bluuebunny/crossref_metadata_2025 huggingface dataset:
Protein expressed by the ho2 gene of the cyanobacterium Synechocystis sp. PCC 6803 is a true heme oxygenase
Authors: Zhang Xuhong , Migita Catharina T. , Sato Michihiko , Sasahara Masanao , Yoshida Tadashi
Published: October 2006

Two isoforms of a heme oxygenase gene, ho1 and ho2, with 51% identity in amino acid sequence have been identified in the cyanobacterium Synechocystis sp. PCC 6803. Isoform‐1, Syn HO‐1, has been characterized, while isoform‐2, Syn HO‐2, has not. In this study, a full‐length ho2 gene was cloned using synthetic DNA and Syn HO‐2 was demonstrated to be highly expressed in Escherichia coli as a soluble, catalytically active protein. Like Syn HO‐1, the purified Syn HO‐2 bound hemin stoichiometrically to form a heme–enzyme complex and degraded heme to biliverdin IXα, CO and iron in the presence of reducing systems such as NADPH/ferredoxin reductase/ferredoxin and sodium ascorbate. The activity of Syn HO‐2 was found to be comparable to that of Syn HO‐1 by measuring the amount of bilirubin formed. In the reaction with hydrogen peroxide, Syn HO‐2 converted heme to verdoheme. This shows that during the conversion of hemin to α‐meso‐hydroxyhemin, hydroperoxo species is the activated oxygen species as in other heme oxygenase reactions. The absorption spectrum of the hemin–Syn HO‐2 complex at neutral pH showed a Soret band at 412 nm and two peaks at 540 nm and 575 nm, features observed in the hemin‐Syn HO‐1 complex at alkaline pH, suggesting that the major species of iron(III) heme iron at neutral pH is a hexa‐coordinate low spin species. Electron paramagnetic resonance (EPR) revealed that the iron(III) complex was in dynamic equilibrium between low spin and high spin states, which might be caused by the hydrogen bonding interaction between the distal water ligand and distal helix components. These observations suggest that the structure of the heme pocket of the Syn HO‐2 is different from that of Syn HO‐1.
Preparation and characterization of geodin
Authors: Giancola Concetta , Pizzo Elio , Di Maro Antimo , Cubellis Maria Vittoria , D'Alessio Giuseppe
Published: October 2006

Geodin is a protein encoded by a sponge gene homologous to genes from the βγ‐crystallins superfamily. The interest for this crystallin‐type protein stems from the phylogenesis of porifera, commonly called sponges, the earliest divergence event in the history of metazoans. Here we report the preparation of geodin as a recombinant protein from Escherichia coli, its characterization through physico‐chemical analyses, and a model of its 3D structure based on homology modelling. Geodin is a monomeric protein of about 18 kDa, with an all‐beta structure, as all other crystallins in the superfamily, but more prone to unfold in the presence of chemical denaturants, when compared with other homologues from the superfamily. Its thermal unfolding, studied by far‐ and near‐CD, and by calorimetry, is described by a two‐state model. Geodin appears to be structurally similar in many respects to the bacterial protein S crystallin, with which it also shares a significant, albeit more modest stabilizing effect exerted by calcium ions. These results suggest that the crystallin‐type structural scaffold, employed in the evolution of bacteria and moulds, was successfully recruited very early in the evolution of metazoa.
Properties of the recombinant glucose/galactose dehydrogenase from the extreme thermoacidophile, Picrophilus torridus
Authors: Angelov Angel , Fütterer Ole , Valerius Oliver , Braus Gerhard H. , Liebl Wolfgang
Published: October 2006

In Picrophilus torridus, a euryarchaeon that grows optimally at 60 °C and pH 0.7 and thus represents the most acidophilic thermophile known, glucose oxidation is the first proposed step of glucose catabolism via a nonphosphorylated variant of the Entner–Doudoroff pathway, as deduced from the recently completed genome sequence of this organism. The P. torridus gene for a glucose dehydrogenase was cloned and expressed in Escherichia coli, and the recombinant enzyme, GdhA, was purified and characterized. Based on its substrate and coenzyme specificity, physicochemical characteristics, and mobility during native PAGE, GdhA apparently resembles the main glucose dehydrogenase activity present in the crude extract of P. torridus DSM 9790 cells. The glucose dehydrogenase was partially purified from P. torridus cells and identified by MS to be identical with the recombinant GdhA. P. torridus GdhA preferred NADP+ over NAD+ as the coenzyme, but was nonspecific for the configuration at C‐4 of the sugar substrate, oxidizing both glucose and its epimer galactose (Km values 10.0 and 4.5 mm, respectively). Detection of a dual‐specific glucose/galactose dehydrogenase points to the possibility that a ‘promiscuous’ Entner–Doudoroff pathway may operate in P. torridus, similar to the one recently postulated for the crenarchaeon Sulfolobus solfataricus. Based on Zn2+ supplementation and chelation experiments, the P. torridus GdhA appears to contain structurally important zinc, and conserved metal‐binding residues suggest that the enzyme also contains a zinc ion near the catalytic site, similar to the glucose dehydrogenase enzymes from yeast and Thermoplasma acidophilum. Strikingly, NADPH, one of the products of the GdhA reaction, is unstable under the conditions thought to prevail in Picrophilus cells, which have been reported to maintain the lowest cytoplasmic pH known (pH 4.6). At the optimum growth temperature for P. torridus, 60 °C, the half‐life of NADPH at pH 4.6 was merely 2.4 min, and only 1.7 min at 65 °C (maximum growth temperature). This finding suggests a rapid turnover of NADPH in Picrophilus.
Ten years of predictions … and counting
Authors: Cozzetto Domenico , Di Matteo Adele , Tramontano Anna
Published: October 2006

The CASP experiment has been run every other year since 1994. Its objective is to subject the available structure prediction methods to a blind test. This is a short report of the highlights of its last edition.

