Role of white light in reversing UV-B-mediated effects in the N2-fixing cyanobacterium Anabaena BT2

The effects of various irradiances of artificial UV-B (280-315 nm) in the presence or absence of visible light (photosynthetically active radiation) on growth, survival, 14CO2 uptake and ribulose 1,5-bisphosphate carboxylase (RuBISCO) activity were studied in the N2-fixing cyanobacterium Anabaena BT2. We tested the hypothesis whether or not visible radiation offers any protection against UV-B-induced deleterious effects on growth and photosynthesis in Anabaena BT2. Attempts were also made to determine the irradiances of UV-B where inhibitory effects could be mitigated by simultaneous irradiation with visible light. Exposure of cultures to 0.2 W m(-2) or higher irradiance of UV-B caused inhibition of growth and survival and growth ceased above 1.0 W m(-2). 14CO uptake and RuBISCO activity were found to be more sensitive to UV-B and around 60% reduction in 14CO2 uptake and RuBISCO activity occurred after exposure of cultures to 0.4 W m(-2) for 1 h. However, growth, 14CO2 uptake and RuBISCO activity were nearly normal when UV-B (0.4 W m(-2)) and visible light (14.4 W m(-2)) were given simultaneously. Blue radiation (450 nm) was found to be the most effective in photoreactivation against UV-B, better than UV-A or any other light wavelength band. Our results demonstrate that the studied cyanobacterium possesses active photoreactivation mechanism(s) against UV-B-mediated damage which in turn probably allow survival under natural conditions in spite of being continuously exposed to the UV-B component present in the solar radiation. Continued growth of many algae and cyanobacteria in the presence of intense solar UV-B radiation under natural conditions seems to be due to the active role of photoreactivation.     

Influence of temperature and UVR on photosynthesis and morphology of four species of cyanobacteria

During the late austral spring of 2009 we carried out experiments (4days of duration) with four cyanobacteria species, Anabaena sp., Nostoc sp., Arthrospira platensis and Microcystis sp., to assess the combined effects of temperature and solar radiation on photosynthesis performance and morphology. Two experimental temperatures (18°C and 23°C, simulating a 5°C increase under a scenario of climate change) and three radiation treatments (by using different filters/materials) were implemented: (i) P (PAR, 400-700nm), (ii) PA (PAR+UV-A, 320-700nm) and, (iii) PAB (PAR+UV-A+UV-B, 280-700nm). In general, samples under the P treatment had less decrease/higher recovery rates of effective photochemical quantum yield (Y) than those receiving UV-A or UV-A+UV-B. The effects of increased temperature were species-specific: At the end of the experiments, it was seen that increased temperature benefited photosynthetic performance of Anabaena sp. and Nostoc sp. but not of Microcystis sp. and A. platensis. Higher temperature was also associated to an increase in the chain area of Anabaena sp., and to bigger trichomes in A. platensis; however, no morphological effects were observed in Microcystis sp. In addition, in Nostoc sp. the increase in temperature counteracted the UVR impact on the reduction of the chain area. How these effects and mechanisms will affect the trophodynamics and production of aquatic ecosystems is still uncertain, but the specificity of the responses suggests that not all cyanobacteria would be equally benefited by temperature increases therefore affecting the balance and interaction among species in the water column.     

Adaptation of cyanobacteria to UV-B stress correlated with oxidative stress and oxidative damage

Cyanobacteria must cope with the negative effects of ultraviolet B (280-315 nm) (UV-B) stress caused by their obligatory light requirement for photosynthesis. The adaptation of the cyanobacterium Anabaena sp. to moderate UV-B radiation has been observed after 2 weeks of irradiation, as indicated by decreased oxidative stress, decreased damage, recovered photosynthetic efficiency and increased survival. Oxidative stress in the form of UV-B-induced production of reactive oxygen species was measured in vivo with the oxidative stress-sensitive probe 2',7'-dichlorodihydrofluorescein diacetate. Photooxidative damage by UV-B radiation, including lipid peroxidation and DNA strand breakage, was determined by a modified method using thiobarbituric acid reactive substances and fluorometric analysis of DNA unwinding. Photosynthetic quantum yield was determined by pulse amplitude-modulated fluorometry. The results suggest that moderate UV-B radiation results in an evident oxidative stress, enhanced lipid peroxidation, increased DNA strand breaks, elevated chlorophyll bleaching as well as decreased photosynthetic efficiency and survival during the initial exposure. However, DNA strand breaks, photosynthetic parameters and chlorophyll bleaching returned to their unirradiated levels after 4-7 days of irradiation. Oxidative stress and lipid peroxidation appeared to respond later because decreases were observed after 7 days of radiation. The survival curve against irradiation time exhibited a close relationship with the changes in photosynthetic quantum yield and DNA damage, with little mortality after 4 days. Growth inhibition by UV-B radiation was observed during the first 7 days of radiation, whereas normal growth resumed even under UV-B stress thereafter. An efficient defense system was assumed to come into play to repair photosynthetic and DNA damage and induce the de novo synthesis of UV-sensitive proteins and lipids, allowing the organisms to adapt to UV-B stress successfully and survive as well as grow. No induction of mycosporine-like amino acids (MAA) was observed during the adaptation of Anabaena sp. to UV-B stress in our work. The adaptation of the cyanobacterium correlated with and could be caused by the oxidative stress and oxidative damage.     

