Effect Of C60 Research Articles

Fullerene (C60)‐doped zinc‐aluminium layered double hydroxide/polyvinyl alcohol nanocomposites: Synthesis, characterization, and photodegradation of methylene blue from water solution

AbstractIntroductionLayered double hydroxides (LDHs) are widely studied anionite clays consisting of positively‐charged hydroxide nanosheets which is described by the general formula: [M(II)1−xM(III)x(OH)2][An−·mH2O], where M(II) and M(III) are the divalent (e.g., Mg2+, Zn2+, Ca2+, Co2+, Ni2+, etc.) and trivalent (e.g., Al3+, Fe3+, Cr3+, etc.) metal ions, An− and H2O is the interlamellar anion (e.g., Cl¯, Br¯, NO3¯, CO32¯, SO42¯, SeO42¯) for charge‐neutralization and hydrated state, respectively. They have been widely used in different industry sectors, in materials science and research. Polymer/LDH nanocomposites have gained significant attention in recent years.Carbon‐based nanomaterials, like fullerene, carbon nanotubes (CNT), graphene and graphene oxide have attracted significant attention. Fullerene molecules (C60, C70) are used as reinforcing material for polymers to improve their mechanical, thermal, optical, energy storage and charge transport properties.ObjectivesC60‐doped ZnAl‐layered double hydroxide/polyvinyl alcohol nanocomposites were successfully synthesized and their photocatalytic activity for photodegradation of methylene blue (MB) synthetic dye was quantitatively analyzed by ultraviolet (UV) spectroscopy. The effect of C60 on the optical, structural, morphological properties, and photocatalytic activity of LDHs was investigated, and the impact of C60/LDH mass ratio and aging time on the properties was also studied.MethodsFullerene‐doped ZnAl‐LDH/PVA nanocomposites were synthesized via urea hydrolysis and coprecipitation‐coformation method. First, 10 wt% PVA/water solution (40 mL) is added into the mixed solution containing 0.015 mol of Zn(NO3)2·6H2O and 0.005 mol of Al2(SO4)3·9H2O and titrated by 2 M of NaOH and 1 M of NaHCO3 mixed base solution to adjust pH 9. The obtained white slurry was shaken very hard and aged for 1 year. The obtained samples were marked by the mass percentage of C60 as 1% C60@LDH/PVA, 10% C60@LDH/PVA, 20% C60@LDH/PVA, and 60% C60@LDH/PVA.Results and DiscussionThe basal spacing of C60‐doped ZnAl‐LDH was estimated to be 9.217 Å which is wide enough from the general LDH (~7.0 Å). The crystallite size of nanoparticles is 9.217 nm and ~6 nm by Scherrer's equation and Williamson–Hall method from the XRD data, respectively. Rice‐shaped 2D morphology was formed with 100 nm–2 μm width and 500 nm–10 μm in length by SEM. The maximal photodegradation efficiency was found with 20% of C60 doping (PD% = 96.98) after 360 min, where the sorption efficiency with this compound is very high (R% = 85.55).ConclusionsIn the presented work, the effect of C60 on the optical, structural, morphological properties, and photocatalytic activity of LDHs was investigated, and the impact of C60/LDH mass ratio and aging time on the properties was also studied. For the identification of the photocatalytic activity of obtained C60/LDH nanocomposites, MB was used as a model pollutant and the efficiency of the Zn/Al LDH nanocomposite, with various quantities of fullerene, is also evaluated.

Effect of black phosphorus modified by fullerene C60 on the self-lubricating properties of PEEK-based composite coatings

Poly-ether-ether-ketone (PEEK) has many excellent properties for being used as self-lubricating coatings. In order to further improve the friction performance, black phosphorus (BP) was used as filler to prepare BP/PEEK composite coating. BP-C60 was formed by modification of BP edge by fullerene C60 to solve the problem of BP oxidation, so that BP still existed in the sintered PEEK coating. Then, the effects of C60 and BP-C60 on the tribological properties of PEEK coating were studied, and the results showed that the wear rate and friction coefficient of BP-C60/C60/PEEK composite coating were significantly reduced. This was attributed to the synergistic effect of BP and C60, which enhanced the stability of BP and reduced coating porosity.

