bluuebunny/crossref_metadata_2025_split huggingface dataset:
Conformational Parameters of Poly(N‐methyl‐N‐vinylacetamide) Molecules Through the Hydrodynamic Characteristics Studies
Authors: Pavlov George M. , Okatova Olga V. , Mikhailova Anastasia V. , Ulyanova Natalia N. , Gavrilova Irina I. , Panarin Evgenii F. 
Published: May 2010

AbstractWater‐soluble PMVA was synthesized by radical polymerization methods. A number of polymer samples were fractionated in the chloroform‐diethyl ether system. Fractions were studied by molecular hydrodynamics methods (sedimentation velocity, translational isothermal diffusion and viscosity) in H2O and DMF. The molecular masses of fractions were determined and the Kuhn‐Mark‐Houwink‐Sakurada relationships were obtained in the molecular mass range of 3.5 < M × 10−3 g · mol−1 <540. A negative temperature coefficient of the characteristic viscosity was obtained in both solvents. The Kuhn statistic segment length and the hydrodynamic diameter of the molecule were estimated for PMVA. The hydrodynamic volumes, occupied by the molecules of PMVA, poly(1‐vinyl‐2‐pyrrolidone), poly(vinylformamide), and pullulan were compared.magnified image
Self‐Association of Unfolded Outer Membrane Proteins
Authors: Tan Alexandra Ebie , Burgess Nancy K. , DeAndrade Diana S. , Marold Jacob D. , Fleming Karen G. 
Published: May 2010

AbstractWe have investigated self‐association propensities of aqueous unfolded (UAQ) forms of eight outer membrane proteins (OMPs), OmpA, OmpW, OmpX, PagP, OmpT, OmpLa, FadL, and Omp85. We found that high urea concentrations maintain all of these OMPs as monomers and that OmpA and OmpX remain monomeric upon dilution to 1 M urea. A pH screen showed that basic pH supports the least amount of UAQ OMP self‐association, consistent with earlier studies showing that basic pH was optimal for better folding efficiencies. The addition of KCl increased UAQ OMP self‐association, although the magnitudes of the responses were varied. These studies showed that urea can be used to tune the amount of UAQ OMP self‐association and indicate that the presence of some urea may be useful in optimizing folding conditions because it diminishes aggregation.magnified image
Complex Assembly Behavior During the Encapsulation of Green Fluorescent Protein Analogs in Virus Derived Protein Capsules
Authors: Minten Inge J. , Nolte Roeland J. M. , Cornelissen Jeroen J. L. M. 
Published: May 2010

AbstractEnzymes encapsulated in nanocontainers are a better model of the conditions inside a living cell than free enzymes in solution. In a first step toward the encapsulation of multiple enzymes inside the cowpea chlorotic mottle virus (CCMV) capsid, enhanced green fluorescent protein (EGFP) was attached to CCMV capsid proteins. The capsid protein–EGFP complex was then co‐assembled with wild‐type capsid protein (wt CP) in various ratios. At higher complex to wt CP ratios, the number of EGFP per capsid decreased instead of leveling off. We propose that this unexpected behavior is caused by pH‐induced disassembly of the capsid protein–EGFP complex as well as by concentration and ratio dependent dimerization of the complex, making it partially unavailable for incorporation into the capsid.magnified image
Polyoxazoline Thermoresponsive Micelles as Radionuclide Delivery Systems
Authors: Hruby Martin , Filippov Sergey K. , Panek Jiri , Novakova Michaela , Mackova Hana , Kucka Jan , Vetvicka David , Ulbrich Karel 
Published: May 2010