UPTAKE AND BIOCONVERSION OF α-TOCOPHERYL ACETATE TO α-TOCOPHEROL IN SKIN OF HAIRLESS MICE

Abstract— The photoprotective effect of topically applied α-tocopheryl acetate (vitamin E acetate), a stable derivative of α-tocopherol (vitamin E), and its possible bioconversion to the active antioxidant species (α-tocopherol) was examined in skin tissue of female hairless mice (HRS/J) exposed to UV-B irradiation. Our results indicate that topically applied α-tocopheryl acetate is absorbed into and retained by skin tissue. Furthermore, skin tissue from UV-B-irradiated animals that received daily topical α-tocopheryl acetate treatments contained significantly higher levels (P < 0.001) of α-tocopheryl acetate than non-UV-B-irradiated mice that received identical daily topical α-tocopheryl acetate treatments. Finally, free α-tocopherol levels in skin also were significantly increased (P < 0.00 1) by topical applications of α-tocopheryl acetate and skin levels of free α-tocopherol were significantly greater (P < 0.001) in UV-B-irradiated animals that received daily topical α-tocopheryl acetate treatments than in non-UV-Birradiated animals. These results suggest that UV-B irradiation enhances both the absorption of α-tocopheryl acetate and its bioconversion to free α-tocopherol.     

Gel-based proteomics reveals potential novel protein markers of ozone stress in leaves of cultivated bean and maize species of Panama

We examined responses of cultivated bean (Phaseolus vulgaris L. cv. IDIAP R-3) and maize (Zea mays L. cv. Guarare 8128) plants exposed to ozone (O(3)) using a leaf injury assessment and proteomics approach. Plants grown for 16 days in greenhouse were transferred to an O(3) chamber and exposed continuously to 0.2 ppm O(3) or filtered pollutant-free air for up to 72 h. CBB-stained gels revealed changes in ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) protein. By Western analysis changes in marker proteins for O(3) damage in leaves by 1-DE were checked. In bean leaves, two superoxide dismutase (SOD) protein (19 and 20 kDa) were dramatically decreased, while ascorbate peroxidase (APX, 25 kDa), small heat shock protein (HSP, 33 kDa), and a naringenin-7-O-methyltransferase (NOMT, 42 kDa) were increased by O(3). In maize leaves, expression levels of catalase (increased), SOD (decreased), and APX (increased) were drastically changed by O(3) depending on the leaf stage, whereas crossreacting HSPs (24 and 30 kDa) and NOMT (41 kDa) proteins were strongly increased in O(3)-stressed younger leaves. These results indicated a clear modulation of oxidative stress-, heat shock-, and secondary metabolism-related proteins by O(3). Finally, 2-DE at 72 h after O(3) exposure revealed changes (induction/suppression) in expression levels of 25 and 12 protein spots in bean and maize leaves, respectively. Out of these, ten and nine nonredundant proteins in bean and maize, respectively, were identified by MS. A novel pathogenesis-related protein 2 may serve as a potential marker for O(3) stress in bean.     

