bluuebunny/crossref_metadata_2025 huggingface dataset:
High-mobility amorphous In2O3–10wt%ZnO thin film transistors
Authors: Yaglioglu B. , Yeom H. Y. , Beresford R. , Paine D. C.
Published: August 2006

The authors report on the fabrication and characterization of thin film transistors that use sputter deposited amorphous indium zinc oxide both for the channel and source-drain metallizations in a gate-down configuration. The channel and source-drain layers were deposited from a single In2O3–10wt%ZnO ceramic target using dc magnetron sputtering onto an unheated substrate. The carrier densities in the channel (2.1×1017∕cm3) and source/drain regions (3.3×1020∕cm3) were adjusted by changing the reactive oxygen content in the sputter chamber during deposition. The resulting transistors operate as depletion mode n-channel field effect devices with saturation mobility of 20cm2∕Vs and on/off current ratio of 108.
Heat capacity and phonon mean free path of wurtzite GaN
Authors: Danilchenko B. A. , Paszkiewicz T. , Wolski S. , Jeżowski A. , Plackowski T.
Published: August 2006

The authors report lattice specific heat of bulk hexagonal GaN measured by the heat flow method in the temperature range of 20–300K and by the adiabatic method in the range of 5–70K. The best fit with the accuracy of 3% was obtained for the temperature-independent Debye temperature ΘD=365K and Einstein temperature ΘE=880K. The authors relate these temperatures to the function of density of states. Using their results for heat conduction coefficient, they established in the temperature range of 10–100K the explicit dependence of the phonon mean free path on temperature ℓph∝T−2. Above 100K, there is an evidence of contribution of the Umklapp processes, which limits phonon free path at high temperatures.
Sol-gel synthesis and nonlinear optical transmission in Zn(1−x)Mg(x)O (x⩽0.2) thin films
Authors: Suchand Sandeep C. S. , Philip Reji , Satheeshkumar R. , Kumar V.
Published: August 2006

Nanocrystalline Zn1−xMgxO thin films with an average particle diameter of 60nm have been deposited on glass substrates using a sol-gel spin-coating technique. Within the range of compositions, 0⩽x⩽0.20, the optical band gap could be tuned between 3.40 and 3.83eV. The nonlinear optical transmission in the visible spectral region is investigated using ultrafast (100fs) and short (7ns) laser pulses at off-resonant wavelengths. The observed nonlinearity is strong and is comparable to that recently obtained in ZnO nanocomposite layers ion-implanted with Cu+ ions.
Nitrogen related vacancies in GaAs based quantum well superlattices
Authors: Slotte J. , Saarinen K. , Pavelescu E.-M. , Hakkarainen T. , Pessa M.
Published: August 2006

The authors report on the influence of nitrogen incorporation on vacancies in GaAs based superlattices. The samples were molecular beam epitaxy grown on p-type GaAs substrates with the superlattice structure consisting of ten periods of quantum well material separated by GaAs buffers. Three different quantum well compositions were used, Ga0.63In0.37As, Ga0.63In0.37N0.01As0.99, and GaN0.01As0.99. Rapid thermal anneals were performed on each sample set. Positron spectroscopy was used for vacancy detection in the superlattice structure. Annealed GaNAs and GaInNAs superlattice samples were found to contain vacancy-type defects. A comparison with photoluminescence measurements shows that the detected vacancy-type defects are not optically active.
Anisotropic ferro- and piezoelectric properties of sol-gel-grown Bi3.15Nd0.85Ti3O12 films with two different orientations on Pt∕Ti∕SiO2∕Si
Authors: Lu C. J. , Liu X. L. , Chen X. Q. , Nie C. J. , Le Rhun Gwenael , Senz Stephan , Hesse Dietrich
Published: August 2006

Bi 3.15 Nd 0.85 Ti 3 O 12 thin films of two different preferred orientations were sol-gel grown on Pt∕Ti∕SiO2∕Si. Using different heating rates during crystallization, either films containing 65% columnar grains with (104)∕(014) orientation or fine-grained films with a predominant c-axis orientation were obtained. Anisotropic ferroelectric and piezoelectric properties were determined, with a remanent polarization 2Pr=46.4μC∕cm2 and a piezoelectric coefficient d33=17pm∕V in a predominantly (104)∕(014)-oriented film, but only 2Pr=16.7μC∕cm2 and d33=5pm∕V in a predominantly c-axis-oriented film. These values confirm that the polarization vector of this material is close to the crystallographic a axis.
Electrostatic charge distribution on single-walled carbon nanotubes
Authors: Li Chunyu , Chou Tsu-Wei
Published: August 2006

This letter reports a study of charge distribution on single-walled carbon nanotubes. An atomistic moment method is proposed based on classical electrostatics theory and the results of analysis are compared with those obtained from ab initio approach. It is shown that the classical electrostatics is applicable to solving electric problems of nanostructures and the present method is computationally efficient. The effect of tube length, tube diameter, and tube position on nanotube electrostatic charge distributions has also been examined.
Hydrogen-nitrogen complexes in dilute nitride alloys: Origin of the compressive lattice strain
Authors: Bisognin G. , De Salvador D. , Drigo A. V. , Napolitani E. , Sambo A. , Berti M. , Polimeni A. , Felici M. , Capizzi M. , Güngerich M. , Klar P. J. , Bais G. , Jabeen F. , Piccin M. , Rubini S. , Martelli F. , Franciosi A.
Published: August 2006

Hydrogenation of GaAs1−xNx and GaP1−xNx epilayers grown on GaAs(001) and GaP(001) surfaces, respectively, is known to passivate the electronic activity of nitrogen through the formation of specific nitrogen-hydrogen complexes. The same epilayers also undergo a strain reversal from tensile (as grown) to compressive (fully hydrogenated). The authors show that the extent of strain reversal is determined exclusively by the nitrogen concentration. By performing in situ high resolution x-ray diffraction measurements during annealing and photoluminescence studies, the authors demonstrate that the lattice properties of fully hydrogenated GaAs1−xNx are ruled by a H complex, which is different and less stable than that responsible for electronic passivation of nitrogen in GaAs1−xNx.
Signal-to-noise ratio improvement of photon counting using wavelength modulation spectroscopy
Authors: Huang Tao , Dong Shuangli , Guo Xujin , Xiao Liantuan , Jia Suotang
Published: August 2006

