bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanistic insights into Cu(I) cluster transfer between the chaperone CopZ and its cognate Cu(I)-transporting P-type ATPase, CopA
Authors: Singleton Chloe , Hearnshaw Stephen , Zhou Liang , Le Brun Nick E. , Hemmings Andrew M.
Published: September 2009

Multinuclear Cu(I) clusters are common in nature, but little is known about their formation or transfer between proteins. CopZ and CopA from Bacillus subtilis, which are involved in a copper-efflux pathway, both readily accommodate multinuclear Cu(I) clusters. Using the luminescence properties of a multinuclear Cu(I)-bound form of the two N-terminal soluble domains of CopA (CopAab) we have investigated the thermodynamic and kinetic properties of cluster formation and loss. We demonstrate that Cu(I)-bound forms of dimeric CopZ containing more than one Cu(I) per CopZ monomer can transfer Cu(I) to apo-CopAab, leading to the formation of luminescent dimeric CopAab. Kinetic studies demonstrated that transfer is a first-order process and that the rate-determining steps for transfer from CopZ to CopAab and vice versa are different processes. The rate of formation of luminescent CopAab via transfer of Cu(I) from CopZ was more rapid than that observed when Cu(I) was added ‘directly’ from solution or in complex with a cysteine variant of CopZ, indicating that transfer occurs via a transient protein–protein complex. Such a complex would probably require the interaction of at least one domain of CopAab with the CopZ dimer. Insight into how such a complex might form is provided by the high resolution crystal structure of Cu3(CopZ)3, a thus far unique trimeric form of CopZ containing a trinuclear Cu(I) cluster. Modelling studies showed that one of the CopZ monomers can be substituted for either domain of CopAab, resulting in a heterotrimer, thus providing a model for a ‘trapped’ copper exchange complex.
Protein metabolism in leg muscle following an endotoxin injection in healthy volunteers
Authors: Vesali Rokhsareh F. , Cibicek Norbert , Jakobsson Towe , Klaude Maria , Wernerman Jan , Rooyackers Olav
Published: September 2009

The human endotoxin model has been used to study the early phase of sepsis. The aim of the present study was to assess leg muscle protein kinetics after an endotoxin challenge given to healthy human volunteers. Six healthy male subjects were studied in the post-absorptive state before and during 4 h following an intravenous endotoxin bolus (4 ng/kg of body weight). Primed continuous infusion of [2H5]phenylalanine and [2H3]3-methylhistidine in combination with sampling from the radial artery, femoral vein and muscle tissue were used to assess leg muscle protein kinetics. Both two- and three-compartment models were used to calculate protein kinetics. In addition 26S proteasome activity and protein ubiquitination were assessed. An increase in the net release of phenylalanine from the leg following the endotoxin challenge was observed; however, this phenylalanine originates from the free intracellular pool and not from protein. Net protein balance was unchanged, whereas both protein synthesis and breakdown were decreased. Degradation rates of contractile proteins were not affected by endotoxin, as indicated by an unchanged rate of appearance of 3-methylhistidine from leg muscle. In addition, proteasome activity and protein ubiquitination were unaffected by endotoxaemia. In conclusion, intravenous endotoxin administration to healthy volunteers resulted in an increased release of free phenylalanine from skeletal muscle, whereas protein balance was unaffected. Both protein synthesis and breakdown were decreased to a similar extent.
Continuous nanoparticle generation and assembly by atmospheric pressure arc discharge
Authors: Cole Jesse J. , Lin En-Chiang , Barry Chad R. , Jacobs Heiko O.
Published: September 2009

This letter describes a nanoparticle generation and deposition system which combines aspects of high temperature plasmas with room temperature aerosols. The process works at atmospheric pressure and produces nanoparticles of Au or ZnO through cathode erosion inside a dc arc discharge plasma. The particles are positively charged by the arc and form a room temperature aerosol. From the aerosol, nanoparticles assemble on conductive sample surfaces through openings in patterned resist with resolution enhanced by electrodynamic nanolenses. We report that continued operation of the system results in funneled deposition of nanoparticles into well positioned three dimensional nanostructures.
The crystal structures of δ and δ ∗ nitrogen
Authors: Stinton G. W. , Loa I. , Lundegaard L. F. , McMahon M. I.
Published: September 2009

The crystal structures of the high-pressure δ and δ ∗ phases of nitrogen have been investigated using single-crystal x-ray diffraction. The structure of the δ phase is very similar to isostructural γ-O2 and comprises spherically disordered molecules, with a preference for avoiding pointing along the cubic ⟨100⟩ directions, and disklike molecules with a uniform distribution of orientations. The structure of the δ ∗ phase is tetragonal and the space group is identified unambiguously as P42/ncm with unit cell parameters of a=8.603(5) Å and c=5.685(5) Å at 14.5 GPa. The orientations of the partially disordered molecules have been experimentally determined for the first time and are similar to those predicted on the basis of molecular dynamics simulations.
Linear correlation between binding energy and Young’s modulus in graphene nanoribbons
Authors: Zeinalipour-Yazdi Constantinos D. , Christofides Constantinos
Published: September 2009

