Spermidine phosphate trihydrate, C7H19N3.~H3PO4.3H20, is found to have a monoclinic unit cell with dimensions, a= 9.22, b= 26.03, c = 6.58/~, fl= 96.0 °. The space group is P21 and the asymmetric unit contains two formula units. The structure was solved by a sharpened Patterson function and refined by the block-matrix least-squares method with anisotropic temperature parameters to an R value of 0.09 for 2868 observed reflexions.The molecules take a normal extended zigzag chain conformation. The chemical formula of this compound has been shown to be [NH+(CH2)3NH+(CH2)4NH+]2.3[HPO4] 2-. 6H20. The structure consists of two kinds of bands, the molecular band and the phosphate--water band. They are extended along the a axis and joined together alternately side by side in the b direction to form a sheet structure with stripes of the bands. Within the molecular band, the spermidine molecules are arranged in parallel along the b axis as is generally seen in aliphatic long chain compounds. The angle of tilt is 90 °. The phosphatewater band consists of dimer and monomer ions of monohydrogen phosphate which are separated by water molecules, forming a network of hydrogen bonds. The striped sheets are piled up alternately along the c axis through N-H. • • O hydrogen bonds in such a way that the phosphate-water band comes next to the molecular band of spermidine. The structure is discussed in comparison with that of spermine phosphate hexahydrate.
There have been several studies of the metachromasy of basic dyes induced by deoxyribonucleic acid (DNA)1,2) and of the effects of inorganic or organic cations on the metachromasy.3-5)We have recently observed that toluidine blue shows a marked metachromasy with DNA in solution and that this metachromasy can often be hindered by adding another substance, one which interacts with DNA, to the solution. The degree of hindrance is found to depend upon how strongly the added substance interacts with DNA. This finding suggests a simple and easy method of the semiquantitative analysis of interactions between DNA and other substances of a certain type.
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