Ultraviolet-B radiation causes an upregulation of survivin in human keratinocytes and mouse skin

Understanding of the mechanism of ultraviolet (UV)-mediated cutaneous damages is far from complete. The cancer-specific expression of Survivin, a member of the inhibitor of apoptosis family of proteins, coupled with its importance in inhibiting cell death and in regulating cell division, makes it a target for cancer treatment. This study was designed to investigate the modulation of Survivin during UV response, both in vitro and in vivo. We used UV-B-mediated damages in normal human epidermal keratinocytes (NHEK) cells as an in vitro model and SKH-1 hairless mouse model for the in vivo studies. For in vitro studies, NHEK were treated with UV-B and samples were processed at 5, 15, 30 min, 1, 3, 6, 12 and 24 h after treatment. Our data demonstrated that UV-B exposure (50 mJ/cm2) to NHEK resulted in a significant upregulation in Survivin messenger RNA (mRNA) and protein levels. We also observed that UV-B exposure to NHEK resulted in significant (1) decrease in Smac/DIABLO and (2) increase in p53. For in vivo studies, the SKH-1 hairless mice were subjected to a single exposure of UV-B (180 mJ/cm2), and samples were processed at 3, 6, 12 and 24 h after UV-B exposure. UV-B treatment resulted in a significant increase in protein or mRNA levels (or both) of Survivin, phospho-Survivin and p53 and a concomitant decrease in Smac/DIABLO in mouse skin. This study demonstrated, for the first time, the involvement of Survivin (and the associated events) in UV-B response in vitro and in vivo in experimental models regarded to have relevance to human situations.     

The burial of solvent-accessible surface area is a predictor of polypeptide folding and misfolding as a function of chain elongation

The hydrophobic effect is a major driving force in all chemical and biological events involving chain collapse in aqueous solution. Here, we show that the burial of nonpolar solvent-accessible surface area (NSASA) is a powerful criterion to predict the folding and misfolding behavior of small single-domain proteins as a function of chain elongation. This bears fundamental implications for co- and post-translational protein folding in the cell and for understanding the interplay between noncovalent interactions and formation of native-like structure and topology. Comparison between the fraction of NSASA in fully unfolded and folded elongating chains shows that efficient burial of nonpolar surface area is preferentially achieved only when the polypeptide chain is almost complete. This effect has no preferential vectorial character in that it is present upon elongation from both the N and C termini. For incomplete chains that do not have the ability to fold and bury nonpolar surface intramolecularly, the overall hydrophobic nature of the polypeptide chain (expressed as FBA, i.e., fractional buried surface area per residue) dictates the tendency toward misfolding and self-association. N-terminal chains characterized by FBA exceeding 0.73 are likely to misfold and aggregate, if unable to fold intramolecularly.     

HDAC6 inhibitor loaded bimetallene nanosheets with antagonizing thermoresistance for augmented mild photothermal therapy

Photothermal therapy(PTT) induces thermoresistance through cellular heat shock response, which impairs the therapeutic efficacy of the PTT. To resolve this problem, we developed a photothermal theranostics(denoted as PMH), which integrated the photothermal conversion agent of PdMo bimetallene with histone deacetylase 6(HDAC6) selected inhibitor(ACY-1215), showing the synergistic antitumor effect both in vitro and in vivo. Mechanistically, under the photoacoustic imaging(PA) navigation, the relea...     

Structural and Docking Studies of a Nucleoside Diphosphate Kinase 1 (CsNDPK1) from Tea [Camellia sinensis (L.) O. Kuntze]

Nucleoside diphosphate kinase (NDPK, EC 2.7.4.6) is a housekeeping gene, which functions in the general homeostasis of cellular nucleoside triphosphate (NTP) pools. Among the various NDPK isoforms, cytosolic NDPK1 has been shown to be the main NDPK isoform in plants, accounting for more than 70?% of total NDPK activity in plants. For the first time, a full-length cDNA (697?bp), designated as CsNDPK1 was cloned from tea leaves and consisted of a 448-bp open reading frame (ORF) encoding a 147-amino-acid polypeptide with calculated molecular mass of 16.1?kDa and a pI of 6.3. Homology modeling of CsNDPK1 shows that the presented tea NDPK1 also contains several motifs, binding and catalytic sites which are highly conserved among other NDPKs. Docking studies of CsNDPK1 with its substrates (NTPs) are discussed in detail. In summary, we describe a reliable model of CsNDPK1 that can be used in structure-based protein?Cprotein interaction studies for identifying its potential role in intracellular communication and its physiological significance in tea.     