Graphene nanoribbons (GNRs) have been suggested as a promising material for its use as nanoelectromechanical reasonators for highly sensitive force, mass, and charge detection. Therefore the accurate determination of the size-dependent elastic properties of GNRs is desirable for the design of graphene-based nanoelectromechanical devices. In this study we determine the size-dependent Young’s modulus and carbon-carbon binding energy in a homologous series of GNRs, C4n2+6n+2H6n+4 (n=2–12), with the use of all electron first principles computations. An unexpected linearity between the binding energy and Young’s modulus is observed, making possible the prediction of the size-dependent Young’s modulus of GNRs through a single point energy calculation of the GNR ground state. A quantitative-structure-property relationship is derived, which correlates Young’s modulus to the total energy and the number of carbon atoms within the ribbon. In the limit of extended graphene sheets we determine the value of Young’s modulus to be 1.09 TPa, in excellent agreement with experimental estimates derived for graphite and suspended graphene sheets.
A rapid method to estimate Westergren sedimentation rates
Authors: Alexy Tamas , Pais Eszter , Meiselman Herbert J.
Published: September 2009

The erythrocyte sedimentation rate (ESR) is a nonspecific but simple and inexpensive test that was introduced into medical practice in 1897. Although it is commonly utilized in the diagnosis and follow-up of various clinical conditions, ESR has several limitations including the required 60 min settling time for the test. Herein we introduce a novel use for a commercially available computerized tube viscometer that allows the accurate prediction of human Westergren ESR rates in as little as 4 min. Owing to an initial pressure gradient, blood moves between two vertical tubes through a horizontal small-bore tube and the top of the red blood cell (RBC) column in each vertical tube is monitored continuously with an accuracy of 0.083 mm. Using data from the final minute of a blood viscosity measurement, a sedimentation index (SI) was calculated and correlated with results from the conventional Westergren ESR test. To date, samples from 119 human subjects have been studied and our results indicate a strong correlation between SI and ESR values (R2=0.92). In addition, we found a close association between SI and RBC aggregation indices as determined by an automated RBC aggregometer (R2=0.71). Determining SI on human blood is rapid, requires no special training and has minimal biohazard risk, thus allowing physicians to rapidly screen for individuals with elevated ESR and to monitor therapeutic responses.
Parallel trapping of multiwalled carbon nanotubes with optoelectronic tweezers
Authors: Pauzauskie Peter J. , Jamshidi Arash , Valley Justin K. , Satcher Joe H. , Wu Ming C.
Published: September 2009

Here we report the use of optoelectronic tweezers and dynamic virtual electrodes to address multiwalled carbon nanotubes (MWCNTs) with trap stiffness values of approximately 50 fN/μm. Both high-speed translation (>200 μm/s) of individual-MWCNTs and two-dimensional trapping of MWCNT ensembles are achieved using 100,000 times less optical power density than single beam laser tweezers. Modulating the virtual electrode’s intensity enables tuning of the MWCNT ensemble’s number density by an order of magnitude on the time scale of seconds promising a broad range of applications in MWCNT science and technology.
Polarization reversal and backswitching dynamics in epitaxial BaTiO3 thin films
Authors: Li Jianheng , Lin Pao Tai , Wessels B. W.
Published: September 2009

Polarization switching dynamics in polydomain epitaxial barium titanate (BaTiO3) thin films were investigated over the temperature range of 293–363K. To determine domain dynamics, the transient response of the linear electro-optic effect was measured as a function of bias field under pulsed excitation and temperature. Upon removal of the bias pulse, domain backswitching is observed, which is described by the Kohlrausch–Williams–Watts (KWW) extended exponential function in time. From the KWW kinetic parameter ⟨τ⟩ and its temperature and field dependences, the activation field and nucleation energy for polarization reversal are determined. The measured thermal energy barrier for nucleation is in the range of 0.1eV–0.3eV and decreases with the electric field. These values are in good agreement with those recently obtained in molecular dynamics simulation studies of domain nucleation and growth in BaTiO3.
Influence of electric voltage bias on converse magnetoelectric coefficient in piezofiber/Metglas bilayer laminate composites
Authors: Wu Tao , Chung Tien-Kan , Chang Chia-Ming , Keller Scott , Carman Gregory P.
Published: September 2009

Experimental data on a piezofiber/Metglas bilayer composite subjected to both a dc electric voltage bias and a dc magnetic field bias while exciting it with an ac electric driving voltage are presented. As reported in previous studies, a dc magnetic field bias exists to maximize the converse magnetoelectric coefficient. Experimental data show that the optimum dc magnetic field bias is a function of applied dc electric voltage. Furthermore, it is revealed that an optimum dc electric voltage bias exists to further maximize the converse magnetoelectric coefficient.
Interaction between elastic waves and prismatic dislocation loops
Authors: Rodríguez Natalia , Maurel Agnès , Pagneux Vincent , Barra Felipe , Lund Fernando
Published: September 2009

The properties of prismatic dislocation loops, generated by radiation in metals, have remained elusive for decades, and recent advances in computational capabilities as well as transmission electron microscopy have renewed interest in their study. Acoustic and elastic waves could become an interesting, nonintrusive, probe to this end, as they have for other dislocation configurations. What then are the characteristics of elastic wave scattering that would be sensitive to a prismatic loop signature? In this paper, we report the scattering cross section for an elastic wave by a prismatic dislocation loop. It differs in significant ways from the analog quantity in the case of pinned dislocation segments, the most significant being the polarization of the scattered wave. The properties of a coherent wave traveling through an elastic medium filled with randomly placed and randomly oriented such loops are also reported. At long wavelengths, the effective wave velocity and attenuation coefficients resemble those for a similar case with pinned dislocation segments.
Acoustic mirage in two-dimensional gradient-index phononic crystals
Authors: Lin Sz-Chin Steven , Huang Tony Jun
Published: September 2009

