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Photosystem I - based biohybrid photoelectrochemical cells.
Ciesielski PN, Hijazi FM, Scott AM, Faulkner CJ, Beard L, Emmett K, Rosenthal SJ, Cliffel D, Kane Jennings G
(2010) Bioresour Technol 101: 3047-53
MeSH Terms: Biocatalysis, Bioelectric Energy Sources, Electricity, Electrons, Light, Models, Molecular, Photochemistry, Photosystem I Protein Complex, Plants
Show Abstract · Added May 27, 2014
Photosynthesis is the process by which Nature coordinates a tandem of protein complexes of impressive complexity that function to harness staggering amounts of solar energy on a global scale. Advances in biochemistry and nanotechnology have provided tools to isolate and manipulate the individual components of this process, thus opening a door to a new class of highly functional and vastly abundant biological resources. Here we show how one of these components, Photosystem I (PSI), is incorporated into an electrochemical system to yield a stand-alone biohybrid photoelectrochemical cell that converts light energy into electrical energy. The cells make use of a dense multilayer of PSI complexes assembled on the surface of the cathode to produce a photocatalytic effect that generates photocurrent densities of approximately 2 microA/cm(2) at moderate light intensities. We describe the relationship between the current and voltage production of the cells and the photoinduced interactions of PSI complexes with electrochemical mediators, and show that the performance of the present device is limited by diffusional transport of the electrochemical mediators through the electrolyte. These biohybrid devices display remarkable stability, as they remain active in ambient conditions for at least 280 days. Even at bench-scale production, the materials required to fabricate the cells described in this manuscript cost approximately 10 cents per cm(2) of active electrode area.
Copyright 2009 Elsevier Ltd. All rights reserved.
0 Communities
2 Members
0 Resources
9 MeSH Terms
Placement and orientation of individual DNA shapes on lithographically patterned surfaces.
Kershner RJ, Bozano LD, Micheel CM, Hung AM, Fornof AR, Cha JN, Rettner CT, Bersani M, Frommer J, Rothemund PW, Wallraff GM
(2009) Nat Nanotechnol 4: 557-61
MeSH Terms: Biocompatible Materials, Crystallization, DNA, Electrons, Materials Testing, Nanostructures, Nanotechnology, Nucleic Acid Conformation, Oxidation-Reduction, Surface Properties
Show Abstract · Added April 12, 2013
Artificial DNA nanostructures show promise for the organization of functional materials to create nanoelectronic or nano-optical devices. DNA origami, in which a long single strand of DNA is folded into a shape using shorter 'staple strands', can display 6-nm-resolution patterns of binding sites, in principle allowing complex arrangements of carbon nanotubes, silicon nanowires, or quantum dots. However, DNA origami are synthesized in solution and uncontrolled deposition results in random arrangements; this makes it difficult to measure the properties of attached nanodevices or to integrate them with conventionally fabricated microcircuitry. Here we describe the use of electron-beam lithography and dry oxidative etching to create DNA origami-shaped binding sites on technologically useful materials, such as SiO(2) and diamond-like carbon. In buffer with approximately 100 mM MgCl(2), DNA origami bind with high selectivity and good orientation: 70-95% of sites have individual origami aligned with an angular dispersion (+/-1 s.d.) as low as +/-10 degrees (on diamond-like carbon) or +/-20 degrees (on SiO(2)).
0 Communities
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10 MeSH Terms
Interplay of wavelength, fluence and spot-size in free-electron laser ablation of cornea.
Hutson MS, Ivanov B, Jayasinghe A, Adunas G, Xiao Y, Guo M, Kozub J
(2009) Opt Express 17: 9840-50
MeSH Terms: Animals, Computer Simulation, Cornea, Corneal Surgery, Laser, Electrons, In Vitro Techniques, Light, Models, Biological, Radiation Dosage, Scattering, Radiation, Surgery, Computer-Assisted, Swine
Show Abstract · Added May 20, 2014
Infrared free-electron lasers ablate tissue with high efficiency and low collateral damage when tuned to the 6-microm range. This wavelength-dependence has been hypothesized to arise from a multi-step process following differential absorption by tissue water and proteins. Here, we test this hypothesis at wavelengths for which cornea has matching overall absorption, but drastically different differential absorption. We measure etch depth, collateral damage and plume images and find that the hypothesis is not confirmed. We do find larger etch depths for larger spot sizes--an effect that can lead to an apparent wavelength dependence. Plume imaging at several wavelengths and spot sizes suggests that this effect is due to increased post-pulse ablation at larger spots.
