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J J WOLKEN

Publications and source records attributed to J J WOLKEN.

At least 19 recordsLinked to original sources
PubMed1960

Two c-type cytochromes from light- and dark-grown Euglena.

A pigment-protein complex can be extracted, in aqueous 2-percent digitonin, from Euglena grown in the light. When further fractionated by acetone and ammonium sulfate this flagellate yields a c-type cytochrome. By similar extraction of dark-grown, nonphotosynthetic Euglena, another c-type cytochrome can be isolated. The cytochrome from the light-grown Euglena- is like that of cytochrome c isolated from a photosynthetic bacterium. The cytochrome from the dark-grown Euglena is like cytochrome f found in the chloroplasts of higher plants.

Animals↗
PubMed1959

A light-sensitive yellow pigment from the housefly.

Extraction of house-fly heads with neutral phosphate buffer yielded a dark brown solution from which a number of pigments were separated, either wholly or partially, by chromatography on a column of calcium phosphate mixed with celite. One of the pigments was light-sensitive, and had a yellow color, with a spectral absorption maximum at 437 mmicro in phosphate buffer at pH 6.5. Several consecutively eluted fractions from each chromatogram of the house-fly head extract showed the characteristic absorption curve of this pigment with no trace, spectroscopically, of the other pigments of the extract. The products of bleaching the pigment at pH 6.5 had an absorption curve showing plateaus at 440 to 460 mmicro and 350 to 360 mmicro and an inflection at about 250 mmicro. Above pH 8.0 the pigment bleached in the dark giving an absorption maximum at about 380 mmicro, and inflections at 290 mmicro and at about 250 mmicro. With 2.5 to 5 N HCl or H(2)SO(4) an absorption maximum at 470 to 475 mmicro was obtained with either the unbleached or the bleached pigment. With sulfosalicylic acid, ethanol, or heating at 100 degrees C., a part of the pigment was precipitated, leaving a light-stable yellow supernatant. This light-sensitive house-fly pigment cannot as yet be identified with any of the previously known insect pigments or with the photosensitive pigments of other animals, though these latter compounds exhibit some similarity in their spectroscopic properties.

Animals↗
PubMed1957

Photoreceptor structures. III. Drosophila melanogaster.

The eyes of three eye mutants of Drosophila melanogaster were fixed and thin sections studied for its structural detail in the electron microscope. Each ommatidium was found to have seven retinula cells with an equal number of rhabdomeres (visual units). The rhabdomeres average 1.2 micro in diameter and 60 micro in length. Each rhabdomere consists of osmium-fixed dense bands averaging 120 A in thickness, and with less dense interspaces 200 to 400 A. There is an average of 23 dense bands or 46 interfaces per micron within the rhabdomere. The rhabdomere as we have presented it is a single structure of packed rods or tubes. The "fine structure" within the rhabdomere is similar to that observed by electron microscopy for the retinula of the house fly, and to the retinal rods of the vertebrate eye, and to the chloroplasts of plant cells in a variety of animal and plant photoreceptor structures. In addition, the radial arrangements within the ommatidium of radially unsymmetrical units, the rhabdomeres, is probably related to the analysis of polarized light in the insect eye.

Animals↗