7,687 research outputs found
Revivification of confinement resonances in the photoionization of @C endohedral atoms far above thresholds
It is discovered theoretically that significant confinement resonances in an
photoionization of a \textit{multielectron} atom encaged in carbon
fullerenes, A@C, may re-appear and be strong at photon energies far
exceeding the ionization threshold, as a general phenomenon. The reasons
for this phenomenon are unraveled. The Ne photoionization of the
endohedral anion Ne@C in the photon energy region of about a
thousand eV above the threshold is chosen as case study.Comment: 3 pages, 1 figure, Revtex
Phenytoin-induced rhabdomyolysis
Rhabdomyolysis is a potentially life-threatening syndrome that can develop from a variety of causes. The most common causes are muscle injury, alcohol abuse, drugs, toxins and increased muscular activity. Phenytoin is one of the drugs that rarely cause rhabdomyolysis. We present the case of a man who developed rhabdomyolysis following phenytoin treatment
DenseReg: fully convolutional dense shape regression in-the-wild
In this paper we propose to learn a mapping from image pixels into a dense template grid through a fully convolutional network. We formulate this task as a regression problem and train our network by leveraging upon manually annotated facial landmarks “in-the-wild”. We use such landmarks to establish a dense correspondence field between a three-dimensional object template and the input image, which then serves as the ground-truth for training our regression system. We show that we can combine ideas from semantic segmentation with regression networks, yielding a highly-accurate ‘quantized regression’ architecture. Our system, called DenseReg, allows us to estimate dense image-to-template correspondences in a fully convolutional manner. As such our network can provide useful correspondence information as a stand-alone system, while when used as an initialization for Statistical Deformable Models we obtain landmark localization results that largely outperform the current state-of-the-art on the challenging 300W benchmark. We thoroughly evaluate our method on a host of facial analysis tasks, and demonstrate its use for other correspondence estimation tasks, such as the human body and the human ear. DenseReg code is made available at http://alpguler.com/DenseReg.html along with supplementary materials
Bioactive supramolecular peptide nanofibers for regenerative medicine
Cataloged from PDF version of article.Recent advances in understanding of cell-matrix interactions and the role of the extracellular matrix (ECM) in regulation of cellular behavior have created new perspectives for regenerative medicine. Supramolecular peptide nanofiber systems have been used as synthetic scaffolds in regenerative medicine applications due to their tailorable properties and ability to mimic ECM proteins. Through designed bioactive epitopes, peptide nanofiber systems provide biomolecular recognition sites that can trigger specific interactions with cell surface receptors. The present Review covers structural and biochemical properties of the self-assembled peptide nanofibers for tissue regeneration, and highlights studies that investigate the ability of ECM mimetic peptides to alter cellular behavior including cell adhesion, proliferation, and/or differentiation. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Precise determination of the deuteron spin structure at low to moderate Q(2) with CLAS and extraction of the neutron contribution
We present the final results for the deuteron spin structure functions obtained from the full data set collected in 2000-2001 with Jefferson Lab\u27s continuous electron beam accelerator facility (CEBAF) using the CEBAF large acceptance spectrometer (CLAS). Polarized electrons with energies of 1.6, 2.5, 4.2, and 5.8 GeV were scattered from deuteron ((ND3)-N-15) targets, dynamically polarized along the beam direction, and detected with CLAS. From the measured double-spin asymmetry, the virtual photon absorption asymmetry A(1)(d) and the polarized structure function g(1)(d) were extracted over a wide kinematic range (0.05 GeV2 \u3c Q(2) \u3c 5 GeV2 and 0.9 GeV \u3c W \u3c 3 GeV). We use an unfolding procedure and a parametrization of the corresponding proton results to extract from these data the polarized structure functions A(1)(n) and g(1)(n) of the (bound) neutron, which are so far unknown in the resonance region, W \u3c 2 GeV. We compare our final results, including several moments of the deuteron and neutron spin structure functions, with various theoretical models and expectations, as well as parametrizations of the world data. The unprecedented precision and dense kinematic coverage of these data can aid in future extractions of polarized parton distributions, tests of perturbative QCD predictions for the quark polarization at large x, a better understanding of quark-hadron duality, and more precise values for higher-twist matrix elements in the framework of the operator product expansion
Controlled enzymatic stability and release characteristics of supramolecular chiral peptide amphiphile nanofiber gels
Supramolecular bioarchitectures formed by assembly of achiral or chiral building blocks play important roles in various biochemical processes. Stereochemistry of amino acids is important for structural organization of peptide and protein assemblies and structure-microenvironment interactions. In this study, oppositely charged peptide amphiphile (PA) molecules with L-, D- and mixture of L- and D-amino acid conformations are coassembled into supramolecular nanofibers and formed self-supporting gels at pH 7.4 in water. The enzymatic stability of the PA nanofiber gels was studied in the presence of proteinase K enzyme, which digest a broad spectrum of proteins and peptides. The structural changes on the chiral PA nanofibers were also analyzed at different time periods in the presence of enzymatic activity. Controlled release of a model cargo molecule through the chiral PA nanofiber gels was monitored. The diffusivity parameters were measured for all gel systems. Release characteristics and the enzymatic stability of the peptide nanofiber gels were modulated depending on organization of the chiral PA molecules within the supramolecular assemblies. © 2017 Elsevier B.V
