16 research outputs found

    X-ray Studies on Crystalline Complexes Involving Amino Acids and Peptides. XIII. Effect of Chirality on Molecular Aggregation: The Crystal Structures of LL-Arginine DD-Aspartate and LL-Arginine DD-Glutamate Trihydrate

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    The crystal structures of (1) LL-arginine DD-asparate, C6C_6H15N4H_15N_402+.C4H6NO40_2^+.C_4H_6NO_4^- [triclinic, P1, a = 5.239(1), b = 9.544(1), c=14.064(2)A˚c = 14.064(2) \AA, α=85.58(1)\alpha = 85.58(1), β=88.73(1)\beta = 88.73 (1), γ=84.35(1)0\gamma = 84.35 (1)^0, Z = 2] and (2) LL-arginine DD-glutamate trihydrate, C6H15N40.3H20C_6H_15N_40^-.3H_20 [monoclinic, P_2_1, a = 9.968(2), b = 4.652(1), c=19.930(2)A˚c = 19.930 (2) \AA, β=101.20(1)0\beta = 101.20 (1)^0, Z = 2] have been determined using direct methods. They have been refined to R =0.042 and 0.048 for 2829 and 2035 unique reflections respectively [I>2σ(I)][I>2 \sigma (I)]. The conformations of the two arginine molecules in the aspartate complex are different from those observed so far in the crystal structures of arginine, its salts and complexes. In both complexes, the molecules are organized into double layers stacked along the longest axis. The core of each double layer consists of two parallel sheets made up of main-chain atoms, each involving both types of molecules. The hydrogen bonds within each sheet and those that interconnect the two sheets give rise to LLLL-, DDDD- and DLDL-type head-to-tail sequences. Adjacent double layers in (1) are held together by side-chain-side-chain interactions whereas those in (2) are interconnected through an extensive network of water molecules which interact with sidechain guanidyl and carboxylate groups. The aggregation pattern observed in the two LDLD complexes is fundamentally different from that found in the corresponding LLLL complexes

    X-ray Studies on Crystalline Complexes Involving Amino Acids and Peptides. XIII. Effect of Chirality on Molecular Aggregation: The Crystal Structures of L-Arginine D-Aspartate and L-Arginine D-Glutamate Trihydrate

    No full text
    The crystal structures of (1) L-arginine D-asparate, C6HIsN40~.C4H6NO4 [triclinic, P1, a=5.239(1), b=9.544(1), c=14.064(2)A, a=85"58(1), /3=88.73 (1), ~/=84.35 (1) °, Z=2] and (2) L-arginine D-glutamate trihydrate, C6H15N40~-.CsHsNO4.3H20 [monoclinic, P2~, a=9.968(2), b=4.652(1), c=19.930 (2) A, fl = 101.20 (1) °, Z = 2] have been determined using direct methods. They have been refined to R =0.042 and 0.048 for 2829 and 2035 unique reflections respectively [I>2cr(I)]. The conformations of the two arginine molecules in the aspartate complex are different from those observed so far in the crystal structures of arginine, its salts and complexes. In both complexes, the molecules are organized into double layers stacked along the longest axis. The core of each double layer consists of two parallel sheets made up of main-chain atoms, each involving both types of molecules. The hydrogen bonds within each sheet and those that interconnect the two sheets give rise to EL-, DD- and DE-type head-to-tail sequences. Adjacent double layers in (1) are held together by side-chain-side-chain interactions whereas those in (2) are interconnected through an extensive network of water molecules which interact with sidechain guanidyl and carboxylate groups. The aggregation pattern observed in the two LD complexes is fundamentally different from that found in the corresponding EL complexes

    X-ray studies of crystalline complexes involving amino acids and peptides. XIII. Effect of chirality on molecular aggregation: the crystal structures of L-arginine D-aspartate and L-arginine D-glutamate trihydrate

    No full text
    The crystal structures of (1) L-arginine D-asparate, C<SUB>6</SUB>H<SUB>I5</SUB>N<SUB>4</SUB>O<SUB>2</SUB><SUP>+</SUP>· C<SUB>4</SUB>H<SUB>6</SUB>NO<SUB>4</SUB><SUP>-</SUP> [triclinic, P1, a= 5.239(1), b = 9.544(1), c = 14.064(2)Å, α = 85.58(1), β=88.73 (1), γ=84.35 (1) °, Z = 2] and (2) L-arginine D-glutamate trihydrate, C<SUB>6</SUB>H<SUB>15</SUB>N<SUB>4</SUB>O<SUB>2</SUB><SUP>+</SUP>· C<SUB>5</SUB>H<SUB>8</SUB>NO<SUB>4</SUB><SUP>-</SUP>·3H<SUB>2</SUB>O [monoclinic, P2<SUB>1</SUB>, a = 9.968(2), b = 4.652(1), c = 19.930 (2) Å, β = 101.20 (1) °, Z = 2] have been determined using direct methods. They have been refined to R = 0.042 and 0.048 for 2829 and 2035 unique reflections respectively [I&gt;2σ(I)]. The conformations of the two arginine molecules in the aspartate complex are different from those observed so far in the crystal structures of arginine, its salts and complexes. In both complexes, the molecules are organized into double layers stacked along the longest axis. The core of each double layer consists of two parallel sheets made up of main-chain atoms, each involving both types of molecules. The hydrogen bonds within each sheet and those that interconnect the two sheets give rise to LL-, DD- and DL-type head-to-tail sequences. Adjacent double layers in (1) are held together by side-chain-side-chain interactions whereas those in (2) are interconnected through an extensive network of water molecules which interact with sidechain guanidyl and carboxylate groups. The aggregation pattern observed in the two LD complexes is fundamentally different from that found in the corresponding LL complexes
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