Imaging Glycosylation In Vivo by Metabolic Labeling and Magnetic Resonance Imaging

Glycosylation is a ubiquitous post‐translational modification, present in over 50 % of the proteins in the human genome, 1 with important roles in cell–cell communication and migration. Interest in glycome profiling has increased with the realization that glycans can be used as biomarkers of many diseases, 2 including cancer. 3 We report here the first tomographic imaging of glycosylated tissues in live mice by using metabolic labeling and a gadolinium‐based bioorthogonal MRI probe. Significant N‐azidoacetylgalactosamine dependent T₁ contrast was observed in vivo two hours after probe administration. Tumor, kidney, and liver showed significant contrast, and several other tissues, including the pancreas, spleen, heart, and intestines, showed a very high contrast (>10‐fold). This approach has the potential to enable the rapid and non‐invasive magnetic resonance imaging of glycosylated tissues in vivo in preclinical models of disease.     

7‐Fluorotubercidin: a halogenated derivative of a naturally occurring nucleoside antimetabolite

The title compound [systematic name: 4‐amino‐5‐fluoro‐7‐(β‐d ‐ribofuranosyl)‐7H‐pyrrolo[2,3‐d]pyrimidine], C₁₁H₁₃FN₄O₄, exhibits an anti glycosylic bond conformation, with a χ torsion angle of −124.7 (3)°. The furanose moiety shows a twisted C2′‐endo sugar pucker (S‐type), with P = 169.8 (3)° and τ_m = 38.7 (2)°. The orientation of the exocyclic C4′—C5′ bond is +sc (gauche, gauche), with a γ torsion angle of 59.3 (3)°. The nucleobases are stacked head‐to‐head. The extended crystal structure is a three‐dimensional hydrogen‐bond network involving O—H...O, O—H...N and N—H...O hydrogen bonds. The crystal structure of the title nucleoside demonstrates that the C—C bonds nearest the F atom of the pyrrole system are significantly shortened by the electronegative halogen atom.     

Microstructured reaction areas for the deposition of silica

Patterned films with hexagonal structures were prepared by photochemical grafting of hydrophobic poly(acrylic acid 2-ethyl-hexylester) (PEHAA) as barrier and poly(ethylene imine) (PEI) as reaction area. The films have been characterized by ellipsometry, contact angle measurements, and scanning electron microscopy (SEM). These patterned films have been used in silica mineralization experiments by dipping them into a silica precursor solution. Silica deposition occurs only in PEI-coated areas, resulting in regular arrays of lens-shaped silica particles. The deposited silica was investigated by SEM and atomic force microscopy (AFM). Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

MP2 and DFT calculations on circulenes and an attempt to prepare the second lowest benzolog, [4]circulene

MP2 and DFT calculations have been carried out for [n]circulenes for n=3 to 20 in order to predict the strain energy and topology of these cyclically condensed aromatic systems. To synthesise [4]circulene (2), 1,5,7,8-tetrakis(bromomethyl)biphenylene (14) was prepared from the corresponding tetramethyl derivative (8) and subjected to various dehalogenation reactions; all attempts to obtain [2.2]biphenylenophane (7) as a precursor for 2 by this route failed. Treatment of 14 with sodium sulfide furnished the thiaphanes 16 and 17, thermal and photochemical desulfurization of which also failed to provide 7. In a second approach [2.2]paracyclophane was converted to the pseudo-geminal dithiol 23, which was subsequently bridged to the thiaphanes 22 and 24. On flash vacuum pyrolysis at 800 degrees C these were converted exclusively into phenanthrene (30). An approach to dehydrochlorinate the commercial product PARYLENE C to the tetrahydro[4]circulene 7 led only to polymerisation. The X-ray structures of the intermediates 8, 14, 17, 23, 24, 26, and 35 are reported.     

A quantitative analytical model for static dipolar disorder broadening of the density of states at organic heterointerfaces

Understanding the electronic structure of organic-organic heterointerfaces is crucial for many device applications of organic semiconductors. Here we have developed a simple analytical model to describe the effect of static dipolar disorder in a polymer dielectric on the density of states of an adjacent organic semiconductor. The degree of energetic disorder varies strongly with distance from the interface. Using a simple mobility model, we have been able to explain quantitatively both the magnitude as well as the gate voltage dependence of the field-effect mobility for polymer gate dielectrics with different dielectric constants.     

Detection and relative quantification of proteins by surface enhanced Raman using isotopic labels

Accurate quantification of protein content and composition has been achieved using isotope-edited surface enhanced resonance Raman spectroscopy. Synthesis of isotopomeric Rhodamine dye-linked bioconjugation reagents enabled direct labeling of surface lysines on a variety of proteins. When separated in polyacrylamide gels and stained with silver nanoparticles. The spectral signatures reflect the expected statistical distribution of isotopomeric labels on the labeled proteins in the gel matrix format without interference from protein features.     