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12 MeSH Terms
Electrophilic cyclopentenone neuroprostanes are anti-inflammatory mediators formed from the peroxidation of the omega-3 polyunsaturated fatty acid docosahexaenoic acid.
Musiek ES, Brooks JD, Joo M, Brunoldi E, Porta A, Zanoni G, Vidari G, Blackwell TS, Montine TJ, Milne GL, McLaughlin B, Morrow JD
(2008) J Biol Chem 283: 19927-35
MeSH Terms: Alzheimer Disease, Animals, Cell Line, Cyclooxygenase 2, Cyclopentanes, Docosahexaenoic Acids, Electrons, Humans, I-kappa B Kinase, Inflammation, Lipid Peroxidation, Lipopolysaccharides, Macrophages, Mice, Molecular Structure, NF-kappa B, Nitric Oxide Synthase Type II, Signal Transduction
Show Abstract · Added March 5, 2014
The omega-3 polyunsaturated fatty acid docosahexaenoic acid (DHA) possesses potent anti-inflammatory properties and has shown therapeutic benefit in numerous inflammatory diseases. However, the molecular mechanisms of these anti-inflammatory properties are poorly understood. DHA is highly susceptible to peroxidation, which yields an array of potentially bioactive lipid species. One class of compounds are cyclopentenone neuroprostanes (A(4)/J(4)-NPs), which are highly reactive and similar in structure to anti-inflammatory cyclopentenone prostaglandins. Here we show that a synthetic A(4)/J(4)-NP, 14-A(4)-NP (A(4)-NP), potently suppresses lipopolysaccharideinduced expression of inducible nitric-oxide synthase and cyclooxygenase-2 in macrophages. Furthermore, A(4)-NP blocks lipopolysaccharide-induced NF-kappaB activation via inhibition of Ikappa kinase-mediated phosphorylation of IkappaBalpha. Mutation on Ikappa kinase beta cysteine 179 markedly diminishes the effect of A(4)-NP, suggesting that A(4)-NP acts via thiol modification at this residue. Accordingly, the effects of A(4)-NP are independent of peroxisome proliferator-activated receptor-gamma and are dependent on an intact reactive cyclopentenone ring. Interestingly, free radical-mediated oxidation of DHA greatly enhances its anti-inflammatory potency, an effect that closely parallels the formation of A(4)/J(4)-NPs. Furthermore, chemical reduction or conjugation to glutathione, both of which eliminate the bioactivity of A(4)-NP, also abrogate the anti-inflammatory effects of oxidized DHA. Thus, we have demonstrated that A(4)/J(4)-NPs, formed via the oxidation of DHA, are potent inhibitors of NF-kappaB signaling and may contribute to the anti-inflammatory actions of DHA. These findings have implications for understanding the anti-inflammatory properties of omega-3 fatty acids, and elucidate novel interactions between lipid peroxidation products and inflammation.
2 Communities
3 Members
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18 MeSH Terms
Kinetics of a collagen-like polypeptide fragmentation after mid-IR free-electron laser ablation.
Zavalin A, Hachey DL, Sundaramoorthy M, Banerjee S, Morgan S, Feldman L, Tolk N, Piston DW
(2008) Biophys J 95: 1371-81
MeSH Terms: Collagen, Computer Simulation, Electrons, Infrared Rays, Lasers, Models, Chemical, Models, Molecular, Peptides, Radiation Dosage
Show Abstract · Added March 20, 2014
Tissue ablation with mid-infrared irradiation tuned to collagen vibrational modes results in minimal collateral damage. The hypothesis for this effect includes selective scission of protein molecules and excitation of surrounding water molecules, with the scission process currently favored. In this article, we describe the postablation infrared spectral decay kinetics in a model collagen-like peptide (Pro-Pro-Gly)(10). We find that the decay is exponential with different decay times for other, simpler dipeptides. Furthermore, we find that collagen-like polypeptides, such as (Pro-Pro-Gly)(10), show multiple decay times, indicating multiple scission locations and cross-linking to form longer chain molecules. In combination with data from high-resolution mass spectrometry, we interpret these products to result from the generation of reactive intermediates, such as free radicals, cyanate ions, and isocyanic acid, which can form cross-links and protein adducts. Our results lead to a more complete explanation of the reduced collateral damage resulting from infrared laser irradiation through a mechanism involving cross-linking in which collagen-like molecules form a network of cross-linked fibers.
