Photopolymers for Rapid Prototyping of Soluble Mold Materials and Molding of Cellular Biomaterials

Summary. To substitute cross-linked photopolymers in rapid prototyping of mold materials and therefore extend the range of materials which can be casted, organo-soluble photopolymers were developed. Branched bisalkylacrylamides were suitable as base component for such formulations, due to their high reactivity, good mechanical properties, and excellent solubility of the formed polymers. These molding materials were used to prepare cellular biocompatible materials which could be used as bone replacement materials. Biocompatible crosslinkers based on methacrylates from hydrolyzed gelatine or lactic acid ethyleneglycol blockcopolymers and commercially available reactive diluents are the base components of such a formulation. Biocompatibility was investigated by osteoblast-like cells. Cellular biocompatible parts were obtained by thermal polymerization in soluble mould materials prepared by 3D-photoshaping.     

Bestimmung von leichten Elementen in Silicium und Selen durch Ionenaktivierungsanalyse

Zusammenfassung Elemente mit niedriger Kernladungszahl lassen sich durch Aktivierung mit thermischen Neutronen entweder überhaupt nicht oder nur mit sehr geringer Empfindlichkeit bestimmen.In den letzten Jahren gewinnt daher die Bestrahlung mit Ionen (Protonen, Deuteronen, Tritium-, ³He- und ⁴He-Ionen) zur Aktivierungsanalyse der leichten Elemente zunehmend an Bedeutung. Zwischen Ionen- und Neutronenaktivierungen bestehen prinzipielle Unterschiede, die diskutiert werden.Aufgrund ihrer relativ geringen Reichweite in Materie eignen sich Ionen besonders zur Untersuchung von Oberflächen sowie dünnen Aufdampfschichten und Korrosionsschichten. Da die Aktivierungstiefe durch entsprechende Wahl der Versuchsparameter festgelegt werden kann, laßt sich auch die Tiefenverteilung von Fremdstoffen im Matrixmaterial untersuchen.Zur Bestimmung von Sauerstoff, Stickstoff und Kohlenstoff werden Protonen- und Deuteronenreaktionen herangezogen; aber auch Elemente wie Bor und Aluminium lassen sich dureh Ionenaktivierung erfassen. Bei einer Einschußenergie der Ionen von 3,0 MeV, einer Flußdichte von 5 A/cm² und einer Bestrahlungszeit, die der Halbwertszeit des zu aktivierenden Elementes entspricht, liegt die Bestimmungsempfindlichkeit für die genannten Elemente im Bereich von 1–100 ppb.Über die Bestimmung von Kohlenstoff in Silicium und Sauerstoff in aufgedampften Selenschichten wird berichtet.

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Determination of light elements in silicon and selenium by ion-activation analysis

Elements with low atomic number either cannot be determined at all by activation with thermal neutrons or only with very poor detection limit.In recent years, irradiation with ions (protons, deuterons, tritium ions, ³He- and ⁴He-ions) for activation analysis of the light elements has therefore gained increasing importance. There are basic differences between ion and neutron activation, which are discussed.Because of their relatively small range in matter, ions are particularly suited for analyzing surfaces as well as thin deposited films and corrosion layers. Since the activation depth can be established in advance by appropriate selection of the analysis parameters, the distribution of foreign matter in the matrix material can also be analyzed.Proton and deuteron reactions are employed to determine the presence of oxygen, nitrogen and carbon, but other elements such as boron and aluminium can also be detected by ion activation. The detection limit attained in analyzing the elements mentioned is within the range of 1 to 100 ppb with an ion bombarding energy of 3.0 MeV, a flux density of 5 A/cm² and an irradiation period which corresponds to the half-life of the element to be activated.A report is given on the determination of carbon in silicon and oxygen in thin-deposited selenium films and the results are discussed.

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Vortrag bei der Tagung Analytische Probleme der Reindarstellung von Halbleitern, Wiesbaden, 24.–25. 9. 1968.

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Herrn Prof. Dr. W. Gebauhr danken wir für viele anregende Diskussionen. Für die Mithilfe bei der Bestrahlung und Auswertung sind wir Frau K. Appler, Frl. E. Lüders und Herrn H. Pfann zu Dank verpflichtet.     

