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1Author    G. Ennas, A. Musinu, G. Paschina, G. Piccaluga, G. PinnaRequires cookie*
 Title    Effect of Cooling Rate on the Structure of Sodium Borate Glasses  
 Abstract    Sodium borate glasses with two different compositions have been prepared using cooling rates in the range 7 • 10" C/s-2 • 10 2 °C/s. Structural characterization has been carried out by X-ray diffraction, and glass transition temperatures have been measured by Differential Scanning Calorimetry. The samples exhibit slightly different density values and glass transition temperatures. However, radial distribution functions appear extremely similar and the sodium coordination shell does not change in going from fast to slowly quenched glasses, showing that the short and medium range order is not affected by thermal treatment. 
  Reference    Z. Naturforsch. 48a, 599—604 (1993); received January 19 1993 
  Published    1993 
  Keywords    Glass, structure, diffraction 
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 TEI-XML for    default:Reihe_A/48/ZNA-1993-48a-0599.pdf 
 Identifier    ZNA-1993-48a-0599 
 Volume    48 
2Author    Z.Requires cookie*
 Title    Versuche zur Kondensation von H exam ethyl-4.4-bis(m ethyIam ino)cyclo- 1.2.4-trisila-diazan * Preparation  
 Abstract    Attem pts for the Condensation of Hexamethyl-4.4-bis(methylamino)cyclo-1 ,2,4-trisila-diazane M e r t e n S c h l i n g m a n n u n d U l r ic h W a n n a g a t Braunschweig, 
  Reference    (Z. Naturforsch. 32b, 954—955 [1977]; eingegangen am 31. Mai 1977) 
  Published    1977 
  Keywords    Properties, Structure, Spiranes 
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 TEI-XML for    default:Reihe_B/32/ZNB-1977-32b-0954_n.pdf 
 Identifier    ZNB-1977-32b-0954_n 
 Volume    32 
3Author    Ingmar Persson, Magnus Sandström, Haruhiko Yokoyama, Monika Chaudhry, JapanRequires cookie*
 Title     
 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 
4Author    A. Guarnieri, A. HuckaufRequires cookie*
 Title    The Rotational Spectrum of (170)Ketene  
 Abstract    The rotational spectrum of H2CC17O in the ground vibrational state has been investigated between 20 and 330 GHz. From 82 /?-branch transitions a set of rotational constants and several centrifugal distortion constants could be derived, employing the Watson 5-reduction formalism. The obtained rotational constants in MHz are: A = 282071.6(223), B = 10013.4764(28), C = 9655.9118(24). The nuclear quadrupole coupling structure of the J'KaiKci <— JKaKc = loi Ooo line has been recorded by means of molecular beam Fourier transform microwave spectroscopy allowing the determination o f the nuclear quadrupole constant Xaa. = -1.534(54) MHz (without considering the spin-rotation interaction). A recalculation of the rs-structure has also been carried out, using the constants of the new isotopomer. The result agrees with the values reported by East et al. in 1995. This is, to our knowledge, the first reported investigation of the H2CC170 rotational spectrum. 
  Reference    Z. Naturforsch. 56a, 440—446 (2001); received April 9 2001 
  Published    2001 
  Keywords    Rotational Spectra, Structure, Ketene, Isotopomer 
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 TEI-XML for    default:Reihe_A/56/ZNA-2001-56a-0440.pdf 
 Identifier    ZNA-2001-56a-0440 
 Volume    56 
5Author    Ulrich Wannagat, Merten Schlingmann, Horst AutzenRequires cookie*
 Title    Anorganische Fünfringsysteme auf der Basis Silicium/ Stickstoff/Heteroelement * Inorganic Fivemembered Ring Systems Basing upon Silicon, Nitrogen and "Hetero Elements"  
  Reference    (Z. Naturforsch. 31b, 621—640 [1976]; eingegangen am 2. Oktober 1975) 
  Published    1976 
  Keywords    Survey, Preparation, Properties, Structure, Spiranes 
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 TEI-XML for    default:Reihe_B/31/ZNB-1976-31b-0621.pdf 
 Identifier    ZNB-1976-31b-0621 
 Volume    31 
6Author    Ulrich Wannagat, Gerd EiseleRequires cookie*
 Title    Neue Silaza-und Silaoxaza-spiro[4.4]nonane und [4.5]decane* Novel Silaza-and Silaoxaza-spiro[4,4]nonanes and [4,5]decanes  
 Abstract    The formerly unknown spiro systems C-F (Scheme I) with silicon in the spiral center and C, Si, N and O in the framework were synthesized via reactions 2-6 and confirmed in their structure by elemental analysis and spectroscopic data (Table I). 