Photon counting has been widely used in weak light detection. However, the low signal-to-noise ratio (N, N is the mean counts) significantly limits the detection sensitivity. In this letter, we present a method that uses wavelength modulation spectroscopy to improve the signal-to-noise ratio of photon counting. Five times improvement of signal-to-noise ratio in 1Hz bandwidth at best has been obtained in 2f harmonic detection.
Field induced photoluminescence quenching and enhancement of CdSe nanocrystals embedded in SiO2
Authors: Achtstein A. W. , Karl H. , Stritzker B.
Published: August 2006

The authors describe the operation of an electro-optical photoluminescence quenching device based on CdSe nanoclusters formed using sequential ion implantation of Cd+ and Se+ in thermally grown SiO2 on silicon. A sample geometry consisting of a semitransparent gold electrode on top and an ohmic contact to the p-doped Si on the reverse side of the device was chosen to apply high electric fields. Under high field strength an effective photoluminescence quenching and enhancement with a dynamical range of more than one order in magnitude have been observed. Field induced Stark shift has not been seen most probably due to polarization effects.
X-ray absorption of Zn1−xCoxO thin films: A local structure study
Authors: Martínez-Criado G. , Segura A. , Sans J. A. , Homs A. , Pellicer-Porres J. , Susini J.
Published: August 2006

In this study, the application of synchrotron radiation microprobe to the analysis of Co incorporation in Zn1−xCoxO is reported. From the Co and Zn fluorescence line intensity ratio, the Co concentrations were deduced. A combination of fluorescence mapping with x-ray absorption spectroscopic techniques made possible to examine not only the uniform elemental distribution but also the short range structural order with the Co content. In Zn1−xCoxO films grown by pulsed laser depositions the Co atoms are in tetrahedral site configuration, corresponding to a substitutional site in wurtzite structure. Within the experimental accuracy, no significant bond length deviation from the pure ZnO structure was observed in the considered compositional range.
Characterization and hydrogen storage properties of Pt–C60 compound
Authors: Wang X. L. , Tu J. P.
Published: August 2006

Platinum fulleride (Pt–C60) compound was synthesized by a chemical method. The Pt–C60 compound was amorphous according to x-ray diffraction results. X-ray photoelectron spectroscopy and Raman spectroscopy results indicated that there existed charge transfer from Pt to C60. The total hydrogen absorption amount of the compound is about 1.6wt%, but the work temperature is relatively high. The hydrogen storage properties of Pt–C60 compound are related to the valence electron dispersion of Pt.
High slew rate, ultrastable direct-coupled readout for dc superconducting quantum interference devices
Authors: Oukhanski Nikolai , Stolz Ronny , Meyer Hans-Georg
Published: August 2006

A very fast and thermostable readout electronics for dc superconducting quantum interference devices (SQUIDs) is presented. The authors have applied a concept which gives them the opportunity to combine several, at first sight contradictory, important parameters for the SQUID system user. With their flux-locked-loop electronics they could reach more than 16MΦ0∕s slew rate while using a 1.3m cable between the electronics and a conventional low transition temperature SQUID (with a maximum peak-peak voltage of the flux-to-voltage transfer function of ⩾63μV). By making use of thermocurrent compensation in the first stage of the amplifier they have achieved a thermal drift of about 5nV∕K for a temperature range between 0 and 65°C. The system demonstrated a white noise voltage level of ∼0.32nV∕Hz1∕2, with a flicker noise corner frequency of about 0.1Hz.
Energy transfer between colloidal semiconductor nanocrystals in an optical microcavity
Authors: Guo Li , Krauss Todd D. , Poitras Carl B. , Lipson Michal , Teng Xiaowei , Yang Hong
Published: August 2006

The authors have studied nonradiative energy transfer between semiconductor nanocrystals (NCs) placed in a Fabry-Pérot microcavity. The spectrally integrated fluorescence from a monolayer of single sized NCs in the cavity is enhanced by a factor of 4.8 compared to free space. For a monolayer of mixed sized NCs, the acceptor NC fluorescence intensity is enhanced by an additional factor of 2.7 due to energy transfer processes. When the cavity mode is resonant with the acceptor NC fluorescence emission maximum, donor NC emission is completely suppressed, providing a narrow spectral output.
Unstable Electrochemical Flows in a Pore System
Authors: Moore BD , McKillen MN , Dorst W , Prins H
Published: August 2006

Starting from the
Navier-Stokes and Nernst-Planck equations, an explanation is proposed for the
so-called pressure-volume flow limit cycle which can be observed when a polymer
filter of weak ion-exchange capacity is subjected to both an electrochemical and
pressure gradient. It is indicated that the streaming current cannot be
neglected in cases of unstable flow, whereas it may be left out of
consideration for stationary regimes. The source of oscillation is shown to
arise from non-linearity in the Maxwell pressure tensor. Although not including
inertial forces, the present treatment seems satisfactory as a first approach,
if boundary conditions are carefully evaluated.
Oxygen Reduction on Sodium Tungsten Bronze Electrodes and the Effects of Adsorbed Platinum
Authors: Fredlein RA
Published: August 2006

