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1995 (1)
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1Author    Ingmar Persson, Magnus Sandström, Haruhiko Yokoyama, Monika Chaudhry, JapanRequires cookie*
 Abstract    tr u c tu r e o f th e S o lv a te d S tr o n tiu m a n d B a riu m I o n s in A q u e o u s, D im e th y l S u lfo x id e a n d P y r id in e S o lu tio n , a n d C r y s ta l S tr u c tu r e o f S tr o n tiu m a n d B a r iu m H y d r o x id e O c t a h y d r a te Dedicated to Prof. Hitoshi Ohtaki on the occasion of his 60th birthday Single crystal X-ray data, collected at 298 K, are used to redetermine the crystal structure of the non-isomorphic compounds [Sr(H20)8](0H)2 and [Ba(H20)8](0H)2. The eight water oxygen atoms form distorted Archimedean antiprisms around the octahydrated metal ions with mean metal ion-oxygen distances 2.62 and 2.79 Ä for strontium and barium, respectively. A second coordination shell of 24 hydrogen-bonded oxygen atoms with mean metal ion-oxygen distances M • • • O" 4.76 and 4.80 A, respectively, is observed. The hydroxide ions in both structures have an unusual hydrogen bond arrangement with 5 bonds accepted and one donated. The structure of the solvated strontium and barium ions in aqueous, dimethyl sulfoxide and pyridine solutions has been studied by means of large angle X-ray scattering and extended X-ray absorption fine structure spectroscopy techniques. In aqueous solution independent determinations of the first-sphere metal-oxygen coordination by the two techniques resulted in the bond lengths Sr-O 2.63 (2) and Ba-O 2.81 (3) A, and for both metal ions a hydration number of 8.1 (3). The second coordination spheres are very diffuse with only about 13 water molecules at similar M • • • O" distances as in the crystal structures and 2-3 water molecules closer to the metal ions. In dimethyl sulfoxide solution both ions were found to coordinate 6.0 (5) solvent molecules with the distances Sr-O 2.54(1), Sr -S 3.77(1) A, and Ba-O 2.76(1), Ba -S 3.99(1) A. For the solvated ions in pyridine solution EXAFS measurements yielded the distances Sr-N 2.57 (2) and Ba-N 2.78 (3) A, with a probable solvation number of 6. Correlations of hydration enthalpies and partial molar volumes with experimental M-O bond distances in aqueous solution are used to discuss hydration numbers and bond character for all of the alkaline earth metal ions. 
  Reference    Z. Naturforsch. 50a, 21—37 (1995); received November 8 1994 
  Published    1995 
  Keywords    Barium, Strontium, Hydration, Solvation, Structure 
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 TEI-XML for    default:Reihe_A/50/ZNA-1995-50a-0021.pdf 
 Identifier    ZNA-1995-50a-0021 
 Volume    50 
2Author    H. Janzen, E. Matuszak, E. V. Goldammer, AnnenBundesrepublik Deutschland, H. R. WenzelRequires cookie*
 Title    Thermodynamic and Magnetic Resonance Studies on the Hydration of Polymers: II. Protein-Water Interactions in Powdered Ribonuclease  
 Abstract    ESR studies on spin-labeled amorphous RNase A as a function of varying concentrations of sorbed H 2 0 and D 2 0 will be presented. A relaxation analysis of saturation transfer (ST-)ESR spectra of l4 N('H) nitroxide spin-label molecules essentially fixed at amino acid residue His-105 will be given. A characteristic correlation has been observed between the microdynamic behavior — express-ed by the rotational correlation times of the paramagnetic label — and the macroscopic thermo-dynamic entropy for the sorption process of H 2 0 and D 2 0 at RNase. This correlation is particu-larly pronounced at low water concentrations, viz., n H20 /n protein < 100. A significant difference in this concentration range exists between the two systems "RNase-H 2 0" and "RNase-D 2 0", which is manifested not only by the thermodynamic data but also by the microdynamic behavior ex-tracted from the corresponding non-linear ESR absorption line shapes. 
  Reference    Z. Naturforsch. 43c, 285—293 (1988); received December 18 1987 
  Published    1988 
  Keywords    Protein, Structure, Hydration, NMR, Thermodynamic 
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 TEI-XML for    default:Reihe_C/43/ZNC-1988-43c-0285.pdf 
 Identifier    ZNC-1988-43c-0285 
 Volume    43 
3Author    Bai Zhu, G.Wilse RobinsonRequires cookie*
 Title    Sheng  
 Abstract    The structure and properties of a 1.791 molal aqueous LiF solution is investigated by performing molecular dynamics simulations using a water model with both bond flexibility and instantaneously responsive polarization. On average, each cation is in close contact with about one anion. This causes a strong overlap of the hydration shells and an almost complete breakdown of the surround­ ing water structure. While the lone pairs of the hydration waters in the first Li+ shell occupy preferentially tetrahedral positions, the orientational distribution of the solvent molecules around F~ is quite uniform. By comparing various autocorrelation functions of water molecules in the solution and in the pure liquid, the influence of solvated ions on the translational, rotational and vibrational motions of hydration water can be studied. M o le c u la r D y n a m ic s S tu d y o f a n A q u e o u s L iF S o lu tio n 
  Reference    Z. Naturforsch. 46a, 221—228 (1991); received October 4 1990 
  Published    1991 
  Keywords    Hydration, Ions, Water, Solubility, Ion-pairs 
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 TEI-XML for    default:Reihe_A/46/ZNA-1991-46a-0221.pdf 
 Identifier    ZNA-1991-46a-0221 
 Volume    46 
4Author    Heinz-Jürgen Steinhoff, Klaus Lieutenant, Jürgen SchhtterRequires cookie*
 Title    Residual Motion of Hemoglobin-Bound Spin Labels as a Probe for Protein Dynamics  
 Abstract    The residual m otion o f spin labels bound to cysteine (393 o f m ethem oglobin and oxyhem oglobin has been analyzed as a function o f temperature and hydration. The rotational diffusion o f the whole protein m olecule has been prevented or restricted by crystallization, lyophilization or by high viscosity o f the solution. The residual motion o f the labels is characterized by an angle o f the limited m otion cone and their rotational correlation time using computer simulations o f the E P R spectra. Two types o f m otion can be separated due to different correlation times and different dependenceson temperature and hydration. O ne o f these m otional mechanisms can be shown to be determ ined by protein fluctuations. Correlation tim es o f these fluctuations decrease from 2 x 10 s s at T = 220 K to 10 9 s at T = 300 K in the sam ples o f high water concentration. Strong correlation betw een the properties of the hydration shell and these fluctuations are observed. 
  Reference    Z. Naturforsch. 44c, 280 (1989); received O ctober 24 1988 
  Published    1989 
  Keywords    Protein Dynam ic, Electron Paramagnetic R esonance, Spin Label, H em oglobin, Hydration 
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 TEI-XML for    default:Reihe_C/44/ZNC-1989-44c-0280.pdf 
 Identifier    ZNC-1989-44c-0280 
 Volume    44