  Reference    Z. Naturforsch. 33b, 471—474 (1978); eingegangen am 28. Februar 1978 
  Published    1978 
  Keywords    Preparation, Properties, Spiranes, Structure 
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 TEI-XML for    default:Reihe_B/33/ZNB-1978-33b-0471.pdf 
 Identifier    ZNB-1978-33b-0471 
 Volume    33 
7Author    H. J. Keller, W. Moroni, D. Nöthe, M. Scherz, J. WeissRequires cookie*
 Title    und 5.10-Dihydro-5.10-diethylphenaziniumtriiodid  
 Abstract    Molecular and Crystal Structure of 5.10-Dihydro-5,10-dimethylphenaziniumtriiodide and 5,10-Dihydro-5,10-diethylphenazinium triiodide Oxidation of 5,10-dihydro-5,10-dimethylphenazine and 5,10-dihydro-5,10-diethyl-phenazine under different reaction conditions leads to several iodine containing solids. The preparation and X-ray structure of two of them, 5,10-dihydro-5,10-dimethyl-phenaziniumtriiodide (3) and 5,10-dihydro-5,10-diethylphenaziniumtriiodide (4) are reported here. Compound 3 crystallizes in space group P 2i/n with lattice parameters a = 8.552(6) A, b = 16.953(2) A, c= 12.157(9) A and ß= 103.46(2)° with four formula units in the unit cell. The structure was refined to an i?-value of 0.046 using 2387 independent reflections. The lattice constains distinct, slightly distorted triiodide ions and bent 5,10-dihydro-5,10-dimethylphenazinium radical cations. Compound 4 crystallizes in the same space group P2i/n with lattice parameters a = 8.531(6) A, b = 8.332(21) A, c = 13.320(15) A and ß— 94.44(19)° with two formula units in the unit cell. The structure was refined to an i?-value of 0.076 using 1195 independent reflections. The lattice contains strictly linear symmetrical triiodide ions and planar centrosymmetrical 5,10-dihydro-5,10-diethyl-phenazinium radical cations. 
  Reference    Z. Naturforsch. 33b, 838—842 (1978); eingegangen am 27. April 1978 
  Published    1978 
  Keywords    Radical Cations, Structure, ESR 
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 TEI-XML for    default:Reihe_B/33/ZNB-1978-33b-0838.pdf 
 Identifier    ZNB-1978-33b-0838 
 Volume    33 
8Author    Joachim Fuchs, Hernan GuevaraRequires cookie*
 Title    Struktur und Eigenschaften des Kahumhydrogendiarsenit-Hemihydrats, KHAS204 1/2 H20 Structure and Properties of the Potassiumhydrogendiarsenite-hemihydrate, KHAS2O4 -1/2 H2O  
 Abstract    KHAS2O4 • 1/2 H2O crystallizes in the tetragonal space group I 4/m with the lattice constants a = 14,480 A, c = 5,250 A. The anion forms infinite chains, [HAs204]n n_ , in the direction of the c axis. Arsenic is surrounded by three oxygens in trigonal pyramidal co-ordinations. Ultracentrifuge work shows that the solution contains monomeric species, probably [ASO(OH)2]~. Raman spectra gave no evidence for the existence of As-H-bonds either in the solid or in solution. 
  Reference    Z. Naturforsch. 35b, 1344—1348 (1980); eingegangen am 20. Juni 1980 
  Published    1980 
  Keywords    Polyarsenite, Structure, Raman Spectra, Ultracentrifuge 
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 TEI-XML for    default:Reihe_B/35/ZNB-1980-35b-1344.pdf 
 Identifier    ZNB-1980-35b-1344 
 Volume    35 
9Author    Hans Geiger, Harald HombergRequires cookie*
 Title    Fluoreszenz und Struktur von Flavonen, II Der Einfluß von Hydroxygruppen in 6-, 8-und 2'-Stellung* Fluorescence and Structure of Flavones, II The Influence of Hydroxy Groups at Positions 6, 8 and 2'  
 Abstract    The fluorescence spectra of various 2'-, 6-and 8-hydroxy-, methoxy-, and glucosyloxy-flavones adsorbed on cellulose alone and with added shift reagents are reported. The correlation between fluorescence and structure of these compounds is discussed. 
