Horst-Dieter Försterling

Pulsed Laser Light Forces Cancer Cells to Absorb Anticancer Drugs – The Role of Water in Nanomedicine

Abstract: Anticancer drugs executing their function intracellularly enter cancer cells via diffusive processes. Complementary to these slow processes, cells can be forced to incorporate drugs by convection – a more efficient transport process. Transmembrane convection is induced by moderately intense pulsed laser light (or light emitting diodes) changing the structure of nanoscopic water layers in cells. This is a fundamental difference with the method of photodynamic therapy. In a model system we demonstrate that a total irradiation time of one minute is sufficient to completely inhibit proliferation of cancer cells. Transmembrane convection protects healthy cells from extended chemotherapy exposure, could be exploited to overcome multidrug resistance, and is a promising new tool in a variety of therapies as well as in skin rejuvenation.

The role of radicals in the Belousov-Zhabotinsky reaction

A new theory of the Belousov-Zhabotinsky (BZ) reaction, the Radicalator model, is presented. This model is based on a negative feedback loop involving a fast reaction between malonyl and bromine dioxide radicals. Experimental evidence for the validity of the model is given for BZ systems in 3 M and 1 M sulfuric acid solution.

Polyreactive antibodies in multidonor-derived immunoglobulin G: theory and conclusions drawn from experiments.

Multidonor-derived (md) preparations of IgG antibodies, agents of therapeutic potential, contain molecules interacting at clonal concentrations (concns) and with affinities recently estimated to cover a considerable range. Here we demonstrate that polyreactivity of the monomeric molecules represents the essential driving force of formation of the main reaction product, the IgG-dimers. This conclusion is obtained by applying the principles of the law of mass action to dimer formation by polyreactive monomeric reactants. In addition, general interrelationships involving the mean number of reactants per reactor, the experimental dimer portion (w/w) and the mean concentrations of monomers in a polyreactive and monoreactive antibody system are derived. These interrelationships, together with quantitative results obtained from simplified computational kinetic models of polyreactive antibodies, allow to estimate a remarkably high value for the mean number of reactants per reactor, exceeding 60 for the underlying IgG preparation obtained from pooled human plasma units of 5000 donors. Moreover, the potential origin and other consequences of polyreactivity are outlined.

Chemical mechanism of the radical feedback loop in the classical BZ reaction. Malonyl bromite and oxalic acid as flow-through intermediates

High-pressure liquid chromatography (HPLC) and measurements of the CO2 produced were performed in the induction period of the classical Belousov–Zhabotinsky (BZ) reaction (malonic acid–bromate–cerium catalyst in sulfuric acid medium). It was found that oxalic acid is a flow-through intermediate of the reaction. This was confirmed with an independent qualitative test with thiobarbituric acid. The concentration of oxalic acid grows in the induction period together with that of bromomalonic acid and dibromomalonic acid intermediates. It is known that there are two negative feedback loops in the BZ reaction: one is ia bromide and the other ia organic free radicals. Oxalic acid and also CO2 are products of this second loop where organic radicals react with BrO2 radicals. The induction period was chosen for the present experimental studies because the above radical–radical reactions are most intense during that time. Based on the experimental results mechanistic proposals are made for the radical feedback loop. A method to accumulate multivalent organic acids present in very low concentrations in the BZ reaction was also developed. Applying this and a thermal decomposition method ethenetetracarboxylic acid (EETA) was identified as an oxidation product of ethanetetracarboxylic acid (ETA).

Contribution of malonyl radical control in the classical Belousov-Zhabotinsky reaction

Abstract In the original theory of the Belousov-Zhabotinsky reaction it is assumed that the oscillations are exclusively controlled by bromide ions. From uv/vls and ESR experiments on BZ systems started with Ce4 + we conclude that malonyl radicals play an important role as additional intermediates. The experiments are in agreement with calculations based on the Radicalator model.

Rate of the Bromous Acid-Bromide Reaction Measured in a Br2-HOBr Buffer System in Sulfuric Acid Solution

In the Belousov-Zhabotinsky system bromine species of oxidation states - 1 to 5 are important for the start and for the inhibition of the autocatalytic reaction steps. Especially, the reaction of Br- with HBrO2 competes with the oxidation of Ce3+ by BrO2 formed from HBrO2 and HBrO3. In our investigation the reaction of Br- with HBrO2 (solvent 1 M sulfuric acid) is followed spectroscopically in a mixture of bromine and hypobromous acid, which system works as a buffer for bromide. Including experiments on the hydrolysis of Br2 and on the solubility product of AgBr in 1 M sulfuric acid solution direct information about the rate constant kl of the Br-/HBrO2 reaction is obtained (k1 = 2.5 × 106 M-2 s-1 at 20 °C and 4× 106 M-2 s-1 at 25°C, which values are valid in the range of 0.01 to 1 M sulfuric acid).

Zwischenmolekulare Kräfte und Aggregation

Zunachst wollen wir die Gesetzmasigkeiten betrachten, die zur Bildung von kondensierten und geordneten Molekulanhaufungen (z. B. Kristallen) fuhren; im nachsten Kapitel werden wir dann auf das Verhalten verdunnter und ungeordneter Molekulanhaufungen naher eingehen. Zur Bildung von kondensierten und geordneten Molekulanhaufungen ist es notig, das die einzelnen Bausteine Krafte aufeinander ausuben. Wir wollen diese Krafte an Aggregaten aus geladenen Bausteinen (Beispiel: Ionenkristalle und Metalle) sowie an Aggregaten aus ungeladenen Bausteinen (Beispiel: Molekulkristalle) untersuchen.

Wellen-Partikel-Dualität

Wir stellen uns die Frage: besteht Licht aus Teilchen (Partikel) oder handelt es sich um eine Wellenerscheinung? Je nach dem Experiment, das wir zu dieser Frage anstellen, fallt die Antwort verschieden aus. Die Partikelnatur zeigt sich bei jeder Nachweismethode des Lichts (z. B. Photoeffekt, photochemischer Vorgang bei der Schwarzung einer Photoplatte, Sehvorgang). Auf eine Wellennatur des Lichts schliesen wir aus den Interferenzerscheinungen (z. B. Beugung an einer Kante oder an einem Spalt).

Wärmeaustausch bei chemischen Reaktionen

Wir haben uns bisher mit den Prinzipien beschaftigt, die fur das Verstandnis von Energieanderungen bei Prozessen wichtig sind. Jetzt wollen wir diese Prinzipien auf den Ablauf chemischer Reaktionen anwenden.

Periodensystem der Elemente

Wir haben bisher den Aufbau leichter Elemente (Wasserstoff, Helium und Lithium) kennengelernt. Elemente bestehen aus Atomen mit jeweils gleicher Kernladungszahl Z (Anzahl der Protonen). Durch Hinzufugen je eines Protons und eines Elektrons sind wir von Wasserstoff (Z = 1) zum Helium (Z = 2) und schlieslich zum Lithium (Z = 3) gelangt. In entsprechender Weise konnen wir uns den Aufbau schwererer Elemente vorstellen (Tabelle 4.1).