Search PubMed⌕ Search

Biomedical subjects

W Hoffmann

Publications and source records attributed to W Hoffmann.

At least 253 records · Page 14Linked to original sources
PubMed1980

Protein rotation and chromophore orientation in reconstituted bacteriorhodopsin vesicles.

Bacteriorhodopsin has been reconstituted into lipid vesicles with dipalmitoyl and dimyristoyl phosphatidylcholine. Circular dichroism (CD) measurements show that the proteins are in a monomeric state above the main lipid phase transition temperature (Tc), 41 and 23 degrees C for dipalmitoyl and dimyristoyl phosphatidylcholine, respectively. Below Tc, the CD spectrum is the same as that found for the purple membrane. The latter result implies that the orientation of the chromophore at these temperatures is most likely the same as in the purple membrane (70 degrees +/- 5 degrees from the normal to the membrane plane). Transient dichroism measurements show that below Tc the proteins are immobile, while above this temperature protein rotation around an axis normal to the plane of the membrane is occurring. In addition, from the data the angle of the chromophore for the rotating proteins with respect to the rotational diffusion axis can be calculated. This angle is found to be 30 degrees +/- 3 degrees and 29 degrees +/- 4 degrees in dimyristoyl phosphatidylcholine and dipalmitoyl phosphatidylcholine, respectively. This is considerably smaller than the value of 70 degrees +/- 5 degrees for the natural biomembrane. A reversible reorientation of the chromophore above and below the respective main Tc transition temperature could explain the change of angle observed provided that all the molecules rotate above Tc.

Bacteriorhodopsins↗
PubMed1980

Bacteriorhodopsin, boundary lipid and protein conformers: a spin label study.

A spin label study, as a function of temperature, has been made with the bacteriorhodopsin membrane using a stearic acid spin label. The ESR spectra show a strong variation with temperature and the presence of isosbestic points. The spectra are interpreted as indicating the presence of a two-component system with an activation energy (approx. 14 kcal/mol) corresponding to a protein conformational change. This activation energy is similar to that deduced from recent flash photolysis studies. It is concluded that the spin label is sensitive to the temperature-dependent protein conformational change in this membrane system.

Bacterial Proteins↗
PubMed1980

Pion dosimetry with thermoluminescent materials.

Various thermoluminescent materials (6LiF, 7LiF, Li2B4O7:Mn, CaSO4:Dy, CaF2:Mn, CaF2-Dy, CaF2:Tm) were irradiated with pi- mesons throughout the depth dose distribution of a beam with central momentum of 176 MeV/c. Doses from 0.05 to 2 Gy were used and linearity and reproducibility were investigated. For LiF, CaF2:Dy and CaF2:Tm, low- and high-temperature peaks were analysed separately. CaF2:Tm was found to be the most suitable for pi- dosimetry since the total dose and the high LET component could be determined using the integral TL signal and the peak height ratio of the 150 degrees C and 240 degrees C peaks. In the dose range used, both peak responses are linear with dose and the sensitivity of the materials is 10 times that of LiF. The reproducibility was +/- 3%. The high temperature peak of 7LiF is too small to be determined accurately and the high temperature peak of CaF2:Dy decreases with increasing LET in the same way was the low temperature peak does, so that no LET information can be extracted.

Calcium Fluoride↗
PubMed1979

Rotational motion and evidence for oligomeric structures of sarcoplasmic reticulum Ca2+-activated ATPase.

The rotational motion of the sarcoplasmic reticulum Ca2+-activated ATPase (ATP phosphohydrolase, EC 3.6.1.3) has been investigated by measuring the decay of laser flash-induced dichroism with the covalently attached triplet probe eosin isothiocyanate. The Arrhenius plot for rotational mobility indicates two discontinuities at approximately 15 degrees C and approximately 35 degrees C. The experimental data are rationalized in terms of a sudden conformeric change in the ATPase at 15 degrees C and a temperature-dependent equilibrium existing between the conformationally altered ATPase and oligomeric forms of it in the temperature range 15-35 degrees C. The enzymatic activity, as indicated by a discontinuity in the Arrhenius plot for the rate of ATP hydrolysis, appears to be sensitive only to the change at 15 degrees C. There is a strong correlation between the activation energy below 15 degrees C for rotational motion (33.6 +/- 2.2 kcal/mol) and enzymatic activity (34 +/- 4 kcal/mol).