AbstractThermoresponsive polymer micelles are promising drug and radionuclide carriers with a strong passive targeting effect into solid tumors. We have synthesized ABA triblock copolymers poly[2‐methyl‐2‐oxazoline‐block‐(2‐isopropyl‐2‐oxazoline‐co‐2‐butyl‐2‐oxazoline)‐block‐2‐methyl‐2‐oxazoline]. These polymers are molecularly dissolved in aqueous millieu below the cloud point temperature (CPT) of the thermoresponsive central block and above CPT form polymer micelles at CMC 5–10 × 10−5 g · mL−1 with diameter ≈200 nm. The phenolic moiety introduced into the copolymer allowed radionuclide labeling with iodine‐125 ongoing in good yield with sufficient in vitro stability under model conditions.magnified image
Ultrasonically Induced Release from Nanosized Polymer Vesicles
Authors: Pangu Gautam D. , Davis Kevin P. , Bates Frank S. , Hammer Daniel A. 
Published: May 2010

AbstractVesicles made from synthetic diblock copolymers, polymersomes, have great potential for targeted imaging and drug delivery. Ultrasound is gaining attention as a therapeutic tool in addition to its use in diagnostics. We report on the response of nanoscale vesicles made from PEO‐b‐PBD copolymers to ultrasound at 20 kHz. Leakage of a fluorescent dye from vesicle core was measured to study the permeation. Ultrasound causes significant leakage from the core above threshold intensity, suggesting that leakage is governed by acoustic cavitation. Size measurements and direct visualization of vesicles show that ultrasound does not completely rupture them into fragments but causes transient poration. The extent of leakage inversely depends on membrane thickness and directly depends on sonication time and intensity.magnified image
Efficient Encapsulation of Plasmid DNA in pH‐Sensitive PMPC–PDPA Polymersomes: Study of the Effect of PDPA Block Length on Copolymer–DNA Binding Affinity
Authors: Lomas Hannah , Du Jianzhong , Canton Irene , Madsen Jeppe , Warren Nicholas , Armes Steven P. , Lewis Andrew L. , Battaglia Giuseppe 
Published: May 2010

AbstractWe report the self‐assembly of a series of amphiphilic diblock copolymers comprising a biocompatible, hydrophilic block, poly(2‐methacryloyloxyethyl phosphorylcholine) (PMPC) and a pH‐sensitive block, poly(2‐(diisopropylamino)ethyl methacrylate) (PDPA), into a dispersion of colloidally stable, nanometer‐sized polymersomes at physiological pH and salt concentration. The pH‐sensitivity of the PDPA block affords the electrostatic interaction of these block copolymers with nucleic acids at endocytic pH, as a result of the protonation of its tertiary amine groups at pH values below its pKa. Herein we investigate the effect of PDPA block length on the binding affinity of the block copolymer to plasmid DNA.magnified image
Fabrication of Photonic/Microfluidic Integrated Devices Using an Epoxy Photoresist
Authors: Kowpak Thomas , Watts Benjamin R. , Zhang Zhiyi , Zhu Shiping , Xu Changqing 
Published: May 2010

AbstractUsing a single layer of SU‐8 photoresist to fabricate optical waveguide cores and microfluidic channels on Pyrex glass is an ideal way to achieve photonic/microfluidic integration on a single chip. To address the problem of poor bonding, a thin nanoscale intermediate polymer layer was applied to reduce the stress generated from the material processing while maintaining strong adhesion between the patterning polymer layer and Pyrex. It was found that a 186–600 nm thick intermediate layer of a specialty epoxy photoresist effectively served the purpose without deteriorating the optical performance of the involved waveguides. Quality photonic/microfluidic integrated devices with satisfied optical performance were fabricated.magnified image
Performance of MWCNT/HDPE Nanocomposites at High Strain Rates
Authors: Al‐Lafi Waleed , Jin Jie , Xu Sunxi , Song Mo 
Published: May 2010