‘Men who wish to know about the world must learn about it in its particular details’ (Heraclitus of Ephesus, 535–475 bc).
Flow Mechanism of Glaciers on Soft Beds
Authors: Iverson Neal R. , Hanson Brian , Hooke Roger LeB. , Jansson Peter
Published: October 2006

Subhourly measurements of bed deformation, bed shear strength, subglacial water pressure, and surface speed at Storglaciären, a glacier in northern Sweden, showed that the shear-strain rates of the bed decrease during periods of high water pressure and surface speed. High water pressures appear to be accompanied by a reduction in the coupling of ice with the bed that is sufficient to reduce or eliminate shearing. The instability of large ice masses may result from similar decoupling rather than from pervasive bed deformation, as has been commonly thought.
Quasars and a Dwarf Star Break the Rules in Tucson
Authors: Travis John
Published: October 2006

Earlier this month, more than 2000 astronomers convened in Tucson, Arizona, for the American Astronomical Society's largest meeting ever. Even the war drums beaten by a few local Apaches and their supporters, protesting a University of Arizona telescope project, could not drown out lecture-hall and corridor discussions of topics such as naked quasars, flaring stars, and planetary searches.
Arcs and Clumps in the Uranian λ Ring
Authors: Showalter Mark R.
Published: October 2006

Careful reprocessing of the Voyager images reveals that the Uranian λ ring has marked longitudinal variations in brightness comparable in magnitude to those in Saturn's F ring and Neptune's Adams ring. The ring's variations show a dominant five-cycle (72-degree) periodicity, although additional structure down to scales of about 0.5 degree is also present. The ring's shape is defined by a small overall eccentricity plus a six-cycle (60-degree) sinusoidal variation of radial amplitude around 4 kilometers. Both of these properties can be explained by the resonant perturbations of a moon at a semimajor axis of 56,479 kilometers, but no known moon orbits at this location. Unfortunately, the mass required suggests that such a body should have been imaged by Voyager.
Climate-Related, Long-Term Faunal Changes in a California Rocky Intertidal Community
Authors: Barry J. P. , Baxter C. H. , Sagarin R. D. , Gilman S. E.
Published: October 2006

Changes in the invertebrate fauna of a California rocky intertidal community between the period 1931 to 1933 and the period 1993 to 1994 indicate that species' ranges shifted northward, consistent with predictions of change associated with climate warming. Of 45 invertebrate species, the abundances of eight of nine southern species increased and the abundances of five of eight northern species decreased. No trend was evident for cosmopolitan species. Annual mean shoreline ocean temperatures at the site increased by 0.75°C during the past 60 years, and mean summer maximum temperatures from 1983 to 1993 were 2.2°C warmer than for the period 1921 to 1931.
Forearc Deformation and Great Subduction Earthquakes: Implications for Cascadia Offshore Earthquake Potential
Authors: McCaffrey Robert , Goldfinger Chris
Published: October 2006

The maximum size of thrust earthquakes at the world's subduction zones appears to be limited by anelastic deformation of the overriding plate. Anelastic strain in weak forearcs and roughness of the plate interface produced by faults cutting the forearc may limit the size of thrust earthquakes by inhibiting the buildup of elastic strain energy or slip propagation or both. Recently discovered active strike-slip faults in the submarine forearc of the Cascadia subduction zone show that the upper plate there deforms rapidly in response to arc-parallel shear. Thus, Cascadia, as a result of its weak, deforming upper plate, may be the type of subduction zone at which great (moment magnitude ≈ 9) thrust earthquakes do not occur.
Electrochemical Detection of Single Molecules
Authors: Fan Fu-Ren F. , Bard Allen J.
Published: October 2006

The electrochemical behavior of a single molecule can be observed by trapping a small volume of a dilute solution of the electroactive species between an ultramicroelectrode tip with a diameter of ∼15 nanometers and a conductive substrate. A scanning electrochemical microscope was used to adjust the tip-substrate distance (∼10 nanometers), and the oxidation of [(trimethylammonio)methyl] ferrocene (Cp
2
FeTMA
+
) to Cp
2
FeTMA
2+
was carried out. The response was stochastic, and anodic current peaks were observed as the molecule moved into and out of the electrode-substrate gap. Similar experiments were performed with a solution containing two redox species, ferrocene carboxylate (Cp
2
FeCOO
-
) and Os(bpy)
3
2+
(bpy is 2,2′-bipyridyl).
A Net Sink for Atmospheric CH
3
Br in the East Pacific Ocean
Authors: Lobert Jürgen M. , Butler James H. , Montzka Stephen A. , Geller Laurie S. , Myers Richard C. , Elkins James W.
Published: October 2006

Surface waters along a cruise track in the East Pacific Ocean were undersaturated in methyl bromide (CH
3
Br) in most areas except for coastal and upwelling regions, with saturation anomalies ranging from + 100 percent in coastal waters to –50 percent in open ocean areas, representing a regionally weighted mean of –16 (–13 to –20) percent. The partial lifetime of atmospheric CH
3
Br with respect to calculated oceanic degradation along this cruise track is 3.0 (2.9 to 3.6) years. The global, mean dry mole fraction of CH
3
Br in the atmosphere was 9.8 ± 0.6 parts per trillion, with an interhemispheric ratio of 1.31 ± 0.08. These data indicate that ∼8 percent (0.2 parts per trillion) of the observed interhemispheric difference in atmospheric CH3Br could be attributed to an uneven global distribution of oceanic sources and sinks.
Evidence from Ion Chromatography Experiments That Met-Cars Are Hollow Cage Clusters
Authors: Lee Seonghoon , Gotts Nigel G. , von Helden Gert , Bowers Michael T.
Published: October 2006