We report the design of a two-dimensional gradient-index phononic crystal (GRIN PC) structure, which effectively demonstrates the “acoustic mirage” effect on the wavelength scale. Using the GRIN PC, the propagating direction of acoustic waves can be continuously bent along an arc-shaped trajectory by gradually tuning the filling ratio of PCs. We investigate the acoustic mirage effect through both plane wave expansion and finite-difference time-domain methods. By controlling the incident angle or operating frequency, the arc-shaped trajectory of acoustic wave propagation can be dynamically adjusted. The GRIN PC structure is composed of steel cylinders, positioned in a square lattice, and immersed in an epoxy. It can be fabricated through a simple process and seamlessly integrated with existing acoustic devices. In addition, we establish that such an acoustic effect can be used in the design of tunable acoustic waveguides, which could find applications in acoustic switching, filtering, and biosensing.
Theoretical investigation on the magnetocaloric effect in garnets R3Fe5O12 where (R=Y and Dy)
Authors: von Ranke P. J. , Alho B. P. , Plaza E. J. R. , Carvalho A. Magnus G. , de Sousa V. S. R. , de Oliveira N. A.
Published: September 2009

In this work the magnetocaloric effect in ferrimagnetic rare-earth iron garnets R3Fe5O12 where R=Y and Dy was theoretically investigated considering a model Hamiltonian, which takes into account three coupled magnetic sublattices in the mean field approximation. In Dy3Fe5O12 the inverse magnetocaloric effect was predicted and associated with the compensation temperature. Our theoretical results for the adiabatic temperature change in both compounds are in good agreement with the experimental data.
Stability of relative equilibria of three vortices
Authors: Aref Hassan
Published: September 2009

Three point vortices on the unbounded plane have relative equilibria wherein the vortices either form an equilateral triangle or are collinear. While the stability analysis of the equilateral triangle configurations is straightforward, that of the collinear relative equilibria is considerably more involved. The only comprehensive analysis available in the literature, by Tavantzis and Ting [Phys. Fluids 31, 1392 (1988)], is not easy to follow nor is it very physically intuitive. The symmetry between the three vortices is lost in this analysis. A different analysis is given based on explicit formulas for the three eigenvalues determining the stability, including a new formula for the angular velocity of rotation of a collinear relative equilibrium. A graphical representation of the space of vortex circulations is introduced, and the resultants between various polynomials that enter the problem are used. This approach adds considerable transparency to the solution of the stability problem and provides more physical understanding. The main results are summarized in a diagram that gives both the stability and instability of the various collinear relative equilibria and their sense of rotation.
Extended ensemble approach for deriving transferable coarse-grained potentials
Authors: Mullinax J. W. , Noid W. G.
Published: September 2009

Coarse-grained (CG) models provide a computationally efficient means for investigating biological and soft-matter processes that evolve on long time scales and large length scales. The present work introduces an extended ensemble framework for calculating transferable CG potentials that accurately reproduce the structure of atomistic models for multiple systems. This framework identifies a generalized potential of mean force (PMF) as the appropriate CG potential for reproducing the structural correlations of an atomistic extended ensemble. A variational approach is developed for calculating transferable potentials that provide an optimal approximation to this PMF. Calculations for binary mixtures of alkanes and alcohols demonstrate that the extended ensemble potentials provide improved transferability relative to potentials calculated for a single system.
Chemical dynamics of the formation of the ethynylsilylidyne radical (SiCCH(X Π2)) in the crossed beam reaction of ground state silicon atoms (Si(P3)) with acetylene (C2H2(X ∑g+1))
Authors: Kaiser R. I. , Gu X.
Published: September 2009

The reaction dynamics of ground state silicon atoms (Si(P3)) with the acetylene molecule (C2H2(X ∑g+1)) were investigated at a collision energy of 101.6±1.6 kJ mol−1 under single collision conditions in a crossed molecular beam machine. We found that the reaction dynamics proceeded via an addition of the silicon atom to the π-electrons of the acetylene molecule at a single carbon atom forming a Cs symmetric SiC2H2(X A3″) intermediate. The latter either emitted a hydrogen atom leading to the linear SiCCH(X Π2) product or underwent a hydrogen migration to the SiCCH2(X A32) isomer prior to the decomposition of the latter to SiCCH(X Π2) plus atomic hydrogen. The overall reaction to form the SiCCH(X Π2) plus atomic hydrogen products was determined to be highly endoergic by 84±6 kJ mol−1. No evidence of a molecular hydrogen elimination channel was found at this collision energy. Our study predicts that this endoergic neutral-neutral reaction can lead to the formation of an organosilicon transient species, i.e., the linear SiCCH(X Π2) radical, in high-temperature environments like in the circumstellar envelope of the carbon star IRC+10 216, where temperatures of a few 1000 K exist close to the central star.
Optical determination of Young’s modulus of InAs nanowires
Authors: Lexholm Monica , Karlsson Ivan , Boxberg Fredrik , Hessman Dan
Published: September 2009