Chemical synthesis and enzymatic assembly of fragments of the DNA coding immunodominant epitopes of human immunodeficiency virus

More than twenty 13- to 55-membered oligo(poly)nucleotides have been synthesized by the H-phosphonate solid-phase method in the manual variant using an original procedure. From the oligonucleotides obtained, seven DNA duplexes coding immunodominant epitopes of HIV-1 proteins have been formed: 598–609 and 737–748 gp41, 91–115 and 105–115 gag, and 940–951 pol and a number of its mutants. The ligase assembly and polymerization of the DNA duplexes obtained has been carried out. The efficiency of ligation amounted to from 60 to 90%. The possibility of their directed polymerization was determined by the flanking of the duplexes by partially completed half-sites of restrictases BamHI and XhoI. Abbreviations adopted: HIV-1 — human immunodeficiency virus, type 1; (+)-chain — the coding chain — and (−)-chain the chain complementary to the coding chain of the DNA duplex; CPG — controlled-pore glass; PAAG — polyacrylamide gel; Py — pyridine.     

Altitudinal Variation of Metabolites,Mineral Elements and Antioxidant Activities of Rhodiola crenulata (Hook.f. & Thomson) H.Ohba

Rhodiolacrenulata (Hook.f. & Thomson) H.Ohba is an alpine medicinal plant that can survive in extreme high altitude environments. However, its changes to extreme high altitude are not yet clear. In this study, the response of Rhodiola crenulata to differences in altitude gradients was investigated through chemical, ICP-MS and metabolomic methods. A targeted study of Rhodiola crenulata growing at three vertical altitudes revealed that the contents of seven elements Ca, Sr, B, Mn, Ni, Cu, and Cd, the phenolic components, the ascorbic acid, the ascorbic acid/dehydroascorbate ratio, and the antioxidant capacity were positively correlated with altitude, while the opposite was true for total ascorbic acid content. Furthermore, 1165 metabolites were identified: flavonoids (200), gallic acids (30), phenylpropanoids (237), amino acids (100), free fatty acids and glycerides (56), nucleotides (60), as well as other metabolites (482). The differential metabolite and biomarker analyses suggested that, with an increasing altitude: (1) the shikimic acid-phenylalanine-phenylpropanoids-flavonoids pathway was enhanced, with phenylpropanoids upregulating biomarkers much more than flavonoids; phenylpropanes and phenylmethanes upregulated, and phenylethanes downregulated; the upregulation of quercetin was especially significant in flavonoids; upregulation of condensed tannins and downregulation of hydrolyzed tannins; upregulation of shikimic acids and amino acids including phenylalanine. (2) significant upregulation of free fatty acids and downregulation of glycerides; and (3) upregulation of adenosine phosphates. Our findings provide new insights on the responses of Rhodiola crenulata to extreme high altitude adversity.     

Mathematical analysis and numerical simulations for the HSP70 synthesis model

The heat shock proteins (HSPs) protect the other proteins in the process of folding under stressful conditions such as oxygen deprivation, hypothermy or presence of alcohol. They have also an important role in tumour invasion. In this paper, the existence, uniqueness and permanence properties for the solution of the mathematical model which focuses on the synthesis of HSP70 is proved. Moreover the numerical simulations are performed by using FDM, namely a combination of backward and forward Euler methods, and the results confirm the expected behaviour of the solution.     

Regulation of macrophage-specific gene expression by degenerated lipoproteins

The effect of aggregated low-density lipoprotein (agLDL) on cell viability and macrophage-specific gene expression using human peripheral blood monocytes in culture was investigated. AgLDL suppressed activation-induced cell death of phorbol ester-treated macrophages. The inhibition of apoptosis was accompanied by downregulation of apoptosis-promoting proteases, including interleukin-1beta-converting enzyme (ICE) and CPP32 and upregulation of anti-apoptotic cytokine (interleukin-1beta (IL-1beta)). In contrast, macrophage-colony stimulating factor (M-CSF) enhanced cell death of lipid-bearing macrophages, suggesting that the anti-atherogenic action of M-CSF is at least in part mediated through apoptotic elimination of macrophages. Then, we attempted to isolate the genes specifically induced by agLDL in macrophages using a subtraction-based cloning strategy. One of the genes isolated, termed LIG (LDL-inducible gene), encodes a human homolog of E2 ubiquitin-conjugating enzyme. Ubiquitination of multiple intracellular proteins was observed in agLDL-treated macrophages, which coincided with upregulation of LIG. These results suggest that LIG acts as a direct mediator of foam cell formation through polyubiquitination and subsequent degradation of cellular proteins with apoptosis-inducing properties. The regulation of apoptosis by macrophage-specific gene expression may contribute to foam cell formation and atherosclerosis.     