Ion chromatography studies were performed to assess various models proposed for the structure of M
8
C
12
species, the met-cars. A laser desorption source was used to make a sequence of titanium-carbon clusters centered around Ti
8
C
12
+
. The Ti
8
C
12
+
was determined to be a hollow cage cluster, with the dodecahedron structure originally proposed giving the best fit to experiment; cubic structures could be excluded. Collisional breakup of Ti
8
C
12
+
yielded only Ti
7
C
12
+
under the experimental conditions described herein, and modeling indicated that the cage structure was retained. Both Ti
8
C
11
+
and Ti
8
C
13
+
were made by the cluster source, and again, dodecahedral-type cage structures were consistent with experiment. The extra carbon atom in Ti
8
C
13
+
was attached exohedrally to a single titanium atom. No evidence for an endohedral species was found.
Viscous Dissipation in Three-Dimensional Convection with Temperature-Dependent Viscosity
Authors: Balachandar S. , Yuen D. A. , Reuteler D. M. , Lauer G. S.
Published: October 2006

Numerical simulations of three-dimensional convection with temperature-dependent viscosity and viscous heating at realistic Rayleigh numbers for Earth's mantle reveal that, in the strongly time-dependent regime, very intense localized heating takes place along the top portion of descending cold sheets and also at locations where the ascending plume heads impinge at the surface. For a viscosity contrast of 100, these localized heat sources exceed the internal heating due to the radioactive decay of chondritic materials by more than an order of magnitude. The horizontally averaged viscous dissipation is concentrated in the top of the convecting layer and has a magnitude comparable with that of radioactive heating.
Conducting Layered Organic-inorganic Halides Containing 〈110〉-Oriented Perovskite Sheets
Authors: Mitzi D. B. , Wang S. , Feild C. A. , Chess C. A. , Guloy A. M.
Published: October 2006

Single crystals of the layered organic-inorganic perovskites, [NH
2
C(I)=NH
2
]
2
(CH
3
NH
3
)

m

Sn

m

I

3
m
+2

, were prepared by an aqueous solution growth technique. In contrast to the recently discovered family, (C
4
H
9
NH
3
)
2
(CH
3
NH
3
)

n
-1

Sn

n

I

3
n
+1

, which consists of 〈100〉-terminated perovskite layers, structure determination reveals an unusual structural class with sets of
m
〈110〉-oriented CH
3
NH
3
SnI
3
perovskite sheets separated by iodoformamidinium cations. Whereas the
m
= 2 compound is semiconducting with a band gap of 0.33 ± 0.05 electron volt, increasing
m
leads to more metallic character. The ability to control perovskite sheet orientation through the choice of organic cation demonstrates the flexibility provided by organic-inorganic perovskites and adds an important handle for tailoring and understanding lower dimensional transport in layered perovskites.
Direct Observations of Excess Solar Absorption by Clouds
Authors: Pilewskie Peter , Valero Francisco P. J.
Published: October 2006

Aircraft measurements of solar flux in the cloudy tropical atmosphere reveal that solar absorption by clouds is anomalously large when compared to theoretical estimates. The ratio of cloud forcing at an altitude of 20 kilometers to that at the surface is 1.58 rather than 1.0, as predicted by models. These results were derived from a cloud radiation experiment in which identical instrumentation was deployed on coordinated stacked aircraft. These findings indicate a significant difference between measurements and theory and imply that the interaction between clouds and solar radiation is poorly understood.
Lipid Tubule Self-Assembly: Length Dependence on Cooling Rate Through a First-Order Phase Transition
Authors: Thomas Britt N. , Safinya Cyrus R. , Plano Robert J. , Clark Noel A.
Published: October 2006

The formation kinetics and self-assembly of multilamellar tubules of the diacetylenic phospholipid 1,2-bis(tricosa-10,12-diynoyl)-
sn
-glycerol-3-phosphocholine formed under controlled cooling rates were studied by x-ray diffraction and optical, atomic force, and scanning electron microscopy. Tubule formation was driven by a reversible first-order phase transition from an intralamellar, chain-melted L
α
phase to a chain-frozen L
β
, phase. These observations are the basis of a highly efficient method of tubule production in which tubule lengths can be controlled, between 1 and 100 micrometers, by varying the cooling rate. These tubules can be made in suspensions with 10 percent lipid by mass, far exceeding the lipid solubility limit.
Dike Injection and the Formation of Megaplumes at Ocean Ridges
Authors: Lowell Robert P. , Germanovich Leonid N.
Published: October 2006

A simple hydrologic model of seawater circulation at ocean ridge axes implies that the transient occurrence of large volumes of buoyant, heated water in the oceanic water column (megaplumes) can be attributed to the emplacement of dikes in oceanic crust. For dikes to generate megaplume flow, the permeability of both the recharge areas and the upflow zone must be greater than that required for ordinary black smokers. An increase in permeability in the upflow zone by several orders of magnitude results from dike emplacement, and megaplume discharge ceases as the dike cools. Vigorous black smoker venting may not persist very long at a megaplume site after the event occurs.
Metallic Glasses
Authors: Greer A. Lindsay
Published: October 2006