  Reference    Z. Naturforsch. 38b, 253—257 (1983); eingegangen am 21. September 1982 
  Published    1983 
  Keywords    Flavonoids, Fluorescence Spectra, Structure 
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 TEI-XML for    default:Reihe_B/38/ZNB-1983-38b-0253.pdf 
 Identifier    ZNB-1983-38b-0253 
 Volume    38 
10Author    Gert Heller, Joachim PickardtRequires cookie*
 Title    Über ein Ikosaborat-Ion in hydratisierten Kalium-und Natriumkupferpolyboraten On an Icosaborate Ion in Hydrated Potassium and Sodium Copper Polyborates  
 Abstract    K s H{Cu 4 O[B, 0 O 32 (OH) 8 ]}-33 H.O, M = 1925.46 g/mol, triclinic, PI, a = 1627.4(7), b = 1799.6(9), and c = 1365.2(5) pm; a = 96.37(5), ß = 110.93(5), and y = 111.36(5)°; Z = 2; D m = 1.96 (flotation) and D x = 1.91. Mg-m~ 3 ; R = 0.155 for 5022 observed reflections, and Na 5 H{Cu 4 O[B 20 O 32 (OH) 8 ]}. 32 H 2 0, M = 1825.62 g/mol, tetragonal, 14, a = 1866 and c = 1042 pm; Z — 2; D m = 1.63 and D x = 1.67 Mg-nT 3 have been investigated. The structure of the anion icosaboro-,«4-oxo-tetracuprate(II)(6—) contains the largest known isolated borate ion with 20 boron atoms. Each borate ion is a prophyrine-like ring, and encloses four Cu ions in a nearly planar Cu 4 0 cation, thus forming a chelate-like complex. While the anion structure is clear, the positions of the alkalimetal ions and the water molecules are not yet known, although an exact analysis and thermoanalytic determinations confirm the formula. 
  Reference    Z. Naturforsch. 40b, 462—466 (1985); eingegangen am 29. Oktober 1984 
  Published    1985 
  Keywords    Icosaborates, Heteropolyanions Polyborates, Structure 
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 TEI-XML for    default:Reihe_B/40/ZNB-1985-40b-0462.pdf 
 Identifier    ZNB-1985-40b-0462 
 Volume    40 
11Author    Karl Häberle, Martin DrägerRequires cookie*
 Title    Über Polygermane, XVIII [1] Drucksynthese der mehrfach funktionellen Digermane Ph 6 _"Ge 2 Cl" (n = 2, 3, 4) und von Ph 2 GeCl 2 On Polygermanes, XVIII [1] Synthesis of the Multifunctional Digermanes Ph 6 _"Ge 2 Cl" (n = 2, 3, 4) and of Ph 2 GeCl 2 under Pressure  
 Abstract    Reaction of Ph 6 Ge 2 with liquid HCl under pressure leads to di-, tri-and tetrachloro phenyl-digermanes. The yield of higher chlorinated products increases with increasing pressure. The analogous reaction of Ph 4 Ge yields Ph 2 GeCl 2 quantitatively. The Ge-Ge bond is most unstable in the case of Ph 3 Ge 2 Cl 3 both chemically and thermally. The crystal structure of Ph 2 Ge 2 Cl 4 has been determined (R = 0.057), Ge-Ge 241.3(1) pm. 