The Tafel slopes for oxygen
reduction on sodium tungsten bronze electrodes are changed from -4RT/F to -2RT/F
by adsorption of platinum from solution. Adsorbed platinum reduces the time to
attain steady-state conditions but does not catalyse the reaction. Photo-excitation
experiments show that the flat band potential is a function of CH+.
Results are interpreted in terms of a thin surface layer of low donor density
which is non-degenerate in the potential range of oxygen reduction. It is shown
that, without adsorbed platinum, changes in the equilibrium potential
difference across the surface layer equal those across the Helmholtz layer due
to the presence of hydrogen donors in the lattice and results in -4RT/F Tafel
slopes. It is proposed that adsorbed platinum forms surface states pinning the
Fermi level at the surface and causing changes in the potential difference to
occur entirely across the Helmholtz layer; this results in -2RT/F slopes.
Some Metal-Ion Complexes with Ligands Formed by Reactions of Amines with Aliphatic Carbonyl Compounds. VII. Copper(II) Compounds of Some β-Imino Amines, Formed by Reaction of Copper(II) Chelate Amine Complexes with 4-Amino-4-methylpentan-2-one
Authors: Morgan KR , Martin JWL , Curtis NF
Published: August 2006

Compounds of copper(II)
with chelated β-imino amines are formed by
reaction between 4-amino-4-methylpentan-Zone (amp) and copper(II) complexes of
ethane-1,2-diamine, propane-1,2- and -1,3-diamine,
meso-l,2-diphenylethane-l,2-diamine, 2-(2-aminoethyl)pyridine,
3-azapentane-1,5-diamine, 3-azahexane-1,6-diamine, 4-azaheptane-1,7-diamine,
3,6-diazaoctane-1,8-diamine, 4,8-diazaundecane-1,11-diamine, 3-(2-aminoethyl)-3-azapentane-1,5-diamine
and 4,6,6-trimethyl-3,7-diazanon-3-ene-1,9-diamine. Compounds with one β-imino amine group were formed for all the amines, except
1,2-diphenylethane-1,2-diamine and propane-1,3-diamine, and compounds with tetradentate ligands with two β-imino
amine groups were formed with the aliphatic diamines.
The imine group of the compounds is relatively resistant to hydrolysis.
Organothallium Compounds. XVI. Formation of Tris(polyfluorophenyl)thallium(III) Compounds by Reaction of Bromobis(polyfluorophenyl) thallium(III) Compounds with Metal Polyfluorobenzenesulfinates
Authors: Phillips RJ , Deacon GB
Published: August 2006

The
tris(polyfluorophenyl)thallium(III) compounds R3Tl (R = C6F5,
p-HC6F4 or o-HC6F4) have been
obtained by reaction of bromobis(polyfluorophenyl) thallium(III)
compounds with the corresponding barium (R = C6Fs or p-HC6F4) or
thallium(1) (R = o-HC6F4)
polyfluorobenezensulfinates in boiling pyridine, and
have been isolated as the complexes R,Tl(diox) (diox = 1,4-dioxan). The
reactions are considered to proceed by formation and desulfination
of polyfluorobenzenesulfinatobis (polyfluorophenyl)thallium(III)
intermediates. Sulfur dioxide elimination has also been observed on reaction of
(p-HC6F4)2TlBr with barium bis(pentafluorobenzenesulfinate). The barium sulfinates were prepared by metathesis from the
corresponding lithium salts and underwent little decomposition in boiling
pyridine. Thallium(1) 2,3,4,5-tetrafluorobenzenesulfinate was obtained by
neutralization of the corresponding sulfinic acid with thallium(I) hydroxide,
and decomposed into thallium(I) sulfate, bis(2,3,4,5-tetrafluorophenyl)
sulfide, bis(2,3,4,5-tetrafluorophenyl) disulfide and
1,2,3,4-tetrafluorobenzene in boiling pyridine. Desulfination
occurred on reaction of silver nitrate with lithium pentafluorobenzenesulfinate
in water giving silver sulfite and pentafluorobenzene.
Studies in Negative-Ion Mass Spectrometry. XII. Electron Attachment to a Series of Bis(1,1,1,5,5,5-hexafluoropentane-2,4-dionato)-metal Complexes
Authors: Dakternieks DR , Fraser IW , Garnett JL , Gregor IK
Published: August 2006

Results of
electron-attachment reactions in the gas phase as well as negative-ion mass
spectra are given for a series of bis(1,1,1,5,5,5-hexafluoropentane-2,4-dionato)metal(1)
complexes, (ML2), with the divalent metals MgII, MnII,
Co11, Nil1, Cu11 and ZnII. While
molecular, [ML2]- or [ML2]-, and
ligand, [L]-, ions are present in the negative-ion mass spectra, the
lability of the ligand C-F and C-CF3 bonds enables rearrangement
processes involving fluorine atom transfers to become significant in the
decompositions of both molecular and fragment ions, particularly for the class
(a) metals, for which significant
yields of [MLF2] and [MLF] negative ions were obtained. Thus, the
predominant fragmentation pathway for such metal-containing complexes, for
which metastable peaks have been assigned, occurs in the sequence
[ML2]- -(*) → (MLF2]-
- (8) → [L]-
or alternatively
[ML2]- -(*) → (MLF2]-
- (8) → [L]-
with the latter
fragmentation in these sequences involving the elimination of the divalent
metal fluoride, MF2.
Kinetics, Stoichiometry and Mechanism in the Bromination of Aromatic Heterocycles. VI. Aqueous Bromination of Furan, Pyrrole and Thiophen
Authors: Williamson J , Coller BAW
Published: August 2006

Furan is oxidized to butenedial by electrogenerated
bromine in aqueous solution, while thiophen under the same conditions is
converted into 2-bromo-and 2,5-dibromo-thiophen. The reaction of pyrrole appears to approach the encounter-controlled limit.
For transfer of Br+ from Br2 (aq., 25�C)
to the 2(5)-positions in these systems, bimolecular rate constants, kobi/dm3
mol-1 s-1, are as follows :
furan
thiophen 2-bromothiophen 108-1010
2x90 x 104 � 5% 2 x 5.2 x 104 � 4% 2.65 x 104 � 2%

Reaction pathways leading
to substitution, addition and oxidation are reviewed.
A Study of Cations Derived from exo-2-Aryl-1,3,3- and exo-2-Aryl-1,5,5-trimethylbicyclo[2,2,1] heptan-endo-2-ols
Authors: Coxon JM , Steel PJ
Published: August 2006

