PubMed · 5778676
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G Sherman, E Fujimori. 1969. Chlorophyll-dioxane interaction in the solid state.. https://doi.org/10.1016/0003-9861(69)90079-4
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The ionization potential and electron affinities of the purines and pyrimidines in DNA and RNA were calculated with the AM1 semiempirical method. The values support the experimental values. The electron affinities are significant, and positive, such that donor-acceptor interactions can, and indeed should play a role in the stacking of bases in nucleic acids. Based on the confirmation of the experimental values by the theoretical calculations, reliable values of the experimental hardness and electronegativity were calculated.
A synthetic siderophore, O-Trensox (L), has been designed and synthesized to improve iron nutrition of plants. The affinity for iron of this ligand [pFe(III) = 29.5 and pFe(II) = 17.9] is very high compared with EDTA. In spite of its high and specific affinity for iron, O-Trensox was found to be able to prevent, and to reverse, iron chlorosis in several plant species grown in axenic conditions. It also allows the iron nutrition and growth of Acer pseudoplatanus L. cell suspensions. The rate of iron metabolization was monitored by 59Fe radioiron. Ferritins, the iron storage proteins, are shown to be the first iron-labelled proteins during iron metabolization and to be able to further dispatch the metal. Using Fe(III)-Trensox, the rate of iron incorporation into ferritin was found to be higher than when using Fe-EDTA, but slower than with Fe-citrate, the natural iron carrier in xylem. During a plant cell culture, the extracellular concentrations of iron complex and free ligand were measured; changes in their relative amounts showed that the iron complex is dissociated extracellularly and that only iron is internalized. This suggests a high affinity for iron of a putative carrier on the plasmalemma. In contrast with Fe-citrate and Fe-EDTA complexes, Fe(III)-Trensox is not photoreducible. Its ability to induce radical damage as a Fenton reagent was tested using supercoiled DNA as target molecule. Unlike Fe-citrate and Fe-EDTA, Fe(II)-Trensox and Fe(III)-Trensox were proven to be harmless even during ascorbate-driven reduction, while Fe-EDTA and Fe-citrate generate heavy damage to DNA.
The charge-density distribution in the crystal structure of the nucleoside beta-cytidine at 123 K has been determined from X-ray diffraction data (Ag K alpha, lambda = 0.5608 A) using all 7233 reflections with sin theta/lambda < or = 1.14 A-1. Maps of electrostatic potential for the cytosine base in cytidine are similar to those derived from previous charge-density studies of cytosine monohydrate and 1-beta-D-arabinosyl-cytosine, after taking chemical differences into account. These results were obtained from pseudoatom multipole refinements including kappa as a variable to describe the expansion or contraction of the spherical valence shell for each atom type. A new structure refinement of this type has also been carried out for cytosine monohydrate. A survey of kappa values for hydrogen indicates that this is a variable which is not well determined experimentally. Variations in kappa H are relayed into the population parameters obtained for other pseudoatoms and can have a small but significant effect on molecular properties, such as the dipole moment. Assuming an average theoretical value of kappa H = 1.24, the molecular dipole moments calculated from the monopole and dipole pseudoatom population parameters are 17 (4) and 8.2 (15) Debye for cytidine nucleoside and cytosine in the monohydrate, respectively. Systems of atomic point charges are presented for cytidine, cytosine and water. These are generally satisfactory in reproducing the experimentally determined molecular electrostatic potentials and dipole moments.