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9 MeSH Terms
6450 nm wavelength tissue ablation using a nanosecond laser based on difference frequency mixing and stimulated Raman scattering.
Edwards GS, Pearlstein RD, Copeland ML, Hutson MS, Latone K, Spiro A, Pasmanik G
(2007) Opt Lett 32: 1426-8
MeSH Terms: Animals, Brain, Electrons, Equipment Design, Lasers, Optics and Photonics, Oscillometry, Rats, Rats, Sprague-Dawley, Scattering, Radiation, Spectrum Analysis, Raman, Time Factors
Show Abstract · Added May 20, 2014
A four-stage laser system was developed, emitting at a wavelength of 6450 nm with a 3-5 ns pulse duration, < or = 2 mJ pulse energy, and 1/2 Hz pulse repetition rate. The laser system successfully ablated rat brain tissue, where both the collateral damage and the ablation rate compare favorably with that previously observed with a Mark-III Free-Electron Laser.
0 Communities
1 Members
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12 MeSH Terms
Scanning electrochemical microscopy determination of organic soluble MPC electron-transfer rates.
Peterson RR, Cliffel DE
(2006) Langmuir 22: 10307-14
MeSH Terms: Electrochemistry, Electrons, Gold, Kinetics, Membranes, Artificial, Microscopy, Scanning Tunneling, Sensitivity and Specificity, Sulfhydryl Compounds, Surface Properties
Show Abstract · Added January 20, 2015
In this paper, we describe a novel method for measuring the forward heterogeneous electron-transfer rate constant (kf) through the thiol monolayer of gold monolayer protected clusters (MPCs) in solution using scanning electrochemical microscopy (SECM). Applying the equations for mixed mass-transfer and electron-transfer processes, we develop a new formula using only the diffusion coefficient and the tip radius and use it as part of a new method for evaluating SECM approach curves. This method is applied to determine the electron-transfer rates from a series of SECM approach curves for monodisperse hexanethiol MPCs and for polydisperse hexanethiol, octanethiol, decanethiol, dodecanethiol, and 2-phenyethylthiol gold MPCs. Our results show that as the alkanethiol length increases the rate of electron transfer decreases in a manner consistent with the previously proposed tunneling mechanism for the electron transfer in MPCs. However, the effective tunneling coefficient, Beta, is found to be only 0.41 A-1 for alkanethiol passivated MPCs compared to typical values of 1.1 A-1 for alkanethiols as self-assembled monolayers on two-dimensional gold substrates. Similar SECM approach curve results for Pt and Au MPCs indicate that the electron-transfer rate is dependent mostly on the composition of the thiol layer and not on differences in the core metal.
0 Communities
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9 MeSH Terms
Optic nerve sheath fenestration with endoscopic accessory instruments versus the free electron laser (FEL).
Joos KM, Shah RJ, Robinson RD, Shen JH
(2006) Lasers Surg Med 38: 846-51
MeSH Terms: Animals, Electrons, Endoscopes, Equipment Design, Eye, Goats, Laser Therapy, Minimally Invasive Surgical Procedures, Models, Animal, Ophthalmologic Surgical Procedures, Optic Nerve, Surgical Flaps
Show Abstract · Added March 19, 2018
BACKGROUND AND OBJECTIVE - The free electron laser (FEL) can efficiently produce an optic nerve sheath fenestration using an endoscopic approach. To develop a surgical protocol, this study compared effectiveness of available accessory endoscopic instruments to endoscopic FEL delivery effectiveness in producing optic nerve sheath fenestrations.
STUDY DESIGN/MATERIALS AND METHODS - An endoscope was used to perform optic nerve sheath fenestrations on goat optic nerves. Accessory endoscopic instruments and glass-hollow waveguides (250 and 320 microm in diameter) were inserted into the instrument channel for comparison. FEL energy (6.45 microm, 30 Hz) was delivered to the tissue through the waveguides and histological analysis was performed.
RESULTS - The endoscopic instruments alone were unable to incise the optic nerve sheath. The FEL successfully incised the sheath and the biopsy forceps extricated the circular flap.
CONCLUSIONS - Endoscopic optic nerve sheath fenestration using FEL energy followed by biopsy forceps for sheath extrication produced good results, thereby creating a feasible protocol for optic nerve sheath fenestration.
0 Communities
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12 MeSH Terms
RNA-Binding affinities and crystal structure of oligonucleotides containing five-atom amide-based backbone structures.
