52 research outputs found

    Determination of Peptide<b>–</b>Surface Adsorption Free Energy for Material Surfaces Not Conducive to SPR or QCM using AFM

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    The interactions between peptides and proteins with material surfaces are of primary importance in many areas of biotechnology. While surface plasmon resonance spectroscopy (SPR) and quartz crystal microbalance (QCM) methods have proven to be very useful in measuring fundamental properties characterizing adsorption behavior, such as the free energy of adsorption for peptide–surface interactions, these methods are largely restricted to use for materials that can readily form nanoscale-thick films over the respective sensor surfaces. Many materials including most polymers, ceramics, and inorganic glasses, however, are not readily suitable for use with SPR or QCM methods. To overcome these limitations, we recently showed that desorption forces (<i>F</i><sub>des</sub>) obtained using a standardized AFM method linearly correlate to standard-state adsorption free energy values (Δ<i>G°</i><sup><i></i></sup><sub>ads</sub>) measured from SPR in phosphate buffered saline (PBS: phosphate buffered 140 mM NaCl, pH 7.4). This approach thus provides a means to determine Δ<i>G°</i><sup><i></i></sup><sub>ads</sub> for peptide adsorption using AFM that can be applied to any flat material surface. In this present study, we investigated the <i>F</i><sub>des</sub>–Δ<i>G°</i><sup><i></i></sup><sub>ads</sub> correlation between AFM and SPR data in PBS for a much broader range of systems including eight different types of peptides on a set of eight different alkanethiol self-assembled monolayer (SAM) surfaces. The resulting correlation was then used to estimate Δ<i>G°</i><sup><i></i></sup><sub>ads</sub> from <i>F</i><sub>des</sub> determined by AFM for selected bulk polymer and glass/ceramic materials such as poly­(methyl methacrylate) (PMMA), high-density polyethylene (HDPE), fused silica glass, and a quartz (100) surface. The results of these studies support our previous findings regarding the strong correlation between <i>F</i><sub>des</sub> measured by AFM and Δ<i>G°</i><sup><i></i></sup><sub>ads</sub> determined by SPR, and provides a means to estimate Δ<i>G°</i><sup><i></i></sup><sub>ads</sub> for peptide adsorption on macroscopically thick samples of materials that are not conducive for use with SPR or QCM

    A Display Module Implemented by the Fast High-Temperatue Response of Carbon Nanotube Thin Yarns

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    Suspending superaligned multiwalled carbon nanotube (MWCNT) films were processed into CNT thin yarns, about 1 μm in diameter, by laser cutting and an ethanol atomization bath treatment. The fast high-temperature response under a vacuum was revealed by monitoring the incandescent light with a photo diode. The thin yarns can be electrically heated up to 2170 K in 0.79 mS, and the succeeding cool-down time is 0.36 mS. The fast response is attributed to the ultrasmall mass of the independent single yarn, large radiation coefficient, and improved thermal conductance through the two cool ends. The millisecond response time makes it possible to use the visible hot thin yarns as light-emitting elements of an incandescent display. A fully sealed display with 16 × 16 matrix was successfully fabricated using screen-printed thick electrodes and CNT thin yarns. It can display rolling characters with a low power consumption. More applications can be further developed based on the addressable CNT thermal arrays

    A Display Module Implemented by the Fast High-Temperatue Response of Carbon Nanotube Thin Yarns

    No full text
    Suspending superaligned multiwalled carbon nanotube (MWCNT) films were processed into CNT thin yarns, about 1 μm in diameter, by laser cutting and an ethanol atomization bath treatment. The fast high-temperature response under a vacuum was revealed by monitoring the incandescent light with a photo diode. The thin yarns can be electrically heated up to 2170 K in 0.79 mS, and the succeeding cool-down time is 0.36 mS. The fast response is attributed to the ultrasmall mass of the independent single yarn, large radiation coefficient, and improved thermal conductance through the two cool ends. The millisecond response time makes it possible to use the visible hot thin yarns as light-emitting elements of an incandescent display. A fully sealed display with 16 × 16 matrix was successfully fabricated using screen-printed thick electrodes and CNT thin yarns. It can display rolling characters with a low power consumption. More applications can be further developed based on the addressable CNT thermal arrays