Encapsulation of a zinc phthalocyanine derivative in self-assembled peptide nanofibers
Cataloged from PDF version of article.In this article, we demonstrate encapsulation of octakis(hexylthio) zinc phthalocyanine molecules by non-covalent supramolecular organization within self-assembled peptide nanofibers. Peptide nanofibers containing octakis(hexylthio) zinc phthalocyanine molecules were obtained via a straight-forward one-step self-assembly process under aqueous conditions. Nanofiber formation results in the encapsulation and organization of the phthalocyanine molecules, promoting ultrafast intermolecular energy transfer. The morphological, mechanical, spectroscopic and non-linear optical properties of phthalocyanine containing peptide nanofibers were characterized by TEM, SEM, oscillatory rheology, UV-Vis, fluorescence, ultrafast pump-probe and circular dichroism spectroscopy techniques. The ultrafast pump-probe experiments of octakis(hexylthio) zinc phthalocyanine molecules indicated pH controlled non-linear optical characteristics of the encapsulated molecules within self-assembled peptide nanofibers. This method can provide a versatile approach for bottom-up fabrication of supramolecular organic electronic devices. © 2012 The Royal Society of Chemistry
Thalassemia mutations in Gaziantep, Turkey
Ninety-eight postnatal and six prenatal cases of thalassemia were studied by the reverse dot-blot hybridization technique in the city of Gaziantep, Turkey. We found the following mutations: IVS 1.110 (G>A) in 29.1%, IVS 2.1 (G>A) in 12.3%, IVS 1.1 (G>A) in 7.7%, Codon 8 (-AA) in 5.6%, -30 (T>A) in 4.6%, IVS 1.6 (T>C) in 4.6%, Codon 39 (C>T) in 3.6%, Codon 44 (-C) in 3.1%, IVS 2.745 (C>G) in 1.5%, Codon 8/9 (+G) in 2.1%, Codon 36/37 (-T) in 2.1%, IVS 1.5 (G>C) in 2.1%, Codon 22 (7pb del) in 0.5%, Codon 5 (-CT) in 0.5% while 20.9% were undetermined. 54 of the thalassemia patients were homozygotes, 12 were compound heterozygous and 31 were heterozygotes. In one allele of 5 thalassemia patients, - thalassemia mutation (3.7 single gene deletions in 1 patient, anti-3.7 gene triplication in 4 patients) wasdetermined at the same time. Finally, this is the first comprehensive study in this region and percentage of and - globin genes mutation is 2.6 and 79.4%, respectively
Amyloid Inspired Self-Assembled Peptide Nanofibers
Cataloged from PDF version of article.Amyloid peptides are important components in many degenerative
diseases as well as in maintaining cellular metabolism. Their unique stable structure
provides new insights in developing new materials. Designing bioinspired selfassembling
peptides is essential to generate new forms of hierarchical nanostructures.
Here we present oppositely charged amyloid inspired peptides (AIPs),
which rapidly self-assemble into nanofibers at pH 7 upon mixing in water caused
by noncovalent interactions. Mechanical properties of the gels formed by selfassembled
AIP nanofibers were analyzed with oscillatory rheology. AIP gels
exhibited strong mechanical characteristics superior to gels formed by self-assembly
of previously reported synthetic short peptides. Rheological studies of gels
composed of oppositely charged mixed AIP molecules (AIP-1 + 2) revealed superior mechanical stability compared to individual
peptide networks (AIP-1 and AIP-2) formed by neutralization of net charges through pH change. Adhesion and elasticity
properties of AIP mixed nanofibers and charge neutralized AIP-1, AIP-2 nanofibers were analyzed by high resolution force−
distance mapping using atomic force microscopy (AFM). Nanomechanical characterization of self-assembled AIP-1 + 2, AIP-1,
and AIP-2 nanofibers also confirmed macroscopic rheology results, and mechanical stability of AIP mixed nanofibers was higher
compared to individual AIP-1 and AIP-2 nanofibers self-assembled at acidic and basic pH, respectively. Experimental results were
supported with molecular dynamics simulations by considering potential noncovalent interactions between the amino acid
residues and possible aggregate forms. In addition, HUVEC cells were cultured on AIP mixed nanofibers at pH 7 and biocompatibility
and collagen mimetic scaffold properties of the nanofibrous system were observed. Encapsulation of a zwitterionic
dye (rhodamine B) within AIP nanofiber network was accomplished at physiological conditions to demonstrate that this network
can be utilized for inclusion of soluble factors as a scaffold for cell culture studies. Copyright © 2012 American Chemical Societ
Catalytic supramolecular self-assembled peptide nanostructures for ester hydrolysis
Essential amino acids in catalytic sites of native enzymes are important in nature inspired catalyst designs. Active sites of enzymes contain the coordinated assembly of multiple amino acids, and catalytic action is generated by the dynamic interactions among multiple residues. However, catalysis studies are limited by the complex and dynamic structure of the enzyme; and it is difficult to exclusively attribute a given function to a specific residue. Minimalistic approaches involving artificial catalytic sites are promising for the investigation of the enzyme function in the absence of non-essential protein components, and self-assembling peptide nanostructures are especially advantageous in this context. Here we demonstrate the design and characterization of an enzyme-mimetic catalytic nanosystem presenting essential residues (Ser, His, Asp). The function of each residue and its combinations on the nanostructures in hydrolysis reaction was studied. The catalytic self-assembled nanostructures were used for efficient ester hydrolysis such as a model substrate (pNPA) and a natural substrate (acetylcholine) highlighting the key role of self-assembly in catalytic domain formation to test the efficiency of the de novo designed catalyst as a catalytic triad model. © The Royal Society of Chemistry 2016
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