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  • 1
    Electronic Resource
    Electronic Resource
    A Molecular Dynamics Model of HIV-1 Reverse Transcriptase Complexed with DNA: Comparison with Experimental Structures (2000)
    Springer
    Journal of molecular modeling 6 (2000), S. 575-586 
    Details
    ISSN: 0948-5023
    Keywords: HIV-1 reverse transcriptase ; Minor groove binding track ; Particle-mesh Ewald
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract We have built a molecular dynamics model for human immunodeficiency virus (HIV-1) reverse transcriptase (RT) complexed with a 19/18-mer template/primer by combining the structural information of a low resolution crystal structure of a HIV-1 RT/DNA complex (1hmi) with that of a high resolution crystal structure of unliganded HIV-1 RT (1rtj). The process involved slow forcing of the α-carbons of 1rtj onto those of 1hmi using constrained MD simulations, while immersing the protein in aqueous solution. A similar technique was used to build the bent all-atom DNA duplex, which was then docked into the modeled protein. The resulting model complex was refined using molecular dynamics simulation with the Particle-mesh Ewald method employed to accommodate long-range electrostatic interactions. New parameters of the Amber force field that affect DNA twist are tested and largely validated. The model has been used successfully to explain the results of vertical scanning mutagenesis of residue 266 (Trp266). Recently, the low resolution crystal structure of the HIV-1 RT/DNA complex has been refined to a 2.8 Å resolution (2hmi) and a crystal structure of a HIV-1/RT/dTTP ternary complex has been determined at 3.2 Å resolution (1rtd). A detailed structural comparison of the prior model structure and the two experimental structures becomes possible. Overall, the three structures share many similarities. The root mean square deviations of the α-carbons for the individual subdomains among the three structures are within the same ranges. The secondary structure assignments in the three structures are nearly identical. Key protein-DNA contacts such as those in the region of the primer grip are also similar in the three structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s0089400060575
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  • 2
    Electronic Resource
    Electronic Resource
    A minor groove binding track in reverse transcriptase (1997)
    [s.l.] : Nature Publishing Group
    Nature structural biology 4 (1997), S. 194-197 
    Details
    ISSN: 1072-8368
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] Proteins that bind with high affinity to specific DNA sequences often do so through hydrogen bonding and electrostatic interactions between the DNA major groove and defined protein structural elements, such as helix-turn-helix motifs, β-ribbon recognition elements and Zn-binding domains1. ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nsb0397-194
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  • 3
    Electronic Resource
    Electronic Resource
    Evidence for Veratryl Alcohol as a Redox Mediator in Lignin Peroxidase-Catalyzed Oxidation (1995)
    s.l. : American Chemical Society
    Biochemistry 34 (1995), S. 5060-5065 
    Details
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/bi00015a017
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  • 4
    Electronic Resource
    Electronic Resource
    Evolution of the dielectric breakdown in Co/Al2O3/Co junctions by annealing (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 586-589 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The temperature and dielectric stability of magnetic tunnel junctions are important requirements for magnetic memory devices and their integration in the semiconductor process technology. We have investigated the changes of the tunneling magnetoresistance (TMR), the barrier properties (height, thickness, and asymmetry) and the dielectric stability upon isochronal annealing up to 410 °C in Co/Al2O3/Co junctions with an artificial antiferromagnet as a pinning layer. Besides a small decrease of the TMR signal after annealing up to 230 °C, a strong decrease between 300 and 350 °C is found. According to Auger and transmission electron microscopy investigations, this decrease is mainly due to interdiffusion of the metallic layers. The dielectric breakdown is characterized by voltage ramp experiments. The size-averaged breakdown voltage improves from 1.35 V for the as prepared junctions to 1.55 V by annealing at 300 °C. At higher temperatures the breakdown voltage decreases strongly to 0.8 V (at 380 °C). Simultaneously, the typical breakdown process changes from few sudden current jumps to a large number of small steps. The breakdown properties are discussed within a statistical model and related to structural changes of the barrier. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1329352
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  • 5
    Electronic Resource
    Electronic Resource
