929 research outputs found
Analysing protein competition on self-assembled mono-layers studied with quartz crystal microbalance
The mechanisms by which proteins adsorb to surfaces of biomaterials have long been of interest. The
present work started with the premise that small/hard and large/soft proteins will yield different sets
of normalized frequency shift and dissipation signals when studied with a quartz crystal microbalance.
The aim was to evaluate the usefulness of these raw data to study protein competition using protein incubations
in sequence and from mixtures of albumin (BSA) and gamma-globulin (BGG) at various ratios.
Increasing the concentration of BSA decreases the adsorption of subsequently incubated BGG. For BSA/
BGG mixtures the dissipation is similar for all logarithmic molar ratios BGG/BSA below 1 but soon
decreases when the molar ratio of BSA/BGG (and opposite for the normalized frequency shift) is above
1, indicating preferential binding of BGG. Modelling indicated that differences in the film shear modulus
and viscosity depend more on the properties of the self-assembling mono-layers (SAMs) than on the proteins.
Films high in BSA tentatively differ in film shear modulus and viscosity from that of films high in
BGG but only on the hydrophobic surfaces. The results were encouraging as the raw data were deemed to
be able to point at protein adsorption competition.The authors thank the Portuguese National Science and Technology Foundation (FCT) for the Project Grants PTDC/FIS/68517/2006 and PTDC/FIS/68209/2006, and personal Grant BPD/39331/2007 for J.B
Morphology and miscibility of chitosan/soy protein blended membranes
A physico-chemical characterization of blended membranes composed by chitosan and soy protein has been carried out in order to
probe the interactions that allow membranes to be formed from these biopolymer mixtures. These membranes are developed aiming at
applications in wound healing and skin tissue engineering scaffolding. The structural features of chitosan/soy blended membranes were
investigated by means of solid state carbon nuclear magnetic resonance (NMR), infrared spectroscopy (FTIR), contact angle, and atomic
force microscopy. FTIR investigations suggested that chitosan and soy may have participated in a specific intermolecular interaction.
The proton spinâlattice relaxation experiments in the rotating frame on blended membranes indicated that independently of the preparation
conditions, the blend components are not completely miscible possibly due to a weak polymerâprotein interaction. It was also
shown that the blended systems showed a rougher surface morphology which was dependent of soy content in the blend system
Fluorescence probe techniques to monitor protein adsorption-induced conformation changes on biodegradable polymers
The study of protein adsorption and any associated conformational changes on interaction with biomaterials is of great importance in the area of implants and tissue constructs. This study aimed to evaluate some fluorescent techniques to probe protein conformation on a selection of biodegradable polymers currently under investigation for biomedical applications. Because of the fluorescence emanating from the polymers, the use of monitoring intrinsic protein fluorescence was precluded. A highly solvatochromic fluorescent dye, Nile red, and a well-known protein label, fluorescein isothiocyanate, were employed to study the adsorption of serum albumin to polycaprolactone and to some extent also to two starch-containing polymer blends (SPCL and SEVA-C). A variety of fluorescence techniques, steady state, time resolved, and imaging were employed. Nile red was found to leach from the protein, while fluorescein isothiocyanate proved useful in elucidating a conformational change in the protein and the observation of protein aggregates adsorbed to the polymer surface. These effects were seen by making use of the phenomenon of energy migration between the fluorescent tags to monitor interprobe distance and the use of fluorescence lifetime imaging to ascertain the surface packing of the protein on polymer
Application of fluorescence techniques to the study of protein adsorption and packing on biomaterial surfaces
[Excerpt] The ways proteins compete for the surface of biomaterials and
change conformation are believed to be important for the host response
to implants. It is possible to elucidate information on
packing and any induced conformational change by making use of
different fluorescence techniques on fluorescently labelled proteins.