(Zr6B)Cl12(MeCN)6][Ph4B].1.6MeCN: an easily-accessible starting material for zirconium cluster chemistry and [(Zr6B)Cl12(Pyr6)][Ph4B].2{(PyrH)[Ph4B]}, a first reaction product

In an attempt to produce a convenient starting material for the development of new interstitially centered, octahedral zirconium cluster compounds by solution-chemical methods, a new approach, using Na[Ph4B] to withdraw all six outer chlorides by precipitating them as NaCl, was explored. From a solution of K 2[(Zr 6B)Cl15] and Na[Ph4B] in acetonitrile, the tetraphenylborate salt [(Zr6B)Cl12(MeCN)6][Ph4B].1.6 MeCN (1) was obtained with high yield. It contains the [(Zr6B)Cl(i)12(MeCN)(a)6](+) ion (2) with an octahedral metal core. The crystal structure of 1, which possesses high solubility in several organic solvents, is reported. Treatment of 1 with pyridine gave the new cluster phase [(Zr6B)Cl12(Pyr6][Ph4B].2{(PyrH)[Ph4B]} (3), which was characterized as well by X-ray crystallography. An advantage of both title phases is that they contain Lewis acidic zirconium cluster units, which might be useful as catalysts, with the additional advantage of tuneable redox properties.     

Novel multichiral diols and diamines by highly stereoselective pinacol coupling of planar chiral [2.2]paracyclophane derivatives

The TiCl4/Zn-mediated intermolecular pinacol coupling of the planar chiral carbonyl compounds [2.2]paracyclophane-4-carbaldehyde, 4-acetyl[2.2]paracyclophane (ketone) and the four regioisomeric 5-, 7-, 12- and 13-methoxy[2.2]paracyclophane-4-carbaldehydes as well as the pTosOH-Zn/Cu-promoted coupling of their N-substituted imines is described. Coupling of the enantiomerically pure substrates (most of carbonyl compounds and all imines) occurs stereoselectively giving rise to diastereomerically pure 1,2-diols and 1,2-diamines. Racemic aldehydes and ketone react with different degrees of stereoselectivity (depending on the substituents in certain positions) and produce one to three diastereomers. 7-methoxy[2.2]paracyclophane-4-carbaldehyde undergoes a tandem pinacol coupling-pinacol rearrangement to yield bis-(7-methoxy[2.2]paracyclophane-4-yl)acetaldehyde. Coupling of the racemic imines produces a mixture of single racemic D,L-diamine and single meso-diamine in each case. The stereoselective formation of the asymmetric centres is governed by the planar chiral [2.2]paracyclophanyl moiety. The techniques elaborated are extended to the intramolecular coupling of [2.2]paracyclophane-4,13-dicarbaldehyde and its bis-N-phenylimine, resulting in stereoselective formation of the chiral triply-bridged diol and exclusive formation of the meso-diamine. X-Ray investigations of several diols and diamines have been carried out and the structural features of these derivatives are discussed.     

Synthesis and binding studies of 2-arylapomorphines

From codeine, four different 2-aryl substituted apomorphines were synthesised in 6 steps each. Oxidation of codeine with IBX followed by acid catalysed rearrangement gave morphothebaine, which was selectively triflylated at the 2-position and subsequently O-acetylated at the 11-position. The resulting triflate was coupled in a Suzuki-Miyaura type reaction with a series of 4-substituted arylboronic esters which, after deprotection, gave the desired 2-aryl apomorphines. The analogues were tested for affinity towards a range of dopaminergic, serotonergic and adrenergic receptors. 2-(4-Hydroxyphenyl)-apomorphine exhibited high affinity for the dopamine D2 receptor. A putative ligand-receptor interaction was put forward.     

The effect of diotic and dichotic level-randomization on the binaural masking-level difference

Detection thresholds for tones in narrow-band noise were measured for two binaural configurations: N(o)S(o) and N(o)S(pi). The 30-Hz noise band had a mean overall level of 65 dB SPL and was centered on 250, 500, or 5000 Hz. Signals and noise were simultaneously gated for 500, 110, or 20 ms. Three conditions of level randomization were tested: (1) no randomization; (2) diotic randomization--the stimulus level (common to both ears) was randomly chosen from an uniformly distributed 40-dB range every presentation interval; and (3) dichotic randomization--the stimulus levels for each ear were each independently and randomly chosen from the 40-dB range. Regardless of binaural configuration, level randomization had small effects on thresholds at 500 and 110 ms, implying that binaural masking-level differences (BMLDs) do not depend on interaural level differences for individual stimuli. For 20-ms stimuli, both diotic and dichotic randomization led to markedly poorer performance than at 500- and 110-ms durations; BMLDs diminished with no randomization and dichotic randomization but not with diotic randomization. The loss of BMLDs at 20 ms, with degrees-of-freedom (2WT) approximately 1, implies that changes in intracranial parameters occurring during the course of the observation interval are necessary for BMLDs when mean-level and mean-intracranial-position cues have been made unhelpful.