    Novel cathode for field-emission applications (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 2528-2532 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A CsI salt-based cathode which is capable of producing a modest perveance, 10 s of A/cm2 electron beam for several microseconds pulse lengths, and has little susceptibility to diode closure has been experimentally characterized. This explosive field-emission CsI-coated carbon fiber cathode has operated in modest 10−5 Torr vacuums at voltages up to 160 kV, and can easily be configured to provide space-charge-limited solid or annular electron beams in arbitrarily large diameter configurations. The CsI cathode has demonstrated negligible closure for 2 μs pulses, and has operated for 200 shots with no degradation in cathode performance. Data on the operating performance of this salt cathode, including effective gap time history and streak photographs demonstrating uniformity of the current density, are presented. A comparison of CsI cathode performance with a velvet explosive field emitting cathode used in electron-beam production is also presented. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146504
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  • 6
    Electronic Resource
    Electronic Resource
    Efficient, compact power supply for repetitively pulsed, "triggerless" cathodic arcs (1999)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 4532-4535 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A power supply for "triggerless," repetitively pulsed cathodic arcs has been developed. It is based on a thyristor-switched, high-voltage, high-current, pulse-forming network (PFN). It can provide high pulsed currents (up to 2 kA), with duration of 600 μs, and pulse repetition rate of up to 10 Hz. Higher repetition rates are possible at lower current. The rectangular pulse shape and amplitude are reproducible to within a few percent. Cathodic arc initiation is extremely reliable because the charging voltage is much higher than the minimum starting voltage for the triggerless arc initiation method. The energy utilization efficiency is very high by intentionally mismatching load and PFN impedances and by using an efficiency-enhancing diode; the stored energy is dissipated primarily in the arc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1150106
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  • 7
    Electronic Resource
    Electronic Resource
    048
Retroviral Delivery of A Dominant Negative TGF-beta Receptor II Mitigates Scar in a Rabbit Model of Scar Hypertrophy (2004)
    Oxford, UK; Malden, USA : Blackwell Science Ltd/Inc.
    Wound repair and regeneration 12 (2004), S. 0 
    Details
    ISSN: 1524-475X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Effective blockade of the pluripotent cytokine TGF-beta as a means of cutaneous scar reduction is a strategy with great potential. This desired effect may be achieved through the overexpression of mutant TGF beta receptors within the wound milieu. Our goal was to examine the effects of dominant negative mutant TGF-beta receptor II (dnTGFRII) protein expression in a well-established rabbit ear model of hypertrophic scarring. Serial injections of a retroviral construct encoding a truncated TGFβRII and the marker green fusion protein (pMSCV-rIIdn-GFP) were performed in 7mm punch wounds at day 10 and day 14 (two-day injection group) or day 8, 10, 12 (three-day injection group) post wounding. Delivery of a null vector (pMSCV-GFP) at the same time points served as a negative control. Histomorphometric analysis of wounds harvested at day 28 revealed a statistically significant reduction (33%) in the scar elevation index in 2-day treated and a more modest reduction in SEI (17.5%) in the 3-day treated arm compared to null-treated controls. Confocal microscopy confirmed stable transfection of the construct in both peri-wound tissue as well as rabbit dermal fibroblasts transfected in vitro. Optimization of this novel application in retroviral gene therapy could lead to effective anti-scarring strategies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1067-1927.2004.0abstractau.x
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  • 8
    Electronic Resource
    Electronic Resource
    041
Aged Rats Display Increased Ischemia-Reperfusion Skin Injury in the in vivo Magnet Model (2004)
    Oxford, UK; Malden, USA : Blackwell Science Ltd/Inc.
    Wound repair and regeneration 12 (2004), S. 0 
    Details
    ISSN: 1524-475X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Introduction: Ischemia-reperfusion (IR) injury is commonly associated with numerous pathologies including pressure sores, venous stasis ulcers, and lower extremity diabetic ulcers. The purpose of this study is to further investigate the relationship between age and ischemia-reperfusion skin injury in a rat model utilizing magnets for the purpose of injury creation.
Methods: Magnets were designed for subcutaneous placement and calibrated such that a second magnet placed externally over them would cause compression that exceeds capillary perfusion pressure (ischemia). Removing the external magnet results in reperfusion of the skin. After placing subcutaneous magnets in aged and young Fisher 344 rats, repeated cycles of external magnet placement and removal were performed. 