Animals↗
PubMed1979

[Initial reports on experiences in working with special groups in child day care centers].

A decisive condition for advancement at an early stage is the detection of physical damage. In this connection the GDR Ministry of Public Health has published guidelines for the establishment of special groups for infants suffering from physical damage, at ordinary creches (Verfügungen und Mitteilungen 15/1976). In 1976/77 a total of eight special groups with 64 children were set up at creches in the city of Erfurt. The criteria for assigning children to such groups were age and the type/degree of damage, with the aim of having homogeneous group structures. Advancement was through an all-day teaching process, in which parents were involved by giving them guidance, inviting them for discussion evenings and calling on their homes. A description is given of the approach to teaching and methods and planning (written timetables for specific months, weeks and days), all of which are essential in creating adequate educational conditions taking into account individual differences in the level of performance and the prevailing primary damage (e.g. disablement, impaired hearing, marked milieu damage).

Brain Damage, Chronic↗
PubMed1979

[Comparison of anthropometric and radiometric skull measurements of the first two years of life. 1st Part: Method of measurements and problems (author's transl)].

In 150 healthy boys and girls (1; 1,5; 2 years) seven anthropometric and several radiometric parameters (lengths, angles, planes) of the skull were determined. The methods are defined: anthromopetric measurements of the head taken after Martin (1959), radiometrics after Schmid and Filthuth, planimetric data collected after Wechselberg and Wessely.

Cephalometry↗
PubMed1979

[Comparison of anthropometric and radiometric skull measurements of the first two years of life. 2nd Part: Results (normal values) of kephalometric data -- results of linear metrics of the skull and planimetric results of x-ray analysis (author's transl)].

Statistical criteria allow the results of researches on head resp. skull measurements of more than 1200 infants of Erfurt to be taken as normal values, yielding slightly larger figures as up to now in use. Optimum appreciation of growth requires combination of all methods mentioned.

Cephalometry↗
PubMed1979

[Possibilities and limits for palsied children in the general polytechnical school (author's transl)].

Some children with cerebral palsy attend the ten-form general polytechnical school. To this end, several prerequisites have to be fulfilled and other essential arrangements to be developed in cooperation with specially trained teachers. The learning conditions have to be fitted to the improving abilities of children during the educational process. Factors of influence and cooperation modes are discussed.

Adolescent↗
PubMed1978

Two distinct rhodopsin molecules within the disc membrane of vertebrate rod outer segments.

The kinetics of the metarhodopsin I-II reaction have been measured over a wide range of temperatures (1-37C ) and pH values (4.5-8) with suspensions containing fragments of bovine rod outer segments. It was found that for all conditions the occurrence of metarhodopsin II could be described by two independent first-order processes. The fast component: slow component amplitude ratio depends upon pH and temperature. The kinetics of the lumi-metarhodopsin I reaction show the same pH dependence for the fast component: slow component amplitude ratio as the one observed for the metarhodopsin II signals. All the results observed could be described with the assumption that rhodopsin itself exists in two conformational states before bleaching which are in a pH and temperature-dependent equilibrium. This hypothesis is confirmed by its ability to explain some apparently anomalous observations in the literature.

Animals↗
PubMed1978

Inhibition of beef-brain and dog-heart (Na+ + k+) activated adenosine triphosphatase by carbon-3 branched cardenolides.

Twenty-two C-3 branched cardenolides were investigated as inhibitors of beef-brain and dog-heart (Na+ + k+) activated adenosine triphosphatase. The synthetic compounds had lower inhibitory strength than digitoxigenin, and there was no indication of an improved safety index. Structure--activity relationships show that increased steric shielding of the 3-OH group results in reduced inhibition.

Animals↗