According to theoretical studies, narrow graphene nanoribbons with atomically precise armchair edges and widths of o2 nm have a bandgap comparable to that in silicon (1.1 eV), which makes them potentially promising for logic applications. Different top-down fabrication approaches typically yield ribbons with width 410 nm and have limited control over their edge structure. Here we demonstrate a novel bottom-up approach that yields gram quantities of high-aspect-ratio graphene nanoribbons, which are only B1 nm wide and have atomically smooth armchair edges. These ribbons are shown to have a large electronic bandgap of B1.3 eV, which is significantly higher than any value reported so far in experimental studies of graphene nanoribbons prepared by top-down approaches. These synthetic ribbons could have lengths of 4100 nm and self-assemble in highly ordered few-micrometer-long 'nanobelts' that can be visualized by conventional microscopy techniques, and potentially used for the fabrication of electronic devices.

ConclusionsWe have synthesized four isostructural porphyrinic MOFs and investigated their photoredox catalytic activities toward three representative organic transformations including aerobic hydroxylation of arylboronic acids, oxidative primary amine coupling, and the Mannich reaction.Compared to their molecular model compounds, porphyrinic MOF-based photocatalysts exhibit a considerably enhanced photostability and excellent recyclability. Most importantly, metalation with high-valent metal cations (In III and Sn IV ) significantly modifies the electronic structure of the porphyrin and provides a highly oxidizing photoexcited state that undergoes efficient reductive quenching processes to facilitate subsequent organic transformations. Porphyrin metalation indeed provides a convenient approach to fine-tune and optimize the photoredox catalytic activities of MOFs.

Porphyromonas gingivalis , a recognized periodontal pathogen, synthesizes free ceramides as well as other phosphorylated ceramide lipids. The purpose of this study was to separate complex lipids of P. gingivalis by high-performance liquid chromatography (HPLC) and determine the structures and biological activities of the major ceramide classes. Using gas chromatography-mass spectrometry, electrospray tandem mass spectrometry (ESI-MS/MS) and NMR analyses, three major classes of dihydroceramides were identified in specific HPLC fractions, with all classes containing the same dihydroceramide base structures (

Cyclopropylamines inactivate cytochrome P450 enzymes which catalyze their oxidative N-dealkylation. A key intermediate in both processes is postulated to be a highly reactive aminium cation radical formed by single electron transfer (SET) oxidation of the nitrogen center, but direct evidence for this has remained elusive. To address this deficiency and identify the fate of the cyclopropyl group lost upon N-dealkylation, we have investigated the oxidation of N-cyclopropyl-N-methylaniline (3) by horseradish peroxidase, a well-known SET enzyme. For comparison, similar studies were carried out in parallel with N-isopropyl-N-methylaniline (9) and N,N-dimethylaniline (8). Under standard peroxidatic conditions (HRP, H(2)O(2), air), HRP oxidizes 8 completely to N-methylaniline (4) plus formaldehyde within 15-30 min, whereas 9 is oxidized more slowly (<10% in 60 min) to produce only N-isopropylaniline (10) and formaldehyde (acetone and 4 are not formed). In contrast to results with 9, oxidation of 3 is complete in <60 min and affords 4 (20% yield) plus traces of aniline. By using [1'-(14)C]-3, [1'-(13)C]-3, and [2',3'-(13)C]-3 as substrates, radiochemical and NMR analyses of incubation mixtures revealed that the complete oxidation of 3 by HRP yields 4 (0.2 mol), beta-hydroxypropionic acid (17, 0.2 mol), and N-methylquinolinium (16, 0.8 mol). In buffer purged with pure O(2), the complete oxidation of 3 yields 4 (0.7 mol), 17 (0.7 mol), and 16 (0.3 mol), while under anaerobic conditions, 16 is formed quantitatively from 3. These results indicate that the aminium ion formed by SET oxidation of 3 undergoes cyclopropyl ring fragmentation exclusively to generate a distonic cation radical (14+*) which then partitions between unimolecular cyclization (leading, after further oxidation, to 16) and bimolecular reaction with dissolved oxygen (leading to 4 and 17 in a 1:1 ratio). Neither beta-hydroxypropionaldehyde, acrolein, nor cyclopropanone hydrate are formed as SET metabolites of 3. The synthetic and analytical methods developed in the course of these studies should facilitate the application of cyclopropylamine-containing probes to reactions catalyzed by cytochrome P450 enzymes.

Berberine (4) is responsible for the activity of an extract of a commercial root sample of Hydrastis canadensis against multiply drug resistant Mycobacterium tuberculosis. Two new quinic acid feruloyl esters, compounds 2 and 3, have been isolated from the same source along with canadine (1c), 8-oxotetrahydrothalifendine (1), and beta-hydrastine (5). These were found to be inactive. The structures of the new compounds were elucidated from spectral (1H, 13C, HMQC, HMBC, and H-H COSY) and chemical evidences.