The reactions of exo-2-aryl-1,3,3- and exo-2-aryl-1,5,5-trimethylbicyclo[2,2,1]heptan-endo-2-ols in strong acid are reported.
The equilibration of 2-(4'-methoxyphenyl)-3,3,endo-6-trimethylbicyclo- [2,2,1]hept-2-yl cation and the exo-6-methyl isomer both formed from
2-(4'-methoxyphenyl)-1,3,3- trimethylbicyclo[2,2,1]hept-2-yl
cation is considered to occur by an elimination-addition mechanism. At higher
temperatures the bicyclic skeleton collapses to give
monocyclic allylic cations. The 13C N.M.R.
spectra of these ions are reported.
The Synthesis of Diepoxide Analogues of Fumagillin
Authors: Harvey WE , Miners JO
Published: August 2006

Pathways from cyclohexanone
to compounds of the general type 4-(1',2'-epoxy-1'-methylalkyl)-
1-oxaspiro[2,5]octane (5), the simplest diepoxide analogues of the antibiotic
fumagillin (1a), are described. The sequence involves the initial formation of
6-acetyl-1,4-dioxaspiro[4,5]decane (2a) which is converted into a
2-alkenylcyclohexanone through the Wittig reaction. Subsequent spiro
epoxidation of the cyclic ketone and peracid
epoxidation of the side chain double bond affords the diepoxides
(5a-c). In most respects the synthetic diepoxides
possess the same stereochemistry as the equivalent functionality of fumagillin.
The Constituents of Australian Pimelea spp. I. The Isolation and Structure of the Toxin of Pimelea simplex and P. trichostachya Form B Responsible for St. George Disease of Cattle
Authors: Freeman P , Ritchie E , Taylor W
Published: August 2006

Systematic extraction of Pimelea simplex F. Muell.,
which causes St. George disease of cattle, led to the isolation of the
diterpenoid orthoester, simplexin
(1), as an active principle. Other toxicsubstances isolated were 12β-acetoxyhuratoxin
(10) and the tigliane ester derivative (11) related to
mancinellin; huratoxin was
found to be present in freshly collected plant material but it could not be
separated satisfactorily from simplexin. In addition,
loliolide (13) and a mixture of saturated and
unsaturated fatty acids were isolated. Simplexin was
obtained also from P. trichostachya
Lindl. Form B.
Synthesis of Analogues of GABA. II. 4-Alkyl-4-aminobut-2-enoic Acids and a New Synthesis of Some Vinyl α-Amino Acids
Authors: Allan RD
Published: August 2006

A series of
4-alkyl-4-aminobut-2-enoic acids (2)-(5) has been prepared as conformationally
restricted analogues of GABA. The synthetic route which involved allylic bromination followed by displacement with ammonia
also gave vinyl glycine analogues (7)-(9) as readily purified by-products of
the reaction. The low biological activity in
vitro against GABA uptake, binding and enzyme systems of (E)-2-aminocyclohexylideneacetic acid (4)
and (E)-2-aminocyclopentylideneacetic acid (5) has been interpreted in terms of
steric hindrance by the ring-forming methylene groups at the particularactive sites concerned.
Synthesis of Analogues of GABA. III. All Four Stereoisomers of 3-Aminocyclopentanecarboxylic Acid and a Stereochemical Correlation with Amidinomycin
Authors: Allan RD , Johnston GAR , Twitchin B
Published: August 2006

All four stereoisomers of 3-aminocyclopentanecarboxylic acid have
been prepared as analogues of the inhibitory neurotransmitter GABA. The amino
acid degradation product from the antibiotic amidinomycin
corresponds to cis-(1R,3S)-3-aminocyclopentanecarboxylic
acid and thus amidinomycin is (1R,3S)-N-(2'-amidinoethyl)-3-aminocyclopentane-1-carboxamide (10). A key
reaction was the stereoselective reduction of
3-hydroxyiminocyclopentanecarboxylic acid (8) to the corresponding
cis amino acid (2).
Alkaloids of Darlingia darlingiana
Authors: Bick IRC , Gillard JW , Leow H
Published: August 2006

The structures of eleven
alkaloids isolated from Darlingia darlingiana
(F. Muell.) L. A. S. Johnson, a Queensland
proteaceous tree, have been determined. They comprise a tropene, two pyranotropanes, and eight pyrrolidine
alkaloids.
Halogenated Metabolites of the Red Alga Plocamium cruciferum
Authors: Bates P , Blunt JW , Hartshorn MP , Jones AJ , Munro MHG , Robinson WT , Yorke SC
Published: August 2006

The organic extract of Plocamium cruciferum
gave a complex mixture of fatty acid methyl esters (26%), the tribromotrichloroalkene (12),(7%), n-heptadecane
(0.4%), phytol(12%) and the unusual hydroxy bisnor-monoterpene (15) (43%). The absolute stereochemistry
of the polyhalogenated alkene
(12) was established by X-ray crystallography.
A Study of Chemical Reactions in Molten Sodium-Potassium Hydrogen Sulfate Eutectic. II. The Reactions of Metal Oxides
Authors: Meehan BJ , Tariq SA
Published: August 2006

The reactions of sixteen
metal oxides with molten sodium-potassium hydrogen sulfate eutectic were
studied. It was found that Ag2O, MgO, ZnO, COO, NiO, CuO, Al2O3, Fe2O3
and V2O5 reacted with the melt to produce their
respective melt-soluble cations, sulfate and water, while CaO,
BaO, Cr2O3 and SnO2
reacted to form insoluble metal sulfates and water. Whereas manganese(IV) oxide
reacted with the melt to produce manganese(III) sulfate, water and oxygen,
tin(IV) oxide reacted to form tin(IV) sulfate, water and sulfur dioxide. The
stoichiometries of these reactions have been determined.
A Simple Method of Calculating Dissociation Constants of Carboxylic Acids and Phenols in Various Solvents
Authors: Poh B
Published: August 2006