    Duration of Chemotherapy for Small Cell Lung Cancer: A Meta-Analysis

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    <div><p>Background</p><p>Maintenance chemotherapy is widely provided to patients with small cell lung cancer (SCLC). However, the benefits of maintenance chemotherapy compared with observation are a subject of debate.</p><p>Methodology and Principal Findings</p><p>To identify relevant literature, we systematically searched the Medline, Embase, and Cochrane Central Register of Controlled Trials databases. Eligible trials included patients with SCLC who either received maintenance chemotherapy (administered according to a continuous or switch strategy) or underwent observation. The primary outcome was 1-year mortality, and secondary outcomes were 2-year mortality, overall survival (OS), and progression-free survival (PFS). Of the 665 studies found in our search, we identified 14 relevant trials, which together reported data on 1806 patients with SCLC. When compared with observation, maintenance chemotherapy had no effect on 1-year mortality (odds ratio [OR]: 0.88; 95% confidence interval [CI]: 0.66–1.19; P = 0.414), 2-year mortality (OR: 0.82; 95% CI: 0.57–1.19; P = 0.302), OS (hazard ratio [HR]: 0.87; 95% CI: 0.71–1.06; P = 0.172), or PFS (HR: 0.87; 95% CI: 0.62–1.22; P = 0.432). However, subgroup analyses indicated that maintenance chemotherapy was associated with significantly longer PFS than observation in patients with extensive SCLC (HR, 0.72; 95% CI: 0.58–0.89; P = 0.003). Additionally, patients who were managed using the continuous strategy of maintenance chemotherapy appeared to be at a disadvantage in terms of PFS compared with patients who only underwent observation (HR, 1.27; 95% CI: 1.04–1.54; P = 0.018).</p><p>Conclusions/Significance</p><p>Maintenance chemotherapy failed to improve survival outcomes in patients with SCLC. However, a significant advantage in terms of PFS was observed for maintenance chemotherapy in patients with extensive disease. Additionally, our results suggest that the continuous strategy is inferior to observation; its clinical value needs to be investigated in additional trials.</p></div

    Conformal Fe<sub>3</sub>O<sub>4</sub> Sheath on Aligned Carbon Nanotube Scaffolds as High-Performance Anodes for Lithium Ion Batteries

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    A uniform Fe<sub>3</sub>O<sub>4</sub> sheath is magnetron sputtered onto aligned carbon nanotube (CNT) scaffolds that are directly drawn from CNT arrays. The Fe<sub>3</sub>O<sub>4</sub>–CNT composite electrode, with the size of Fe<sub>3</sub>O<sub>4</sub> confined to 5–7 nm, exhibits a high reversible capacity over 800 mAh g<sup>–1</sup> based on the total electrode mass, remarkable capacity retention, as well as high rate capability. The excellent performance is attributable to the superior electrical conductivity of CNTs, the uniform loading of Fe<sub>3</sub>O<sub>4</sub> sheath, and the structural retention of the composite anode on cycling. As Fe<sub>3</sub>O<sub>4</sub> is inexpensive and environmentally friendly, and the synthesis of Fe<sub>3</sub>O<sub>4</sub>–CNT is free of chemical wastes, this composite anode material holds considerable promise for high-performance lithium ion batteries

    Ice-Assisted Transfer of Carbon Nanotube Arrays

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    Decoupling the growth and the application of nanomaterials by transfer is an important issue in nanotechnology. Here, we developed an efficient transfer technique for carbon nanotube (CNT) arrays by using ice as a binder to temporarily bond the CNT array and the target substrate. Ice makes it an ultraclean transfer because the evaporation of ice ensures that no contaminants are introduced. The transferred superaligned carbon nanotube (SACNT) arrays not only keep their original appearance and initial alignment but also inherit their spinnability, which is the most desirable feature. The transfer-then-spin strategy can be employed to fabricate patterned CNT arrays, which can act as 3-dimensional electrodes in CNT thermoacoustic chips. Besides, the flip-chipped CNTs are promising field electron emitters. Furthermore, the ice-assisted transfer technique provides a cost-effective solution for mass production of SACNTs, giving CNT technologies a competitive edge, and this method may inspire new ways to transfer other nanomaterials

    Flow diagram of the literature search and trials selection process.

