The chemistry of graphene oxide is discussed in this critical review Particular emphasis is directed toward the synthesis of graphene oxide, as well as its structure Graphene oxide as a substrate for a variety of chemical transformations, including its reduction to graphene-like materials, is also discussed This review will be of value to synthetic chemists interested in this emerging field of materials science, as well as those investigating applications of graphene who would find a more thorough treatment of the chemistry of graphene oxide useful in understanding the scope and limitations of current approaches which utilize this material (91 references)

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The chemistry of graphene oxide

Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Phd by thesis

The hydrogen bond is the most important of all directional intermolecular interactions. It is operative in determining molecular conformation, molecular aggregation, and the function of a vast number of chemical systems ranging from inorganic to biological. Research into hydrogen bonds experienced a stagnant period in the 1980s, but re-opened around 1990, and has been in rapid development since then. In terms of modern concepts, the hydrogen bond is understood as a very broad phenomenon, and it is accepted that there are open borders to other effects. There are dozens of different types of X-H.A hydrogen bonds that occur commonly in the condensed phases, and in addition there are innumerable less common ones. Dissociation energies span more than two orders of magnitude (about 0.2-40 kcal mol(-1)). Within this range, the nature of the interaction is not constant, but its electrostatic, covalent, and dispersion contributions vary in their relative weights. The hydrogen bond has broad transition regions that merge continuously with the covalent bond, the van der Waals interaction, the ionic interaction, and also the cation-pi interaction. All hydrogen bonds can be considered as incipient proton transfer reactions, and for strong hydrogen bonds, this reaction can be in a very advanced state. In this review, a coherent survey is given on all these matters.

The hydrogen bond in the solid state.

The transition metal dichalcogenides are about 60 in number. Two-thirds of these assume layer structures. Crystals of such materials can be cleaved down to less than 1000 A and are then transparent in the region of direct band-to-band transitions. The transmission spectra of the family have been correlated group by group with the wide range of electrical and structural data available to yield useful working band models that are in accord with a molecular orbital approach. Several special topics have arisen; these include exciton screening, d-band formation, and the metal/insulator transition; also magnetism and superconductivity in such compounds. High pressure work seems to offer the possibility for testing the recent theory of excitonic insulators.

The transition metal dichalcogenides discussion and interpretation of the observed optical, electrical and structural properties

Copper is an essential trace element in living systems, present in the parts per million concentration range. It is a key cofactor in a diverse array of biological oxidation-reduction reactions. These involve either outer-sphere electron transfer, as in the blue copper proteins and the Cu{sub A} site of cytochrome oxidase and nitrous oxide redutase, or inner-sphere electron transfer in the binding, activation, and reduction of dioxygen, superoxide, nitrite, and nitrous oxide. Copper sites have historically been divided into three classes based on their spectroscopic features, which reflect the geometric and electronic structure of the active site: type 1 (T1) or blue copper, type 2 (T2) or normal copper, and type 3 (T3) or coupled binuclear copper centers. 428 refs.

Multicopper Oxidases and Oxygenases

Es wird uber die beiden Orthothioborate Li3BS3 (Pnma; a = 8,144(1) A, b = 10,063(2) A, 6,161(1) A; Z = 4) und LiSrBS3 (Pnma; a = 7,557(1) A, b = 9,083(2) A, c = 7,049(1) A; Z = 4) berichtet. Die beiden neuen Phasen wurden durch Hochtemperatur-Schmelzreaktion aus den Metallsulfiden, amorphem Bor und Schwefel bei 700°C dargestellt. Beide Verbindungen enthalten isolierte, planare [BS3]3−-Anionen. Die Lithiumionen sind vierfach (Li3BS3) bzw. sechsfach (LiSrBS3) von Schwefel umgeben, das Strontiumion weist eine achtfache Schwefelkoordination auf. Li3BS3 und LiSrBS3 bilden neue A3BX3 bzw. AA′BX3-Strukturtypen.