The Effect of C60 and Pentacene Adsorbates on the Electrical Properties of CVD Graphene on SiO2

Graphene is an excellent 2D material for vertical organic transistors electrodes due to its weak electrostatic screening and field-tunable work function, in addition to its high conductivity, flexibility and optical transparency. Nevertheless, the interaction between graphene and other carbon-based materials, including small organic molecules, can affect the graphene electrical properties and therefore, the device performances. This work investigates the effects of thermally evaporated C60 (n-type) and Pentacene (p-type) thin films on the in-plane charge transport properties of large area CVD graphene under vacuum. This study was performed on a population of 300 graphene field effect transistors. The output characteristic of the transistors revealed that a C60 thin film adsorbate increased the graphene hole density by (1.65 ± 0.36) × 1012 cm-2, whereas a Pentacene thin film increased the graphene electron density by (0.55 ± 0.54) × 1012 cm-2. Hence, C60 induced a graphene Fermi energy downshift of about 100 meV, while Pentacene induced a Fermi energy upshift of about 120 meV. In both cases, the increase in charge carriers was accompanied by a reduced charge mobility, which resulted in a larger graphene sheet resistance of about 3 kΩ at the Dirac point. Interestingly, the contact resistance, which varied in the range 200 Ω-1 kΩ, was not significantly affected by the deposition of the organic molecules.

A molecular dynamics simulation study to investigate the effect of C60 on thermo- mechanical and elastic properties of DGEBA/DETA nanocomposites

Molecular dynamics simulations were performed to investigate the effect of fullerenes (C60) on the thermal and mechanical properties of a cross-linked epoxy system composed of epoxy resin DGEBA and curing agent DETA. Hence, a comparative investigation was performed on the thermal and mechanical properties of DGEBA/DETA reinforced with 2.3 wt% C60 and neat epoxy systems. Properties such as glass transition temperature (GTT), coefficients of thermal expansion (CTE), and elastic properties at different cross-linking densities. Simulation results indicated that the GTT of the epoxy increased by about 25 K due to the presence of C60. The effect of C60 on the CTE was very less, and at higher crosslinking densities, an increase in CTE before the glass transition was observed. It was also observed that the effect of C60 on mechanical properties is dependent on the crosslinking density. The young’s modulus of the epoxy/C60 system at a high strain rate showed a drastic decrease as compared to the neat epoxy system at higher crosslinking densities. The highest value of young’s modulus of the epoxy/C60 system was observed at 65% crosslinking density.

Lactococcus lactis subsp. cremoris C60 induces macrophages activation that enhances CD4+ T cell-based adaptive immunity.

Lactococcus lactis subsp. cremoris C60 is a probiotic strain that induces diverse functional modifications in immune cells. In this report, as a novel effect of C60 on myeloid lineage cells, we show that C60 enhances the immunological function of macrophages that consequently promotes CD4+ T cell activity in an antigen-dependent manner. Heat-killed (HK) C60 induced the production of pro-inflammatory cytokines in thioglycolate-elicited peritoneal macrophages (TPMs) much stronger than Toll-like receptor (TLR) ligand stimulation. The HK-C60 treatment also augmented the expression of antigen-presenting and co-stimulatory molecules, such as major histocompatibility complex (MHC) class II, CD80, and CD86, as well as antigen uptake in TPMs. These HK-C60-mediated functional upregulations in TPMs resulted in the promotion of CD4+ T cell activation in an antigen-dependent manner. Interestingly, the TPMs that originated from the mice fed the HK-C60 diet showed pre-activated characteristics, which was confirmed by the upregulation of cytokine production and antigen presentation-related molecule expression under lipopolysaccharide (LPS) stimulation. Furthermore, the antigen-dependent CD4+ T cell activation was also enhanced by the TPMs. This implied that antigen presentation activity was enhanced in the TPMs that originated from the HK-C60 diet mice. Thus, C60 effectively upregulates the immunological function of macrophages that directly connects to CD4+ T cell-based adaptive immunity.

Early Aggregation Kinetics of Alzheimer’s Aβ16–21 in the Presence of Ultrafine Fullerene Particles and Ammonium Nitrate

