Contribution of Secondary Structure Changes to the Surface Activity of Proteins.

A major difference between proteins and surfactants is that proteins are capable of changing their structure during refolding processes in the adsorbed state. It is often reported that these interfacial structure changes increase the surface activity of proteins. In order to investigate this, the surface activity of 5 proteins was determined in foam fractionation experiments, where pH and ionic strength were adjusted separately to gain the maximum surface activity for each protein. Infrared Reflection Absorption Spectroscopy was performed for each protein to analyze the changes in secondary structure after adsorption. In order to investigate quick structural changes, transmission Fourier Transform Infrared spectroscopy was performed to gain information about the secondary structure of the dissolved, non-adsorbed proteins. It was found that most proteins maintain a native-like conformation when adsorbed at the interface. With increasing time, most of the proteins investigated increased the amount of ß-sheets at the interface. This slow process went along with a slow increase in surface pressure. A correlation between structural changes on molecular level and surface activity on macroscopic level could not be found. However, the absolute increase of surface pressure at the very beginning of the adsorption process correlated with the surface activity of the proteins, suggesting that the slow processes on molecular level do not have a considerable impact on macroscopic surface activity.

[Dose-volume histograms and 3-D planning in breast-saving therapy of breast carcinoma]. / Dosis-Volumen-Histogramme und 3D-Planung bei der brusterhaltenden Therapie des Mammakarzinoms.

AIM: Improvement of the dose homogeneity in radiation treatment of the intact breast using 3D-planning and dose volume histograms. PATIENTS AND METHOD: 3D-planning, including the calculation of dose volume histograms of the planning target volume, was performed on 15 patients, who underwent radiation therapy with tangential photon beams. A standard plan and 2 modified or optimized plans were evaluated. Different dosimetric parameters like maximum dose, mean dose, standard deviation and the fractional volume which receives doses from 95 to 105% of the reference dose were compared and correlated with breast size. RESULTS: With increasing breast size standard planning leads to increased overdosage, both in magnitude and volume. Individual optimization by modifying weights and wedges gives no improvement in dose homogeneity, whereas a photon energy of 10 MV results in a more homogeneous dose distribution. The drawback of the higher energy is the increased underdosage of the skin. CONCLUSION: Using the standard geometry of tangential fields the dose homogeneity cannot be improved significantly by 3D-planning, compared to our standard technique.

Antibacterial efficacy of Fabry's tinctura on the resident flora of the skin at the forehead. Study of bacterial population dynamics in stratum corneum and infundibulum after single and repeated applications.

The in-vivo antibacterial activity of Fabry's tinctura (FT), a 3 w% salicylic acid, 1 w% phenoli liquefacti containing 50 v/v% isopropanol used in dermatology for the treatment of erythrasma, pityriasis versicolor, acne vulgaris a.o. on the human resident skin flora was assessed by a new test method in comparison to 60 v/v% isopropanol. The test method consists of a detergent scrub method (DSM) in combination with the cyanoacrylate method (CAM) thus allowing the quantitative determination of bacterial densities in two depth compartments of human skin, separately for bacterial genera. The most important innovation of this test method is that its arrangement, especially the separate evaluation of the genera of the resident flora, makes it possible to examine the ability of an antimicrobial agent to invade different depth compartments by its bioactivity against the resident flora and to measure short-and-long-term efficacies under physiological conditions. Our findings in 120 volunteers indicate that compared to 60% isopropanol FT is able to reduce bacterial density in superficial and deep skin compartments immediately after a single application equally well, but for a significantly longer period. In repeated applications, 60% isopropanol does not produce a cumulative or long-lasting effect, but it causes an abundant rebound growth of Propionibacterium spp. in the lower skin compartment. FT, however, shows a cumulative antibacterial effect at the surface and in the depth persisting up to four days after the last application. It is concluded that by its salicylic acid and phenolic content FT is an effective drug for the topical antimicrobial therapy of skin diseases.