The structure of the protein-solvent interface is the subject of controversy in theoretical studies and requires direct experimental characterization. Three proteins with known atomic resolution crystal structure (lysozyme, Escherichia coli thioredoxin reductase, and protein R1 of E. coli ribonucleotide reductase) were investigated in parallel by x-ray and neutron scattering in H 2 O and D 2 O solutions. The analysis of the protein-solvent interface is based on the significantly different contrasts for the protein and for the hydration shell. The results point to the existence of a first hydration shell with an average density Ϸ10% larger than that of the bulk solvent in the conditions studied. Comparisons with the results of other studies suggest that this may be a general property of aqueous interfaces.Hydration, ion binding, and hydrophobic effects are major factors in the stabilization of the tertiary and quaternary structure as well as in the interactions between macromolecules. Despite their importance, macromolecule-solvent interactions are understood inadequately because of the considerable difficulty associated with their experimental study (for a review, see ref.

In a field experiment, the effect of foliar Zn applications on the concentration of Zn in seeds of a bread wheat cultivar (Triticum aestivum L. cv. Balatilla) was studied during different stages of seed development. In addition, a staining method using dithizone (DTZ: diphenyl thiocarbazone) was applied to (1) study the localization of Zn in seeds, (2) follow the remobilization of Zn during germination, and (3) develop a rapid visual Zn screening method for seed and flour samples. In all seed development stages, foliar Zn treatments were effective in increasing seed Zn concentration. The highest Zn concentration in the seeds was found in the first stage of seed development (around the early milk stage); after this, seed Zn concentration gradually decreased until maturity. When reacting with Zn, DTZ forms a red-colored complex. The DTZ staining of seed samples revealed that Zn is predominantly located in the embryo and aleurone parts of the seeds. After 36 h of germination, the coleoptile and roots that emerged from seeds showed very intensive red color formation and had Zn concentrations up to 200 mg kg ÿ1 , indicating a substantial remobilization of Zn from seed pools into the developing roots (radicle) and coleoptile. The DTZ staining method seems to be useful in ranking flour samples for their Zn concentrations. There was a close relationship between the seed Zn concentrations and spectral absorbance of the methanol extracts of the flour samples stained with DTZ. The results suggest that (1) accumulation of Zn in seeds is particularly high during early seed development, (2) Zn is concentrated in the embryo and aleurone parts, and (3) the DTZ staining method can be used as a rapid, semiquantitative method to estimate Zn concentrations of flour and seed samples and to screen genotypes for their Zn concentrations in seeds.

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Eukaryotic elongation factor 2 (EF-2) was shown to bind to F-a&n as assayed by co-sedimentation. In the presence of guanosine-5'-O-(3-thiotriphosphate) (GTPyS) binding was increased fourfold. At saturation level a molar ratio of about 0.12 EF-2 per F-a&n (subunit) was observed. Our results suggest a single type of binding site with an apparent dissociation constant of 0.85 PM. The stoichiometry was independent of the filament length, and ADP-ribosylation had no effect on the binding. Experimental data indicated the involvement of SH-groups of both EF-2 and actin in the binding. The interaction EF-2 with F-a&in appeared to be inhibited competitively by EF-la and non-competitively by G-actin.