One of the environmental health and safety concerns is the toxicological impact of ultrafine particles (UFPs) and secondary inorganic ions on human health, particularly on the development of neurodegenerative diseases. According to recent research studies, UFPs can be absorbed to human blood and have a toxicological effect on human organs. Due to their small particle size, UFPs can translocate to the human brain and contribute to the progression of neurodegenerative diseases. In this work, a molecular dynamics study was performed to investigate the impact of carbon-based UFP, mimicked by fullerene C60 molecule, on the aggregation of amyloid β (Aβ) peptides, which is related to the progression of Alzheimer’s disease. Moreover, the synergistic effect of the UFP and environmental pollutants was analyzed at various concentrations of the ions found in the environmental realm. In particular, the effect of C60 on the aggregation kinetics of eight Aβ16–21 peptides, the segment of Aβ peptide, was studied in the presence of NH4NO3 by varying the salt concentrations from 50 to 150 mM. Overall, the results showed the formation of large amounts of β-sheets in the systems with a slow initial rate of the aggregation of Aβ16–21 peptide octamer. In the absence of the UFP, the slowest initial rate of the aggregation of Aβ16–21 peptide octamer was observed at 50 mM salt concentration, while, in the presence of C60, the slowest aggregation kinetics of Aβ16–21 peptides was observed at 150 mM salt concentration. Moreover, in general, the presence of carbon-based UFP reduced the interpeptide interactions and decreased the initial rate of the aggregation of peptides due to the binding of peptides to C60.

Antioxidant Potential of Aqueous Dispersions of Fullerenes C60, C70, and Gd@C82.

The antioxidant potential (capacity and activity) of aqueous fullerene dispersions (AFD) of non-functionalized C60, C70, and Gd@C82 endofullerene (in micromolar concentration range) was estimated based on chemiluminescence measurements of the model of luminol and generation of organic radicals by 2,2′-azobis(2-amidinopropane) dihydrochloride (ABAP). The antioxidant capacity was estimated by the TRAP method, from the concentration of half-suppression, and from the suppression area in the initial period. All three approaches agree and show that the antioxidant capacity of AFDs increased in the order Gd@C82 < C70 < C60. Mathematical modeling of the long-term kinetics data was used for antioxidant activity estimation. The effect of C60 and C70 is found to be quenching of the excited product of luminol with ABAP-generated radical and not an actual antioxidant effect; quenching constants differ insignificantly. Apart from quenching with a similar constant, the AFD of Gd@C82 exhibits actual antioxidant action. The antioxidant activity in Gd@C82 is 300-fold higher than quenching constants.

Thermal behaviour of poly(methyl methacrylate)/fullerene composite films

ABSTRACTPoly(methyl methacrylate) films and poly(methyl methacrylate)/fullerene composite films were fabricated by casting from toluene solutions. The mass fraction of fullerene (C60) was varied from 0.05–3 wt. %. The effect of the fullerene (C60) content on the thermal degradation parameters of the composite films was evaluated by thermogravimetric (TG) analysis. It was found that the incorporation of C60 improved the thermal stability of the polymers. The films eventually decomposed in three stages. Incorporation of fullerene caused a change in the distribution of mass loss over the stages of degradation in comparison with the pristine polymer. Using differential scanning calorimetry (DSC), the phase transitions from the glassy state to the elastic one was studied for the examined polymeric materials. New data relating to the effect of C60 on the glass transition temperature of composites with low weight fractions of filler were obtained. Specifically, for films containing up to 0.1 wt. % of C60, a single glass transition temperature was found, whereas for composites with a higher concentration of filler, two glass transition temperatures were recorded.

The effect of C60 on the optical absorption properties of HPPH photosensitizer

The optical absorption properties of the clinical photosensitizer (HPPH) and HPPH-C60 dyads (HPPH-C60 (1), HPPH-C60 (2) and HPPH-C60 (3)) have been calculated by density functional theory (DFT) and time dependent density functional theory (TD-DFT). Based on the optimized geometrical structures of three HPPH-C60 dyads, their binding energies, the charges populations and the excited energies are calculated specifically. The results show that the different binding sites between C60 and HPPH induce the different binding energy. The maximum binding energy and the significant charge transfer occur at C60 and nitrogen atoms of HPPH in HPPH-C60(1). At the same time, the excited energies of three HPPH-C60 dyads are smaller than that of HPPH. The maximum absorption peak of the HPPH-C60(1) reaches near infrared 961.69nm.

Antioxidant activities of [60]fullerene derivatives from chalcone, flavone and flavanone: A ONIOM approach via H-atom and electron transfer mechanism

Antioxidant properties of C60 flavonoid conjugates were computationally examined via their O–H bond dissociation enthalpies (BDEs) and ionization energies (IEs) using two-layer ONIOM and PM6 methods, respectively. Eight ONIOM((RO)B3LYP/6-311++G(2df,2p):PM6) models were evaluated by computing BDE(O–H)s of a series of polyphenol. Synthetic mechanism of C60 flavonoid conjugates was also explored via the potential energy surfaces of reaction between C60 and malonate flavonoid derivatives (chalcone, flavone and flavanone) at the B3LYP/6-31G(d)//PM6. Antioxidant activities of C60 flavonoid conjugates were discussed via hydrogen atom transfer, single electron transfer mechanisms and the effect of C60 on the BDE(O–H)s and IEs of these compounds.