Amorphous metallic alloys, relative newcomers to the world of glasses, have properties that are unusual for solid metals. The metallic glasses, which exist in a very wide variety of compositions, combine fundamental interest with practical applications. They also serve as precursors for exciting new nanocrystalline materials. Their magnetic (soft and hard) and mechanical properties are of particular interest.
Spatially Resolved Visible Luminescence of Self-Assembled Semiconductor Quantum Dots
Authors: Leon R. , Petroff P. M. , Leonard D. , Fafard S.
Published: October 2006

Ensembles of defect-free InAlAs islands of ultrasmall dimensions embedded in AlGaAs have been grown by molecular beam epitaxy. Cathodoluminescence was used to directly image the spatial distribution of the quantum dots by mapping their luminescence and to spectrally resolve very sharp peaks from small groups of dots, thus providing experimental verification for the discrete density of states in a zero-dimensional quantum structure. Visible luminescence is produced by different nominal compositions of In

x

Al(

1–
x
)

As-Al

y

Ga

(1–
y
)

As.
Design and Application of Electron-Transporting Organic Materials
Authors: Strukelj Marko , Papadimitrakopoulos Fotis , Miller Timothy M. , Rothberg Lewis J.
Published: October 2006

Operating lifetime is the main problem that complicates the use of polymeric light-emitting diodes (LEDs). A class of electron transport (ET) polymers [poly(aryl acrylate) and poly(aryl ether)s] is reported in which moieties with high electron affinities are covalently attached to stable polymer backbones. Devices based on poly(
p
-phenylenevinylene) (PPV) prepared with these materials exhibited a 30-fold improvement in stability and, in one case, dramatically lower (10 volts versus about 30 volts) operating voltage relative to those having conventional ET layers. The current-carrying capacity of indium tin oxide-PPV-polymeric ET layer-aluminum LEDs was also increased by a factor of 30. These improvements lead to an enhancement in power efficiency of nearly an order of magnitude. Choosing polymers with high glass transition temperatures increases device lifetime.
Atmospheric Methyl Bromide (CH
3
Br) from Agricultural Soil Fumigations
Authors: Yagi K. , Williams J. , Wang N. -Y. , Cicerone R. J.
Published: October 2006

The treatment of agricultural soils with CH
3
Br (MeBr) has been suggested to be a significant source of atmospheric MeBr which is involved in stratospheric ozone loss. A field fumigation experiment showed that, after 7 days, 34 percent of the applied MeBr had escaped into the atmosphere. The remaining 66 percent should have caused an increase in bromide in the soil; soil bromide increased by an amount equal to 70 percent of the applied MeBr, consistent with the flux measurements to within 4 percent. Comparison with an earlier experiment in which the escape of MeBr to the atmosphere was greater showed that higher soil pH, organic content and soil moisture, and deeper, more uniform injection of MeBr may in combination reduce the escape of MeBr.
A Strategy for the Chemical Synthesis of Nanostructures
Authors: Müller Wolfgang T. , Klein David L. , Lee Thomas , Clarke John , McEuen Paul L. , Schultz Peter G.
Published: October 2006

Highly localized chemical catalysis was carried out on the surface groups of a self-assembled monolayer with a scanning probe device. With the use of a platinum-coated atomic force microscope tip, the terminal azide groups of the monolayer were catalytically hydrogenated with high spatial resolution. The newly created amino groups were then covalently modified to generate new surface structures. By varying the nature of the catalyst and the chemical composition of the surface, it may be possible to synthesize molecular assemblies not readily produced by existing microfabrication techniques.
Orientational and Magnetic Ordering of Buckyballs in TDAE-C
60
Authors: Mihailovic D. , Arcon D. , Venturini P. , Blinc R. , Omerzu A. , Cevc P.
Published: October 2006

Spin ordering in the low-temperature magnetic phase is directly linked to the orientational ordering of C
60
molecules in organically doped fullerene derivatives. Electron spin resonance and alternating current susceptometry measurements on tetrakis(dimethylamino)ethylene-C
60
(TDAE-C
60
) (Curie temperature
T
c
= 16 kelvin) show a direct coupling between spin and merohedral degrees of freedom. This coupling was experimentally demonstrated by showing that ordering the spins in the magnetic phase imprints a merohedral order on the solid or, conversely, that merohedrally ordering the C
60
molecules influences the spin order at low temperature. The merohedral disorder gives rise to a distribution of π-lectron exchange interactions between spins on neighboring C
60
molecules, suggesting a microscopic origin for the observed spinglass behavior of the magnetic state.
Global Mean Sea Level Variations from TOPEX/POSEIDON Altimeter Data
Authors: Nerem R. S.
Published: October 2006

The TOPEX/POSEIDON satellite altimeter mission has measured global mean sea level every 10 days over the last 2 years with a precision of 4 millimeters, which approaches the requirements for climate change research. The estimated rate of sea level change is +3.9 ± 0.8 millimeters per year. A substantial portion of this trend may represent a short-term variation unrelated to the long-term signal expected from global warming. For this reason, and because the long-term measurement accuracy requires additional monitoring, a longer time series is necessary before climate change signals can be unequivocally detected.
Dust Measurements at High Ecliptic Latitudes
Authors: Baguhl M. , Hamilton D. P. , Grün E. , Fechtig H. , Kissel J. , Linkert D. , Linkert G. , Riemann R. , Staubach P. , Dermott S. F. , Hanner M. S. , Polanskey C. , Lindblad B.-A. , Mann I. , McDonnell J. A. M. , Morfill G. E. , Schwehm G. , Zook H. A.
Published: October 2006