Purification of the 90 kDa heat shock protein (hsp90) and simultaneous purification of hsp70/hsc70, hsp90 and hsp96 from mammalian tissues and cells using thiophilic interaction chromatography

Heat shock proteins (HSPs) hsp70/hsc70, hsp90 and hsp96 were separated from mammalian cells and tissues on a gel obtained by the reaction of β‐mercaptoethanol with divinyl sulfone‐activated Sepharose CL‐6B (thiophilic gel or T‐gel). Hsp90 revealed a much higher affinity towards the T‐gel than the other HSPs. One‐step thiophilic interaction chromatography of proteins resulted in a more than 80% purity and 85% yield of hsp90. Based on this observation, a simple and efficient method for the purification of hsp90 and a procedure for the simultaneous purification of several HSPs (hsp70/hsc70, hsp90 and hsp96) using thiophilic interaction chromatography was developed. All the HSPs were recovered with a high yield and purity (90–99%). The results indicated that the thiophilic gel is a highly efficient affinity matrix for the purification of hsp90 and can be used in the protocols of purification of different HSPs from cells and tissues of various animal species. Copyright © 2009 John Wiley & Sons, Ltd.     

Temperature stress tolerance of conifer seedlings after exposure to UV-B radiation

Ground-level UV-B radiation has increased globally due to a thinning stratospheric ozone layer. We estimated the effects of increased UV-B on 10 conifer species grown in chambers in greenhouses with supplemental UV-B. Species were selected from a wide range of geographic locations. Plant material of two ages (germinants, first growing season; seedlings, second season) were exposed to three levels of UV-B from ambient (at Victoria, B.C., Canada) to three times ambient (12 kJ m(-2) d(-1)) for up to four months. Frost hardiness and heat tolerance of shoots were estimated from changes in chlorophyll fluorescence after exposure to test temperatures. There were no significant differences among seed sources from different elevations in their response to temperature stresses. When UV-B increased above the ambient level, three species (interior Douglas-fir, Engelmann spruce, and interior lodgepole pine) increased in frost hardiness and four (grand fir, interior spruce, yellow-cedar, and western redcedar) decreased. Two species (western redcedar and western hemlock) increased in heat tolerance when UV-B increased to the 12 kJ level. The main differences in stress tolerance were between the triple ambient and the other two treatments, not between ambient and double ambient, suggesting that any changes in UV-B would have to be large to elicit physiological changes in conifer seedlings.     

Synthetic lethal screening identifies compounds activating iron-dependent, nonapoptotic cell death in oncogenic-RAS-harboring cancer cells

We screened small molecules to identify two compounds, which we named RSL3 and RSL5, that have increased lethality in the presence of oncogenic RAS. Counter screening with biologically active compounds defined aspects of the mechanism of action for RSL3 and RSL5, such as a nonapoptotic, MEK-dependent, and iron-dependent oxidative cell death. Erastin, a previously reported compound with RAS-selective lethality, showed similar properties. RNA interference experiments targeting voltage-dependent anion channel 3 (VDAC3), a target of erastin, demonstrated that RSL5 is a scaffold that acts through VDACs to activate the observed pathway. RSL3 activated a similar death mechanism but in a VDAC-independent manner. We found that cells transformed with oncogenic RAS have increased iron content relative to their normal cell counterparts through upregulation of transferrin receptor 1 and downregulation of ferritin heavy chain 1 and ferritin light chain.     

Differential expression of molecular chaperones in brain of patients with Down syndrome

Heat shock proteins (HSPs) in their molecular capacity as chaperones have been reported to regulate the apoptotic pathway and also play a critical role in protein conformational diseases such as Alzheimer's disease (AD). As all Down syndrome (DS) brains display AD-like neuropathology, neuronal loss in DS was shown to be mediated by apoptosis. We decided to investigate the expression patterns of HSPs in seven brain regions of adults with DS using two-dimensional polyacrylamide gel electrophoresis (2-DE). Following 2-DE, approximately 120 protein spots were successfully identified by matrix-assisted laser desorption/ionization--mass spectrometry (MALDI-MS) followed by quantification of the identified proteins. We unambiguously identified and quantified nine different chaperone proteins. Accordingly, all but three chaperone proteins did exhibit a significant change in expression. HSP 70 RY, heat shock cognate (HSC) 71 and glucose-regulated protein (GRP) 75 showed a significant decrease (P < 0.05) in DS temporal cortex whereas HSP 70.1 and GRP 78 were significantly increased (P<0.05) in cerebellum. Whilst T-complex 1 (TCP-1) epsilon subunit showed a significant decrease (P< 0.05) in parietal cortex, a similar extent of increase (P<0.05) as that observed in cerebellum was obtained in parietal levels of GRP 78. Alpha-crystallin B, HSP 60 and GRP 94 did not show any detectable changes in expression patterns. This report presents the first approach to quantify nine different chaperones simultaneously at the protein level in different brain regions and provides evidence for aberrant chaperone expression patterns in DS. The relevance of this aberrant expression patterns are discussed in relation to the biochemical and neuropathological abnormalities in DS brain.     