Structural considerations from dielectric measurements on the aliphatic alcohols

Precise static dielectric constants are reported for methanol, ethanol, andn-propanol at 10,25, and 40° C and at pressures up to 3 kbar. The measurements were carried out by a low-frequency bridge method using a threeterminal, all-glass cell. An uncertainty of 0.05% is claimed for the data. The results are compared to data from previous investigations, whith the agreement in the absolute magnitude poor but the agreement in the pressure coefficient reasonable in most cases. The data are analyzed in terms of the Kirkwood correlation factorg _K as obtained from the Fröhlich equation. In all cases, theg _K factor decreases with increased pressure. The problems involved in calculating this factor from the experimental data are discussed, and it is shown that the trends ing _K are very dependent upon the assumptions made in isolating the liquid dipole moment from its gas-phase value. This fact also indicates that an interpretation of theg _K values in terms of stepwise association of correlation dipoles is premature at this time.     

High-resolution four-dimensional 1H-13C NOE spectroscopy using methyl-TROSY, sparse data acquisition, and multidimensional decomposition

An approach for recording four-dimensional (4D) methyl (1)H-(13)C-(13)C-(1)H NOESY spectra with high resolution and sensitivity is presented and applied to Malate Synthase G (723 residues, 82 kDa). Sensitivity and resolution have been optimized using a highly deuterated, methyl-protonated sample in concert with methyl-TROSY, sparse data sampling in the three indirect dimensions, and 4D spectral reconstruction using multidimensional decomposition (MDD). A sparse data acquisition protocol is introduced that ensures that sufficiently long indirect acquisition times can be employed to exploit the decreased relaxation rates associated with methyl-TROSY, without increasing the duration of the 4D experiment beyond acceptable measurement times. In this manner, only a fraction ( approximately 30%) of the experimental data that would normally be needed to achieve a spectrum of high resolution is acquired. The reconstructed 4D spectrum is of similar resolution and sensitivity to three-dimensional (3D) (13)C-edited NOE spectra, is straightforward to analyze, and resolves ambiguities that emerge when 3D data sets only are considered.     

High pressure studies of isoquinoline luminescence in polymeric media

The fluorescence peak of isoquinoline increases strongly in intensity with increasing pressure in polymethylmethacrylate (PMMA) and in polyisobutylene (PIB). In polyvinylalcohol the intensity decreases as the pressure increases. In all three cases the emission peak shifts to lower energy as the pressure increases. The results are consistent with the hypothesis that the ππ* state lies higher in energy than the nπ* state in non-hydrogen bonding solvents, but that the situation is reversed in hydrogen bonding solvents.     

Side chain assignments of Ile delta 1 methyl groups in high molecular weight proteins: an application to a 46 ns tumbling molecule

A sensitive 3D NMR pulse scheme, (H)C(CA)NH-COSY, is presented for the assignment of (13)C(delta)(1) Ile chemical shifts in large perdeuterated, methyl-protonated proteins. The nonlinearity of branched amino acids, such as Ile, significantly degrades the quality of TOCSY schemes which transfer magnetization from methyl carbons to the backbone (13)C(alpha) positions, and in applications to high molecular weight proteins (correlation times on the order of 40-50 ns), this compromises the sensitivity of spectra used for methyl assignment. The experiment presented utilizes COSY-based transfer steps and refocuses undesirable (13)C-(13)C scalar couplings that degrade the efficiency of TOCSY transfers. The (H)C(CA)NH-COSY scheme is tested on an (15)N,(13)C,(2)H-[Leu, Val, Ile (delta 1 only)]-methyl-protonated maltose binding protein (MBP)/beta-cyclodextrin complex at 5 degrees C (molecular tumbling time 46 +/- 2 ns), facilitating the assignment of (13)C(delta 1) chemical shifts for 18 of the 19 Ile residues for which backbone assignments were previously obtained. Both sensitivity and resolution of the resulting spectra are shown to be significantly better than those for a similar TOCSY-based approach.     

Versatile solid-phase synthesis of secondary amines from alcohols. Development of an N-Boc-(o-nitrobenzene)sulfonamide linker

The development of a versatile amine releasing linker based on the modified o-nitrobenzene sulfonamide protective group is described. This new N-Boc-o-nitrobenzenesulfonamide (Boc-ONBS) linker enables the elaboration on resin of primary and secondary amines by sequential substitution of the sulfonamide moiety using the Mitsunobu reaction. A 16-member array of secondary and Boc protected primary amines was then prepared using this linker.     

Asymmetric halogeno-bridged complexes: new reagents in organometallic synthesis and catalysis

Several methods to synthesize bimetallic complexes in which two different metal fragments are connected by halide bridges are described. Using simple starting materials a large pool of structurally defined bimetallic complexes with unique chemical reactivities can be prepared in short time. Applications in organometallic synthesis and homogeneous catalysis are discussed.