The Hammett equation
correlating the dissociation constants (K for the substituted acid and K0
for the unsubstituted acid) of members of a closely
related series of acids is given by log(K/K0)
= pσ.
Previously, it has been shown that the p
values in other solvents can be calculated from the p value in water. In this work it is shown that the pK0 values in other solvents
can also be calculated from the pK0
value in water. Therefore, we can now calculate the pK
values in various solvents.
Analysis of the interaction between RGD-expressing adenovirus type 5 fiber knob domains and αvβ3 integrin reveals distinct binding profiles and intracellular trafficking
Authors: Lord Rosie , Parsons Maddy , Kirby Ian , Beavil Andrew , Hunt James , Sutton Brian , Santis George
Published: August 2006

Adenovirus (Ad) vectors are used widely for experimental and therapeutic gene transfer. Ad-mediated gene delivery is often inefficient and, thus, there is considerable interest in developing Ad vectors that overcome biological barriers to efficient virus uptake. For this strategy to succeed, it is imperative that the interaction between such Ad vectors and their novel receptors is well understood. In this study, three surface-exposed loops (HI, CD and IJ loops) on the Ad5 fiber knob domain were selected as sites for insertion of an αvβ3 integrin-binding RGD sequence. Three RGD-containing Ad5 fiber knob-domain mutants were produced as recombinant proteins and all were shown to interact with soluble αvβ3 integrin by using biomolecular cell-free assays. Cell adsorption and subsequent internalization and intracellular trafficking of each of these proteins were assessed by confocal microscopy. Whilst the Ad5 fiber knob domain expressing the RGD sequence in the HI and CD loops bound with similar association and dissociation profiles, the fiber knob domain expressing the RGD sequence in the IJ loop bound with slower association and faster dissociation rates. By using molecular modelling, it was shown that the Ad5 fiber knob domain in which the RGD peptide was expressed in the IJ loop was only capable of binding to one αvβ3 integrin molecule per trimer. In contrast, fiber knob domains in which the RGD peptide was expressed in the HI and CD loops were capable of binding to one integrin molecule per monomer. These differences in the interactions between each mutant and αvβ3 may explain our observation that the three RGD-bearing Ad5 fiber knob domains demonstrated similar internalization rates, but distinct patterns of endosomal transport and escape.
Entry of hepatitis C virus pseudotypes into primary human hepatocytes by clathrin-dependent endocytosis
Authors: Codran Audrey , Royer Cathy , Jaeck Daniel , Bastien-Valle Michèle , Baumert Thomas F. , Kieny Marie Paule , Pereira Carlos Augusto , Martin Jean-Pierre
Published: August 2006

Hepatitis C virus (HCV) is a major cause of chronic hepatitis worldwide. Studies of the early steps of HCV infection have been hampered by the lack of convenient in vitro or in vivo models. Although several cell-surface molecules that mediate the binding of HCV envelope proteins to target cells have been identified, mechanisms of viral entry into human hepatocytes are still poorly understood. Vesicular stomatitis virus/HCV pseudotyped viruses expressing the HCV envelope glycoproteins on the viral envelope were generated and it was found that their entry into human hepatocytes required co-expression of E1 and E2 on the pseudotype surface. Neutralization of pseudotype infection by anti-HCV antibodies suggested that cellular entry was mediated by HCV envelope glycoproteins and by previously characterized cell-surface molecules, including CD81. An entry assay based on the release of a fluorochrome from labelled HCV pseudotypes provided evidence for a pH-dependent fusion of the pseudotype envelope with a cellular compartment. By using a panel of endocytosis inhibitors, it is postulated that penetration of HCV into primary cultures of hepatocytes takes place by clathrin-mediated endocytosis.
Influenza A virus NS1 protein does not suppress RNA interference in mammalian cells
Authors: Kok Kin Hang , Jin Dong-Yan
Published: August 2006

Influenza A virus NS1 protein has been shown to suppress RNA interference (RNAi) in plants and Drosophila. Although it has not been demonstrated experimentally, NS1 has also been thought to inhibit RNAi in mammals as well as being an antagonist of interferon. In this study, the influence of NS1 protein from influenza virus strain A/WSN/33 on RNAi in mammalian cells was investigated. While transiently or stably expressed NS1 was fully competent to inhibit the interferon pathway in cultured cells, it did not suppress RNAi-mediated silencing of different reporter genes. These findings imply a significant difference in RNAi mechanism between mammals and plants.
Characterization of norovirus 3Dpol RNA-dependent RNA polymerase activity and initiation of RNA synthesis
Authors: Rohayem Jacques , Jäger Katrin , Robel Ivonne , Scheffler Ulrike , Temme Achim , Rudolph Wolfram
Published: August 2006

Norovirus (NV) 3Dpol is a non-structural protein predicted to play an essential role in the replication of the NV genome. In this study, the characteristics of NV 3Dpol activity and initiation of RNA synthesis have been examined in vitro. Recombinant NV 3Dpol, as well as a 3Dpol active-site mutant were expressed in Escherichia coli and purified. NV 3Dpol was able to synthesize RNA in vitro and displayed flexibility with respect to the use of Mg2+ or Mn2+ as a cofactor. NV 3Dpol yielded two different products when incubated with synthetic RNA in vitro: (i) a double-stranded RNA consisting of two single strands of opposite polarity or (ii) the single-stranded RNA template labelled at its 3′ terminus by terminal transferase activity. Initiation of RNA synthesis occurred de novo rather than by back-priming, as evidenced by the fact that the two strands of the double-stranded RNA product could be separated, and by dissociation in time-course analysis of terminal transferase and RNA synthesis activities. In addition, RNA synthesis was not affected by blocking of the 3′ terminus of the RNA template by a chain terminator, sustaining de novo initiation of RNA synthesis. NV 3Dpol displays in vitro properties characteristic of RNA-dependent RNA polymerases, allowing the implementation of this in vitro enzymic assay for the development and validation of antiviral drugs against NV, a so far non-cultivated virus and an important human pathogen.
Proteome alterations in human host cells infected with coxsackievirus B3
Authors: Rassmann Alexander , Henke Andreas , Zobawa Monica , Carlsohn Marc , Saluz Hans-Peter , Grabley Susanne , Lottspeich Friedrich , Munder Thomas
Published: August 2006