Chemical synthesis and enzymatic assembly of fragments of the DNA coding immunodominant epitopes of human immunodeficiency virus

More than twenty 13- to 55-membered oligo(poly)nucleotides have been synthesized by the H-phosphonate solid-phase method in the manual variant using an original procedure. From the oligonucleotides obtained, seven DNA duplexes coding immunodominant epitopes of HIV-1 proteins have been formed: 598–609 and 737–748 gp41, 91–115 and 105–115 gag, and 940–951 pol and a number of its mutants. The ligase assembly and polymerization of the DNA duplexes obtained has been carried out. The efficiency of ligation amounted to from 60 to 90%. The possibility of their directed polymerization was determined by the flanking of the duplexes by partially completed half-sites of restrictases BamHI and XhoI.Abbreviations adopted: HIV-1 — human immunodeficiency virus, type 1; (+)-chain — the coding chain — and (–)-chain the chain complementary to the coding chain of the DNA duplex; CPG — controlled-pore glass; PAAG — polyacrylamide gel; Py — pyridine.D. I. Ivanovskii Institute of Virology, USSR Academy of Medical Sciences, Moscow. V. A. Engel'gardt Institute of Molecular Biology, USSR Academy of Sciences, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 393–399, May–June, 1990.     

Catalysis of the electrochemical oxygen reduction in room-temperature ionic liquids on a pyrolytic graphite electrode by iron-containing superoxide dismutase

Catalysis of the electrochemical oxygen reduction reaction (ORR) on a pyrolytic graphite electrode (PGE) by iron-containing superoxide dismutase (Fe-SOD) is investigated for the first time using cyclic voltammetry and electrochemical impedance spectroscopy. The study is carried out in three room-temperature ionic liquids (RTILs), namely, 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF₄), 1-propyl-3-methylimidazolium tetrafluoroborate (PMIBF₄), and 1-butyl-3-methylimidazolium tetrafluoroborate (EMIBF₄). The results demonstrate that in EMIBF₄, Fe-SOD exhibits the most satisfactory catalysis for ORR, with the standard rate constant of ORR on bare PGE, k _s, increasing from 3.9 to 5.1 times 10⁻³ cm s⁻¹, while in PMIBF₄ and BMIBF₄ containing Fe-SOD k _s increases from 2.6 to 3.6 and from 1.4 to 2.2 times 10⁻³ cm s⁻¹, respectively. In addition to the increased k _s, adding Fe-SOD renders the formal potential of ORR more positive. To accelerate the electron transfer, multi-walled carbon nanotubes (MWCNTs) are employed to modify PGE, consequently, yielding the dramatically increased peak current and k _s. For MWCNTs-modified PGE in EMIBF₄ free of Fe-SOD, k _s increases from 3.9 to ∼7.1 times 10⁻³ cm s⁻¹. The ORR catalysis by Fe-SOD in the presence of Fe-SOD is also evidenced by the formal-potential shift in the positive direction. With MWCNTs accounting for the larger k _s and Fe-SOD being responsible for the formal-potential shift, the catalysis of ORR is satisfactory. Chronocoulmetry experiments proved that some Fe-SOD could be adsorbed on PGE. After analyzing the results, dismutation of superoxide anion O ₂ ⁻ by Fe-SOD is thought to be the main reason for the formal-potential shift. The different polarity of RTILs is probably partly responsible for different k _s obtained in different RTILs. Basing on an earlier proposition, the catalysis of ORR by MWCNTs in RTILs is discussed. Published in Russian in Elektrokhimiya, 2007, Vol. 43, No. 9, pp. 1137–1146. The text was submitted by the authors in English.