6,510 research outputs found
Recommended from our members
Self-assembly of Fmoc-tetrapeptides based on the RGDS cell adhesion motif
Self-assembly in aqueous solution has been investigated for two Fmoc [Fmoc ¼ N-(fluorenyl)-9-methoxycarbonyl] tetrapeptides comprising the RGDS cell adhesion motif from fibronectin or the scrambled sequence GRDS. The hydrophobic Fmoc unit confers amphiphilicity on the molecules, and
introduces aromatic stacking interactions. Circular dichroism and FTIR spectroscopy show that the self-assembly of both peptides at low concentration is dominated by interactions among Fmoc units, although Fmoc-GRDS shows b-sheet features, at lower concentration than Fmoc-RGDS. Fibre X-ray diffraction indicates b-sheet formation by both peptides at sufficiently high concentration. Strong
alignment effects are revealed by linear dichroism experiments for Fmoc-GRDS. Cryo-TEM and smallangle
X-ray scattering (SAXS) reveal that both samples form fibrils with a diameter of approximately 10 nm. Both Fmoc-tetrapeptides form self-supporting hydrogels at sufficiently high concentration. Dynamic shear rheometry enabled measurements of the moduli for the Fmoc-GRDS hydrogel, however syneresis was observed for the Fmoc-RGDS hydrogel which was significantly less stable to shear. Molecular dynamics computer simulations were carried out considering parallel and antiparallel b-sheet configurations of systems containing 7 and 21 molecules of Fmoc-RGDS or Fmoc-GRDS, the results being analyzed in terms of both intermolecular structural parameters and energy contributions
Optical amplification enhancement in photonic crystals
Improving and controlling the efficiency of a gain medium is one of the most
challenging problems of laser research. By measuring the gain length in an opal
based photonic crystal doped with laser dye, we demonstrate that optical
amplification is more than twenty-fold enhanced along the Gamma-K symmetry
directions of the face centered cubic photonic crystal. These results are
theoretically explained by directional variations of the density of states,
providing a quantitative connection between density of the states and light
amplification
Deep into the Water Fountains: The case of IRAS 18043-2116
(Abridged) The formation of large-scale (hundreds to few thousands of AU)
bipolar structures in the circumstellar envelopes (CSEs) of post-Asymptotic
Giant Branch (post-AGB) stars is poorly understood. The shape of these
structures, traced by emission from fast molecular outflows, suggests that the
dynamics at the innermost regions of these CSEs does not depend only on the
energy of the radiation field of the central star. Deep into the Water
Fountains is an observational project based on the results of programs carried
out with three telescope facilities: The Karl G. Jansky Very Large Array
(JVLA), The Australia Telescope Compact Array (ATCA), and the Very Large
Telescope (SINFONI-VLT). Here we report the results of the observations towards
the WF nebula IRAS 180432116: Detection of radio continuum emission in the
frequency range 1.5GHz - 8.0GHz; HO maser spectral features and radio
continuum emission detected at 22GHz, and H ro-vibrational emission lines
detected at the near infrared. The high-velocity HO maser spectral
features, and the shock-excited H emission detected could be produced in
molecular layers which are swept up as a consequence of the propagation of a
jet-driven wind. Using the derived H column density, we estimated a
molecular mass-loss rate of the order of Myr. On the
other hand, if the radio continuum flux detected is generated as a consequence
of the propagation of a thermal radio jet, the mass-loss rate associated to the
outflowing ionized material is of the order of 10Myr.