  Reference    Z. Naturforsch. 42b, 323 (1987); eingegangen am 15. September/24. November 1986 
  Published    1987 
  Keywords    Functional Digermanes, Synthesis, Structure 
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 TEI-XML for    default:Reihe_B/42/ZNB-1987-42b-0323.pdf 
 Identifier    ZNB-1987-42b-0323 
 Volume    42 
12Author    WolfdieterA. Schenk, Nicolai Burzlaff, Hans BurzlaffRequires cookie*
 Title    Chiral Thioaldehyde Complexes of Rhenium, X-Ray Structure Determination of [Cp(NO )(Ph3P)R e(i/2-S=CHPh)]PF6 [1]  
 Abstract    Chiral thiolate com plexes [C p(N O)(Ph3P)R eSC H 2R] (R = Ph, 4-C6H 4Cl, 4-C6H4OM e, H, Me) are obtained from [C p(N O)(Ph3P)R eC H 3] by acid cleavage in the presence of thiol and subsequent deprotonation. Small amounts of (chloromethyl)thioether com plexes [C p(N O)(Ph3P)R eS(C H 2C l)C H 2R ]BF4 are formed when dichloromethane is used as a sol­ vent in this reaction. Hydride abstraction using [Ph3C]PF6 converts the thiolate com plexes into ionic thioaldehyde com plexes [C p(N O)(Ph3P)Re(?72-S=CHR)]PF6. These are obtained as pure (RR.SS)-diastereom ers as shown spectroscopically and by X-ray structure determ i­ nation of [C p(N O)(Ph3P)Re(?/2-S=CHPh)]PF6. Crystals are monoclinic, space group 12/a (No. 15), a = 25.877(3), b = 18.785(2), c = 13.768(1) A , ß = 104.93(1)°, Z -8. 
  Reference    Z. Naturforsch. 49b, 1633 (1994); received April 21 1994 
  Published    1994 
  Keywords    Rhenium Complexes, Thioaldehyde, Structure 
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 TEI-XML for    default:Reihe_B/49/ZNB-1994-49b-1633.pdf 
 Identifier    ZNB-1994-49b-1633 
 Volume    49 
13Author    Uwe Hartmann, Heinrich VahrenkampRequires cookie*
 Title    Zinkkomplexe von Sulfonamiden Zinc Complexes of Sulfonamides  
 Abstract    The diuretic sulfonamides furosemid (FLFur) and hydrochlorothiazid (H 2Hyt) were used as ligands in zinc complexes. Spectroscopic data indicate that in [(H Fur)Z n(H 2 0)2 ]C1 0 4 and (H Fur)2Zn the furosemid ligand is bound to zinc via its carboxylate and amine functions while (Fur)Z n(N H 3)2 is a coordination polymer with Zn-carboxylate and Zn-sulfonimide coordination. A structure determination shows (H yt)Zn(N H 3)2 to be a coordination polymer as well, with both deprotonated sulfonamide functions forming Z n -N bonds. 
  Reference    Z. Naturforsch. 49b, 1725—1730 (1994); eingegangen am 11. Mai 1994 
  Published    1994 
  Keywords    Zinc Complexes, Sulfonamide Ligands, Structure 
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 TEI-XML for    default:Reihe_B/49/ZNB-1994-49b-1725.pdf 
 Identifier    ZNB-1994-49b-1725 
 Volume    49 
14Author    Z. NaturforschRequires cookie*
 Title    Synthesis of Cationic Ruthenium Thioketene Complexes through Intramolecular 1,2-Elimination [1]  
 Abstract    Halfsandwich thiocarboxylate complexes [CpRu(PR3)->(SC(0)CH2R')] ((P R 3)2 = (PPh3)2, Ph2PCH 2PPh2 (dppm), Ph2PC2H4PPh2 (dppe); R' = C6H 5, 4-C6H4Me, 4-C6H 4OMe, 4-C6H4C1) are obtained from the corresponding thiolate complexes [CpRu(PR3)2SH] and acyl chlorides. The structure of [CpRu(dppm)(SC(0)CHTPh)] was determined: monoclinic space group P2j/c (No. 14), a = 9.229(2), b = 16.680(3),"c = 21.447(5)Ä, ß = 90.751(12)°, Z = 4. Reaction of the thiocarboxylate complexes with the anhydrides of either trifluoro-acetic acid or trifluoromethanesulfonic acid gives thioketene complexes [CpRu(dppm) (?;2-S=C=CHR')]PF(s. H ie structure of [CpRu(dppm)0/2-S= C = C H Ph)]PF6 was deter­ mined: monoclinic space group P2,/c (No. 14), a -13.814(5), b -15.338(2), c = 17.057(7) Ä, ß = 93.74(2)°, Z = 4. 
