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K Harlos

Publications and source records attributed to K Harlos.

6 recordsLinked to original sources
PubMed1992

Crystal structure at 2.8 A resolution of a soluble form of the cell adhesion molecule CD2.

The crystal structure of a soluble form of the T lymphocyte antigen CD2 provides the first complete view of the extracellular region of a cell adhesion molecule. The topology of the molecule, which comprises two immunoglobulin-like domains, is the same as that of the first two domains of CD4 but the relative domain orientation is altered by a fairly flexible linker region. The putative ligand-binding beta-sheet forms a flat surface towards the top of the molecule. Crystal contacts between these surfaces suggest a plausible model for the adhesive interaction.

Amino Acid Sequence↗
PubMed1979

Influence of pH on phosphatidic acid multilayers. A rippled structure at high pH values.

The influence of pH on the structure of 1,2-(ditetradecyl)-phosphatidic acid was investigated by differential scanning calorimetry and freeze-fracture electron microscopy. At pH 13.5--14 (2.6 M K+), where phosphatidic acid has two negative charges, calorimetric scans show a small transition (pretransition) below the main phase transition temperature. Freeze-fracture studies of the same dispersions reveal regular band patterns (so-called ripples) in the plane of the bilayers, when the lipid is quenched from below the main phase transition temperature. This rippled structure is similar to the well-known rippled structure of phosphatidylcholines.

Calorimetry, Differential Scanning↗
PubMed1979

Electrostatic interactions at charged lipid membranes. Electrostatically induced tilt.

The changes in bilayer structure induced by surface charges in the case of an ionizable lipid were studied by X-ray diffraction, Raman spectroscopy, and film-balance measurements. With increasing surface charge in the ordered phase, the X-ray results show a decrease in bilayer thickness, whereas the hydrocarbon chain packing stays essentially constant, the Raman data signify that the internal chain ordering does not change, and the monolayer studies show a lateral expansion of the bilayer. These results are interpreted in terms of a tilt of the chains caused by the surface charges on the polar heads. The tilt angle between the direction of the chains and the bilayer normal is obtained by a detailed theoretical evaluation. The tilt allows for a better understanding of the electrostatically induced shift of the phase transition temperature and of the shift induced by the binding of water in the case of lecithin in contrast ethanolamine.

Hydrogen-Ion Concentration↗
PubMed1978

Pretransitions in the hydrocarbon chains of phosphatidylethanolamines. A wide angle X-ray diffraction study.

The hydrocarbon chain packing of fully hydrated phosphatidylethanolamine multilayers is investigated by X-ray diffraction. An analysis of the wide angle reflections (short spacings) as a function of temperature indicates that, apart from the well-known ordered-disordered lipid phase transition, a second transition takes place at lower temperatures. This transition, which is in the present paper referred to as the pretransition, is characterized by a transformation of the hydrocarbon chain packing. A first model for the chain lattice is presented, which gives rise to the expectation that similar pretransitions might be found with other phospholipids.

Chemical Phenomena↗