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Biomedical subjects

F Kopp

Publications and source records attributed to F Kopp.

51 records · Page 3Linked to original sources
PubMed1979

Hydrophobic membrane protein from chromatophores of Rhodospirillum rubrum. Structural and spectroscopic studies of monolayers and multilayers.

A hydrophobic, lipid- and pigment-free polypeptide from the chromatophore membrane of Rhodospirillum rubrum was spread from chloroform/methanol, pyridine and formic acid solutions at an air-water interface. Surface pressure versus area isotherms of the monolayers formed at the interface were partially dependent upon the spreading solvent used. From the surface area at 20 dynes/cm compression, an average molecular area of 12.9 nm2/molecule was calculated for a polypeptide monolayer spread from chloroform/methanol. Multilayers built up on germanium plates at different surface pressures were subjected to attenuated total reflection infrared spectroscopy. In all cases the amide I and II absorption bands were typical of alpha-helical and random conformations. Electron microscopy of transferred monolayers replicated by rotary platinum shadowing revealed domains of regular texture in specimens prepared at 20 dynes/cm. Such domains were virtually absent in specimens prepared at 10 and 30 dynes/cm. Light optical diffractometry of the ordered arrays yielded a smallest repetitive area of 13.5 nm2 which agrees well with the molecular area obtained from the monolayer surface. Although no drastic changes in secondary structure were detected in the course of this study, some conformational changes are indicated by solvent-dependent differences in the surface pressure versus area isotherms.

Bacterial Chromatophores↗
PubMed1976

Radiation damage in tripalmitin layers studied by means of infrared spectroscopy and electron microscopy.

Structural deteriorations in biomembranes, as inevitably induced while structural information is gathered by electron optical methods, were evaluated by infrared spectroscopy. Tripalmitin model membranes were irradiated with 100 keV-electrons in an electron microscope. The intensity decay of group vibrations over the dose reveals the sequence of damage in the polar and nonpolar part of the molecule. The C-C backbone, being the most important structural feature, shows a significant latency effect up to 0.6 e-/A2 and is completely disordered by 3 e-/A2, corresponding to about three inelastic processes per molecule.

Electrons↗
PubMed1975

Instability of Langmuir-Blodgett layers of barium stearate, cadmium arachidate and tripalmitin, studied by means of electron microscopy and infrared spectroscopy.

Results of an investigation of the stability of n-layers of barium stearate, cadmium arachidate and tripalmitin by means of electron microscopy and attenuated total reflection infrared spectroscopy are reported. Odd and even numbered barium starate n-layers with n - 1,2,3,4,5 are found to rearrange spontaneously from a regular film into ultrastructures of irregular, flat islands of varying thickness. The kinetics of the phase transformation of the first layer depends on the substrate, that of n-layers appears to be dependent on n, the temperature, and the surrounding medium. The kinetic behaviour of odd and even numbered layers is distinctly different. Similar studies on cadmium arachidate layers reveal much slower kinetics of the rearrangement process. In the case of tripalmitin n-layers it is shown that electron microscopy and infrared spectroscopy yield valuable complementary information about ultrastructure and molecular structure of the layers in correlation with the rearrangement process, which also occurs with this system. Consequences of the results of this paper for work published in various fields are briefly discussed.

Barium↗
PubMed1975

[Development of germ cells in chick ovarian medulla].

Ovaries from chick embryos and chicken have been investigated with a view to the evolution of germ cells in the medullary. They can enter meiosis and reach pachytene. They seem to be eliminated by the way of the lacunas. Some observations can be utilized in a discussion about the initiation of the meiosis and the evolution of the ovocytes.

Aging↗
PubMedDate not supplied

Screening for molecules interacting with proteasomes in Thermoplasma acidophilum.

Thermoplasma acidophilum cell extracts were fractionated by gel filtration. Proteasomes were eluted as two major peaks. The first one (molecular mass(r) about 2 MDa) contained proteasomes associated with DNA/protein complexes. Proteasomes eluted in the other peak were partially resolved into three subpeaks and based on their preferential hydrolysis of casein, Z-GGL-MCA, and suc-LLVY-MCA, were designated C, L and Y, respectively. Further purification of proteasomes from peak Y resulted in a homogenous enzyme preparation, whereas proteasomes purified from peak C contained a homomultimeric protein composed of 20 kDa subunits. Thus, association of proteasomes with this protein seems to be responsible for the observed increase in molecular mass and for inhibition of caseinolytic activity by Ca2+-ions.

Archaeal Proteins↗