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Biomedical subjects

O Glatter

Publications and source records attributed to O Glatter.

28 records · Page 2Linked to original sources
PubMed1995

Physicochemical behavior of the ganglioside GM3 in dilute aqueous solution.

The aggregative properties of the ganglioside GM3 have been studied with small-angle X-ray scattering and dynamic light scattering in dilute aqueous solutions. Dynamic light scattering experiments show that GM3 solutions are very polydisperse containing a large amount of small aggregates (hydrodynamic radius of 7-9 nm) in addition to a quite broad distribution of aggregates with an average hydrodynamic radius of 50-60 nm and a small fraction of very large aggregates (> 200 nm). This together with small-angle X-ray scattering scattering experiments and model calculations suggests the coexistence of a lamellar phase (vesicles or extended lamellae) with small aggregates (modelled as lamellar platelets). The latter can also be viewed as lamellar fragments coming from GM3 vesicles which constantly break and reform.

G(M3) Ganglioside↗
PubMed1995

Structural analysis of porcine brain nitric oxide synthase reveals a role for tetrahydrobiopterin and L-arginine in the formation of an SDS-resistant dimer.

Nitric oxide synthases (NOSs), which catalyze the formation of the ubiquitous biological messenger molecule nitric oxide, represent unique cytochrome P-450s, containing reductase and mono-oxygenase domains within one polypeptide and requiring tetrahydrobiopterin as cofactor. To investigate whether tetrahydrobiopterin functions as an allosteric effector of NOS, we have analyzed the effect of the pteridine on the conformation of neuronal NOS purified from porcine brain by means of circular dichroism, velocity sedimentation, dynamic light scattering and SDS-polyacrylamide gel electrophoresis. We report for the first time the secondary structure of NOS, showing that the neuronal isozyme contains 30% alpha-helix, 14% antiparallel beta-sheet, 7% parallel beta-sheet, 19% turns and 31% other structures. The secondary structure of neuronal NOS was neither modulated nor stabilized by tetrahydrobiopterin, and the pteridine did not affect the quaternary structure of the protein, which appears to be an elongated homodimer with an axial ratio of approximately 20/1 under native conditions. Low temperature SDS-polyacrylamide gel electrophoresis revealed that tetrahydrobiopterin and L-arginine synergistically convert neuronal NOS into an exceptionally stable, non-covalently linked homodimer surviving in 2% SDS and 5% 2-mercaptoethanol. Ligand-induced formation of an SDS-resistant dimer is unprecedented and suggests a novel role for tetrahydrobiopterin and L-arginine in the allosteric regulation of protein subunit interactions.

Allosteric Regulation↗
PubMed1994

Phase behavior of the antineoplastic ether lipid 1-O-octadecyl-2-O-methyl-glycero-3-phosphochloline.

The physicochemical properties of the antineoplastic etherphospholipid 1-O-octadecyl-2-O-methyl-glycero-3-phosphochline were examined in the concentration range 1-35% (w/w) lipid, as a function of temperature (range -10 degrees C to 40 degrees C) and of different aqueous solvents by dynamic light scattering, small- and wide-angle X-ray scattering, differential scanning calorimetry and ultrasonic speed measurements. On cooling the lipid dispersion undergoes a phase transition near 6 degrees C, transforming slowly from a micellar into a lamellar gel phase with interdigitating hydrocarbon chains. The lamellar repeat distance is nearly constant over the hydration range 65-90% buffer (d = 5.09-5.14 nm). The size of the micelles in terms of the hydrodynamic radius is 3.8 +/- 0.1 nm, the polydispersity is low. Their average shape is spherical. The electron density distribution across the micelle gives 2.5 nm for the extension of the hydrocarbon chains and 1.5 nm for the polar moiety. The existence of micelles was verified up to a concentration of 35% lipid. Throughout this concentration range size and shape do not change significantly. The kinetics of formation of the low-temperature phase is slow on cooling, increasing with increasing concentration. Upon heating the phase behavior shows a hysteresis. The extended lamellar organizations start to break down into smaller aggregates near 3 degrees C. The micellar phase is reformed near 20 degrees C.

Antineoplastic Agents↗
PubMed1992

Shape change of human blood platelets: reliable and fast detection by quasi-elastic light scattering.

Quasi-elastic light scattering has been used for the first time to obtain reliable information about the morphology of platelets under physiological conditions within a short time. By measuring two independent parameters (electrophoretic mobility and diffusion coefficient) it is possible to distinguish between different stages of shape change on the one hand, and between shape change and binding of particles to the platelet surface without shape change on the other hand.

Adult↗
PubMed1978

The structure of human-plasma low-density lipoprotein B. An X-ray small-angle scattering study.

1. X-ray small-angle scattering of human plasma lipoprotein B of the low-density fraction (rho = 1.016--1.060 g.cm-3) has been recorded to high precision at different electron density contrasts. 2. The overall structure of the particles is characterized by a quasi-spherical shape and radial symmetry. A maximum diameter of 23 nm and a molecular weight of 2.4 X 10(6) have been determined. 3. The internal structure is described in terms of a model consisting of spherical layers with different electron densities indicating that the neutral lipids are arranged in the core of the molecule up to a radius of about 8 nm surrounded by a monolayer of free cholesterol, phospholipids and protein. The neural lipids are shown to be in an ordered, liquid crystalline state at 4 degrees C and to undergo a thermotropic transition into a disordered state at higher temperatures.

Cholesterol↗
PubMed1977

The lipid bilayer structure of the abnormal human plasma lipoprotein X. An X-ray small-angle-scattering study.

The structure of the abnormal lipoprotein X occurring in the plasma of patients with obstructive jaundice was investigated by X-ray small-angle scattering. The data were analyzed by discussing the distance distribution functions obtained directly from the experimental data by Fourier transformation, involving no a priori assumptions. The results provide evidence for lipoprotein X being essentially a random distribution of lamellae with a thickness of 5.1 nm and are consistent with hollow spherical (vesicular) structures of outer diameters greater than 30 nm with some overall size heterogeneity. Under the experimental conditions chosen, lipoprotein concentrations between 0.01 and 0.18 g/ml in in buffers of low ionic strength, lateral stacking as observed in negative-stain electron microscopy does not occur. The electron density profile perpendicular to the lamellar plane indicates that a lipid bilayer is the underlying structural principle, with the protein moieties partly bound within the polar head-group regions and partly occluded in soluble form in the vesicle interior.

Cholestasis↗