Results: Visual analysis of the skin revealed statistically significant greater areas of injury in the aged rats relative to their younger counterparts (37.4 ± 13.3% vs. 24.1 ± 14.8%, P 〈 .02)
Conclusions: Aged rats demonstrate an increased degree of injury relative to their younger counterparts in response to ischemia-reperfusion injury. Future studies will attempt to delineate differences in the markers of IR injury (such as myeloperoxidase and vitamin E levels) in aged versus young rats, giving insight to the mechanisms responsible for the impaired wound healing seen in the elderly.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1067-1927.2004.0abstractan.x
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  • 9
    Electronic Resource
    Electronic Resource
    045
Adenoviral HTERT Transfection Results in Altered Phospho-erk Activity in Human Dermal Fibroblasts (2004)
    Oxford, UK; Malden, USA : Blackwell Science Ltd/Inc.
    Wound repair and regeneration 12 (2004), S. 0 
    Details
    ISSN: 1524-475X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Introduction: Telomeres are nucleoprotein structures at the ends of each chromosome. Due to the inability of DNA polymerase to replicate the full length of the chromosome, up to 50–200 base pairs of the telomere are lost during each successive round of cell division. In adult human somatic cells, telomerase is not active resulting in progressive loss of telomere length and entry into replicative senescence as observed in cell culture. hTERT is the catalytic subunit of telomerase, an enzyme which maintains telomere length. Transfection of human dermal fibroblasts (HDFs) by hTERT has been shown to reverse the senescent phenotype seen in aging HDFs in vitro. ERK (p44/42) is a MAP kinase which functions as a critical intermediary in the determination of cell growth and differentiation. Activation of ERK occurs through phosphorylation of threonine and tyrosine residues. 
Methods: In order to delineate some of the cellular mechanisms by which hTERT functions, we treated adenoviral hTERT (Ad-hTERT) transfected HDFs with TGFB1, and assayed phosphorylated ERK activity by Western blotting.
Results: Ad-hTERT treated HDFs demonstrated a 2–3 fold increase in phospho-ERK activity. In addition, our preliminary findings show that Ad-hTERT transfected HDFs have increased TGFB1, TGFB1-Receptor I and II, and COL1A1 gene expression by real-time rtPCR. 
Conclusions: Increased phosphor-ERK activity as well as increased TGFB1, TGFB1-Receptor I and II, and COL1A1 gene expression is seen in hTERT transfected HDF’s. Further studies will focus on defining other intermediary changes resulting from Ad-hTERT tranfection.Funding source: Geron Corporation
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1067-1927.2004.0abstractar.x
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  • 10
    Electronic Resource
    Electronic Resource
    106
Lentivirus and Adeno-Associated Virus Mediated Targeted Gene Transfection in Low-Oxygen Environment (2004)
    Oxford, UK; Malden, USA : Blackwell Science Ltd/Inc.
    Wound repair and regeneration 12 (2004), S. 0 
    Details
    ISSN: 1524-475X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: A critical limitation of using retroviral vectors for gene therapy is their inability to infect non-dividing cells. Although, the adenoviral vectors have the advantage of being able to infect both dividing and non-dividing cells, they elicit inflammatory response, thus making the interpretation of in vivo experiments harder. Adeno-associated virus (AAV) and Lentiviral vectors do not have those limitations, however, scant information is available about their transfection efficiency under low-oxygen tension. To determine if low-oxygen microenvironment affects viral vector-mediated gene transfection, we have used two other viral vectors, Adeno-associated virus (AAV) and Lentiviral constructs in vitro and in vivo to express foreign genes in hypoxic cultured human dermal fibroblasts and ischemic rat wounds. Both cultured normoxic and hypoxic (1% O2) human dermal fibroblasts were identically transfected by the AAV vector. A lenti6-LacZ construct was injected onto the periphery of rat ischemic and non-ischemic wound (106 pfu/wound) at the time of wounding. Wounds were harvested at post-operative day 7. Frozen sections of the wounds were fixed in cold acetone and stained with a in situ β-gal staining kit. Intense expression of β-gal was observed without any inflammatory response. No significant difference of transfection efficiency was observed between the ischemic and non-ischemic wounds. Thus our data indicates that both AAV and Lentiviral vectors are suitable to use in gene-therapy experiments in both ischemic and non-ischemic cells and tissues in vitro and in vivo.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1067-1927.2004.0abstractcz.x
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