AbstractPerformance of HDPE/MWCNT composite at high strain rate up to 104 s−1 was investigated in a split Hopkinson pressure bar. The results revealed that the incorporation of MWCNTs into HDPE can enhance the impact strength of HDPE. High strain rate impact has a significant influence on morphology, density, crystallinity and melting temperature of the composite. With increase in strain rate, the densities of both HDPE and HDPE/MWCNT composite decreased. The drop of the density of HDPE/MWCNT composite was quicker than that of HDPE density. This could be the reason that much more cracks were formed in the HDPE/MWCNT composite, which could result in high energy dissipation, during SHPB test. The corporation of MWCNTs did lead to the decrease in yield stress.magnified image
Efficient Liposomal Nanocarrier‐mediated Oligodeoxynucleotide Delivery Involving Dual Use of a Cell‐Penetrating Peptide as a Packaging and Intracellular Delivery Agent
Authors: Saw Phei Er , Ko Young Tag , Jon Sangyong 
Published: May 2010

AbstractThe effective use of oligonucleotide therapeutics, such as antisense oligodeoxynucleotides (ODNs) and small interfering RNAs (siRNAs), requires efficient delivery systems capable of intracellular penetration. Cell‐penetrating peptides (CPPs), including arginine‐rich peptides, have been extensively studied as tools for enhancing intracellular uptake efficiency of various bioactive molecules, including nanoparticles and liposomes. CPPs also have an ability to form tight complexes with nucleic acids, such as ODNs and siRNAs, making CPPs effective as packaging agents. Here, we constructed a CPP‐modified liposome loaded with complexes of nona‐arginine (9R) and NF‐κB decoy ODNs, and evaluated intracellular uptake and anticancer activity in vitro. We found that 9R/ODN complexes were efficiently loaded into liposomes that were effectively internalized into U87MG glioblastoma cells and sensitized cells to the effects of paclitaxel. To the best of our knowledge, this is the first report describing the dual use of 9R CPP as a cell penetrating and a complexing agent within a single nanoparticle.magnified image
Novel Triblock Oligopeptides as Efficient Nonviral Vectors: Characterisation and Further Insights
Authors: Seow Wei Yang , Yang Yi‐Yan , George Andrew J. T. 
Published: May 2010

AbstractThe delivery of immunomodulatory genes into the cornea prior to transplantation is one promising strategy to improve graft survival rates. We recently reported a class of novel triblock oligopeptides that could mediate efficient gene transfer into corneal endothelial cells. Now these peptides are characterised further and it is show that they lack distinct secondary structures. Peptide complexes are also demonstrated to be weakly haemolytic and transfection efficiency is shown to be sensitive to several experimental conditions. SEM and FRET confocal images are used to study the particle morphology and to show that they condense their DNA cargo well.magnified image
Water‐Soluble Conjugated Polymers for Fluorescent‐Enzyme Assays
Authors: Feng Fude , Liu Libing , Yang Qiong , Wang Shu 
Published: May 2010

AbstractEnzyme assays are receiving more and more research and application interest because of the rapidly increasing demands of clinical diagnosis, environmental analysis, drug discovery, and molecular biology. Water‐soluble light‐harvesting conjugated polymers (CPs) coordinate the action of a large number of absorbing units to afford an amplified fluorescence signal, which makes them useful as optical platforms in highly sensitive chemical and biological sensors. This Feature Article highlights recent developments of water‐soluble CPs for fluorescent assays of enzymes. Different signal transduction mechanisms, such as electron transfer, fluorescence resonance energy transfer (FRET), and aggregation or conformation changes of CPs, are employed in these assays according to the dissimilar nature of enzymes. Potential challenges and future research directions in these approaches based on CPs are also discussed.magnified image
pDNA/poly(L‐lysine) Polyplexes Functionalized with a pH‐Sensitive Charge‐Conversional Poly(aspartamide) Derivative for Controlled Gene Delivery to Human Umbilical Vein Endothelial Cells
Authors: Sanjoh Mai , Hiki Shigehiro , Lee Yan , Oba Makoto , Miyata Kanjiro , Ishii Takehiko , Kataoka Kazunori 
Published: May 2010