We present a study of Young’s modulus of epitaxially grown InAs nanowires with diameters from 40 to 95 nm. The dynamic behavior of the nanowires is investigated using optical stroboscopic imaging. The Young’s modulus, evaluated using the eigenfrequencies of the fundamental and the first excited modes in air, decreases for smaller diameters. To avoid the influence of the electric field on the resonance frequency, we use the free ring-down response to a voltage step rather than driving with a harmonic voltage.
All-electron calculation of nonadiabatic couplings from time-dependent density functional theory: Probing with the Hartree–Fock exact exchange
Authors: Hu Chunping , Sugino Osamu , Tateyama Yoshitaka
Published: September 2009

We present the all-electron scheme of calculating nonadiabatic couplings (NACs) from time-dependent density functional theory (TDDFT) using atomic orbital basis. The formal expression for calculating NAC from linear response TDDFT [Hu et al., J. Chem. Phys. 127, 064103 (2007)] can be straightforwardly adapted to the all-electron TDDFT scheme. However, in contrast to the planewave basis, the nuclear coordinate dependence of atomic orbital basis needs to be considered when constructing the matrix elements of the nuclear derivative of Hamiltonian. Practical calculations show that the contribution of atomic orbital basis (“Pulay term”) is significant and comparable to that of the Hellmann–Feynman term. In particular, we probe the all-electron formalism of NAC with the Hartree–Fock exact exchange, which serves as the prerequisite for hybrid functionals. It is validated that in the present framework the sum rule of NAC is rigorously satisfied, which has not been the case in the pseudopotential planewave calculations. Reasonably good results can be obtained in the vicinity of various Renner–Teller (and also Jahn–Teller) intersections when the intersection point is not too closely approached, while further tests show that correlation effects should be taken into account in general cases.
A simple model of directional interactions for proteins
Authors: Li Xiaofei , Gunton J. D. , Chakrabarti A.
Published: September 2009

We study a simple two patch model of globular protein solutions. The model consists of a hard sphere interaction, together with a weak isotropic attraction, decorated with stronger attractive patch-patch interactions. The isotropic and anisotropic attractions are modeled with square well potentials with an interaction range of 1.2σ, where σ is the hard sphere diameter. We have calculated its phase diagram and found a metastable fluid-fluid phase separation curve. We have also obtained the different stable crystal structures at various temperatures. The orientationally ordered, body-centered crystal (bcc-o) lattice is the crystal structure that has the lowest energy; it is stable at lower temperatures and moderate pressures. The orientationally ordered face-centered crystal (fcc) lattice has a higher energy and becomes stable with respect to bcc-o at high pressures and lower temperatures. Finally, at high temperatures when the entropy effect becomes important, the orientational order is lost and an orientationally disordered fcc lattice becomes stable.
Electron diffractive imaging of nano-objects using a guided method with a dynamic support
Authors: Dronyak Roman , Liang Keng S. , Stetsko Yuri P. , Lee Ting-Kuo , Feng Chi-Kai , Tsai Jin-Sheng , Chen Fu-Rong
Published: September 2009

We present a phase recovery technique that utilizes a guiding method with a dynamic support to reconstruct the shape and exit wave of a single MgO nanoparticle in a coherent electron diffraction experiment. The proposed method provides an optimal solution deduced from the electron diffraction pattern alone. The recovered shape has spatial resolution 3.1 nm. The complex exit wave encodes the projected atomic structure of the nanocrystal with resolution about 0.15 nm, and agrees with a multislice simulation. The possibility of imaging nanosized objects at diffraction-limited resolution using a field emission electron microscope is thus demonstrated.
Nonthermal and screening effects on the inelastic Compton scattering in Lorentzian plasmas
Authors: Kim Hwa-Min , Jung Young-Dae
Published: September 2009

The nonthermal and screening effects on the inelastic Compton scattering process are investigated in Lorentzian plasmas. The screened atomic wave functions and energies for the hydrogenic ion in Lorentzian plasmas are obtained by the Rayleigh–Ritz variational method. The transition matrix element for the inelastic Compton scattering process in Lorentzian plasmas is also obtained as a function of the spectral index and plasma parameters by the two photon-perturbation Hamiltonian. It is found that the nonthermal character of the Lorentzian plasma suppresses the inelastic Compton scattering cross section. In addition, the nonthermal effects are found to be significant for 2<κ<5, where κ is the spectral index of the Lorentzian plasma.
Low density 1.55 μm InAs/InGaAsP/InP (100) quantum dots enabled by an ultrathin GaAs interlayer
Authors: van Veldhoven P. J. , Chauvin N. , Fiore A. , Nötzel R.
Published: September 2009

The authors report the formation of low density InAs/InGaAsP/InP (100) quantum dots (QDs) by metalorganic vapor phase epitaxy enabled by an ultrathin GaAs interlayer. For small InAs amount and low group-V flow rate, the QD density is reduced to below 10 QDs/μm2. Increasing the group-V flow rate slightly increases the QD density and shifts the QD emission wavelength into the 1.55 μm telecommunication region. Without GaAs interlayer, the QD density is drastically increased. This is attributed to the suppression of As/P exchange during QD growth by the GaAs interlayer avoiding the formation of excess InAs.
Managing catchments for multiple objectives: the implications of land use change for salinity, biodiversity and economics
Authors: Bathgate Andrew , Seddon Julian , Finalyson John , Hacker Ron
Published: September 2009