Coxsackievirus B3 (CVB3) is a common factor in human myocarditis. The interplay between host factors and virus components is crucial for the fate of the infected cells. Despite that, host protein responses, which characterize CVB3-induced diseases, have not yet been determined in detail. To investigate the nature of modified protein patterns in infected human cells compared with uninfected cells, two-dimensional gel electrophoresis in combination with matrix-assisted laser desorption/ionization-mass spectrometry were used. The regulated proteins, e.g. nucleophosmin (nucleolar protein B23), lamin, the RNA-binding protein UNR and the p38 mitogen-activated protein kinase, were sorted according to their functional groups and interpreted in the context of the myocarditis process.
Dengue virus NS4B interacts with NS3 and dissociates it from single-stranded RNA
Authors: Umareddy Indira , Chao Alex , Sampath Aruna , Gu Feng , Vasudevan Subhash G.
Published: August 2006

Dengue virus, a member of the family Flaviviridae of positive-strand RNA viruses, has seven non-structural proteins: NS1, NS2A, NS2B, NS3, NS4A, NS4B and NS5. Except for enzymic activities contained within NS3 and NS5, the roles of the other proteins in virus replication and pathogenesis are not well defined. In this study, a physical interaction between NS4B and the helicase domain of NS3 was identified by using a yeast two-hybrid assay. This interaction was further confirmed by biochemical pull-down and immunoprecipitation assays, both with purified proteins and with dengue virus-infected cell lysates. NS4B co-localized with NS3 in the perinuclear region of infected human cells. Furthermore, NS4B dissociated NS3 from single-stranded RNA and consequently enhanced the helicase activity of NS3 in an in vitro unwinding assay. These results suggest that NS4B modulates dengue virus replication via its interaction with NS3.
E (XSR) element contributes to the oncogenicity of Avian leukosis virus (subgroup J)
Authors: Chesters Peter M. , Smith Lorraine P. , Nair Venugopal
Published: August 2006

Among the six subgroups of Avian leukosis virus (ALV) that infect chickens, subgroup J (ALV-J) was isolated from meat-type chickens where it predominantly induces myeloid leukosis (ML) and erythroblastosis (EB). The sequence of HPRS-103, the ALV-J prototype virus, shows several distinct features, one of which is the presence of a distinct hairpin stem–loop structure called the E (also called XSR) element in the 3′ untranslated region. In order to determine the role of the E element in ALV-induced pathogenicity, a comparison was made of the oncogenicity of viruses derived from the provirus clones of parental and E element-deleted HPRS-103 viruses in two genetically distinct lines of birds. In line 15I birds, deletion of the E element had profound effects on virus replication in vivo, as only 55 % of birds showed evidence of infection, compared with 100 % infection by the parental virus. Furthermore, none of the line 15I birds infected with this virus developed tumours, indicating that the E element does contribute to the oncogenicity of the virus. On the other hand, deletion of the E element had only a marginal effect on the incidence of tumours in line 0 birds. These results indicate that, although the E element per se is not absolutely essential for tumour induction by this subgroup of viruses, it does contribute to oncogenicity in certain genetic lines of chicken.
Role of the putative heparan sulfate glycosaminoglycan-binding site of the adenovirus type 5 fiber shaft on liver detargeting and knob-mediated retargeting
Authors: Bayo-Puxan Neus , Cascallo Manel , Gros Alena , Huch Meritxell , Fillat Cristina , Alemany Ramon
Published: August 2006

Liver tropism hampers systemic administration of adenovirus in gene therapy and virotherapy. In consequence, tumour targeting requires the combination of capsid modifications that abrogate liver transduction and redirect adenoviral vectors to tumour cells. Coxsackievirus and adenovirus receptor (CAR), integrins and heparan sulfate glycosaminoglycans (HSG) are receptors involved in adenovirus type 5 (Ad5) entry into cells. The in vitro and in vivo properties of Ad5 vectors unable to bind CAR, integrins and HSG with and without Arg–Gly–Asp (RGD) inserted at the HI loop of the fiber were studied. As was previously observed with CAR-ablated vectors, CAR and integrin double binding-ablated vectors transduced hepatocytes less efficiently in vitro but not in vivo. On the contrary, the role of HSG on Ad5 infectivity was evident in vitro only when CAR binding was abrogated, but the shaft mutation that ablated HSG binding on the background of a normal capsid was sufficient to abrogate liver transduction in vivo. The insertion of amino acids RGD at the HI loop in a shaft-mutated fiber only partially rescued integrin-mediated infectivity. These results indicate that the shaft mutation precluded HSG binding and affected the structure of the fiber. The insertion of ligands at the hexon or protein IX may be required to benefit from the fiber shaft mutation-detargeting properties.
Cell death in bovine parvovirus-infected embryonic bovine tracheal cells is mediated by necrosis rather than apoptosis
Authors: Abdel-Latif Lubna , Murray Byron K. , Renberg Rebecca L. , O'Neill Kim L. , Porter Heidi , Jensen James B. , Johnson F. Brent
Published: August 2006