AbstractAn efficient endosome‐escaping function was integrated into the polyplex of plasmid DNA (pDNA) with poly(L‐lysine) (PLys) to improve its gene transfection efficiency through electrostatic coating with charge‐conversional polymer (CCP). CCP showed charge‐conversional function responding to endosomal pH, leading to the release of pDNA/PLys polyplex into the cytoplasm. The cells took up the intact CCP‐integrated ternary polyplex, which exerted appreciably higher transfection efficiency with lower cytotoxicity than pDNA/PLys polyplex against human umbilical vein endothelial cells (HUVECs). This is consistent with the facilitated endosomal escape of the CCP‐integrated ternary polyplex compared to the pDNA/PLys polyplex as directly observed with confocal laser‐scanning microscopy.magnified image
Sensing Diffraction Gratings of Antigen‐Responsive Hydrogel for Human Immunoglobulin‐G Detection
Authors: Ye Gang , Yang Canqiang , Wang Xiaogong 
Published: May 2010

AbstractSensing diffraction gratings of antigen‐responsive hydrogel were developed for human immunoglobulin‐G (H‐IgG) detection. The IgG‐sensing gratings were fabricated by soft lithographic duplication of photoinduced surface relief gratings on azo polymer films to the hydrogel surfaces. The quantitative detection of H‐IgG was achieved by detecting modulation of the diffraction efficiency when the gratings were exposed to antigen solutions. The gratings showed high sensitivity and specificity for the H‐IgG detection. The detection could be performed at a reasonably fast rate with good reusability. In the process, no fluorophore labeling or additional signal enhancement was required.magnified image
Light‐Responsive Block Copolymers
Authors: Schumers Jean‐Marc , Fustin Charles‐André , Gohy Jean‐François 
Published: May 2010

AbstractStimuli‐responsive polymers are the subject of intense research because they are able to show responses to various environmental changes. Among those stimuli, light has attracted much attention since it can be localized in time and space and it can also be triggered from outside of the system. In this paper, we review light‐responsive block copolymers (LRBCs) that combine characteristic features of block copolymers, e.g., self‐assembly behavior, and light‐responsive systems. The different photo‐responsive moieties that have been incorporated so far in block copolymers as well as the proposed applications are discussed.magnified image
Functionalization of Fullerenes with Cyclopentadienyl and Anthracenyl Capped Polymeric Building Blocks via Diels–Alder Chemistry
Authors: Nebhani Leena , Barner‐Kowollik Christopher 
Published: May 2010

AbstractCyclopentadienyl (Cp) capped polymers [polyethylene glycols (PEGs), $\overline M _{\rm n}$ = 2 000 g · mol−1], react readily with fullerenes in a 1:1 molar ratio (relative to the amount of fullerenes and Cp‐end groups) at ambient temperature within 5 min in the absence of any catalyst in a Diels–Alder (DA) reaction to provide fullerene‐PEG hybrids. Similarly, anthracenyl capped PEGs react with fullerenes (in a 1:3 molar ratio) in DA reactions to yield the corresponding hybrids, albeit over a period of 1.5 h at 80 °C and a lesser conversion. The efficiency of the transformation is monitored via electrospray ionization mass spectrometry (ESI‐MS), demonstrating that the fullerenes can be transformed into polymer hybrids; most efficiently when Cp‐functional polymer is used as the diene. In addition, the obtained hybrids were subjected to UV/Vis as well as thermogravimetric analysis further underpinning the formation of mono‐substituted C60‐PEG hybrids [wt.‐%exp 70 ± 5 (PEG), 30 ± 5 (C60), wt.‐%theo 68 (PEG), 32 (C60)].magnified image
Analysis of the Adequacy of the Representation of Entanglement Effects by Chain Loops
Authors: Martins José A. 
Published: May 2010