The presence of a rotating disk could be a plausible explanation for the
mass-loss rates estimated.Comment: 10 pages, 5 figures. Accepted for publication in A&
A Role for DPPX Modulating External TEA Sensitivity of Kv4 Channels
Shal-type (Kv4) channels are expressed in a large variety of tissues, where they contribute to transient voltage-dependent K+ currents. Kv4 are the molecular correlate of the A-type current of neurons (ISA), the fast component of ITO current in the heart, and also of the oxygen-sensitive K+ current (KO2) in rabbit carotid body (CB) chemoreceptor cells. The enormous degree of variability in the physiological properties of Kv4-mediated currents can be attributable to the complexity of their regulation together with the large number of ancillary subunits and scaffolding proteins that associate with Kv4 proteins to modify their trafficking and their kinetic properties. Among those, KChIPs and DPPX proteins have been demonstrated to be integral components of ISA and ITO currents, as their coexpression with Kv4 subunits recapitulates the kinetics of native currents. Here, we explore the presence and functional contribution of DPPX to KO2 currents in rabbit CB chemoreceptor cells by using DPPX functional knockdown with siRNA. Additionally, we investigate if the presence of DPPX endows Kv4 channels with new pharmacological properties, as we have observed anomalous tetraethylammonium (TEA) sensitivity in the native KO2 currents. DPPX association with Kv4 channels induced an increased TEA sensitivity both in heterologous expression systems and in CB chemoreceptor cells. Moreover, TEA application to Kv4-DPPX heteromultimers leads to marked kinetic effects that could be explained by an augmented closed-state inactivation. Our data suggest that DPPX proteins are integral components of KO2 currents, and that their association with Kv4 subunits modulate the pharmacological profile of the heteromultimers
Nonlinear Interaction of Transversal Modes in a CO2 Laser
We show the possibility of achieving experimentally a Takens-Bogdanov
bifurcation for the nonlinear interaction of two transverse modes ()
in a laser. The system has a basic O(2) symmetry which is perturbed by
some symmetry-breaking effects that still preserve the symmetry. The
pattern dynamics near this codimension two bifurcation under such symmetries is
described. This dynamics changes drastically when the laser properties are
modified.Comment: 16 pages, 0 figure
Temporal and spatial variations of the absolute reflectivity of Jupiter and Saturn from 0.38 to 1.7 m with PlanetCam-UPV/EHU
We provide measurements of the absolute reflectivity of Jupiter and Saturn
along their central meridians in filters covering a wide range of visible and
near-infrared wavelengths (from 0.38 to 1.7 m) that are not often
presented in the literature. We also give measurements of the geometric albedo
of both planets and discuss the limb-darkening behavior and temporal
variability of their reflectivity values for a period of four years
(2012-2016). This work is based on observations with the PlanetCam-UPV/EHU
instrument at the 1.23 m and 2.2 m telescopes in Calar Alto Observatory
(Spain). The instrument simultaneously observes in two channels: visible (VIS;
0.38-1.0 m) and short-wave infrared (SWIR; 1.0--1.7 m). We obtained
high-resolution observations via the lucky-imaging method. We show that our
calibration is consistent with previous independent determinations of
reflectivity values of these planets and, for future reference, provide new
data extended in the wavelength range and in the time. Our results have an
uncertainty in absolute calibration of 10--20\%. We show that under the
hypothesis of constant geometric albedo, we are able to detect absolute
reflectivity changes related to planetary temporal evolution of about 5-10\%.Comment: 13 pages, 18 figures, (in press
Circulating kisspeptin and anti-müllerian hormone levels, and insulin resistance in women with polycystic ovary syndrome: a systematic review, meta-analysis, and meta-regression
Objective: This systematic review and meta-analysis aimed to summarize the available evidence regarding circulating kisspeptin and anti-müllerian hormone (AMH) and the homeostasis model assessment of insulin resistance (HOMA-IR) index in adolescents and women with and without polycystic ovary syndrome (PCOS). Method: We performed a comprehensive literature search in Medline, Embase, Cochrane, Scopus, and Web of Science for studies evaluating circulating kisspeptin levels in women with and without PCOS published until September 24th, 2020. Co-primary outcomes were the HOMA-IR index and AMH. The quality of included studies was assessed using the Newcastle-Ottawa Scale. Random-effects models were used to estimate outcomes, and effects reported as mean difference (MD) or standardized MD (SMD) and their 95 % confidence interval (CI). The systematic review and meta-analysis was registered in the International Prospective Register of Systematic Reviews (PROSPERO) as number CRD42020205030. Results: We evaluated 18 studies including, 1282 PCOS cases and 977 controls. Participants with PCOS were younger (MD = −2.38 years, 95 %CI -4.32 to -0.44), with higher BMI (MD = 1.16, 95 % CI 0.54–1.78), waist-to-hip ratio (MD = 0.04, 95 %CI 0.02 to 0.05), circulating kisspeptin (SMD = 1.15, 95 %CI 0.68–1.62), luteinizing hormone (SMD = 1.29, 95 %CI 0.76–1.83), AMH (SMD = 0.97, 95 %CI 0.60–1,34), total testosterone (SMD = 2.48, 95 %CI 1.73–3.23), free testosterone (SMD = 1.37, 95 %CI 0.56–2.17), and dehydroepiandrosterone sulphate (SMD = 0.72, 95 %CI 0.32–1.13) levels, and Ferriman-Gallwey score (SMD = 5.08, 95 %CI 2.76–7.39), and lower sex hormone-binding globulin level (SMD = −1.34, 95 %CI −2.15 to −0.52). Besides, participants with PCOS had higher HOMA-IR index (SMD = 0.76, 95 %CI 0.35–1.17), and circulating insulin (SMD = 0.75, 95 %CI 0.30–1.19), leptin (SMD = 2.82, 95 %CI 1.35–4.29), and triglycerides (SMD = 2.15, 95 %CI 1.08–3.23) levels than participants without the syndrome. The meta-regression did not identify significant factors influencing circulating kisspeptin. Conclusion: Patients with PCOS showed higher kisspeptin, LH, insulin, AMH, and androgen levels and HOMA-IR index, and lower sex hormone-binding globulin levels than those without the syndrome
- …