Along Ulysses' path from Jupiter to the south ecliptic pole, the onboard dust detector measured a dust impact rate that varied slowly from 0.2 to 0.5 impacts per day. The dominant component of the dust flux arrived from an ecliptic latitude and longitude of 10° ± 10° and 280° ± 30° which indicates an interstellar origin. An additional flux of small particles, which do not come from the interstellar direction and are unlikely to be zodiacal dust grains, appeared south of -45° latitude. One explanation is that these particles are beta-meteoroids accelerated away from the sun by radiation pressure and electromagnetic forces.
Calorimetric Measurement of the Energy Difference Between Two Solid Surface Phases
Authors: Yeo Y. Y. , Wartnaby C. E. , King D. A.
Published: October 2006

A recently designed single-crystal surface calorimeter has been deployed to measure the energy difference between two solid surface structures. The clean Pt{100} surface is reconstructed to a stable phase in which the surface layer of platinum atoms has a quasi-hexagonal structure. By comparison of the heats of adsorption of CO and of C
2
H
4
on this stable Pt{100}-hex phase with those on a metastable Pt{100}-(1×1) surface, the energy difference between the two clean phases was measured as 20 ± 3 and 25 ± 3 kilojoules per mole of surface platinum atoms.
Observation of Shoemaker-Levy Impacts by the Galileo Photopolarimeter Radiometer
Authors: Martin Terry Z. , Orton Glenn S. , Travis Larry D. , Tamppari Leslie K. , Claypool Ian
Published: October 2006

The Galileo Photopolarimeter Radiometer experiment made direct photometric observations at 678 and 945 nanometers of several comet Shoemaker-Levy 9 fragments impacting with Jupiter. Initial flashes occurred at (fragment G) 18 July 1994 07:33:32, (H) 18 July 19:31:58, (L) 19 July 22:16:48, and (Q1) 20 July 20:13:52 [equivalent universal time coordinated (UTC) observed at Earth], with relative peak 945-nanometer brightnesses of 0.87, 0.67, 1.00, and 0.42, respectively. The light curves show a 2-second rise to maximum, a 10-second plateau, and an accelerating falloff. The Q1 event, observed at both wavelengths, yielded a color temperature of more than 10,000 kelvin at its peak.
Ecological Experiments with Model Systems
Authors: Lawton John H.
Published: October 2006

Some of the classic experiments in ecology have involved real organisms interacting in the laboratory, that is, model systems. Ecologists are increasingly using model systems to investigate problems of global environmental change and questions about the assembly, persistence, and stability of complex communities. Model laboratory systems are a halfway house between mathematical models and the full complexity of the field, and they yield powerful insights into the dynamics of populations and ecosystems.
Synthesis and Application of Modulated Polymer Gels
Authors: Hu Zhibing , Zhang Xiaomin , Li Yong
Published: October 2006

A class of environmentally responsive materials based on the spatial modulation of the chemical nature of gels is proposed and demonstrated here. The modulation was achieved by limiting the interpenetration of part of one gel network with another gel network. The gels so produced have an internally heterogeneous or modulated structure. Three simple applications based on the modulated gels are described here: a bigel strip, a shape memory gel, and a gel "hand." The bigel strip bends almost to a circle in response to a temperature increase or an increase in solvent concentration. The shape memory gel changes its shape from a straight line to a pentagon to a quadrangle as the temperature increases. These transitions from one shape to another are reversible. The gel "hand" in water can grasp or release an object simply by an adjustment of the temperature.
Controlled Acceleration and Inhibition of Bergman Cyclization by Metal Chlorides
Authors: Warner Benjamin P. , Millar Susan P. , Broene Richard D. , Buchwald Stephen L.
Published: October 2006

The Bergman cyclization has been the subject of renewed interest with the discovery of naturally occurring enediyne-based antitumor agents that cleave DNA by means of an aromatic diradical. These natural substrates have a means to trigger this cycloaromatization process. Control of this reaction by substrate modification would allow aromatic diradicals to be generated selectively. In the studies presented here it is disclosed that the Bergman cyclization of 1,2-bis(diphenyl phosphinoethynyl)benzene was accelerated by a factor of >30,000 by the addition of palladium(II) chloride or platinum(II) chloride and was inhibited by the addition of mercury(II) chloride.
Deimos: An Obstacle to the Solar Wind
Authors: Sauer K. , Dubinin E. , Baumgärtel K. , Bogdanov A.
Published: October 2006

Two isolated solar wind disturbances about 5 minutes in duration were detected aboard the Russian spacecraft Phobos-2 upon its crossing the wake of the martian moon Deimos about 15,000 kilometers downstream from the moon on 1 February 1989. These plasma and magnetic events are interpreted as the inbound and outbound crossings of a Mach cone that is formed as a result of an effective interaction of the solar wind with Deimos. Possible mechanisms such as remanent magnetization, cometary type interaction caused by heavy ion or charged dust production, and unipolar induction resulting from the finite conductivity of the body are discussed. Although none of the present models is fully satisfactory, neutral gas emission through water loss by Deimos at a rate of about 10
23
molecules per second, combined with a charged dust coma, is favored.
Biological Controls on Coral Sr/Ca and δ
18
O Reconstructions of Sea Surface Temperatures
Authors: de Villiers Stephanie , Nelson Bruce K. , Chivas Allan R.
Published: October 2006

Coral strontium/calcium ratios have been used to infer that the tropical sea surface temperature (SST) cooled by as much as 6°C during the last glacial maximum. In contrast, little or no change has been inferred from other marine-based proxy records. Experimental studies of the effect of growth rate and the magnitude of intraspecific differences indicate that biological controls on coral skeletal strontium/calcium uptake have been underestimated. These results call into question the reliability of strontium/calcium-based SST reconstructions.
Midwife to Global Megaprojects Given More Time to Deliver
Authors: Balter Michael
Published: October 2006