AbstractIt is generally considered that polymer chains are intertwined or “entangled” – because they cannot penetrate each other – and that these entanglements are responsible for melt elastic properties. There is no physical definition of entanglement. They are considered to be binary interactions between polymer chains and represented with the looping picture or by slip‐links. The interaction energy of chain loops and of two Kuhn monomers is evaluated for several polymers. It is lower than the melt thermal energy, implying that chain loops or any other binary interactions between chain segments cannot account for the properties assigned to entanglements.magnified image
Nonbalanced SSFP‐based quantitative magnetization transfer imaging
Authors: Gloor Monika , Scheffler Klaus , Bieri Oliver 
Published: May 2010

AbstractThe previously reported concept for quantitative magnetization transfer (MT) imaging using balanced steady‐state free precession (SSFP) is applied to nonbalanced SSFP sequences. This offers the possibility to derive quantitative MT parameters of targets with high‐susceptibility variations such as the musculoskeletal system, where balanced SSFP suffers from off‐resonance‐related signal loss. In the first part of this work, an extended SSFP free induction decay (SSFP‐FID) signal equation is derived based on a binary spin‐bath model. Based on this new description, quantitative MT parameters such as the fractional pool size, magnetization exchange rate, and relaxation times can be assessed. In the second part of this work, MT model parameters are derived from an ex vivo muscle sample, in vivo human femoral muscle, and in vivo human patellar cartilage. Motion sensitivity issues are discussed and results from two‐pool SSFP‐FID are compared to results from two‐pool balanced SSFP and common quantitative MT models. In summary, this work demonstrates that SSFP‐FID allows for quantitative MT imaging of targets with high‐susceptibility variations within short acquisition times. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.
In vivo MRI measurement of fetal blood oxygen saturation in cardiac ventricles of fetal sheep: A feasibility study
Authors: Wedegärtner Ulrike , Kooijman Hendrik , Yamamura Jin , Frisch Michael , Weber Christoph , Buchert Ralph , Huff Anna , Hecher Kurt , Adam Gerhard 
Published: May 2010

AbstractThe purpose of this study was to assess the feasibility to determine fetal blood oxygen saturation (sO2) with T2‐weighted MR sequences using a fetal sheep model. T2 measurements were performed on a 1.5‐T scanner using a T2 preparation pulse in combination with a three‐dimensional balanced steady‐state free precession sequence repeated at different echo times. Eight sheep fetuses were examined during a control, hypoxic, and recovery phase to perform T2‐weighted scans of the fetal blood in the heart. Signal intensities in the left and right ventricle were measured to calculate the MR blood sO2. During each phase, fetal carotid artery sO2 was directly measured and correlated with MR sO2. A Bland‐Altman plot was performed. Fetal carotid artery sO2 was 69% sO2 during control, 16% sO2 during hypoxemia, and 67% sO2 during recovery. Mean values of the MR sO2 were 49% sO2 and 40% sO2 for control, 6% sO2 and 3% sO2 for hypoxemia, and 51% sO2 and 43% sO2 for recovery in left ventricle and right ventricle, respectively. Mean values of fetal carotid artery sO2 and MR sO2 were highly correlated (left ventricle: r = 0.87, right ventricle: r = 0.89). According to the Bland‐Altman plot, MR sO2 was lower compared to fetal carotid artery sO2 (left ventricle: 15%, right ventricle: 20%). Based on our preliminary results, it seems to be possible to assess fetal sO2 with MR oximetry. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.
Modeling the influence of TR and excitation flip angle on the magnetization transfer ratio (MTR) in human brain obtained from 3D spoiled gradient echo MRI
Authors: Helms Gunther , Dathe Henning , Dechent Peter 
Published: May 2010