Employing probe-probe resonance energy transfer (RET) allows
inter and intra protein interactions to be distinguished. Homo resonance
energy transfer (hRET) avoids many problems with having
two different probes and means that labelling and subsequent purification
can be done in one step. [...]Portuguese Foundation for Science and
Technology, project PROTEOLIGHT (PTDC/FIS/68517/2006)
and J.B. grant SFRH/BPD/17584/2004. European Union NoE
EXPERTISSUES (NMP3-CT-2004-500283) and European Union
FP6 STREP project HIPPOCRATES (NMP3-CT-2003-505758).info:eu-repo/semantics/publishedVersio
Hybrid biodegradable membranes of silane-treated chitosan/soy protein for biomedical applications
In recent years, progress in the field of hybrid materials has been accelerated through use of the solâgel process for creating materials and devices, which benefit from the incorporation of both inorganic and organic components. In this work, organicâinorganic hybrid membranes were prepared from tetraethoxysilane and a blend system composed of chitosan and soy protein. By introducing a small amount of siloxane bond into the chitosan/soy protein system, the chitosan/soy protein hybrid membranes were improved in terms of structure, topography and mechanical properties. It appears that the chitosan/soy protein hybrid membranes were formed by discrete inorganic moieties entrapped in the chitosan/soy protein blend, which improved the stability and mechanical performance assessed by the dynamic mechanical analysis as compared to chitosan/soy protein membrane. Also, in vitro cell culture studies evidenced that the chitosan/soy protein hybrid membranes are non-cytotoxic over a mouse fibroblast-like cell line. The hybrid membranes of silane-treated chitosan/soy protein developed in this work have potential in biomedical applications, including tissue engineering.This work was financially supported by the Portuguese Foundation for Science and Technology - FCT (Grant SFRH/BPD/45307/2008, SFRH/BPD/21786/2009, SFRH/BPD/39331/2007 and SFRH/BD/64601/2009), 'Fundo Social Europeu' - FSE and 'Programa Diferencial de Potencial Humano - POPH' and was partially supported by the FEDER through POCTEP 0330_IBEROMARE_1_P
PEPPo: Using a Polarized Electron Beam to Produce Polarized Positrons
An experiment demonstrating a new method for producing polarized positrons has been performed at the CEBAF accelerator at Jefferson Laboratory. The PEPPo (Polarized Electrons for Polarized Positrons) concept relies on the production of polarized e+/eâ pairs originating from the bremsstrahlung radiation of a longitudinally polarized electron beam interacting within a 1.0 mm tungsten pair-production target. This paper describes preliminary results of measurements using an 8.2 MeV/c electron beam with polarization 84% to generate positrons in the range of 3.1 to 6.2 MeV/c with polarization as high as âŒ80%
Surface engineered carboxymethylchitosan/poly(amidoamine) dendrimer nanoparticles for intracellular targeting
Novel highly branched biodegradable macromolecular systems have been developed by grafting carboxymethylchitosan
(CMCht) onto low generation poly(amidoamine) (PAMAM) dendrimers. Such structures organize into sphere-like nanoparticles
that are proposed to be used as carriers to deliver bioactive molecules aimed at controlling the behavior of stem cells,
namely their proliferation and differentiation. The nanoparticles did not exhibit significant cytotoxicity in the range of
concentrations below 1 mg mL"1, and fluorescent probe labeled nanoparticles were found to be internalized with highly
efficiency by both human osteoblast-like cells and rat bone marrow stromal cells, under fluorescence-activated cell sorting and
fluorescence microscopy analyses. Dexamethasone (Dex) has been incorporated into CMCht/PAMAM dendrimer nanoparticles
and release rates were determined by high performance liquid chromatography. Moreover, the biochemical data demonstrates
that the Dex-loaded CMCht/PAMAM dendrimer nanoparticles promote the osteogenic differentiation of rat bone marrow
stromal cells, in vitro. The nanoparticles exhibit interesting physicochemical and biological properties and have great potential to
be used in fundamental cell biology studies as well as in a variety of biomedical applications, including tissue engineering and
regenerative medicine
Regulation of inositol 5-phosphatase activity by the C2 domain of SHIP1 and SHIP2
SHIP1, an inositol 5-phosphatase, plays a central role in cellular signaling. As such, it has been implicated in many conditions. Exploiting SHIP1 as a drug target will require structural knowledge and the design of selective small molecules. We have determined apo, and magnesium and phosphate-bound structures of the phosphatase and C2 domains of SHIP1. The C2 domains of SHIP1 and the related SHIP2 modulate the activity of the phosphatase domain. To understand the mechanism, we performed activity assays, hydrogen-deuterium exchange mass spectrometry, and molecular dynamics on SHIP1 and SHIP2. Our findings demonstrate that the influence of the C2 domain is more pronounced for SHIP2 than SHIP1. We determined 91 structures of SHIP1 with fragments bound, with some near the interface between the two domains. We performed a mass spectrometry screen and determined four structures with covalent fragments. These structures could act as starting points for the development of potent, selective probes
Precision Electron-Beam Polarimetry using Compton Scattering at 1 GeV
We report on the highest precision yet achieved in the measurement of the
polarization of a low energy, (1 GeV), electron beam, accomplished
using a new polarimeter based on electron-photon scattering, in Hall~C at
Jefferson Lab. A number of technical innovations were necessary, including a
novel method for precise control of the laser polarization in a cavity and a
novel diamond micro-strip detector which was able to capture most of the
spectrum of scattered electrons. The data analysis technique exploited track
finding, the high granularity of the detector and its large acceptance. The
polarization of the A, ~GeV electron beam was measured with a
statistical precision of ~1\% per hour and a systematic uncertainty of
0.59\%. This exceeds the level of precision required by the \qweak experiment,
a measurement of the vector weak charge of the proton. Proposed future
low-energy experiments require polarization uncertainty ~0.4\%, and this
result represents an important demonstration of that possibility. This
measurement is also the first use of diamond detectors for particle tracking in
an experiment.Comment: 9 pages, 7 figures, published in PR
Strange Quark Contributions to Parity-Violating Asymmetries in the Backward Angle G0 Electron Scattering Experiment
We have measured parity-violating asymmetries in elastic electron-proton and
quasi-elastic electron-deuteron scattering at Q^2 = 0.22 and 0.63 GeV^2. They
are sensitive to strange quark contributions to currents in the nucleon, and to
the nucleon axial current. The results indicate strange quark contributions of
< 10% of the charge and magnetic nucleon form factors at these four-momentum
transfers. We also present the first measurement of anapole moment effects in
the axial current at these four-momentum transfers.Comment: 5 pages, 2 figures, changed references, typo, and conten
- âŠ