An international forum aimed at preparing the way for international “big science” projects has had a mixed record. But it has just been given a new lease on life and a new focus. Can it deliver?
Religion and Gene Patenting
Authors: Cole-Turner Ronald
Published: October 2006

The author responds to a statement opposing the patenting of life issued by religious leaders. He argues that, in contrast to this statement being a continuation of a long-standing conflict between religion and science, religious bodies have historically been supportive of science and that new channels of communication are opening between the two communities.
Prion-Inducing Domain of Yeast Ure2p and Protease Resistance of Ure2p in Prion-Containing Cells
Authors: Masison Daniel C. , Wickner Reed B.
Published: October 2006

The genetic properties of the [URE3] non-Mendelian element of
Saccharomyces cerevisiae
suggest that it is a prion (infectious protein) form of Ure2p, a regulator of nitrogen catabolism. In extracts from [URE3] strains, Ure2p was partially resistant to proteinase K compared with Ure2p from wild-type extracts. Overexpression of Ure2p in wild-type strains induced a 20- to 200-fold increase in the frequency with which [URE3] arose. Overexpression of just the amino-terminal 65 residues of Ure2p increased the frequency of [URE3] induction 6000-fold. Without this “prion-inducing domain” the carboxyl-terminal domain performed the nitrogen regulation function of Ure2p, but could not be changed to the [URE3] prion state. Thus, this domain induced the prion state in trans, whereas in cis it conferred susceptibility of the adjoining nitrogen regulatory domain to prion infections.
Elastic Properties of Flux-Line Arrays in High Transition Temperature Superconductors Probed by Two-Sided Decoration
Authors: Yoon Seokwon , Yao Zhen , Dai Hongjie , Lieber Charles M.
Published: October 2006

The elastic constants of magnetic flux-line lattices in copper oxide superconductors have remained uncharacterized despite their essential role in determining important phenomena such as melting. Here the absolute values of the elastic moduli of flux-line arrays have been probed by correlating the positions of individual flux lines emerging from opposite sides of Bi
2
Sr
2
CaCu
2
O
8
(BSCCO) superconductors. These experiments demonstrate that the compressional and shear moduli of the flux-line lattice are three orders of magnitude smaller than the values predicted by standard models. The origin of these changes in the moduli and the general applicability of this approach to other materials are discussed. In addition, there is a remarkable correspondence between the excitations of the flux-line arrays and those of superfluid helium.
Pseudotachylites Generated in Shock Experiments: Implications for Impact Cratering Products and Processes
Authors: Fiske Peter S. , Nellis William J. , Lipp Magnus , Lorenzana Hector , Kikuchi Masae , Syono Yasuhiko
Published: October 2006

Laboratory hypervelocity impact experiments in which quartz was shock-loaded from 42 to 56 gigapascals imply that type A pseudotachylites form by strain heating and contribute to the loss of strength of rocks in the central uplift of large impact structures. Shock impedance-matched aluminum sample containers, in contrast to steel containers, produced nearly single-wave pressure loading, and enhanced deformation, of silicate samples. Strain heating may act with shock heating to devolatilize planetary materials and destroy extraterrestrial organic material in an impact.
Altered DNA Recognition and Bending by Insertions in the α2 Tail of the Yeast a1/α2 Homeodomain Heterodimer
Authors: Jin Yisheng , Mead Janet , Li Thomas , Wolberger Cynthia , Vershon Andrew K.
Published: October 2006

The yeast MATα2 and MATa1 homeodomain proteins bind cooperatively as a heterodimer to sites upstream of haploid-specific genes, repressing their transcription. In the crystal structure of α2 and a1 bound to DNA, each homeodomain makes independent base-specific contacts with the DNA and the two proteins contact each other through an extended tail region of α2 that tethers the two homeodomains to one another. Because this extended region may be flexible, the ability of the heterodimer to discriminate among DNA sites with altered spacing between α2 and a1 binding sites was examined. Spacing between the half sites was critical for specific DNA binding and transcriptional repression by the complex. However, amino acid insertions in the tail region of α2 suppressed the effect of altering an a1/α2 site by increasing the spacing between the half sites. Insertions in the tail also decreased DNA bending by a1/α2. Thus tethering the two homeodomains contributes to DNA bending by a1/α2, but the precise nature of the resulting bend is not essential for repression.
Gene Therapy in Peripheral Blood Lymphocytes and Bone Marrow for ADA
−
Immunodeficient Patients
Authors: Bordignon Claudio , Notarangelo Luigi D. , Nobili Nadia , Ferrari Giuliana , Casorati Giulia , Panina Paola , Mazzolari Evelina , Maggioni Daniela , Rossi Claudia , Servida Paolo , Ugazio Alberto G. , Mavilio Fulvio
Published: October 2006

Adenosine deaminase (ADA) deficiency results in severe combined immunodeficiency, the first genetic disorder treated by gene therapy. Two different retroviral vectors were used to transfer ex vivo the human ADA minigene into bone marrow cells and peripheral blood lymphocytes from two patients undergoing exogenous enzyme replacement therapy. After 2 years of treatment, long-term survival of T and B lymphocytes, marrow cells, and granulocytes expressing the transferred ADA gene was demonstrated and resulted in normalization of the immune repertoire and restoration of cellular and humoral immunity. After discontinuation of treatment, T lymphocytes, derived from transduced peripheral blood lymphocytes, were progressively replaced by marrow-derived T cells in both patients. These results indicate successful gene transfer into long-lasting progenitor cells, producing a functional multilineage progeny.
Max Planck Institutes Brace for Change
Authors: Kahn Patricia
Published: October 2006

