Influence of solvent in controlling peptide−surface interactions

Protein binding to surfaces is an important phenomenon in biology and in modern technological applications. Extensive experimental and theoretical research has been focused in recent years on revealing the factors that govern binding affinity to surfaces. Theoretical studies mainly focus on examining the contribution of the individual amino acids or, alternatively, the binding potential energies of the full peptide, which are unable to capture entropic contributions and neglect the dynamic nature of the system. We present here a methodology that involves the combination of nonequilibrium dynamics simulations with strategic mutation of polar residues to reveal the different factors governing the binding free energy of a peptide to a surface. Using a gold-binding peptide as an example, we show that relative binding free energies are a consequence of the balance between strong interactions of the peptide with the surface and the ability for the bulk solvent to stabilize the peptide

Invariant Peano curves of expanding Thurston maps

We consider Thurston maps, i.e., branched covering maps $f\colon S^2\to S^2$ that are postcritically finite. In addition, we assume that $f$ is expanding in a suitable sense. It is shown that each sufficiently high iterate $F=f^n$ of $f$ is semi-conjugate to $z^d\colon S^1\to S^1$, where $d$ is equal to the degree of $F$. More precisely, for such an $F$ we construct a Peano curve $\gamma\colon S^1\to S^2$ (onto), such that $F\circ \gamma(z) = \gamma(z^d)$ (for all $z\in S^1$).Comment: 63 pages, 12 figure

Enzymatically activated emulsions stabilised by interfacial nanofibre networks

We report on-demand formation of emulsions stabilised by interfacial nanoscale networks. These are formed through biocatalytic dephosphorylation and self-assembly of Fmoc(9-fluorenylmethoxycarbonyl)-dipeptide amphiphiles in aqueous/organic mixtures. This is achieved by using alkaline phosphatase which transforms surfactant-like phosphorylated precursors into self-assembling aromatic peptide amphiphiles (Fmoc-tyrosine-leucine, Fmoc-YL) that form nanofibrous networks. In biphasic organic/aqueous systems, these networks form preferentially at the interface thus providing a means of emulsion stabilisation. We demonstrate on-demand emulsification by enzyme addition, even after storage of the biphasic mixture for several weeks. Experimental (Fluorescence, FTIR spectroscopy, fluorescence microscopy, electron microscopy, atomic force microscopy) and computational techniques (atomistic molecular dynamics) are used to characterise the interfacial self-assembly process

The Lyman Alpha Reference Sample: III. Properties of the Neutral ISM from GBT and VLA Observations

We present new H I imaging and spectroscopy of the 14 UV-selected star-forming galaxies in the Lyman Alpha Reference Sample (LARS), aimed for a detailed study of the processes governing the production, propagation, and escape of Ly$\alpha$ photons. New H I spectroscopy, obtained with the 100m Green Bank Telescope (GBT), robustly detects the H I spectral line in 11 of the 14 observed LARS galaxies (although the profiles of two of the galaxies are likely confused by other sources within the GBT beam); the three highest redshift galaxies are not detected at our current sensitivity limits. The GBT profiles are used to derive fundamental H I line properties of the LARS galaxies. We also present new pilot H I spectral line imaging of 5 of the LARS galaxies obtained with the Karl G. Jansky Very Large Array (VLA). This imaging localizes the H I gas and provides a measurement of the total H I mass in each galaxy. In one system, LARS 03 (UGC 8335 or Arp 238), VLA observations reveal an enormous tidal structure that extends over 160 kpc from the main interacting systems and that contains $>$10$^9$ M$_{\odot}$ of H I. We compare various H I properties with global Ly$\alpha$ quantities derived from HST measurements. The measurements of the Ly$\alpha$ escape fraction are coupled with the new direct measurements of H I mass and significantly disturbed H I velocities. Our robustly detected sample reveals that both total H I mass and linewidth are tentatively correlated with key Ly$\alpha$ tracers. Further, on global scales, these data support a complex coupling between Ly$\alpha$ propagation and the H I properties of the surrounding medium.Comment: Preprint form, 16 figures, accepted in Ap

The Effects Of Caffeine On Early Second Half Sprint Performance In NCAA DIII Women’s Soccer Players

Objective The purpose of this study was to examine the effects of caffeine on early second half sprint performance in 21 NCAA DIII women’s soccer players. The caffeine dosage attempted to approximate a liquid dosage many student athletes typically consume. Design In a randomized double blind repeated measures design, subjects began the protocol after ingestion of caplets containing 3 mg.kg-1 of caffeine (CAF) and after ingestion of placebo (PLA) caplets. Pre-game, warm-up, and first half conditions were designed to maximize external validity. Methods An adapted version of the Loughborough Intermittent Shuttle Test was applied to replicate first half activity. Sprint performance was measured with the Running Based Anaerobic Sprint Test. Mean power, maximum power, and minimum power, were assessed under each condition. Repeated measures MANOVA was used to determine if there were significant mean vector differences between the trials. Results Although mean, maximum, and minimum power in the CAF trial increased 3.2%, 3.4%, and 4% respectively, MANOVA results showed no statistically significant differences in the mean vector for power variables (Λ = .752, p \u3e .05). Conclusions The lack of statistical significance in this study is likely attributed to the relationship between a small, although contextually plausible, relative caffeine dosage and an extended exercise time. The results also suggest caffeine ingestion of 3 mg.kg-1 should not be considered capable of improving sprint performance at the start of the second half