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    <p>Flow diagram of the literature search and trials selection process.</p

    Adsorption-Induced Changes in Ribonuclease A Structure and Enzymatic Activity on Solid Surfaces

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    Ribonuclease A (RNase A) is a small globular enzyme that lyses RNA. The remarkable solution stability of its structure and enzymatic activity has led to its investigation to develop a new class of drugs for cancer chemotherapeutics. However, the successful clinical application of RNase A has been reported to be limited by insufficient stability and loss of enzymatic activity when it was coupled with a biomaterial carrier for drug delivery. The objective of this study was to characterize the structural stability and enzymatic activity of RNase A when it was adsorbed on different surface chemistries (represented by fused silica glass, high-density polyethylene, and poly­(methyl-methacrylate)). Changes in protein structure were measured by circular dichroism, amino acid labeling with mass spectrometry, and in vitro assays of its enzymatic activity. Our results indicated that the process of adsorption caused RNase A to undergo a substantial degree of unfolding with significant differences in its adsorbed structure on each material surface. Adsorption caused RNase A to lose about 60% of its native-state enzymatic activity independent of the material on which it was adsorbed. These results indicate that the native-state structure of RNase A is greatly altered when it is adsorbed on a wide range of surface chemistries, especially at the catalytic site. Therefore, drug delivery systems must focus on retaining the native structure of RNase A in order to maintain a high level of enzymatic activity for applications such as antitumor chemotherapy

    Cyclopropanations via Heme Carbenes: Basic Mechanism and Effects of Carbene Substituent, Protein Axial Ligand, and Porphyrin Substitution

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    Catalytic carbene transfer to olefins is a useful approach to synthesize cyclopropanes, which are key structural motifs in many drugs and biologically active natural products. While catalytic methods for olefin cyclopropanation have largely relied on rare transition-metal-based catalysts, recent studies have demonstrated the promise and synthetic value of iron-based heme-containing proteins for promoting these reactions with excellent catalytic activity and selectivity. Despite this progress, the mechanism of iron-porphyrin and hemoprotein-catalyzed olefin cyclopropanation has remained largely unknown. Using a combination of quantum chemical calculations and experimental mechanistic analyses, the present study shows for the first time that the increasingly useful Cî—»C functionalizations mediated by heme carbenes feature an Fe<sup>II</sup>-based, nonradical, concerted nonsynchronous mechanism, with early transition state character. This mechanism differs from the Fe<sup>IV</sup>-based, radical, stepwise mechanism of heme-dependent monooxygenases. Furthermore, the effects of the carbene substituent, metal coordinating axial ligand, and porphyrin substituent on the reactivity of the heme carbenes was systematically investigated, providing a basis for explaining experimental reactivity results and defining strategies for future catalyst development. Our results especially suggest the potential value of electron-deficient porphyrin ligands for increasing the electrophilicity and thus the reactivity of the heme carbene. Metal-free reactions were also studied to reveal temperature and carbene substituent effects on catalytic vs noncatalytic reactions. This study sheds new light into the mechanism of iron-porphyrin and hemoprotein-catalyzed cyclopropanation reactions and it is expected to facilitate future efforts toward sustainable carbene transfer catalysis using these systems

    Subgroup analysis for 1-year mortality, 2-year mortality, OS, and PFS.

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    <p>Subgroup analysis for 1-year mortality, 2-year mortality, OS, and PFS.</p
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