The helper-independent bovine parvovirus (BPV) was studied to determine its effect on host embryonic bovine tracheal (EBTr) cells: whether the ultimate outcome of infection results in apoptotic cell death or cell death by necrosis. Infected cells were observed for changes marking apoptosis. Observations of alterations in nuclear morphology, membrane changes, apoptotic body formation, membrane phosphatidylserine inversions, caspase activation and cell DNA laddering in infected cells were not indicative of apoptosis. On the other hand, at the end of the virus replication cycle, infected cells released viral haemagglutinin and infectious virus particles, as would be expected from cell membrane failure. Moreover, the infected cells released lactate dehydrogenase (LDH), release of which is a marker of necrosis. LDH release into the cell medium correlated directly with viral m.o.i. and time post-infection. Furthermore, assessment of mitochondrial dehydrogenase activity was consistent with cell death by necrosis. Taken together, these findings indicate that cell death in BPV-infected EBTr cells is due to necrosis, as defined by infected-cell membrane failure and release of the cell contents into the extracellular environment.
Evidence of ancient papillomavirus recombination
Authors: Varsani Arvind , van der Walt Eric , Heath Livio , Rybicki Edward P. , Williamson Anna Lise , Martin Darren P.
Published: August 2006

An open question amongst papillomavirus taxonomists is whether recombination has featured in the evolutionary history of these viruses. Since the onset of the global AIDS epidemic, the question is somewhat less academic, because immune-compromised human immunodeficiency virus patients are often co-infected with extraordinarily diverse mixtures of human papillomavirus (HPV) types. It is expected that these conditions may facilitate the emergence of HPV recombinants, some of which might have novel pathogenic properties. Here, a range of rigorous analyses is applied to full-genome sequences of papillomaviruses to provide convincing statistical and phylogenetic evidence that evolutionarily relevant papillomavirus recombination can occur.
Role of human cytomegalovirus UL131A in cell type-specific virus entry and release
Authors: Adler Barbara , Scrivano Laura , Ruzcics Zsolt , Rupp Brigitte , Sinzger Christian , Koszinowski Ulrich
Published: August 2006

The human cytomegalovirus (HCMV) genes UL128, UL130 and UL131A are essential for endothelial cell infection. Complementation of the defective UL131A gene of the non-endotheliotropic HCMV strain AD169 with wild-type UL131A in cis in an ectopic position restored endothelial cell tropism. The UL131A protein was found in virions in a complex with gH. Coinfection of fibroblasts with UL131A-negative and -positive viruses restored the endothelial cell tropism of UL131A-negative virions by complementing the virions with UL131A protein. Virus entry into endothelial cells, but not into fibroblasts, was blocked by an antipeptide antiserum to pUL131A. AD169, cis-complemented with wild-type UL131A, showed an impaired release of infectious particles from fibroblasts. A comparable defect in virus release was observed when UL131A was expressed ectopically in a virus background already expressing an intact copy of UL131A. In contrast, virus release from infected endothelial cells was not affected by UL131A. These data suggest a dual role for pUL131A in virus entry and virus exit from infected cells.
A humanized murine monoclonal antibody protects mice either before or after challenge with virulent Venezuelan equine encephalomyelitis virus
Authors: Hunt Ann R. , Frederickson Shana , Hinkel Christopher , Bowdish Katherine S. , Roehrig John T.
Published: August 2006

A humanized monoclonal antibody (mAb) has been developed and its potential to protect from or cure a Venezuelan equine encephalomyelitis virus (VEEV) infection was evaluated. The VEEV-neutralizing, protective murine mAb 3B4C-4 was humanized using combinatorial antibody libraries and phage-display technology. Humanized VEEV-binding Fabs were evaluated for virus-neutralizing capacity, then selected Fabs were converted to whole immunoglobulin (Ig) G1, and stable cell lines were generated. The humanized mAb Hy4-26C, designated Hy4 IgG, had virus-neutralizing capacity similar to that of 3B4C-4. Passive antibody protection studies with purified Hy4 IgG were performed in adult Swiss Webster mice. As little as 100 ng Hy4 IgG protected 90 % of mice challenged with 100 intraperitoneal (i.p.) mean morbidity (MD50) doses of virulent VEEV (Trinidad donkey) 24 h after antibody transfer; also, 500 μg Hy4 IgG protected 80 % of mice inoculated with 100 intranasal MD50doses of VEEV. Moreover, 10 μg passive Hy4 IgG protected 70 % of mice from a VEEV challenge dose as great as 107i.p. MD50. Hy4 IgG also protected mice from challenge with another epizootic VEEV variety, 1C (P676). Importantly, therapeutic administration of the humanized mAb to mice already infected with VEEV cured 90 % of mice treated with Hy4 IgG within 1 h of VEEV inoculation and 75 % of mice treated 24 h after virus infection.
Gene organization and complete sequence of the Hyphantria cunea nucleopolyhedrovirus genome
Authors: Ikeda Motoko , Shikata Masamitsu , Shirata Noriko , Chaeychomsri Sudawan , Kobayashi Michihiro
Published: August 2006

The whole-genome sequence of the Hyphantria cunea nucleopolyhedrovirus (HycuNPV) was analysed. The entire nucleotide sequence of the HycuNPV genome was 132 959 bp long, with a G+C content of 45.1 mol%. A total of 148 open reading frames (ORFs) consisting of more than 50 aa were encoded by the genome. HycuNPV shares more than 122 ORFs with other lepidopteran group I NPVs, including Autographa californica MNPV, Bombyx mori NPV, Choristoneura fumiferana MNPV (CfMNPV), Choristoneura fumiferana defective NPV, Epiphyas postvittana MNPV and Orgyia pseudotsugata MNPV (OpMNPV). Six ORFs are identified as being unique to HycuNPV. Most of the HycuNPV ORFs showed higher similarity to CfMNPV and OpMNPV ORFs than to those of the other group I NPVs. HycuNPV encodes two conotoxin-like homologues (ctls), which are observed only in OpMNPV in group I NPVs. HycuNPV encodes three inhibitors of apoptosis (iaps), hycu-iap-1, hycu-iap-2 and hycu-iap-3, a feature that it shares only with CfMNPV. In addition, six homologous regions (hrs) are identified in the HycuNPV genome. These hrs are located in regions similar to those of the OpMNPV hrs, but different from most of the CfMNPV hrs. Based on the close phylogenetic relationship and conservation of group I NPV-specific genes, such as gp64, ie-2 and ptp-1, it is concluded that HycuNPV belongs to the group I NPVs and is most similar to CfMNPV or OpMNPV.
High-density lipoproteins reduce the neutralizing effect of hepatitis C virus (HCV)-infected patient antibodies by promoting HCV entry
Authors: Voisset Cécile , de Beeck Anne Op , Horellou Pauline , Dreux Marlène , Gustot Thierry , Duverlie Gilles , Cosset François-Loic , Vu-Dac Ngoc , Dubuisson Jean
Published: August 2006