Policy developed for the management of natural resources in agricultural landscapes in recent years has emphasised the need for an integrated approach. Operationally however, natural resource objectives have been pursued independently with little consideration of the link between components of ecosystems and therefore the possibility of trade-offs between components. In the absence of this information, decision makers cannot adequately assess the cost-effectiveness of alternative strategies for improving the condition of the natural resource base. The aim of this study is to assess the extent of trade-offs between multiple catchment objectives viz. biodiversity, stream salinity, stream yield, salt load, sequestration of carbon and farm profit in the Little River Catchment in Central New South Wales. Seven scenarios describing different land use alternatives for the catchment were assessed using spatial datasets of catchment characteristics. A suite of models was used to determine the impact of land use change on these characteristics over a 50-year timeframe. The results of the analysis indicate that changes in farm production methods may deliver small improvements in some indicators of catchment health. However, significant improvements would require the establishment of large areas of woody perennials and this is only likely to occur with significant public investment, given the consequent large reduction in farm profit. Trade-offs between several catchment indicators were identified. Significantly the benefits of reducing stream salinity were outweighed by the losses resulting from reduced stream flow. Generally, the financial benefits of improving the indicators of resource condition were low relative to the investment required. It was concluded therefore that the environmental value of these improvements would need to be substantial to justify the investment.
Economic value of grazing vegetative wheat (Triticum aestivum L.) crops in mixed-farming systems of Western Australia
Authors: Doole Graeme J. , Bathgate Andrew D. , Robertson Michael J.
Published: September 2009

Livestock production in Western Australian mixed-farming systems has traditionally been constrained by a profound scarcity of feed in autumn–early winter when crop stubbles and pasture residues from the previous growing season have been exhausted. This study investigates the profitability of partially filling this ‘feed gap’ through the grazing of vegetative wheat crops. Whole-farm bioeconomic modelling is used to provide insight into the relative value of grazing and grain production in both low- and high-rainfall areas of Western Australia. Dual-purpose wheat crops are a valuable source of feed in high-rainfall areas as they provide an affordable alternative to expensive grain supplements for a short period in winter. This also allows annual pastures to establish more vigorously by reducing grazing pressure on young plants. Model output suggests farm profit can increase by over 10% with the grazing of vegetative wheat crops in high-rainfall regions; however, these results are logically shown to be strongly related to the assumed rate of yield loss. In contrast, at the parameter values used in this study, grazing wheats are unlikely to be profitable in low-rainfall environments due to depressed crop production and the extended feed gap experienced in these areas. Higher grain prices unequivocally lower the relative advantage of grazing activity since this elevates the cost of foregone grain yield.
Spectroscopic evidence for an engineered, catalytically active Trp radical that creates the unique reactivity of lignin peroxidase
Authors: Smith Andrew T. , Doyle Wendy A. , Dorlet Pierre , Ivancich Anabella
Published: September 2009

The surface oxidation site (Trp-171) in lignin peroxidase (LiP) required for the reaction with veratryl alcohol a high-redox-potential (1.4 V) substrate, was engineered into
Coprinus cinereus
peroxidase (CiP) by introducing a Trp residue into a heme peroxidase that has similar protein fold but lacks this activity. To create the catalytic activity toward veratryl alcohol in CiP, it was necessary to reproduce the Trp site and its negatively charged microenvironment by means of a triple mutation. The resulting D179W+R258E+R272D variant was characterized by multifrequency EPR spectroscopy. The spectra unequivocally showed that a new Trp radical [
g
values of

g
x

= 2.0035(5),

g
y

= 2.0027(5), and

g
z

= 2.0022(1)] was formed after the [Fe(IV)=O Por
•+
] intermediate, as a result of intramolecular electron transfer between Trp-179 and the porphyrin. Also, the EPR characterization crucially showed that [Fe(IV)=O Trp-179
•
] was the reactive intermediate with veratryl alcohol. Accordingly, our work shows that it is necessary to take into account the physicochemical properties of the radical, fine-tuned by the microenvironment, as well as those of the preceding [Fe(IV)=O Por
•+
] intermediate to engineer a catalytically competent Trp site for a given substrate. Manipulation of the microenvironment of the Trp-171 site in LiP allowed the detection by EPR spectroscopy of the Trp-171
•
, for which direct evidence has been missing so far. Our work also highlights the role of Trp residues as tunable redox-active cofactors for enzyme catalysis in the context of peroxidases with a unique reactivity toward recalcitrant substrates that require oxidation potentials not realized at the heme site.
Segregating the significant from the mundane on a moment-to-moment basis via direct and indirect amygdala contributions
Authors: Lim Seung-Lark , Padmala Srikanth , Pessoa Luiz
Published: September 2009

