flow amplitude of U = 248 ± 58 km s−1 in the direction (l, b) = (318° ± 20°, 40° ± 13°), and for 70 h−1 Mpc we find U = 243 ± 58 km s−1, in the same direction. Our measurement gives us a constraint on σ8 of 1.01+1.07−0.58. Our results are in agreement with other recent measurements of the direction of the bulk flow, and our measured amplitude is consistent with a ΛCDM prediction

Visuospatial Integration: Paleoanthropological and Archaeological Perspectives

The visuospatial system integrates inner and outer functional processes, organizing spatial, temporal, and social interactions between the brain, body, and environment. These processes involve sensorimotor networks like the eye–hand circuit, which is especially important to primates, given their reliance on vision and touch as primary sensory modalities and the use of the hands in social and environmental interactions. At the same time, visuospatial cognition is intimately connected with memory, self-awareness, and simulation capacity. In the present article, we review issues associated with investigating visuospatial integration in extinct human groups through the use of anatomical and behavioral data gleaned from the paleontological and archaeological records. In modern humans, paleoneurological analyses have demonstrated noticeable and unique morphological changes in the parietal cortex, a region crucial to visuospatial management. Archaeological data provides information on hand–tool interaction, the spatial behavior of past populations, and their interaction with the environment. Visuospatial integration may represent a critical bridge between extended cognition, self-awareness, and social perception. As such, visuospatial functions are relevant to the hypothesis that human evolution is characterized by changes in brain–body–environment interactions and relations, which enhance integration between internal and external cognitive components through neural plasticity and the development of a specialized embodiment capacity. We therefore advocate the investigation of visuospatial functions in past populations through the paleoneurological study of anatomical elements and archaeological analysis of visuospatial behaviors

FourQ on Embedded Devices with Strong Countermeasures Against Side-Channel Attacks

This work deals with the energy-efficient, high-speed and high-security implementation of elliptic curve scalar multiplication, elliptic curve Diffie-Hellman (ECDH) key exchange and elliptic curve digital signatures on embedded devices using FourQ and incorporating strong countermeasures to thwart a wide variety of side-channel attacks. First, we set new speed records for constant-time curve-based scalar multiplication, DH key exchange and digital signatures at the 128-bit security level with implementations targeting 8, 16 and 32-bit microcontrollers. For example, our software computes a static ECDH shared secret in 6.9 million cycles (or 0.86 seconds @8MHz) on a low-power 8-bit AVR microcontroller which, compared to the fastest Curve25519 and genus-2 Kummer implementations on the same platform, offers 2x and 1.4x speedups, respectively. Similarly, it computes the same operation in 496 thousand cycles on a 32-bit ARM Cortex-M4 microcontroller, achieving a factor-2.9 speedup when compared to the fastest Curve25519 implementation targeting the same platform. A similar speed performance is observed in the case of digital signatures. Second, we engineer a set of side-channel countermeasures taking advantage of FourQ\u27s rich arithmetic and propose a secure implementation that offers protection against a wide range of sophisticated side-channel attacks, including differential power analysis (DPA). Despite the use of strong countermeasures, the experimental results show that our FourQ software is still efficient enough to outperform implementations of Curve25519 that only protect against timing attacks. Finally, we perform a differential power analysis evaluation of our software running on an ARM Cortex-M4, and report that no leakage was detected with up to 10 million traces. These results demonstrate the potential of deploying FourQ on low-power applications such as protocols for the Internet of Things