Über die Reaktion von Δ9,12-Linolsäureester in Wasser, 5. Mitt.: Mechanismus der Glykolysehemmung bei Tumorzellen durch wasserlösliche Fettsäureester-Hydroperoxyde

Zusammenfassung In vorangegangenen Arbeiten dieser Mitteilungsreihe konnte die Hemmwirkung der wasserlöslichen Lipid-hydroperoxyde auf Atmung und Glykolyse vonEhrlich-Ascites-Tumorzellen festgestellt werden.Ferner wurde gefunden, daß die Lipid-hydroperoxyde (LHPO) nicht über eine Schädigung des intrazellulären DPN-Systems wirksam sind und ihrer Hemmwirkung wahrscheinlich eine oxydative Inaktivierung der SH-Enzyme der Glykolysekette zugrunde liegt. Zur experimentellen Prüfung dieser Annahme werden daher zunächst die isolierten Glykolyseenzyme Hexokinase, Glucose-6-phosphat-Dehydrogenase, Aldolase, Glycerinaldehydphosphat-Dehydrogenase (GAPDH) und Lactat-Dehydrogenase (LDH) nach Einwirkung von Präparat LHPO getestet. Die Messungen ergeben, daß nur die GAPDH und die LDH durch Präparat LHPO inaktiviert werden. Bestimmt man nun die Aktivität dieser beiden Enzyme in einem Extrakt, der aus den intakten und mit LHPO inkubierten Tumorzellen gewonnen wurde, so findet man hier eine vollständige Inaktivierung (halbmaximale Dosis 7,1·10^–5m Lipid-hydroperoxyd/l). Damit scheint der Wirkungsmechanismus von Präparat LHPO hinsichtlich der Glykolysehemmung klargestellt.Mit 1 AbbildungHerrn Prof. Dr.A. Zinke anläßlich seines 70. Geburtstages mit den besten Wünschen überreicht.     

Multipolar excitation in triangular nanoprisms

Theoretical studies on the optical properties of gold triangular prisms in solution are presented to determine how structural modifications affect the extinction spectrum. Well-defined trends in the particle extinction are found to depend on the triangular edge length and the prism thickness. Calculations performed on large, thin triangular prisms indicate multipolar excitation and display numerous peaks in the extinction spectrum. The dominant peaks are assigned to different in-plane modes corresponding to the lowest three orders of a multipole expansion. Vector polarization plots are presented to support the peak assignments. Altering the prisms by snipping off the points of the triangular cross section significantly blueshifts the dipole peak, but the higher-order modes are only slightly affected. Snipping off large volumes can lead to the suppression of high-order multipoles in the extinction spectrum.     

What controls the melting properties of DNA-linked gold nanoparticle assemblies?

We report a series of experiments and a theoretical model designed to systematically define and evaluate the relative importance of nanoparticle, oligonucleotide, and environmental variables that contribute to the observed sharp melting transitions associated with DNA-linked nanoparticle structures. These variables include the size of the nanoparticles, the surface density of the oligonucleotides on the nanoparticles, the dielectric constant of the surrounding medium, target concentration, and the position of the nanoparticles with respect to one another within the aggregate. The experimental data may be understood in terms of a thermodynamic model that attributes the sharp melting to a cooperative mechanism that results from two key factors: the presence of multiple DNA linkers between each pair of nanoparticles and a decrease in the melting temperature as DNA strands melt due to a concomitant reduction in local salt concentration. The cooperative melting effect, originating from short-range duplex-to-duplex interactions, is independent of DNA base sequences studied and should be universal for any type of nanostructured probe that is heavily functionalized with oligonucleotides. Understanding the fundamental origins of the melting properties of DNA-linked nanoparticle aggregates (or monolayers) is of paramount importance because these properties directly impact one's ability to formulate high sensitivity and selectivity DNA detection systems and construct materials from these novel nanoparticle materials.     

Crossed beams and theoretical studies of the dynamics of hyperthermal collisions between Ar and ethane

Crossed molecular beams experiments and classical trajectory calculations have been used to study the dynamics of Ar+ethane collisions at hyperthermal collision energies. Experimental time-of-flight and angular distributions of ethane molecules that scatter into the backward hemisphere (with respect to their original direction in the center-of-mass frame) have been collected. Translational energy distributions, derived from the time-of-flight distributions, reveal that a substantial fraction of the collisions transfer abnormally large amounts of energy to internal excitation of ethane. The flux of the scattered ethane molecules increased only slightly from directly backward scattering to sideways scattering. Theoretical calculations show angular and translational energy distributions which are in reasonable agreement with the experimental results. These calculations have been used to examine the microscopic mechanism for large energy transfer collisions ("supercollisions"). Collinear ("head-on") or perpendicular ("side-on") approaches of Ar to the C-C axis of ethane do not promote energy transfer as much as bent approaches, and collisions in which the H atom is "sandwiched" in a bent Ar...H-C configuration lead to the largest energy transfer. The sensitivity of collisional energy transfer to the intramolecular potential energy of ethane has also been examined.     

Growth and melting behaviour of thin in films on Ge(100)

Growth and melting behaviour of thin indium films on Ge(100) have been investigated by Auger-electron spectroscopy (AES), atomic force microscopy (AFM) and perturbed angular correlation (PAC) spectroscopy, respectively. At room temperature inidium is found to grow in three-dimensional islands even at submonolayer coverages. A very rough film surface is observed for thicknesses up to 230 ML. The melting behaviour of such films has been studied by PAC. A reduction of the melting temperature T _m as well as a strong supercooling of the films is observed. The electric field gradient for ¹¹¹In(¹¹¹Cd) in the indium islands is determined as a function of temperature and is used to monitor the local crystalline order of the films up to temperatures just below the melting point.     

Evolution of hexagonal patterns from controlled initial conditions in a Bénard-Marangoni convection experiment

We report quantitative measurements of both wave number selection and defect motion in nonequilibrium hexagonal patterns. A novel optical technique ("thermal laser writing") is used to imprint initial patterns with selected characteristics in a Bénard-Marangoni convection experiment. Initial patterns of ideal hexagons are imposed to determine the band of stable pattern wave numbers while initial patterns containing an isolated penta-hepta defect are imprinted to study defect propagation directions and velocities. The experimental results are compared to recent theoretical predictions.     

“Electronic” Raman scattering in localized mixed-valence systems

We predict that in strongly localized mixed-valence systems “electronic” Raman scattering corresponding to transitions between the coupled potential surfaces can be comparable to or stronger than vibrational resonance Raman scattering. The characteristics of the two patterns depend sensitively on the parameters describing the system and the exciting frequency.     

Laserspectroscopic studies of collective properties of neutron deficient Ba Nuclei

Isotope shifts and hyperfine structure of the BaI resonance-line (λ=553.6 nm) have been measured by dye laser induced resonance fluorescence on an atomic beam for^{135m, 129g, 129m, 126}Ba thus extending previous high resolution measurements of neutron deficient Ba nuclides (N<82). The experimental results, now available for 16Ba isotopes and isomers withA=140?126, are used to deduce differences of rms charge radii, magnetic dipole and electric quadrupole moments. While the groundstates display a pronounced odd-even staggering the h 11/2^? isomers^135mBa and^133mBa show a decreased staggering. Conspicuously the isomer shift of theg 7/2⁺ isomer^129m Ba proves to be negative. The nuclear structure information is discussed in the context of gammaspectroscopic studies of transitional nuclei with 50<N,Z<82 and on the basis of a quasi-particle-plus-triaxial rotor model. The isotope shift discrepancy observed is fairly well described by the droplet model.