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Distribution by Scientific Domains

Physics and Astronomy	40%
Chemistry	40%

Selected Abstracts

Atomic hydrogen in asymptotic giant branch circumstellar environments.

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2006
A case study: X Her
ABSTRACT We report the detection of the H i line at 21 cm from the circumstellar shell around the asymptotic giant branch star X Her using the position-switching technique with the Nançay Radio Telescope. At the star position, the line shows two components: (i) a broad one [full width at half-maximum (FWHM) , 13 km s,1] centred at ,72.2 km s,1 and (ii) a narrow one (FWHM , 4 km s,1) centred at ,,70.6 km s ,1. Our map shows that the source associated to the broad component is asymmetric with material flowing preferentially towards the north-east. This source extends to ,10 arcmin (,0.4 pc) from the star in that direction. On the other hand, the narrow component is detected only at the star position and indicates material flowing away from the observer. The total mass of atomic hydrogen is ,6.5 × 10,3 M, which, within a factor of 2, agrees with the estimate obtained from IRAS data at 60 ,m. [source]

Toru, 6-cm polarimetry of the MilkyWay

ASTRONOMISCHE NACHRICHTEN, Issue 5-6 2006
S. Ry
Abstract We present first results of a radio continuum and polarization survey of the Milky Way at 4.7 GHz carried out with the 32-m radio telescope in Toru,. The survey is much less affected by depolarization effects than previous measurements at lower frequencies. This enables the study of magnetic field structure and its interrelations with particular features in the interstellar medium to much larger distances from the Sun. Our preliminary total power map shows a good association of radio features with galactic star-forming regions while the polarization data reveal an increasing coherence of magnetic fields away from the Galaxy's mid-plane. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

The crystallographic structure of the aldose reductase,IDD552 complex shows direct proton donation from tyrosine 48

ACTA CRYSTALLOGRAPHICA SECTION D, Issue 8 2004
Federico Ruiz
The X-ray crystal structure of human aldose reductase (ALR2) in complex with the inhibitor IDD552 was determined using crystals obtained from two crystallization conditions with different pH values (pH 5 and 8). In both structures the charged carboxylic head of the inhibitor binds to the active site, making hydrogen-bond interactions with His110 and Tyr48 and electrostatic interactions with NADP+. There is an important difference between the two structures: the observation of a double conformation of the carboxylic acid moiety of the inhibitor at pH 8, with one water molecule interacting with the main configuration. This is the first time that a water molecule has been observed deep inside the ALR2 active site. Furthermore, in the configuration with the lower occupancy factor the difference electron-density map shows a clear peak (2.5,) for the H atom in the hydrogen bond between the inhibitor's carboxylic acid and the Tyr48 side-chain O atom. The position of this peak implies that this H atom is shared between both O atoms, indicating possible direct proton transfer from this residue to the inhibitor. This fact agrees with the model of the catalytic mechanism, in which the proton is donated by the Tyr48 hydroxyl to the substrate. These observations are useful both in drug design and in understanding the ALR2 mechanism. [source]

High-resolution structures of bacterially expressed soluble human CD59

ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 8 2007
Kirstin J. Leath
CD59 is a membrane-bound glycoprotein that protects host cells from lysis by inhibiting the terminal pathway of complement, preventing the formation and insertion of the membrane attack complex (MAC). Crystals of bacterially expressed and nonglycosylated recombinant soluble human CD59 have been obtained from three crystallization conditions, each of which gave rise to a distinct crystal form. Each crystal form led to a crystal structure at high resolution (1.15, 1.35 and 1.8,Å). In one of these structures the electron-density map shows an as yet unidentified small molecule in the predicted C8/C9-binding site. The presence/absence of this ligand is linked to alternate conformations of the amino acids implicated in C8/C9 binding. [source]

Floodplains of a regulated southern alpine river (Brenno, Switzerland): ecological assessment and conservation options

AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 6 2002
M. Brunke
Abstract 1.The fifth-order southern alpine Brenno River and its floodplains are severely impaired by embankments, water abstractions and the construction of dams for hydropower generation. The river's annual mean discharge is reduced to 27% of the natural flow and the number of small (50,100 m3 s,1) and medium-sized (101,150 m3 s,1) floods is reduced significantly. 2.Lateral hydrological connectivity has decreased strongly as a result of the flow regulation, whereas the significance of vertical connectivity has increased. The remnants of the middle and lower floodplains still contain springbrooks, ponds, and intermittently connected channels, which are all sustained by emerging groundwater. 3.Aquatic floodplain habitats can be classified partially by faunal composition. The lotic/lentic gradient appears to be a dominant compound factor structuring invertebrate assemblages when considering all aquatic habitats. The exfiltration of groundwater in conjunction with a reduced lateral connectivity enables the occurrence of many stenotopic species. 4.A comparison of present floodplains with those shown on historical maps shows that the fluvial landscape has changed markedly. The proportions of functional floodplain units characterized by autogenic succession and trends to late successional stages (i.e. senescence) have increased. 5.Floodplains of the Brenno river are still considered to represent important ecological areas and they are protected by law. Whilst the legislative protection of floodplains is the basis for conservation, this does not include the restoration of driving hydrological processes. An annual release of small- and medium-sized floods could generate a diversity of disturbances, thereby promoting rejuvenation and counteracting senescence. 6.Alternative conservation options that circumvent ongoing contracts of water use, though generally promising, are limited because of the operation of hydropower schemes. At present the exfiltrations of groundwater mitigate the impacts of flow regulation on the ecological integrity of the floodplains. Copyright © 2002 John Wiley & Sons, Ltd. [source]