Li3BS3 and LiSrBS3: New Orthothioborates with Trigonal Planar Boron Coordination



We report on the two new orthothioborates Li3BS3 (Pnma; a = 8.144(1) A, b = 10.063(2) A, 6.161(1) A; Z = 4) and LiSrBS3 (Pnma; a = 7.557(1) A, b = 9.083(2) A, c = 7.049(1) A: Z = 4). The two new phases were prepared by reaction of the metal sulfides, amorphous boron, and sulfur at 700°C. Both compounds contain isolated, planar [BS3]3−-anions. The lithium ions have fourfold (Li3BS3) and sixfold (LiSrBS3) sulfur coordination, the strontium ion shows an eightfold sulfur coordination. The two compounds represent new A3BX3 resp. AA′BX3 structure types.

Li3BS3 und LiSrBS3: Neue Orthothioborate mit trigonal‐planar koordiniertem Bor

[Ho5(H2O)16(OH)2As6W64O220]25−, a Large Novel Polyoxoanion from Trivacant Keggin Fragments



The novel polyoxotungstate Na7K18[Ho5(H2O)16(OH)2As6W64O220] · 56 H2O (1) was synthesized in aqueous solution and characterized by X-ray structure analysis, elemental analysis and IR spectroscopy. The anion in 1 represents one of the largest polyoxoanions known yet and exhibits an unusual arrangement of six Keggin units. It consists of six trivacant lacunary α-B-(AsW9O33)9− Keggin fragments which are connected by a bridging [Ho5W10(H2O)16(OH)2O22]29+ unit. The five HoIII atoms are coordinated by eight oxygen atoms, forming a square-antiprism.

[Ho5(H2O)16(OH)2As6W64O220]25−, ein großes neuartiges Polyoxoanion aus trivakanten Keggin-Fragmenten

Selenogermanate aus wriger Lsung: Darstellung und Struktur von Na4Ge2Se6 16 H2O

Anorganisch-Chemisches Institut der Universitat Munster, Wilhelm-Klemm-Strasse 8, 48 149 Munster, Germany, Fachgebiet Anorganische ChemieFestkorperchemie der Universitat Duisburg, Lotharstrasse 1, 47057 Duisburg, Germany, Institut f i r Biochemie der Universitat Munster, Wilhelm-Klemm-Strasse 2, 48 149 Munster, Germany, and European Molecular Biology Laboratory, Hamburg Outstation c/o DESY, Notkestrasse 85, 22607 Hamburg, Germany

XAS Investigations on the Iron-Zinc Center of Purple Acid Phosphatase from Red Kidney Beans

Background The anticancer activity of cisplatin derives from its ability to crosslink DNA. Cisplatin-resistance is partially caused by enhanced nucleotide excision repair (NER). Major 1,2-intrastrand crosslinks can create a hydrophobic notch at the damage site, which can be specifically bound by damage-recognition proteins, thus shielded from NER-activity. We aimed at preventing resistance by enhancing this mechanism using more hydrophobic platinum compounds. Methods We synthesized three platinum analogs with increased hydrophobic characteristics. Performing MTT-assays, the efficacy of cisplatin and the novel agents was compared in a fibroblast and eight brain tumour cell lines. Results Among the novel compounds, the most hydrophobic molecule, methylpyridineplatinum, was most cytotoxic (LC50 = 5.84 x 10(-5) M), followed by methylpyrazineplatinum, the second most hydrophobic (LC50 = 1.79 x 10(-4) M), and pyridineplatinum (LC50 = 2.76 x 10(-4) M). Overall, cisplatin revealed highest cytotoxicity (LC50 = 8.77 x 10(-6) M). Conclusions Comparison of the novel compounds supports the hypothesis that increased hydrophobicity contributes to higher antitumour-activity. Other advantageous characteristics of cisplatin might relate to its remaining highest efficacy.

Bernt Krebs

Papers

Li3BS3 und LiSrBS3: Neue Orthothioborate mit trigonal‐planar koordiniertem Bor

[Ho5(H2O)16(OH)2As6W64O220]25−, ein großes neuartiges Polyoxoanion aus trivakanten Keggin-Fragmenten

Selenogermanate aus wriger Lsung: Darstellung und Struktur von Na4Ge2Se6 16 H2O

XAS Investigations on the Iron-Zinc Center of Purple Acid Phosphatase from Red Kidney Beans

Overcoming cisplatin resistance: design of novel hydrophobic platinum compounds.