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The cell of Pyrocystis spp. is covered by an outer layer of material resistant to strong acids and bases. Internal to this layer much of the cell wall is composed of cellulose fibrils. The presence of cellulose fibrils was established by staining raw and ultraviolet-peroxide-cleaned cell walls and by combining X-ray diffraction spectroscopy with electron microscope observation. Carbon replicas of freeze-etched preparations and thin sections of P. lunula walls show outer layer, inside them ca. 24 layers of crossed parallel cellulose fibrils (4-5 nm thick, ca. 12 nm wide), then a region of smaller (ca. 6-12 nm diameter) fibrils in a disperse texture, and then the plasma membrane. Cellulose fibrils in the parallel texture are constructed 3-5 elementary fibrils ca. 3 nm in diameter. Walls of P. fusiformis and P. pseudonctiluca also have cellulose fibrils in a crossed parallel texture similar to those of P. lunula. The Gymnodinium-type swarmer from lunate P. lunula appears to have a cell wall ultrastructure typical of other "naked" dinoflagellates. [ABSTRACT FROM AUTHOR]

X-ray small angle scattering was performed on solutions of the bacteriophages fr and R17. The scattering curves of the phages are nearly identical. The radius of gyration was found to be 105.2 Å, the molecular weight as obtained from a high precision measurement is 3.62 × 106. The radial excess electron density distribution, derived from measurements in 0.02 M Tris-Cl buffer pH 7.2 confabbing 0.15 M NaCl and 1 mM EDTA, indicates that the phages have a mean outer radius of 131.7 Å and consist of a shell and a less dense core. The core consists of RNA as is shown by measurements in sucrose solutions. It contains only about 80% of the RNA, the remaining 20% are considered to penetrate into the shell. Models calculated assuming the mean outer radius of the RNA to be 107.8 Å yield a mean inner radius of the protein shell of 104.0 Å. The amount of water associated with the phages is found to be about 0.9 g/g. [ABSTRACT FROM AUTHOR]

An account is given of the study by means of electron-spin-resonance spectroscopy of free radicals induced in wool and chemically modified wool by X-rays. 'Cystine' radicals are shown to be formed by only a portion of the total number of residues present, and these are associated with amino end-groups. Spectral changes produced by chemical modification of the cystine are explained in terms of superimposed singlet, doublet, and quartet absorptions, and it is proposed that the quartet absorptions originate from free radicals on the alanine side chains. It is shown that X-irradiation in air modifies the wool structure so that previously 'inert' disulphide links are capable of radical formation. [ABSTRACT FROM AUTHOR]