  Reference    (Z. Naturforsch. 52b, 117—124 [1997]; received July 25 1996) 
  Published    1997 
  Keywords    Ruthenium Complexes, Thiocarboxylate, Thioketene, Structure 
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 TEI-XML for    default:Reihe_B/52/ZNB-1997-52b-0117.pdf 
 Identifier    ZNB-1997-52b-0117 
 Volume    52 
15Author    Nicolai Burzlaff, Michael Hagel, WolfdieterA. SchenkRequires cookie*
 Title    Tuning the Steric and Electronic Properties of Chiral Rhenium Thiolate Complexes [1]  
 Abstract    Reaction of the complex [CpRe(NO)(CO)2]BF4 with triisopropylphosphine gives the chiral CO substitution product [CpRe(NO){P(/-Pr)3}(CO)]BF4. The corresponding triphenylphos-phite complex [CpRe(NO){P(OPh)3}(CO)]BF4 may be obtained by oxidative CO removal. Reduction of the remaining CO ligand with NaBH4 furnishes the corresponding methyl com­ plexes [CpRe(NO)(L)(CH3)]. The structure of [CpRe(NO){P(/-Pr)3}(CH3)] was determined: triclinic space group PI (No. 2), a = 8.442(4), b = 9.582(5), c -11.820(8) A, a = 81.81 (4), ß = 87.18(4), 7 = 63.87(5)°, Z = 2. Reaction of the methyl complexes with HBF4 in the presence of thiols gives, after chromatographic workup, the thiolate derivatives [CpRe(NO)(L)(SR)] (L = CO, P(OPh)3, P(/-Pr)3, R = CH2Ph, CH2(4-C6H4C1), CH2(4-C6H4OMe), CH3, C2H5). The structure of [CpRe(NO){P(/-Pr)3}(SCH3)] was determined: monoclinic space group P2i (No. 3), a = 7.0515(7), b = 17.3469(10), c = 7.9727(7) Ä, ß = 114.021(7)°, Z = 2. In both structures, a significant opening of the angle N-Re-X (X = C, S) suggests that antibonding interactions between orbitals of the ligand X and the second-highest MO of the [CpRe(NO)(L)] complex fragment are avoided. 
  Reference    Z. Naturforsch. 53b, 893—899 (1998); received May 5 1998 
  Published    1998 
  Keywords    Rhenium Complexes, Thiolate Ligands, Structure 
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 TEI-XML for    default:Reihe_B/53/ZNB-1998-53b-0893.pdf 
 Identifier    ZNB-1998-53b-0893 
 Volume    53 
16Author    G. Metz, Ruth Marx, K.-H RohmRequires cookie*
 Title    The Quaternary Structure of Yeast Aminopeptidase I 1. Molecular Forms and Subunit Size  
 Abstract    The smallest active form of aminopeptidase I (EC 3.4.11.1) from yeast has a molecular weight of 6.4 X 105. At neutral pH the active enzyme is in equilibrium with two inactive subfragments (Mr = 3 .2 X 1 0 5 and 1.1 X 105) as well as with higher aggregates (Mr 1.2 X 1 0 6). All of these species may be dissociated to give a single type of subunits with a molecular weight of 5.3 X 1 0 4. It is concluded that the active enzyme is a dodecamer whereas the subfragments correspond to dimeric and hexameric forms. 