The neutralizing activity of anti-hepatitis C virus (HCV) antibodies is attenuated by a factor present in human sera, which has been proposed to be high-density lipoproteins (HDLs). HDLs have also been shown to facilitate the entry of HCV pseudoparticles (HCVpp) into target cells. Here, the aim of the study was to determine whether HDL-mediated facilitation of HCVpp and infectious HCV (HCVcc) entry and attenuation of neutralization are two related phenomena. The data indicated that HDLs attenuate neutralization at a constant rate. In addition, as for HDL-mediated facilitation of HCVpp entry, attenuation of neutralization depended on the expression of the scavenger receptor BI (SR-BI) and its selective lipid-uptake function. Finally, kinetic experiments showed that HDL-mediated facilitation of HCVpp entry is more rapid than virus neutralization. Altogether, these observations indicate that HCV is exploiting the physiological activity of SR-BI for promoting its entry into target cells, which consequently also protects the virus against neutralizing antibodies.
Domains of tobacco mosaic virus movement protein essential for its membrane association
Authors: Fujiki Masaaki , Kawakami Shigeki , Kim Ryan W. , Beachy Roger N.
Published: August 2006

A series of deletion mutants of tobacco mosaic virus movement protein (TMV-MP) was used to identify domains of the protein necessary for membrane association. A membrane fraction was isolated from tobacco BY-2 protoplasts infected with wild-type and mutant TMV that produce MP carrying a 3 aa deletion. Deletions that affected membrane association were clustered around the two major hydrophobic regions of MP that are predicted to be transmembrane. Deletions in other hydrophobic regions also reduced membrane association. In addition, a non-functional mutant of MP, in which one of the known phosphorylation sites was eliminated, was not associated with cellular membranes, while a functional second site revertant restored membrane association. This indicates that MP function requires interaction with membrane; however, membrane association was not sufficient for function. Results are consistent with the hypothesis that TMV-MP is an integral or tightly associated membrane protein that includes two hydrophobic transmembrane domains.
In vitro-reassembled plant virus-like particles for loading of polyacids
Authors: Ren Yupeng , Wong Sek-Man , Lim Lee-Yong
Published: August 2006

The coat protein (CP) of certain plant viruses may reassemble into empty virus-like particles (VLPs) and these protein cages may serve as potential drug delivery platforms. In this paper, the production of novel VLPs from the Hibiscus chlorotic ringspot virus (HCRSV) is reported and the capacity to load foreign materials was characterized. VLPs were readily produced by destabilizing the HCRSV in 8 M urea or Tris buffer pH 8, in the absence of calcium ions, followed by removal of viral RNA by ultrahigh-speed centrifugation and the reassembly of the CP in sodium acetate buffer pH 5. The loading of foreign materials into the VLPs was dependent on electrostatic interactions. Anionic polyacids, such as polystyrenesulfonic acid and polyacrylic acid, were successfully loaded but neutrally charged dextran molecules were not. The molecular-mass threshold for the polyacid cargo was about 13 kDa, due to the poor retention of smaller molecules, which readily diffused through the holes between the S domains present on the surface of the VLPs. These holes precluded the entry of large molecules, but allowed smaller molecules to enter or exit. The polyacid-loaded VLPs had comparable size, morphology and surface-charge density to the native HCRSV, and the amount of polyacids loaded was comparable to the weight of the native genomic materials. The conditions applied to disassembly–reassembly of the virions did not change the structural conformation of the CP. HCRSV-derived VLPs may provide a promising nano-sized protein cage for delivery of anionic drug molecules.
A granule cell neuron-associated JC virus variant has a unique deletion in the VP1 gene
Authors: Dang Xin , Koralnik Igor J.
Published: August 2006

The human polyomavirus JC (JCV) typically infects glial cells and is the aetiological agent of progressive multifocal leukoencephalopathy (PML), which occurs in immunosuppressed individuals. The full-length sequence of a granule cell neuron-tropic JCV variant, JCVGCN1, associated with lytic infection of granule cell neurons and cerebellar atrophy in a human immunodeficiency virus-infected patient with PML was determined and compared with the sequence of the JCV isolate from the classic PML lesions present in the hemispheric white matter of the same individual (JCVHWM). A unique deletion was found in the C terminus of the VP1 gene of JCVGCN1, which encodes the major capsid protein, resulting in a frame shift and a total change of the C-terminal amino acid sequence of this protein. This deletion was not present in JCVHWM, suggesting that this mutation may be instrumental in facilitating entry or replication of JCV into granule cell neurons.
The 3′ untranslated regions of Kamiti River virus and Cell fusing agent virus originated by self-duplication
Authors: Gritsun T. S. , Gould E. A.
Published: August 2006

Previously, it was shown that the 3′ untranslated region (3′UTR) of Kamiti River virus (KRV) is nearly twice as long as the 3′UTR of other flaviviruses (1208 nucleotides compared with 730 nucleotides for the longest 3′UTR of any virus in the Tick-borne encephalitis virus species). Additionally, KRV and the closely related Cell fusing agent virus (CFAV) were shown to contain two short, almost perfect repeat sequences of 67 nucleotides. However, the construction of a robust comparative nucleotide alignment has now revealed that the double-length 3′UTR and the direct repeats resulted from the virtually complete duplication of a primordial KRV 3′UTR. We also propose that the CFAV 3′UTR was derived from a KRV-like precursor sequence with a large deletion that nevertheless preserved the two direct repeat sequences. These data provide new insights into the evolution of the flavivirus 3′UTR.