Biomolecule surface patterning may enhance membrane association

Under dehydration conditions, amphipathic Late Embryogenesis Abundant (LEA) proteins fold spontaneously from a random conformation into alpha-helical structures and this transition is promoted by the presence of membranes. To gain insight into the thermodynamics of membrane association we model the resulting alpha-helical structures as infinite rigid cylinders patterned with hydrophobic and hydrophilic stripes oriented parallel to their axis. Statistical thermodynamic calculations using Single Chain Mean Field (SCMF) theory show that the relative thickness of the stripes controls the free energy of interaction of the alpha-helices with a phospholipid bilayer, as does the bilayer structure and the depth of the equilibrium penetration of the cylinders into the bilayer. The results may suggest the optimal thickness of the stripes to mimic the association of such protein with membranes.Comment: Published in ACS Nano http://pubs.acs.org/doi/pdf/10.1021/nn204736

Saturation effect for dependence of the electrical conductivity of planar oriented nematic liquid crystal 6CB on the concentration of Cu7PS6 nanoparticles

The influence of Cu7PS6 nanoparticles with the average size 117 nm on the dielectric properties of planar oriented nematic liquid crystal 6CB has been investigated within the frequency range 10(1) ...10(6) Hz and at the temperature 293 K. It has been shown that when changing the concentration of nanoparticles within the range 0 to 1 wt.%, the conductivity of the liquid crystal changes stronger than its dielectric permittivity. It has been shown that the electrical conductivity increases monotonously with increasing the concentration of nanoparticles. However, for this dependence a saturation effect is observed. The mechanism of this effect was proposed.info:eu-repo/semantics/publishedVersio

Spectropolarimetry of the H-alpha line in Herbig Ae/Be stars

Using the HiVIS spectropolarimeter built for the Haleakala 3.7m AEOS telescope, we have obtained a large number of high precision spectropolarimetrc observations (284) of Herbig AeBe stars collected over 53 nights totaling more than 300 hours of observing. Our sample of five HAeBe stars: AB Aurigae, MWC480, MWC120, MWC158 and HD58647, all show systematic variations in the linear polarization amplitude and direction as a function of time and wavelength near the H-alpha line. In all our stars, the H-alpha line profiles show evidence of an intervening disk or outflowing wind, evidenced by strong emission with an absorptive component. The linear polarization varies by 0.2% to 1.5% with the change typically centered in the absorptive part of the line profile. These observations are inconsistent with a simple disk-scattering model or a depolarization model which produce polarization changes centered on the emmissive core. We speculate that polarized absorption via optical pumping of the intervening gas may be the cause.Comment: Accepted for publication in ApJ Letter

Molecular structure and reactions of 1,1'-bi(acenaphthen-1-ylidene)-2,2'-dione

The molecular structure of 1,1'-bi(acenaphthen-1-ylidene)-2,2'-dione 1, a potential building-block for the synthesis of fullerene fragments, has been investigated by X-ray crystallography and semi-empirical (AM1 and PM3) calculations. There is a good agreement between the calculated and crystal structure which is essentially planar and has E-configuration. In the solid state, molecules of 1 pack in an interesting manner as corrugated sheets sustained by a network of C-H···O hydrogen bonds and resulting in the formation of tetrameric loops. While steric factors limit the reactivity of the carbonyl groups in 1, the ene double bond of the ene-dione moiety present in it exhibits propensity toward [4 + 2]-cycloadditions to furnish novel and highly compressed polycycles 8-10

Spectroscopic signatures of magnetospheric accretion in Herbig Ae/Be stars. I. The case of HD101412

Models of magnetically-driven accretion and outflows reproduce many observational properties of T Tauri stars. This concept is not well established for the more massive Herbig Ae/Be stars. We intend to examine the magnetospheric accretion in Herbig Ae/Be stars and search for rotational modulation using spectroscopic signatures, in this first paper concentrating on the well-studied Herbig Ae star HD101412. We used near-infrared spectroscopic observations of the magnetic Herbig Ae star HD101412 to test the magnetospheric character of its accretion disk/star interaction. We reduced and analyzed 30 spectra of HD101412, acquired with the CRIRES and X-shooter spectrographs installed at the VLT (ESO, Chile). The spectroscopic analysis was based on the He I lambda 10,830 and Pa gamma lines, formed in the accretion region. We found that the temporal behavior of these diagnostic lines in the near-infrared spectra of HD101412 can be explained by rotational modulation of line profiles generated by accreting gas with a period P = 20.53+-1.68 d. The discovery of this period, about half of the magnetic rotation period P_m = 42.076 d previously determined from measurements of the mean longitudinal magnetic field, indicates that the accreted matter falls onto the star in regions close to the magnetic poles intersecting the line-of-sight two times during the rotation cycle. We intend to apply this method to a larger sample of Herbig Ae/Be stars.Comment: 8 pages, 1 table, 7 figures, accepted for publication in A&