AbstractAttempts to optimize the magnetization transfer ratio (MTR) obtained from spoiled gradient echo MRI have focused on the properties of the magnetization transfer pulse. In particular, continuous‐wave models do not explicitly account for the effects of excitation and relaxation on the MTR. In this work, these were modeled by an approximation of free relaxation between the radiofrequency pulses and of an instantaneous saturation event describing the magnetization transfer pulse. An algebraic approximation of the signal equation can be obtained for short pulse repetition time and small flip angles. This greatly facilitated the mathematical treatment and understanding of the MTR. The influence of inhomogeneous radiofrequency fields could be readily incorporated. The model was verified on the human brain in vivo at 3 T by variation of flip angle and pulse repetition time. The corresponding range in MTR was similar to that observed by a 4‐fold increase of magnetization transfer pulse power. Choice of short pulse repetition time and larger flip angles improved the MTR contrast and reduced the influence of radiofrequency inhomogeneity. Optimal contrast is obtained around an MTR of 50%, and noise progression is reduced when a high reference signal is obtained. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.
2D and 3D radial multi‐gradient‐echo DCE MRI in murine tumor models with dynamic R*2‐corrected R1 mapping
Authors: Vautier Julien , Heilmann Melanie , Walczak Christine , Mispelter Joël , Volk Andreas 
Published: May 2010

AbstractDynamic contrast‐enhanced MRI is extensively studied to define and evaluate biomarkers for early assessment of vasculature‐targeting therapies. In this study, two‐dimensional and three‐dimensional radial multi‐gradient‐echo techniques for dynamic R*2‐corrected R1 mapping based on the spoiled gradient recalled signal equation were implemented and validated at 4.7 T. The techniques were evaluated on phantoms and on a respiratory motion animated tumor model. R1 measurements were validated with respect to a standard inversion‐recovery spin‐echo sequence in a four‐compartment phantom covering a range of relaxation rates typically found in tumor tissue. In the range of [0.4, 3] sec−1, R1 differences were less than 10% for both two‐dimensional and three‐dimensional experiments. A dynamic contrast‐enhanced MRI pilot study was performed on a colorectal tumor model subcutaneously implanted in mice at the abdominal level. Low motion sensitivity of radial acquisition allowed image recording without respiratory triggering. Three‐dimensional Ktrans maps and significantly different mean Ktrans values were obtained for two contrast agents with different molecular weights. The radial multi‐gradient‐echo approach should be most useful for preclinical experimental conditions where the tissue of interest experiences physiologic motion, like spontaneous extracerebral tumors developed by transgenic mice, and where dynamic contrast‐enhanced MRI is performed with high‐relaxivity contrast agents. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.
S‐Gal®, A novel 1H MRI reporter for β‐galactosidase
Authors: Cui Weina , Liu Li , Kodibagkar Vikram D. , Mason Ralph P. 
Published: May 2010

AbstractReporter genes and associated enzyme activity are becoming increasingly significant for research in vivo. The lacZ gene and β‐galactosidase (β‐gal) expression have long been exploited as reporters of biologic manipulation at the molecular level, and a noninvasive detection strategy based on proton MRI is particularly attractive. 3,4‐Cyclohexenoesculetin β‐D‐galactopyranoside (S‐Gal®) is a commercial histologic stain, which forms a black precipitate in the presence of β‐gal and ferric ions, suggesting potential detectability by MRI. Generation of the precipitate is now shown to cause strong T2* relaxation, revealing β‐gal activity. A series of tests with the enzyme in vitro and with tumor cells shows that this approach can be used as an assay for β‐gal activity. Proof of principle is shown in human breast tumor xenografts in mice. Upon direct injection of a mixture of 3,4‐cyclohexenoesculetin β‐D‐galactopyranoside and ferric ammonium citrate, intense contrast was observed immediately in MCF7‐lacZ tumors, but not in wild‐type tumors. 3,4‐Cyclohexenoesculetin β‐D‐galactopyranoside activation in combination with ferric ions introduces a novel approach for assaying enzyme activity by MRI in vivo. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.