If the amygdala is involved in shaping perceptual experience when affectively significant visual items are encountered, responses in this structure should be correlated with both visual cortex responses and behavioral reports. Here, we investigated how affective significance shapes visual perception during an attentional blink paradigm combined with aversive conditioning. Behaviorally, following aversive learning, affectively significant scenes (CS+) were better detected than neutral (CS−) ones. In terms of mean brain responses, both amygdala and visual cortical responses were stronger during CS+relative to CS−trials. Increased brain responses in these regions were associated with improved behavioral performance across participants and followed a mediation-like pattern. Importantly, the mediation pattern was observed in a trial-by-trial analysis, revealing that the specific pattern of trial-by-trial variability in brain responses was closely related to single-trial behavioral performance. Furthermore, the influence of the amygdala on visual cortical responses was consistent with a mediation, although partial, via frontal brain regions. Our results thus suggest that affective significance potentially determines the fate of a visual item during competitive interactions by enhancing sensory processing through both direct and indirect paths. In so doing, the amygdala helps separate the significant from the mundane.
Membrane structure and conformational changes of the antibiotic heterodimeric peptide distinctin by solid-state NMR spectroscopy
Authors: Resende Jarbas M. , Moraes Cléria Mendonça , Munhoz Victor H. O. , Aisenbrey Christopher , Verly Rodrigo M. , Bertani Philippe , Cesar Amary , Piló-Veloso Dorila , Bechinger Burkhard
Published: September 2009

The heterodimeric antimicrobial peptide distinctin is composed of 2 linear peptide chains of 22- and 25-aa residues that are connected by a single intermolecular S-S bond. This heterodimer has been considered to be a unique example of a previously unrecorded class of bioactive peptides. Here the 2 distinctin chains were prepared by chemical peptide synthesis in quantitative amounts and labeled with
15
N, as well as
15
N and
2
H, at selected residues, respectively, and the heterodimer was formed by oxidation. CD spectroscopy indicates a high content of helical secondary structures when associated with POPC/POPG 3:1 vesicles or in membrane-mimetic environments. The propensity for helix formation follows the order heterodimer >chain 2 >chain 1, suggesting that peptide-peptide and peptide-lipid interactions both help in stabilizing this secondary structure. In a subsequent step the peptides were reconstituted into oriented phospholipid bilayers and investigated by
2
H and proton-decoupled
15
N solid-state NMR spectroscopy. Whereas chain 2 stably inserts into the membrane at orientations close to perfectly parallel to the membrane surface in the presence or absence of chain 1, the latter adopts a more tilted alignment, which further increases in the heterodimer. The data suggest that membrane interactions result in considerable conformational rearrangements of the heterodimer. Therefore, chain 2 stably anchors the heterodimer in the membrane, whereas chain 1 interacts more loosely with the bilayer. These structural observations are consistent with the antimicrobial activities when the individual chains are compared to the dimer.
Opportunistic pathogens enriched in showerhead biofilms
Authors: Feazel Leah M. , Baumgartner Laura K. , Peterson Kristen L. , Frank Daniel N. , Harris J. Kirk , Pace Norman R.
Published: September 2009

The environments we humans encounter daily are sources of exposure to diverse microbial communities, some of potential concern to human health. In this study, we used culture-independent technology to investigate the microbial composition of biofilms inside showerheads as ecological assemblages in the human indoor environment. Showers are an important interface for human interaction with microbes through inhalation of aerosols, and showerhead waters have been implicated in disease. Although opportunistic pathogens commonly are cultured from shower facilities, there is little knowledge of either their prevalence or the nature of other microorganisms that may be delivered during shower usage. To determine the composition of showerhead biofilms and waters, we analyzed rRNA gene sequences from 45 showerhead sites around the United States. We find that variable and complex, but specific, microbial assemblages occur inside showerheads. Particularly striking was the finding that sequences representative of non-tuberculous mycobacteria (NTM) and other opportunistic human pathogens are enriched to high levels in many showerhead biofilms, >100-fold above background water contents. We conclude that showerheads may present a significant potential exposure to aerosolized microbes, including documented opportunistic pathogens. The health risk associated with showerhead microbiota needs investigation in persons with compromised immune or pulmonary systems.
Gasp, a Grb2-associating protein, is critical for positive selection of thymocytes
Authors: Patrick Michael S. , Oda Hiroyo , Hayakawa Kunihiro , Sato Yoshinori , Eshima Koji , Kirikae Teruo , Iemura Shun-ichiro , Shirai Mutsunori , Abe Takaya , Natsume Tohru , Sasazuki Takehiko , Suzuki Harumi
Published: September 2009

T cells develop in the thymus through positive and negative selection, which are responsible for shaping the T cell receptor (TCR) repertoire. To elucidate the molecular mechanisms involved in selection remains an area of intense interest. Here, we identified and characterized a gene product Gasp (Grb2-associating protein, also called Themis) that is critically required for positive selection. Gasp is a cytosolic protein with no known functional motifs that is expressed only in T cells, especially immature CD4/CD8 double positive (DP) thymocytes. In the absence of Gasp, differentiation of both CD4 and CD8 single positive cells in the thymus was severely inhibited, whereas all other TCR-induced events such as β-selection, negative selection, peripheral activation, and homeostatic proliferation were unaffected. We found that Gasp constitutively associates with Grb2 via its N-terminal Src homology 3 domain, suggesting that Gasp acts as a thymocyte-specific adaptor for Grb2 or regulates Ras signaling in DP thymocytes. Collectively, we have described a gene called Gasp that is critical for positive selection.
Survey on sign language interpreting in China
Authors: Xiao Xiaoyan  , Yu Ruiling
Published: September 2009

