QCM-D on mica for parallel QCM-D-AFM studies

Quartz crystal microbalance with dissipation monitoring (QCM-D) has developed into a recognized method to study adsorption processes in liquid, such as the formation of supported lipid bilayers and protein adsorption. However, the large intrinsic roughness of currently used gold-coated or silica-coated QCM-D sensors limits parallel structural characterization by atomic force microscopy (AFM). We present a method for coating QCM-D sensors with thin mica sheets operating in liquid with high stability and sensitivity. We define criteria to objectively assess the reliability of the QCM-D measurements and demonstrate that the mica-coated sensors can be used to follow the formation of supported lipid membranes and subsequent protein adsorption. This method allows combining QCM-D and AFM investigations on identical supports, providing detailed physicochemical and structural characterization of model membranes.     

Impact of four (13)C-proline isotope labels on the infrared spectra of ribonuclease T1

Ribonuclease T1 was biosynthesized, with all four prolines (13)C-labeled in the peptide C[double bond]O bond, using a proline auxotrophic yeast strain of Saccharomyces cerevisiae. The (13)C- and (12)C-proline isotopomers of ribonuclease T1 were investigated by infrared spectroscopy in the thermally unfolded and natively folded state at 80 and 20 degrees C, respectively. In the thermally unfolded state, both proteins established almost indistinguishable spectral features in the secondary structure sensitive amide I region. In contrast, the spectra measured at 20 degrees C revealed substantial qualitative and quantitative differences, though parallel analysis by circular dichroism suggested identical native folds for both isotopomers. Major spectral differences in the infrared spectra were detected at 1626 and 1679 cm(-1), which are diagnostic marker bands for antiparallel beta-sheets in ribonuclease T1 and at 1645 cm(-1), a region that is characteristic for the infrared absorption of irregular structures. Starting with the known three-dimensional structure of ribonuclease T1, the observed effects of the isotope labeling are discussed on the basis of transition dipole coupling between the (12)C[double bond]O and (13)C[double bond]O groups. The experimental results were confirmed by transition dipole coupling calculations of the amide I manifold of the labeled and unlabeled variant.     

Kernmagnetische Relaxation in Polyisopren

Zusammenfassung Die Temperaturabhängigkeit der longitudinalen ProtonenrelaxationszeitT ₁ in festem und gequollenem cis-Polyisopren (Naturkautschuk) zeigt zwischen –195°C und +150°C bei den Larmorfrequenzen 4, 22, 44 und 86 MHz zwei deutlich getrennte Minima, die zweierlei Kettenbewegungen mit unterschiedlichen Aktivierungsenergien zuzuordnen sind. Das Hochtemperaturminimum läßt sich durch Kinkumlagerungen, das Tieftemperaturminimum durch Methylgruppen-rotation beschreiben. In beiden Fällen muß eine Sprungzeitverteilung nachCole-Davidson eingeführt werden.

---

Summary The temperature dependence of the longitudinal proton relaxation timeT ₁ in solid and swelled cispolyisoprene (natural rubber) shows in the range between –195°C and +150°C at the Larmor frequencies 4, 22, 44 and 86 MHz two well separated minima, which can be ascribed to two kinds of chain segment motion with different activation energies. The high-temperature minimum is interpreted by kink jumps and the low-temperature minimum by methyl-group rotation. In both cases one has to assume aCole-Davidson distribution of jumping times.

---

---

Mit 4 Abbildungen

---

Vorgetragen auf der Arbeitssitzung des Fachausschusses Physik der Hochpolymeren in der Frühjahrstagung 1970 des Regionalverbandes Hessen-Niederrhein-Saar der Deutschen Physikalischen Gesellschaft in Darmstadt, 10.–13. März 1970.     

Struktur und Massenspektren der Reihe Sb(OEt)3-SbCl3

Structure and Mass Spectra of the Series Sb(0Et)₃ – SbCl₃ The crystal and molecular structures of ClSb(OEt)₂, (II) and Cl₂SbOEt (III) are determined by X-ray analysis. Both compounds crystallizes in the monoclinic space group P2₁/c. There are two dimensional planar layers in which the antimony is coordinated distorted octahedral. The mass spectra of the series Sb(OEt)₃–SbCl₃ (I–IV) are determined at 20 and 70 eV and the fragmentation processes are discussed.     

Heterometall-Komplexe mit Dithiometallaten des Typs [M′(MO2S2)2]2− (M  Mo,W; M′  Co,Ni); Darstellung und spektroskopische Eigenschaften

Heterometal Complexes with Dithiometallates of the Type [M′(MO₂S₂)₂]²⁻ (M  Mo, W; M′  Co, Ni); Preparation and Spectroscopic Properties The preparation of R₂[Co(MoO₂S₂)₂], R₂[Co(WO₂S₂)₂], R₂[Ni(MoO₂S₂)₂], and R₂[Ni(WO₂S₂)₂] (R = [(C₆H₅)₄P]) is described in detail. The compounds can be isolated under certain conditions inspite of the instability of the dithiometallates in solution. The i. r. and electronic absorption spectra as well as the reversible redox behaviour (from preliminary CV data) are discussed in relation to the molecular and electronic structure of the complexes.     

Einfluß von γ-Strahlung auf dielektrische und mechanische Eigenschaften von Polymethylmethacrylat und Polypropylen

Zusammenfassung Die dielektrischen und mechanischen Verlustfaktoren und die Dielektrizitätszahl wurden an zwei Hochpolymeren (Polypropylen und Polymethylmethacrylat) unter Einfluß von -Strahlung (maximale Dosis 5·10⁷R) bei Frequenzen zwischen 50 und 10⁴ Hz gemessen. Es zeigte sich eine sehr starke Vergrößerung der Verluste bei Polypropylen im Bereich der Meßtemperatur zwischen 20 und 140°C. Weiterhin konnte eine leichte Verschiebung des Verlustfaktordispersionsbereiches zu höheren Temperaturen beobachtet werden. Die untersuchten dielektrischen und mechanischen Eigenschaften von PMMA änderten sich demgegenüber nur sehr wenig. Es wurde jedoch eine leichte Vergrößerung der Halbwertsbreite des Verlustfaktordispersionsgebietes mit steigender -Dosis festgestellt.

---

Summary The dielectric and mechanical loss factors and the dielectric constant of two high-polymers (polypropylene and polymethylmethacrylate) were investigated after -irradiation (maximum dose 5·10⁷ R). The measurements were done in the frequency range between 50 c/s and 10⁴ c/s and in the temperature range between 20 °C and 140 °C. For polypropylene the loss factor was enlarged and a shift of the dielectric loss factor maximum to higher temperatures was observed. The half-width of the dielectric loss factor of PMMA increased slightly due to -irradiation.

---

---

Mit 4 Abbildungen     

A non-aqueous organometallic route to highly monodispersed copper nanoparticles using [Cu(OCH(Me)CH2NMe2)2

Good quality, highly monodispersed capped copper metal nanoparticles have been synthesised in a non-hydrolytic approach using thermal decomposition of the Cu(II) precursor [Cu(OCH(Me)CH2NMe2)2] in a hot coordinating solvent without further reducing agents; the copper nanoparticles have been characterised by optical spectroscopy (UV/VIS), electron microscopy (TEM), electron diffraction (SAED), and dynamic light scattering (DLS).