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Biomedical subjects

A Baumgärtner

Publications and source records attributed to A Baumgärtner.

11 recordsLinked to original sources
PubMed1997

Protein attraction in membranes induced by lipid fluctuations.

The nonspecific lipid-mediated attraction between two proteins embedded in a bilayer membrane have been investigated for a model system using Monte Carlo simulations. We found two types of attraction with different regimes. A depletion-induced attraction in the range r < sigmaL, where sigmaL is the diameter of a lipid and r is the distance between the surfaces of the two proteins, and a fluctuation-induced attraction in the range 1 < r/sigmaL < 6, which originates from the gradients of density and orientational fluctuations of the lipids around each protein. The effective potential of the latter type of attraction decays exponentially with U(r) approximately exp(r/vi) where the correlation length is vi/sigmaL approximately 3.2 in the present model system.

Diffusion↗
PubMed1996

Insertion and hairpin formation of membrane proteins: a Monte Carlo study.

Some particular effects of a lipid membrane on the partitioning and the concomitant folding processes of model proteins have been investigated using Monte Carlo methods. It is observed that orientational order and lateral density fluctuations of the lipid matrix stabilize the orientation of helical proteins and induce a tendency of spontaneous formation of helical hairpins for helices longer than the width of the membrane. The lateral compression of the lipids on a hairpin leads to the extrusion of a loop at the trans side of the membrane. The stability of the hairpin can be increased by the design of appropriate groups of hydrophilic and hydrophobic residues at the extruded loop. It is shown that in the absence of lipids the orientation of proteins is not stable and the formation of hairpins is absent. Some analogies between the formation of helical hairpins in membranes and the formation of hairpins in polymer liquid crystals are discussed. The simulations indicate that the insertion process follows a well-defined pattern of kinetic steps.

Biophysical Phenomena↗
PubMed1986

[Long-term follow up of the lenses of diabetic patients using Scheimpflug photography linear densitometry].

This article reports on changes in lenses of diabetics, detected by means of Scheimpflug photos. Diabetics aged between 20 and 70 have been undergoing regular ophthalmogical check-ups for 26 months. Linear densitometry of negatives revealed an increase in light scatter at the anterior adjacent clear zone of disjunction (areas 1,2) and the anterior cortex (areas 3,4) in clinically clear lenses over the 26-month period. This change in light scatter is not related to the age of the patients; it is correlated to the duration of diabetes and fasting blood sugar.

Adult↗
PubMed1982

Hypercoagulability after immunotherapy with Corynebacterium parvum in man.

The effect of an immunotherapy with Corynebacterium parvum on the blood coagulation system was investigated in a randomized trial of 18 patients with metastatic breast cancer. All patients received cytostatic therapy. Additionally, C. parvum was given intravenously on day 15 of the cytostatic cycle (group I) or on day 1 (group II) or not at all (group III). Fibrinopeptide A increased within 2 h after intravenous administration of C. parvum in groups I and II and normalized after 24 h (p less than 0.05). Platelet counts decreased continuously in all treatment groups (p less than 0.05). Prothrombin time, fibrinolytic concentration, factor VIII:C and factor VIIIR:Ag were not affected. The fibrinolytic activity showed a slight but not statistically significant increase after intravenous administration of C. parvum. The data suggest that plasma hypercoagulability is induced or enhanced in man even after small intravenous doses of C. parvum.

Bacterial Vaccines↗