Water-soluble C60-(OH)24 fullerene hydroxide as a therapeutic agent against the degeneration of articular cartilage in osteoarthritis

Purpose: During the development of osteoarthritis (OA), mechanical stress on articular cartilage downregulates the stable cellular activities of chondrocytes and induce the production of catabolic factors, such as proinflammatory cytokines and chemokines. In addition, it is well known that chondrocytes produce excess amounts of reactive oxygen species (ROS; superoxide, nitric oxide, hydrogen peroxide and peroxynitrite) in response to mechanical stress. Recent reports have demonstrated that mechanical stress to articular cartilage stimulates excess production of ROS from chondrocytes, consequently resulting in the depolymerization of hyaluronic acid and chondrocyte death. It has been suggested that the generation of ROS and the depletion of cellular antioxidants may be involved in the pathogenesis of OA. C60 fullerene is a molecule composed completely of carbon in a unique spherical structure that has a high reactivity with oxygen free radicals and can potentially act as a free radical scavenger. It has been reported that the antioxidant level of C60 is several hundred-fold higher than that of other antioxidants. Recently, C60 fullerene has shown to inhibit neuronal apoptosis by scavenging oxygen reactive species and protects human skin keratinocytes from ROS-induced cell death after UV stress, suggesting that C60 is a useful agent to protect against the oxygen free radical-induced pathological features in a variety of diseases. Use of C60 could lead to the development of novel therapeutic strategies in the prevention of both chondrocyte aging and cartilage degeneration. To prevent the degeneration of articular cartilage in OA, we have newly developed on water-soluble C60(OH)24 fullerene hydroxide, a strong free radical scavenger, as an anti-oxidative agent. In this study, we examined the therapeutic effects of water-soluble C60(OH)24 on chondrocyte activity and energy metabolism, which were monitored by the production of cartilage component (proteoglycan), matrix degrading enzyme MMP-3, and the uptake of glucose in the cells, respectively. Methods: In the presence or absence of C60(OH)24 (1.0 nM, 10.0 nM, 100.0 nM), human OA chondrocytes were incubated with IL-1β (1.0, 10.0 ng/ml). After the 24-hour incubation period, chondrocyte activities (production of proteoglycan and MMP-3, glucose metabolism) were analyzed. Our previous study revealed that expression of DNA repair enzyme, apurinic/apyrimidinic endonuclease (Apex) 2, in chondrocytes was associated with the degeneration of articular cartilages and was induced by OA-relating catabolic factors. Thus, we also studied effects of C60(OH)24 on the expression of Apex 2 in osteoarthritic chondrocytes. Results: IL-1β significantly inhibited the production of proteoglycan and the glucose uptake in chondrocytes, and accelerated the secretion of MMP-3 from chondrocytes. Even in the presence of IL-1β (1.0 ng/ml, but not 10.0 ng/ml), C60(OH)24 inhibited the IL-1β-induced production of MMP-3, the IL-1β-induced down-regulation of proteoglycan production and glucose metabolism in OA chondrocytes. C60(OH)24 fullerene hydroxide also reduced the OA-relating catabolic factor-induced up-regulation of DNA repair enzyme, Apex 2, in OA chondrocytes. Conclusions: Our data indicated that nM order of water-soluble C60(OH)24 fullerene hydroxide may have a potential to protect against the catabolic factor-induced down-regulation of chondrocyte activities in OA. Our findings provide a novel pathogenic mechanism linking oxidant-mediated degenerative process of articular cartilage in OA.Figure 2. Effect of C60(OH)24 on proteoglycan production in chondrocytesView Large Image Figure ViewerDownload Hi-res image Download (PPT)Figure 3. Effect of C60(OH)24 on glucose uptake into chondrocytesView Large Image Figure ViewerDownload Hi-res image Download (PPT)

Effect of intra-membrane C60 fullerenes on the modulus of elasticity and the mechanical resistance of gel and fluid lipid bilayers.

