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Dietrich Braun 《Angewandte Chemie (International ed. in English)》1976,15(8):451-459
One of the topical problems of macromolecular chemistry is the question of the extent to which macromolecules in solution or in the amorphous solid state can engage in mutual interpenetration. The present article is concerned primarily with recent investigations on cross-linking copolymerization and with inter-and intramolecular reactions of polymers as a contribution to the study of molecular shape. 相似文献
64.
H. -Th. Heimes und D. Braun 《Fresenius' Journal of Analytical Chemistry》1971,254(1):21-27
Zusammenfassung Aus an sich im Makromaßstab bekannten Einzelschritten zur Mineralisation zinnorganischer Verbindungen und zur komplexometrischen Bestimmung von Zinn(IV) wurde eine Mikrobestimmung von Zinn in nieder- und hochmolekularen Organozinnverbindungen entwickelt.Die Mineralisierung der zu analysierenden Verbindung erfolgt mit einer Mischung aus konz. Schwefelsäure und konz. Salpetersäure unter Zusatz von Perchlorsäure. Die Bestimmung des Zinn(IV) erfolgt durch Komplexierung mit einem Überschuß an ÄDTA und Rücktitration mit 0,01 N Kupfer(II)-nitratlösung gegen Naphthylazoxin-S als Metallindicator.An Hand von Beleganalysen wird gezeigt, daß bei Einwaagen zwischen 0,025 und 0,07 mMol zinnorganischer Verbindung mit einer relativen Standardabweichung von rund 0,4% zu rechnen ist.
Neue Anschrift: Chemische Werke Hüls AG 437 Marl, Westfalen. 相似文献
Microdetermination of tin in low and high molecular weight organotin compounds
A procedure has been developed combining the two steps of mineralization of the compound and complexometric titration of tin(IV), known from macroscale analysis.Mineralization is effected by a mixture of conc. sulphuric acid, conc. nitric acid and perchloric acid. The tin(IV) is determined by complexing it with an excess of EDTA and by back-titration with 0.01 N copper(II) nitrate using naphthyl azoxine S as complexometric indicator.Results of test analyses are given showing the relative standard deviation to be about 0.4% with samples containing 0.025 to 0.07 mMol of organotin compound.
Neue Anschrift: Chemische Werke Hüls AG 437 Marl, Westfalen. 相似文献
65.
With the aid of thinlayer chromatography mixtures of tetraorganotin compounds containing no polar groups can be separated and identified if they differ in the number of phenyl groups per molecule or in the nature of their aliphatic residues (alkyl or allyl). For analytical purposes mixtures of 80% hexane and 20% benzene by volume are suitable as mobile phase. For preparative purposes (requiring multiple development) pure hexane or hexane containing 10 to 20% benzene by volume are best suited as mobile phase, where the amount of hexane depends on the problem of separation at hand. The Rf values of the mobile phases vary linearly with the number of the phenyl groups x and decrease with increasing x. The straight lines connecting the Rf values cross at x=4 (tetraphenyltin). Dithizone and silver nitrate are suitable spray reagents for organotin compounds. By spraying the plates with dithizone tetra-, tri-, and di-organotin compounds can be immediately distinguished on the basis of the ensuing colourations. With silver nitrate allyltin compounds and polystannanes can be distinguished from alkyltin compounds; tetra-phenyltin is not coloured by this reagent. 相似文献
66.
Eberling J Braun P Kowalczyk D Schultz M Kunz H 《The Journal of organic chemistry》1996,61(8):2638-2646
The selective C-terminal deprotection of O-glycopeptide (methoxyethoxy)ethyl esters is achieved under mild conditions (pH 6.6, 37 degrees C) by enzymatic hydrolysis using papain or lipase M from Mucor javanicus to give building blocks useful for chain-extending glycopeptide synthesis. On the other hand, the selective removal of acetyl protecting groups from the saccharide portion of glycopeptides is accomplished by alternative enzymatic hydrolysis with lipase WG from wheat germ to furnish model substrates for enzymatic glycosyl transfer reactions in order to extend the carbohydrate side chain of these conjugates. 相似文献
67.
We present analytical expressions to calculate the gradient of the water-accessible surface area of proteins with respect to Cartesian coordinates and dihedral angles. A detailed mathematical analysis leads to corrected equations for the gradient calculation used previously in the ANAREA program. To study the hydrophobic effect of solvent-protein interactions, our expressions have been implemented to further improve the program package FANTOM. We used this version of FANTOM to minimize the ECEPP/2 and the hydrophobic energy of tendamistat. © 1993 John Wiley & Sons, Inc. 相似文献
68.
The three common variants of the vitamin D binding protein, also known as group specific component (Gc), namely types 1S, 1F and 2, as well as some rare variants were studied by thin-layer polyacrylamide gel isoelectric focusing in a pH 4.5-5.4 carrier ampholyte generated pH gradient, additionally containing N-(2-acetamido)-2-aminoethanesulfonic acid (ACES). Prior to isoelectric focusing, whole serum or purified preparations of the vitamin D binding protein were incubated with 25-hydroxycholecalciferol at various ligand/protein ratios. Binding differences were found for the anodal and cathodal isoforms of Gc 1 variants and also for various allelic types. Isoforms with higher isoelectric points generally had a lower affinity for the ligand than the variants with lower isoelectric points. 相似文献
69.
Liane M. Moreau Alexandre Herve Mark D. Straub Dominic R. Russo Rebecca J. Abergel Selim Alayoglu John Arnold Augustin Braun Gauthier J. P. Deblonde Yangdongling Liu Trevor D. Lohrey Daniel T. Olive Yusen Qiao Julian A. Rees David K. Shuh Simon J. Teat Corwin H. Booth Stefan G. Minasian 《Chemical science》2020,11(18):4648
We report the structural properties of ultra-small ThO2 and UO2 nanoparticles (NPs), which were synthesized without strong binding surface ligands by employing a covalent organic framework (COF-5) as an inert template. The resultant NPs were used to observe how structural properties are affected by decreasing grain size within bulk actinide oxides, which has implications for understanding the behavior of nuclear fuel materials. Through a comprehensive characterization strategy, we gain insight regarding how structure at the NP surface differs from the interior. Characterization using electron microscopy and small-angle X-ray scattering indicates that growth of the ThO2 and UO2 NPs was confined by the pores of the COF template, resulting in sub-3 nm particles. X-ray absorption fine structure spectroscopy results indicate that the NPs are best described as ThO2 and UO2 materials with unpassivated surfaces. The surface layers of these particles compensate for high surface energy by exhibiting a broader distribution of Th–O and U–O bond distances despite retaining average bond lengths that are characteristic of bulk ThO2 and UO2. The combined synthesis and physical characterization efforts provide a detailed picture of actinide oxide structure at the nanoscale, which remains highly underexplored compared to transition metal counterparts.ThO2 and UO2 nanoparticles synthesized using a COF-5 template exhibit unpassivated surfaces and provide insight into nanoscale properties of actinides. 相似文献
70.