Munich—With funding for life and no teaching requirements, top Max Planck researchers are inan enviable position. But tight budgets, a wave of upcoming retirements, and the challenge of upgrading science in the eastern states may bring some fundamental changes—some say for the better. A sidebar by Robert Koenig profiles zoologist Hubert Markl, the newly elected president of the Max Planck Society.
Rajewsky to Head EMBL's Italian Lab
Authors: Williams Nigel
Published: October 2006

London—Immunologist Klaus Rajewsky has agreed to head part of an effort to create a major European center for mouse genetics just outside Rome. His involvement is expected to give the plans a big boost.
New Clue to Brain Wiring Mystery
Authors: Barinaga Marcia
Published: October 2006

Berkeley, California—How do billions of neurons make the right connections in the developingbrain? One clue has come from attempts to grow neurons in culture: Only those in the electrically active state respond to neuron-nurturing proteins called neurotrophins.
Freshwater Ecosystems and Their Management: A National Initiative
Authors: Naiman Robert J. , Magnuson John J. , McKnight Diane M. , Stanford Jack A. , Karr James R.
Published: October 2006

Recently, the laws and regulations that govern water quality and endangered aquatic ecosystems have begun being evaluated in light of increased demands on use of fresh water. Naiman
et al.
point out that much of the research aimed at evaluating this important resource is in need of improvement and coordination.
Nanoscale Complexity of Phospholipid Monolayers Investigated by Near-Field Scanning Optical Microscopy
Authors: Hwang Jeeseong , Tamm Lukas K. , Böhm Christine , Ramalingam Tirunelveli S. , Betzig Eric , Edidin Michael
Published: October 2006

Near-field scanning optical microscopy of phospholipid monolayers doped with fluorescent lipid analogs reveals previously undescribed features in various phases, including a concentration gradient at the liquid-expanded/liquid-condensed domain boundary and weblike structures in the solid-condensed phase. Presumably, the web structures are grain boundaries between crystalline solid lipid. These structures are strongly modulated by the addition of low concentrations of cholesterol and ganglioside G
M1
in the monolayer.
T Cell Awareness of Paternal Alloantigens During Pregnancy
Authors: Tafuri Anna , Alferink Judith , Möller Peter , Hämmerling Günter J. , Arnold Bernd
Published: October 2006

During pregnancy a semiallogeneic fetus survives despite the presence of maternal T cells specific for paternally inherited histocompatibility antigens. A mouse transgenic for a T cell receptor recognizing the major histocompatibility (MHC) antigen H-2K
b
was used to follow the fate of T cells reactive to paternal alloantigens. In contrast to syngeneic and third-party allogeneic pregnancies, mice bearing a K
b
-positive conceptus had reduced numbers of K
b
-reactive T cells and accepted K
b
-positive tumor grafts. T cell phenotype and responsiveness were restored after delivery. Thus, during pregnancy maternal T cells acquire a transient state of tolerance specific for paternal alloantigens.
New Clock Gene Cloned
Authors: Barinaga Marcia
Published: October 2006

Organisms from simple, single-celled bacteria to complex mammals have internal biochemical clocks that maintain the daily cycles of behavior known as circadian rhythms. In three reports published in this issue of
Science
(pp.
805
,
808
, and
811
), researchers have cloned a gene called timeless that makes a key protein component of the clock in the fruit fly
Drosophila melanogaster.
By studying how TIM, the protein made by timeless, cooperates with PER, the protein produced by the only other known fruit fly clock gene, researchers are getting a much clearer picture of the molecular workings of the fly's circadian clock.
Slowing a Light Wave—in Order to Catch It
Authors: Taubes Gary
Published: October 2006

By adapting a process for getting laser light from just a few excited atoms, a team of physicists may have found a way to make a device that has attracted a lot of interest recently: a laser-driven accelerator, in which particles would be accelerated to high energies by surfing on an electromagnetic wave.
Functional Brain Imaging Studies of Cortical Mechanisms for Memory
Authors: Ungerleider Leslie G.
Published: October 2006

Recent functional brain imaging studies in humans indicate that learning and memory involve many of the same regions of the cortex that process sensory information and control motor output. The forms of perceptual and motor learning that can occur without conscious recollection are mediated in part by contractions and expansions of representations in the sensory and motor cortex. The same regions are also engaged during the conscious storage and retrieval of facts and events, but these types of memory also bring into play structures involved in the active maintenance of memories “on line” and in the establishment of associative links between the information stored in different sensory areas. Although the picture of memory that is emerging from functional imaging studies is consistent with current physiological accounts, there are puzzles and surprises that will be solved only through a combination of human and animal studies.
Positional Cloning and Sequence Analysis of the
Drosophila
Clock Gene,
timeless
Authors: Myers Michael P. , Wager-Smith Karen , Wesley Cedric S. , Young Michael W. , Sehgal Amita
Published: October 2006

The
Drosophila
genes
timeless
(
tim
) and
period
(
per
) interact, and both are required for production of circadian rhythms. Here the positional cloning and sequencing of
tim
are reported. The
tim
gene encodes a previously uncharacterized protein of 1389 amino acids, and possibly another protein of 1122 amino acids. The arrhythmic mutation
tim
01
is a 64-base pair deletion that truncates TIM to 749 amino acids. Absence of sequence similarity to the PER dimerization motif (PAS) indicates that direct interaction between PER and TIM would require a heterotypic protein association.
Laser Is a Guiding Light for Atoms
Authors: Service Robert F.
Published: October 2006

Atoms on tap? By using a laser beam to guide streams of rubidium atoms through a hollow optical fiber, a team of physicists in Colorado may have found a way to deliver atoms to precise locations for use in areas ranging from nanotechnology to quantum mechanics.
Trimeric G Proteins—Surprise Witness Tells a Tale
Authors: Bourne Henry R.
Published: October 2006

