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H B Stuhrmann

Publications and source records attributed to H B Stuhrmann.

36 records · Page 2Linked to original sources
PubMed1981

Configuration of the four iron atoms in dissolved human hemoglobin as studied by anomalous dispersion.

The anomalous dispersion of iron at its K-absorption edge in small-angle scattering of an aqueous solution of hemoglobin has been used to establish the geometrical arrangement of the four iron atoms in this protein. Although the anomalous contributions are 0.001-0.01 of the total scattering, experiments with synchrotron radiation from the storage ring DORIS have shown that these effects can be measured with an average precision of approximately 10% at each of the 50 points of the scattering curve. The anomalous scattering represents the convolution of the whole structure with the configuration of the four iron atoms of hemoglobin. Analysis in terms of multipoles suggests that tetrahedral symmetry of both the subunit arrangement and the iron structure is a dominant feature. The mean distance between the iron atoms of 26 A derived from this experiment compares well with that derived from crystallographic data.

Hemoglobins↗
PubMed1978

Isolation and characterization of phytoferritin from pea (Pisum sativum) and Lentil (Lens esculenta).

Ferritin was isolated from the seeds of pea (Pisum sativum) and lentil (Lens esculenta). The homogeneity of the phytoferritins was established by polyacrylamide-gel electrophoresis. The subunit molecular weights were respectively 20 300 and 21 400 for hte pea and lentil proteins. A neutron low-angle scattering study established the molecular weight of the oligomer as 480 000 for pea apoferritin and 510 000 for lentil apoferritin. Although the quaternary structure of 24 polypeptide chains is preserved, the phytoferritins have a larger cavity in the interior than mammalian ferritins and can thus potentially store 1.2-1.4 times as much iron. The amino acid composition of the phytoferritins show some similarities to those of mammalian apoferritins; tryptic 'fingerprinting' reveals that there are many differences in the amino acid sequence of plant and mammalian apoferritins.

Amino Acid Sequence↗
PubMed1977

Contrast variation study of specifically deuterated Escherichia coli ribosomal subunits.

A neutron small-angle scattering analysis has been done on partially deuterated 30S and 50S subunits of Escherichia coli ribosomes by the contrast variation method. The results indicate that the central regions of both particles are RNA-rich whereas their exteriors are protein-rich. The segregation of RNA and protein is much greater in the 50S subunit than in the 30S; the 30S subunit approaches a homogeneous mixture of RNA and protein. In both structures the most probable separation between the centers of mass of their protein and RNA distributions is small, although substantial variation of this parameter is possible within experimental error.

Deuterium↗
PubMed1977

Shape of the 50S subunit of Escherichia coli ribosomes.

Extrapolation of a series of low-angle neutron scattering curves to infinitely high contrast gives a scattering function IC(kappa) which is dependent on the shape of the solute molecule. For the 50S subunit of E. coli ribosomes, the first part of the structure determination by neutron scattering, namely the determination of the molecular shape from IC(kappa), is reported. The result is in good agreement with models of the 50S subunit determined by electron microscopy.

Escherichia coli↗
PubMed1976

New low resolution model for 50S subunit of Escherichia coli ribosomes.

Neutron low angle scattering studies of the 50S subunit of E. coli ribosomes with the contrast variation method reveals large fluctuations in the scattering density. A region of relatively low scattering density, rich in proteins, surrounds an RNA-rich core of higher scattering density. The centers of mass of the RNA and protein parts of the 50S subunit are separated by a distance (20 A) that is considerably smaller than that reported in previous studies.

Escherichia coli↗
PubMed1975

Neutron scattering study of human serum low density lipoprotein.

Regions of different proton density in the low density lipoprotein (LDL) particle from human serum have been determined by neutron scattering. From measurements in various H2O/D2O mixtures, the LDL particle appears to be quasi-spherical, with the centers of gravity of the hydrocarbon and polar regions coinciding. The average volume occupied by a particle was found to be 3.2 X 10-6 A-3, with the volume fraction occupied by the hydrocarbons being 60%. The ratius of gyration of the hydrocarbon region was 64 A, while that of the polar region was 100 A. consequently, the core of LDL is predominantly occupied by the hydrocarbon chains, while the outer shell is sparsely occupied by protein emerging from the lipid core.

Deuterium↗
PubMedDate not supplied

Frozen spin targets in ribosomal structure research.

Polarized neutron scattering strongly depends on nuclear spin polarisation, particularly on proton spin polarisation. A single proton in a deuterated environment then is as efficient as 10 electrons in X-ray anomalous diffraction. Neutron scattering from the nuclear spin label is controlled by the polarisation of neutron spins and nuclear spins. Pure deuteron spin labels and proton spin labels are created by NMR saturation. We report on results obtained from the large subunit of E. coli ribosomes which have been obtained at the research reactor of GKSS using the polarized target facility developed by CERN. The nuclear spins were oriented with respect to an external field by dynamic nuclear polarisation. Proton spin polarisations of more than 80% were obtained in ribosomes at temperatures below 0.5 K. At T = 130 mK the relaxation time of the polarized target is one month (frozen spin target). Polarized small-angle neutron scattering of the in situ structure of rRNA and the total ribosomal protein (TP) has been determined from the frozen spin targets of the large ribosomal subunit, which has been deuterated in the TP and rRNA respectively. The results agree with those from neutron scattering in H2O/D2O mixtures obtained at room temperature. This is a necessary prerequisite for the planned determination of the in situ structure of individual ribosomal proteins and especially of that of ribosome bound mRNA and tRNAs.

Deuterium↗