Though research into sign language interpreting (SLI) has been recognized as an integral part of general translation studies, especially of interpreting studies, SLI is yet to make its way into the consciousness of translation studies researchers on the Chinese mainland. This paper presents data collected from two surveys carried out in China, one of the sign language interpreters and one of the deaf community, covering areas including the interpreters’ professional profiles, the SLI market, professional issues, interpreting difficulties, directionality, quality issues and the role of the interpreter. The paper ends with an analysis of the unique challenges facing the professional development of and research into SLI in China.
Address form shifts in interpreted Q&A sessions
Authors: Chang Chia-chien , Wu Michelle Min-chia
Published: September 2009

This paper examines the use of address forms in interpreter-mediated question and answer (Q&A) sessions in international conferences. The address forms analyzed include both the names and the pronouns the questioners used to address the presenters. The data were collected from two conferences held in Taiwan during which Chinese/English simultaneous interpretation were provided. The Q&A pairs were divided into three categories: (1) bilingual/multilingual communication between questioners and presenters who spoke different languages; (2) monolingual communication between questioners and presenters who spoke the same language, (3) English-as-lingua-franca communication between questioners and presenters who spoke different language but chose to use English as a common language. The results show that (1) shifts in address forms occurred most frequently in interpreter-mediated bilingual/multilingual communication, (2) simultaneous interpreters tended to conform to target-culture conventions in their renditions of address forms, even though their decisions were still influenced by the cognitive constraints ubiquitous in the process of simultaneous interpreting.
Entropic organization of interphase chromosomes
Authors: Cook Peter R. , Marenduzzo Davide
Published: September 2009

Chromosomes are not distributed randomly in nuclei. Appropriate positioning can activate (or repress) genes by bringing them closer to active (or inactive) compartments like euchromatin (or heterochromatin), and this is usually assumed to be driven by specific local forces (e.g., involving H bonds between nucleosomes or between nucleosomes and the lamina). Using Monte Carlo simulations, we demonstrate that nonspecific (entropic) forces acting alone are sufficient to position and shape self-avoiding polymers within a confining sphere in the ways seen in nuclei. We suggest that they can drive long flexible polymers (representing gene-rich chromosomes) to the interior, compact/thick ones (and heterochromatin) to the periphery, looped (but not linear) ones into appropriately shaped (ellipsoidal) territories, and polymers with large terminal beads (representing centromeric heterochromatin) into peripheral chromocenters. Flexible polymers tend to intermingle less than others, which is in accord with observations that gene-dense (and so flexible) chromosomes make poor translocation partners. Thus, entropic forces probably participate in the self-organization of chromosomes within nuclei.
Tropomodulin1 is required for membrane skeleton organization and hexagonal geometry of fiber cells in the mouse lens
Authors: Nowak Roberta B. , Fischer Robert S. , Zoltoski Rebecca K. , Kuszak Jerome R. , Fowler Velia M.
Published: September 2009

Hexagonal packing geometry is a hallmark of close-packed epithelial cells in metazoans. Here, we used fiber cells of the vertebrate eye lens as a model system to determine how the membrane skeleton controls hexagonal packing of post-mitotic cells. The membrane skeleton consists of spectrin tetramers linked to actin filaments (F-actin), which are capped by tropomodulin1 (Tmod1) and stabilized by tropomyosin (TM). In mouse lenses lacking Tmod1, initial fiber cell morphogenesis is normal, but fiber cell hexagonal shapes and packing geometry are not maintained as fiber cells mature. Absence of Tmod1 leads to decreased γTM levels, loss of F-actin from membranes, and disrupted distribution of β2-spectrin along fiber cell membranes. Regular interlocking membrane protrusions on fiber cells are replaced by irregularly spaced and misshapen protrusions. We conclude that Tmod1 and γTM regulation of F-actin stability on fiber cell membranes is critical for the long-range connectivity of the spectrin–actin network, which functions to maintain regular fiber cell hexagonal morphology and packing geometry.
Self–class I MHC molecules support survival of naive CD8 T cells, but depress their functional sensitivity through regulation of CD8 expression levels
Authors: Takada Kensuke , Jameson Stephen C.
Published: September 2009

Previous studies have suggested that naive CD8 T cells require self-peptide–major histocompatability complex (MHC) complexes for maintenance. However, interpretation of such studies is complicated because of the involvement of lymphopenic animals, as lymphopenia drastically alters naive T cell homeostasis and function. In this study, we explored naive CD8 T cell survival and function in nonlymphopenic conditions by using bone marrow chimeric donors and hosts in which class I MHC expression is absent or limited to radiosensitive versus radioresistant cells. We found that long-term survival of naive CD8 T cells (but not CD4 T cells) was impaired in the absence of class I MHC. However, distinct from this effect, class I MHC deprivation also enhanced naive CD8 T cell responsiveness to low-affinity (but not high-affinity) peptide–MHC ligands. We found that this improved sensitivity was a consequence of up-regulated CD8 levels, which was mediated through a transcriptional mechanism. Hence, our data suggest that, in a nonlymphopenic setting, self-class I MHC molecules support CD8 T cell survival, but that these interactions also attenuate naive T cell sensitivity by dynamic tuning of CD8 levels.
GM-CSF regulates intimal cell proliferation in nascent atherosclerotic lesions
Authors: Zhu Su-Ning , Chen Mian , Jongstra-Bilen Jenny , Cybulsky Myron I.
Published: September 2009