H. Bourne comments on an unusual polymeric crystal structure for the alpha subunit of the heterotrimeric G protein presented in this issue of
Science
by Mixon
et al
. (
p. 954
). Although he questions the authors' suggestion that G
alpha
might exist as a polymer in the cell, he shows how a domain consisting of the amino and carboxyl terminal ends of the protein, evident in the polymeric structure, may be revealing how G
alpha
catalyzes GTP-GDP exchange.
Tertiary and Quaternary Structural Changes in G
iα1
Induced by GTP Hydrolysis
Authors: Mixon Mark B. , Lee Ethan , Coleman David E. , Berghuis Albert M. , Gilman Alfred G. , Sprang Stephen R.
Published: October 2006

Crystallographic analysis of 2.2 angstrom resolution shows that guanosine triphosphate (GTP) hydrolysis triggers conformational changes in the heterotrimeric G-protein α subunit, G
iα1
. The switch II and switch III segments become disordered, and linker II connecting the Ras and α helical domains moves, thus altering the structures of potential effector and β γ binding regions. Contacts between the α-helical and Ras domains are weakened, possibly facilitating the release of guanosine diphosphate (GDP). The amino and carboxyl termini, which contain receptor and β γ binding determinants, are disordered in the complex with GTP, but are organized into a compact microdomain on GDP hydrolysis. The amino terminus also forms extensive quaternary contacts with neighboring α subunits in the lattice, suggesting that multimers of α subunits or heterotrimers may play a role in signal transduction.
Uncoupling Cell Fate Determination from Patterned Cell Division in the
Drosophila
Eye
Authors: de Nooij Joriene C. , Hariharan Iswar K.
Published: October 2006

Cell proliferation and cell fate specification are under strict spatiotemporal control in the developing
Drosophila
eye. Cells excluded from five-cell preclusters synchronously enter a single additional cell cycle, the second mitotic wave, after which the remaining cells are sequentially recruited. When the second mitotic wave was blocked with the human cyclin-dependent kinase inhibitor p21
CIP1/WAF1
, each cell type was still specified. Hence, cell fate determination is regulated independently of the division pattern of precursor cells. However, the second mitotic wave is needed to generate appropriate numbers of each cell type. Moreover, p21 can arrest precursor cell proliferation and allow appropriate fate choice in vivo.
How Vanished Oceans Drop an Anchor
Authors: Appenzeller Tim
Published: October 2006

At some subduction zones—deep trenches where ocean floor is consumed in the planet's interior—devastating earthquakes are common; others are peaceful. A new theory attributes the difference to the drag of deep, viscous rock on the descending ocean floor. Depending on its direction, this force can cause a subduction zone to jam, generating earthquakes, or keep it working smoothly.
Scientists Hope Competition Will Improve Internet Access
Authors: Kinoshita June
Published: October 2006

Several government and scientific organizations are putting together computer networks and offering connections to the Internet. The resulting competition is providing greater access to the global information superhighway, but it is also limiting the growth of a high-speed backbone for the entire research enterprise.
Incentives Help Researchers Resist Lure of Commerce
Authors: Kinoshita June
Published: October 2006

Beijing—A booming economy is both good and bad news for students thinking of entering science. It is attracting money into high-tech areas such as computer science, but high salaries in the commercial sector are luring many of the best and brightest out of science altogether. In response, the government and many research institutes are offering incentive programs to entice researchers back from abroad, but problems such as chronic housing shortages can be hard to overcome.
Field Research Also Needs the Human Touch
Authors: Mervis Jeffrey
Published: October 2006

Mashan Village—A researcher from Cornell University analyzing sustainable agriculture methods in the rich Tai Lake region of Jiangsu Province has learned that a good working relationship with local, regional, and national officials is essential to carry out a successful project.
Unraveling Immune Privilege
Authors: Streilein J. Wayne
Published: October 2006

J. W. Streilein discusses the concept of immune privilege, which protects from rejection tissues grafted to certain sites in the body. The differences between immune-privileged sites and immune-privileged tissues are illustrated by two recent papers implicating the cell surface protein FasL in immune privilege in the eye (
Science
,
p. 1189
of this issue) and in the testis [D. Bellgrau
et al
.,
Nature
377
, 630 (1995)].
Giant Facets at Ice Grain Boundary Grooves
Authors: Wilen L. A. , Dash J. G.
Published: October 2006

The energy barrier for nucleation on the basal plane of ice has a striking manifestation when the basal orientation is present in a grain boundary groove. As the ice-water interface containing the groove advances, large planar facets grow out of the grain boundary. The facets exhibit dramatic hysteresis, and they can be up to 30 times larger than predicted by equilibrium models. Measurements of the growth direction of the facets yield insight into the nature of the nucleation process. The facets also provide a way to study the relaxation of twist along grain boundaries.
Interdisciplinary Talkfest Prompts Flurry of Questions
Authors: Cohen Jon
Published: October 2006

Irvine, California—An unusual meeting provided young scientists a unique opportunity to learn about scientific developments in fields far removed from their own—and a chance to question leading researchers about their work.
Prompting Complex Patterns to Form Themselves
Authors: Service Robert F.
Published: October 2006

Recently scientists have coaxed inorganic compounds to self-assemble into a hierarchy of successively larger patterns: Atoms arranged in a crystalline lattice lead to larger walls surrounding arrays of pores and finally to bowls and spheres up to 100 micrometers across. These are the first tiny steps toward self-assembled complex objects, such as computer chips.