Pallan PS, von Matt P, Wilds CJ, Altmann KH, Egli M
(2006) Biochemistry 45: 8048-57
MeSH Terms: Amides, Base Sequence, Circular Dichroism, Crystallography, X-Ray, DNA, Dimerization, Electrons, Models, Molecular, Molecular Conformation, Oligonucleotides, RNA, Thermodynamics
Show Abstract · Added March 5, 2014
Among the hundreds of nucleic acid analogues that have been studied over the last two decades only very few exhibit backbones with linkers between residues that are either shorter or longer than the four-atom linker O3'-P-O5'-C5' connecting sugar ring moieties in DNA and RNA. 2'-Deoxyribonucleoside dimers connected by a five-atom linker O3'-CH(CH(3))-CO-NH-CH(2) (*designates a chiral center) were reported to lead to only a slight destabilization of RNA-DNA hybrids in which the DNA strand contained one or several of these amide-linked dimers (De Napoli, L., Iadonisi, A., Montesarchio, D., Varra, M., and Piccialli, G. (1995) Synthesis of thymidine dimers containing a new internucleosidic amide linkage and their incorporation into oligodeoxyribonucleotides, Bioorg. Med. Chem. Lett. 5, 1647-1652). To analyze the influence of various chemistries of such five-atom amide linkers on the RNA-binding affinity of modified DNA strands, we have synthesized five different amide-linked dimers, including structures with homochiral linkers of the type X3'-C*H(CH(3))-CO-NH-CH(2) (X = O, CH(2)) as well as the corresponding analogues carrying methoxy groups at the 2'-position of the 3'-nucleosides. We have conducted a detailed thermodynamic analysis of duplex formation between the modified DNA and RNA, with the DNA strands containing between one and seven consecutive modified dimers. Some of the five-atom-linked dimers lead to significantly higher RNA-binding affinities compared with that of native DNA. Interestingly, the linkers with opposite stereochemistry at the chiral center stabilize duplexes between the modified DNA and RNA to different degrees. CD spectroscopy in solution and a crystal structure of an RNA-DNA duplex with a single amide-linked dimer demonstrate that the longer amide backbones do not disrupt the duplex geometry. These observations provide further evidence that stable cross-pairing between two different types of nucleic acids does not require the numbers of atoms linking their individual residues to match.
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12 MeSH Terms
Regiochemistry of neuroprostanes generated from the peroxidation of docosahexaenoic acid in vitro and in vivo.
Yin H, Musiek ES, Gao L, Porter NA, Morrow JD
(2005) J Biol Chem 280: 26600-11
MeSH Terms: Animals, Arachidonic Acid, Brain, Chromatography, Gas, Chromatography, High Pressure Liquid, Chromatography, Thin Layer, DNA, Docosahexaenoic Acids, Electrons, Gas Chromatography-Mass Spectrometry, In Vitro Techniques, Isoprostanes, Lipid Metabolism, Lipids, Mass Spectrometry, Models, Chemical, Oxidative Stress, Oxygen, Rats, Rats, Sprague-Dawley, Spectrometry, Mass, Electrospray Ionization, Stereoisomerism, Time Factors
Show Abstract · Added May 29, 2014
Isoprostanes (IsoPs) are isomers of prostaglandins that are generated from the free radical-initiated peroxidation of arachidonic acid (C20.4 omega-6). IsoPs exert potent bioactivity and are regarded as the "gold standard" to assess oxidative stress in various human diseases. Analogously, autoxidation of docosahexaenoic acid (DHA, C22.6 omega-3) generates an array of IsoP-like compounds that are termed neuroprostanes (NPs). A major class of NPs identified in vitro and in vivo contains F-type prostane rings and are know as F4-NPs. A number of different F4-NP regioisomers are formed from the peroxidation of DHA. Among the eight possible regioisomeric groups, we hypothesize that 4- and 20-series NPs are generated in greater amounts than other classes because the precursors that lead to regioisomers other than those of the 4- and 20-series can be further oxidized to form novel dioxolane-IsoP-like compounds, analogous to those generated from arachidonate. Various mass spectrometric approaches, including electron capture atmospheric pressure chemical ionization mass spectrometry, were utilized to analyze NPs formed in vitro and in vivo based on their characteristic fragmentation in the gas phase. Experimental results were consistent with our hypothesis that 4- and 20-series NP regioisomers are preferentially generated. The discovery of regioselectivity in the formation of NPs will allow studies of the biological activities of NPs to focus on the more abundantly generated compounds to determine their role in modulating the pathophysiological consequences of DHA oxidation and oxidant stress.
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23 MeSH Terms