The contribution of intimal cell proliferation to the formation of early atherosclerotic lesions is poorly understood. We combined 5-bromo-2′-deoxyuridine pulse labeling with sensitive en face immunoconfocal microscopy analysis, and quantified intimal cell proliferation and Ly-6Chigh monocyte recruitment in low density lipoprotein receptor–null mice. Cell proliferation begins in nascent lesions preferentially at their periphery, and proliferating cells accumulate in lesions over time. Although intimal cell proliferation increases in parallel to monocyte recruitment as lesions grow, proliferation continues when monocyte recruitment is inhibited. The majority of proliferating intimal cells are dendritic cells expressing CD11c and major histocompatibility complex class II and 33D1, but not CD11b. Systemic injection of granulocyte/macrophage colony-stimulating factor (GM-CSF) markedly increased cell proliferation in early lesions, whereas function-blocking anti–GM-CSF antibody inhibited proliferation. These findings establish GM-CSF as a key regulator of intimal cell proliferation in lesions, and demonstrate that both proliferation and monocyte recruitment contribute to the inception of atherosclerosis.
Microbial Flora on the Hands of Health Care Personnel: Differences in Composition and Antibacterial Resistance
Authors: Horn William A. , Larson Elaine L. , McGinley Kenneth J. , Leyden James J.
Published: September 2009

The composition and antibiotic sensitivity pattern of bacteria recovered from the hands of nurses and physicians in two service units of a major teaching hospital were compared with those found in a control population. Significant differences in the composition of bacteria were found in dermatology and oncology unit personnel. Staphylococcus aureus was recovered from 31% of dermatology nurses and 37% of dermatology physicians compared with 20% of oncology nurses, 15% of oncology physicians, and 17% of controls. Oncology personnel had a significantly higher carriage of gramnegative bacteria, yeasts, and multiple antibiotic-resistant, aerobic coryneforms (group JK bacteria). Both dermatology and oncology nursing personnel were colonized by organisms resistant to multiple antibiotics. Methicillin resistance was found in 26% and 66% of the staphylococci recovered from dermatology and oncology nurses respectively. Flora from physicians on the two units had sensitivity patterns similar to controls.
Nosocomial Transmission of HIV in Africa: What Tribute Is Paid to Contaminated Blood Transfusions and Medical Injections?
Authors: Lepage Philippe , Van de Perre Philippe
Published: September 2009

We reviewed the published data on the possible impact of medical injections and blood transfusions on the spread of human immunodeficiency virus (HIV) in Africa. We also compared these results to our experience in Rwanda, central Africa. The importance of medical injections in the epidemic of HIV infection seems to differ from one area to another. The excess of injections experienced by HIV seropositive subjects in Zaire could be secondary to the parenteral treatment of early HIV-related illness or to the treatment of sexually transmitted diseases, rather than being the cause of HIV infection, as suggested by Rwandese studies. In contrast, blood transfusions have been shown to represent an important source of nosocomial HIV infection in many African countries. Effective and relatively inexpensive measures to diminish the iatrogenic spread of HIV infection in developing countries are summarized.
Association of Malnutrition with Nosocomial Infection
Authors: Gorse Geoffrey J. , Messner Roberta L. , Stephens Nancy D.
Published: September 2009

To study the association of malnutrition with nosocomial infection in a general medical and surgical inpatient population, we retrospectively compared 45 patients with nosocomial infection to 45 uninfected control patients, matched using several nonnutritional variables known to predispose to nosocomial infection. Univariate and multivariate analyses were done. Poor nutritional score (derived from serum albumin, total lymphocyte count, and unintentional body weight loss), unintentional body weight loss, low serum albumin level at both time of admission and the first nosocomial infection, and worsening in the nutritional score and serum albumin from admission to the first nosocomial infection were associated with the development of nosocomial infection. Nutritional factors were more abnormal in subgroups of patients with nosocomial pneumonia, urinary tract infection, wound infection, and bacteremia than in controls. The findings suggest that further study of correlations between nutritional factors and nosocomial infections is needed.
Incidence of Nosocomial Aspergillosis in Patients with Leukemia Over a Twenty-Year Period
Authors: Klimowski Linda L. , Rotstein Coleman , Cummings K. Michael
Published: September 2009

The incidence of invasive nosocomial aspergillosis was studied in leukemia patients at an oncology center from 1964 to 1983. A total of 97 cases of aspergillosis occurred in 1,866 patients, yielding an overall case rate of 5.2 cases per 100 patients and an incidence rate of 9.1 per 10,000 patient days. The highest incidence rate was in patients with chronic myelogenous leukemia (13.7 cases per 10,000 patient days), followed by patients with acute myelogenous leukemia (10.6 cases per 10,000 patient days). Subdividing patients after 1978 into those receiving bone marrow transplantation and those who did not demonstrated the predisposition of transplant recipients to aspergillosis. The rates of aspergillosis among those patients who did not receive a bone marrow transplant were highest for patients with acute myelogenous leukemia. Increases in the annual rates of aspergillosis over time coincided with the level of internal renovation activity and major construction projects upwind of patient care facilities.