  Reference    (Z. Naturforsch. 32c, 929 [1977]; received August 2 1977) 
  Published    1977 
  Keywords    Aminopeptidase, Yeast, Structure, Subunit Composition 
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 TEI-XML for    default:Reihe_C/32/ZNC-1977-32c-0929.pdf 
 Identifier    ZNC-1977-32c-0929 
 Volume    32 
17Author    Helmut Formanek, Hermann WeidnerRequires cookie*
 Title    Three Dimensional Structure of the Carbohydrate Moiety of a Lipopolysaccharide. Computer Calculations  
 Abstract    The cell wall of the mutant R 595 of Salmonella minnesola contains a lipopolysaccharide in which only a trisaccharide consisting of three KDO * residues is linked to a lipid termed lipid A. Considering the sterical requirements o f fourteen rotation angles, we have calculated allowed conformation of this trisyccharide unit and its linkage to lipid A. The calculations have been based on averaged crystallographic data of pyranose rings, ester-, N-acetyl-, phosphate-and carboxylgroups. Because of considerable sterical hindrance, there are unique positions for the rotation around the axes 0 3-C 3 of the glucosamine residue and O j -Q o f KDO residue 1 as well as for the rota­ tion of the N-acetylgroup at the C2-atom of glucosamine. Similarly, the rotation angle o f the carboxylgroup on KDO residue 1 and the rotation angles o f the phosphategroup linked to glucos­ amine are highly restricted, while a large range o f angles is allowed for the bond of the ester group to glucosamine. Chemical sequence analysis yields two possibilities for the linkage between the KDO residues 1 and 2. Linkage of 0 4 o f KDO 1 in equatorial position is restricted to a narrow range of angles, whereas the linkage to 0 4 in axial -and to Oa in axial and equatorial position is unfavourable. Furtheron chemical sequence analysis suggests two ways how to link KDO residue 1 and 3. The linkage to the oxygen atom on C7 o f KDO residue 1 can be described by four, the linkage to the oxygen on C6 with three rotation angles. In either case two of the rotations are highly restricted. In the first case the two remaining angles have large rotational freedom, while the second case is sterically unfavorable. The feasibility of the computer calculations has been demonstrated by the construction of a three-dimensional atomic model. 
  Reference    Z. Naturforsch. 36c, 71—8 (1981); received July 10/November 12 1980 
  Published    1981 
  Keywords    Lipopolysaccharide, Carbohydrate Moiety, Structure 
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 TEI-XML for    default:Reihe_C/36/ZNC-1981-36c-0071.pdf 
 Identifier    ZNC-1981-36c-0071 
 Volume    36 
18Author    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 
19Author    Michael SpringborgRequires cookie*
 Title    A Comparison between Polyatecylene and Polycarbonitrile  
 Abstract    Results of a theoretical, comparative study of the electronic properties of trans-polyacetylene and polycarbonitrile are reported. Polyacetylene consists of zigzag chains of CH units, whereas poly-carbonitrile has every second CH unit replaced by an N atom. Ground-state properties (structure, electronic bonds and bands, densities of states, momentum distributions, and reciprocal form factors) of the periodic, infinite, isolated chains are studied by means of first-principles, density-functional calculations. It is demonstrated how the presence of the (nitrogen) heteroatoms in the backbone of polycarbonitrile leads to a partial localization of the electrons. In order to investigate charged chains, model calculations are subsequently performed. These indicate solitons but not polarons to be stable. In total, the analysis demonstrates how the combination of information that can be obtained from various experiments provides a detailed description of the compounds. 
  Reference    Z. Naturforsch. 48a, 159—164 (1993); received November 26 1991 
  Published    1993 
  Keywords    Conjugated polymers, Structure, Electronic structure, Momentum densities, Solitons 
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 TEI-XML for    default:Reihe_A/48/ZNA-1993-48a-0159.pdf 
 Identifier    ZNA-1993-48a-0159 
 Volume    48 
20Author    Haruhiko Yokoyama, Saeko Suzuki, Masuo Goto, Kazuteru Shinozaki, Yuriko Abe, Shin-Ichi IshiguroRequires cookie*
 Title    X -R a  
 Abstract    y D if fr a c tio n S tu d y o f th e S o lv a tio n S tr u c tu r e o f th e C o b a lt (I I) I o n in N ,N -D im e th y lf o rm a m id e S o lu tio n Dedicated to Prof. Hitoshi Ohtaki on the occasion of his 60th birthday The solvation structure of Co2+ in N,N-dimethylformamide (DMF) has been studied by X-ray diffraction measurements on cobalt (II) and magnesium (II) Perchlorate solutions of the same concen­ tration, using an isostructural substitution method. The radial distribution function revealed three distinct peaks assigned to the oxygen, amido carbon (CJ, and nitrogen atoms of six planar DMF molecules in the first coordination sphere around the metal atom. The distance from the cobalt atom to each atom (O, Cx, N) is 213,299, and 423 pm, respectively. This indicates that the Co-O-Cj bond angle is 122-123° and the metal atom is close to the O-Cj-N plane of the DMF molecule. 
  Reference    Z. Naturforsch. 50a, 301—306 (1995); received September 28 1995 
  Published    1995 
  Keywords    Cobalt, N,N-dimethylformamide, Solvation, X-ray, Structure 
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 Identifier    ZNA-1995-50a-0301 
 Volume    50 
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