Penetration and partition of C60 to the lipid bilayer core are both relevant to C60 toxicity, and useful to realise C60 biomedical potential. A key aspect is the effect of C60 on bilayer mechanical properties. Here, we present an experimental study on the mechanical effect of the incorporation of C60 into the hydrophobic core of fluid and gel phase zwitterionic phosphatidylcholine (PC) lipid bilayers. We demonstrate its incorporation inside the hydrophobic lipid core and the effect on the packing of the lipids and the vesicle size using a combination of infrared (IR) spectroscopy, atomic force microscopy (AFM) and laser light scattering. Using AFM we measured the Young's modulus of elasticity (E) of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) in the absence (presence) of intra-membranous C60 at 24.5 °C. E of fluid phase supported bilayers is not altered by C60, but E increases with incorporation of C60 in gel phase bilayers. The increase is higher for longer hydrocarbon chains: 1.6 times for DPPC and 2 times for DSPC. However the mechanical resistance of gel phase bilayers of curved bilayered structures decreases with the incorporation of C60. Our combined results indicate that C60 causes a decrease in gel phase lipid mobility, i.e. an increase in membrane viscosity.

Largely enhanced thermal and mechanical properties of polymer nanocomposites via incorporating C60@graphene nanocarbon hybrid

Although considerable progress has been achieved to create advanced polymer nanocomposites using nanocarbons including fullerene (C60) and graphene, it remains a major challenge to effectively disperse them in a polymer matrix and to fully exert their extraordinary properties. Here we report a novel approach to fabricate the C60@graphene nanocarbon hybrid (C60: ∼47.9 wt%, graphene: ∼35.1%) via three-step reactions. The presence of C60 on a graphene sheet surface can effectively prevent the aggregation of the latter which in turn helps the dispersion of the former in a polymer matrix during melt-processing. C60@graphene is found to be uniformly dispersed in a polypropylene (PP) matrix. Compared with pristine C60 or graphene, C60@graphene further improves the thermal stability and mechanical properties of PP. The incorporation of 2.0 wt% C60@graphene (relative to PP) can remarkably increase the initial degradation temperature by around 59 ° C and simultaneously enhance the tensile strength and Young’s modulus by 67% and 76%, respectively, all of which are higher than those of corresponding PP/C60 (graphene) nanocomposites. These significant performance improvements are mainly due to the free-radical-trapping effect of C60, and the thermal barrier and reinforcing effects of graphene nanosheets as well as the effective stress load transfer. This work provides a new methodology to design multifunctional nanohybrids for creating advanced materials.

Adsorption of Cu(II) on oxidized multi-walled carbon nanotubes in the presence of hydroxylated and carboxylated fullerenes.

The adsorption of Cu(II) on oxidized multi-walled carbon nanotubes (oMWCNTs) as a function of contact time, pH, ionic strength, temperature, and hydroxylated fullerene (C60(OH)n) and carboxylated fullerene (C60(C(COOH)2)n) were studied under ambient conditions using batch techniques. The results showed that the adsorption of Cu(II) had rapidly reached equilibrium and the kinetic process was well described by a pseudo-second-order rate model. Cu(II) adsorption on oMWCNTs was dependent on pH but independent of ionic strength. Compared with the Freundlich model, the Langmuir model was more suitable for analyzing the adsorption isotherms. The thermodynamic parameters calculated from temperature-dependent adsorption isotherms suggested that Cu(II) adsorption on oMWCNTs was spontaneous and endothermic. The effect of C60(OH)n on Cu(II) adsorption of oMWCNTs was not significant at low C60(OH)n concentration, whereas a negative effect was observed at higher concentration. The adsorption of Cu(II) on oMWCNTs was enhanced with increasing pH values at pH < 5, but decreased at pH ≥ 5. The presence of C60(C(COOH)2)n inhibited the adsorption of Cu(II) onto oMWCNTs at pH 4–6. The double sorption site model was applied to simulate the adsorption isotherms of Cu(II) in the presence of C60(OH)n and fitted the experimental data well.

Modification of PCBM Crystallization via Incorporation of C60 in Polymer/Fullerene Solar Cells

AbstractThe morphological effects of the incorporation of C60 into blended thin‐films of poly(3‐hexylthiophene) and [6,6]‐phenyl C61 butyric acid methyl ester (PCBM) are investigated. The results show that addition of C60 readily alters the growth‐rate and morphology of PCBM crystallites under different environmental conditions. The effect of C60 on the growth of large PCBM crystallites is thoroughly characterized using optical microscopy, electron microscopy and UV‐visible absorption spectroscopy. Results show that C60 incorporation modifies fullerene aggregation and crystallization and greatly reduces the average crystallite size at C60 loadings of ≈50 wt% in the fullerene phase. Organic field‐effect transistors (OFETs) are prepared to evaluate the electron mobility of PCBM/C60 films and organic solar cells (OSCs) are fabricated from mixed‐fullerene active layers to evaluate their performance. It is demonstrated that the use of fullerene mixtures in organic electronic applications is a viable approach to produce more stable devices and to control the growth of micrometer‐sized fullerene crystals.