The Lyman Alpha Reference Sample. VIII. Characterizing Lyman-Alpha Scattering in Nearby Galaxies

We examine the dust geometry and Ly{\alpha} scattering in the galaxies of the Lyman Alpha Reference Sample (LARS), a set of 14 nearby (0.02 < $z$ < 0.2) Ly{\alpha} emitting and starbursting systems with Hubble Space Telescope Ly{\alpha}, H{\alpha}, and H{\beta} imaging. We find that the global dust properties determined by line ratios are consistent with other studies, with some of the LARS galaxies exhibiting clumpy dust media while others of them show significantly lower Ly{\alpha} emission compared to their Balmer decrement. With the LARS imaging, we present Ly{\alpha}/H{\alpha} and H{\alpha}/H{\beta} maps with spatial resolutions as low as $\sim$ 40 pc, and use these data to show that in most galaxies, the dust geometry is best modeled by three distinct regions: a central core where dust acts as a screen, an annulus where dust is distributed in clumps, and an outer envelope where Ly{\alpha} photons only scatter. We show that the dust that affects the escape of Ly{\alpha} is more restricted to the galaxies' central regions, while the larger Ly{\alpha} halos are generated by scattering at large radii. We present an empirical modeling technique to quantify how much Ly{\alpha} scatters in the halo, and find that this "characteristic" scattering distance correlates with the measured size of the Ly{\alpha} halo. We note that there exists a slight anti-correlation between the scattering distance of Ly{\alpha} and global dust properties.Comment: 32 pages, 51 figures, accepted to Ap

The Formation of Kiloparsec-scale HI Holes in Dwarf Galaxies

The origin of kpc-scale holes in the atomic hydrogen (H i) distributions of some nearby dwarf irregular galaxies presents an intriguing problem. Star formation histories (SFHs) derived from resolved stars give us the unique opportunity to study past star-forming events that may have helped shape the currently visible Hi distribution. Our sample of five nearby dwarf irregular galaxies spans over an order of magnitude in both total Hi mass and absolute B-band magnitude and is at the low-mass end of previously studied systems. We use Very Large Array Hi line data to estimate the energy required to create the centrally dominant hole in each galaxy. We compare this energy estimate to the past energy released by the underlying stellar populations computed from SFHs derived from data taken with the Hubble Space Telescope. The inferred integrated stellar energy released within the characteristic ages exceeds our energy estimates for creating the holes in all cases, assuming expected efficiencies. Therefore, it appears that stellar feedback provides sufficient energy to produce the observed holes. However, we find no obvious signature of single star-forming events responsible for the observed structures when comparing the global SFHs of each galaxy in our sample to each other or to those of dwarf irregular galaxies reported in the literature. We also fail to find evidence of a central star cluster in FUV or Hα imaging. We conclude that large Hi holes are likely formed from multiple generations of star formation and only under suitable interstellar medium conditions

Lack of Correlation Between Pulmonary Disease and Cystic Fibrosis Transmembrane Conductance Regulator Dysfunction in Cystic Fibrosis: A Case Report

Introduction: Mutations in both alleles of the cystic fibrosis transmembrane conductance regulator gene result in the disease cystic fibrosis, which usually manifests as chronic sinopulmonary disease, pancreatic insufficiency, elevated sodium chloride loss in sweat, infertility among men due to agenesis of the vas deferens and other symptoms including liver disease. Case presentation: We describe a pair of African-American brothers, aged 21 and 27, with cystic fibrosis. They were homozygous for a rare frameshift mutation in the cystic fibrosis transmembrane conductance regulator 3791delC, which would be expected to cause significant morbidity. Although 80% of cystic fibrosis patients are colonized with Pseudomonas aeruginosa by eight years of age, the older brother had no serum opsonic antibody titer to P. aeruginosa by age 13 and therefore would have failed to mount an effective antibody response to the alginate (mucoid polysaccharide) capsule of P. aeruginosa. He was not colonized with P. aeruginosa until 24 years of age. Similarly, the younger brother was not colonized with P. aeruginosa until age 20 and had no significant lung disease. Conclusion: Despite a prevailing idea in cystic fibrosis research that the amount of functional cystic fibrosis transmembrane conductance regulator predicts clinical status, our results indicated that respiratory disease severity in cystic fibrosis exhibits phenotypic heterogeneity. If this heterogeneity is, in part, genetic, it is most likely derived from genes outside the cystic fibrosis transmembrane conductance regulator locus