Optimizing C60 incidence angle for polymer depth profiling by ToF‐SIMS

AbstractThe introduction of C60+ as a sputter ion beam for ToF‐SIMS has made it possible to acquire molecular depth profiles on a wide variety of polymers. However, previous studies have indicated that certain classes of polymers undergo sputter‐induced damage when bombarded with C60+ that prevents obtaining stable molecular secondary ion signals as a function of depth. A number of different analytical parameters have been previously explored in attempts to improve depth profiling of these polymer classes. In this study, the effect of C60+ incident angle on the ability to depth profile polycarbonate (PC) and polystyrene (PS) was investigated at angles from 48° to 76° with respect to the sample normal. This study indicates that the highest sputtering angle provided the best conditions for molecular depth profiling. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Effect of C&lt;sub&gt;60&lt;/sub&gt; on the Photovoltaic Properties of Polypyrrole-C&lt;sub&gt;60&lt;/sub&gt; Heterojunctions

We report here a series of polypyrrole/C60-H3PO4 two-layer photovoltaic cells fabricated by varying the C60 ratio with regard to polypyrrole. It is found that a slight amount of C60 can remarkably improve photovoltaic properties by four orders of magnitude; with C60 ratio the open-circuit voltage and short-circuit current increase, and at higher C60 ratio the photovoltaic working threshold is lowered too, the cell can even work efficiently in dark, more approaching the efficiency under strong illumination. The optimized device yields 1.2 V open-circuit voltage and 14 μA/cm2 short-circuit current, and a power conversion efficiency 0.01%. Our results show that polypyrrole is a potentially good material for photovoltaic cells. The effect of C60 in combination with polypyrrole is discussed.

Thermodynamic characteristics of fullerene-containing poly(methyl methacrylate-co-allyl methacrylate) and the C60-free copolymer analog

The heat capacities of fullerene-containing poly(methyl methacrylate-co-allyl methacrylate) and the C60-free copolymer of the same composition are studied in the temperature interval 8 to 350–450 K via the methods of high-accuracy adiabatic and differential scanning calorimetry. Thermodynamic characteristics of glass transition, standard thermodynamic functions, and temperature intervals of the thermal stability of the samples are estimated. The fractal dimension is calculated, and conclusions about the topological structure of the copolymers are proposed. The effect of C60 on the thermodynamic characteristics of the copolymer is studied.

Low temperature radiolysis of fullerene C60 and its solutions in isopropylbenzene and N-vinylpyrrolidone

Low-temperature (77 K) radiolysis of solid fullerene C60 and its glassy solutions in isopropylbenzene (IPB) and N-vinylpyrrolidone (N-VP) has been investigated with the use of ESR spectroscopy. Radiationchemical yields for the formation of paramagnetic centers (GPMC, 1/100 eV) have been determined to be ∼0.001 for pure fullerene and 0.3 and 0.7 for its solutions in IPB and N-VP, respectively. The low value of GPMC for fullerene indicates a high stability of this form of carbon. The increase in GPMC in solutions as compared to the pure solvents (0.15 for IPB and 0.3 for N-VP) indicates the sensitizing effect of C60.

Effect of the β-amyloid peptide Aβ25–35 and fullerene C60 on the activity of enzymes in erythrocytes

The effect of the beta-amyloid peptide Abeta25-35 and fullerene C60 on the activity of the cytoplasmic enzymes lactate dehydrogenase (LDH) and glutathione peroxidase (GLP), and membrane-bound phosphofructokinase (PFK) and Na+,K(+)-ATPase in human erythrocytes has been studied. When used in combination, the cytotoxins decrease the activity of LDH and PFK in a nonadditive manner; in this case, Abeta25-35 protects PFK against the inhibitory effect of C60. The activity of LDH, GLP, and PFK decreases within the first 2-20 min of incubation of erythrocytes with Abeta25-35 in the absence of glucose. The addition of glucose sharply decreases the inhibitory action of Abeta25-35 on LDH and GLP but does not affect the fourfold decrease in activity of PFK; the activity of membrane-bound Na+,K(+)-ATPase does not depend on the presence of glucose. Possible mechanisms of interaction of Abeta25-35 and fullerene C60 with the erythrocyte membrane and enzymes are discussed.