Synthesis of Well‐Defined Adenosine Diphosphate Ribose Oligomers

The post‐translational modification of proteins that is known as adenosine diphosphate ribosylation (ADPr) regulates a wide variety of important biological processes, such as DNA‐damage repair and cellular metabolism. This modification is also involved in carcinogenesis and the process of aging. Therefore, a better understanding of the function of ADP‐ribosylation is crucial for the development of novel therapeutics. To facilitate the elucidation of the biology of ADPr, the availability of well‐defined fragments of poly(ADP‐ribose) is essential. Herein we report a solid‐phase synthetic approach for the preparation of ADP‐ribose oligomers of exactly defined length. The methodology is exemplified by the first reported synthesis of an ADP‐ribose dimer and trimer.     

Bioorthogonal Deprotection on the Dendritic Cell Surface for Chemical Control of Antigen Cross‐Presentation

The activation of CD8⁺ T‐cells requires the uptake of exogenous polypeptide antigens and proteolytic processing of these antigens to octamer or nonamer peptides, which are loaded on MHC‐I complexes and presented to the T‐cell. By using an azide as a bioorthogonal protecting group rather than as a ligation handle, masked antigens were generated—antigens that are not recognized by their cognate T‐cell unless they are deprotected on the cell using a Staudinger reduction.     

Acceptor Reactivity in the Total Synthesis of Alginate Fragments Containing α‐L‐Guluronic Acid and β‐D‐Mannuronic Acid

The total synthesis of mixed‐sequence alginate oligosaccharides, featuring both β‐D ‐mannuronic acid (M) and α‐L ‐guluronic acid (G), is reported for the first time. A set of GM, GMG, GMGM, GMGMG, GMGMGM, GMGMGMG, and GMGGMG alginates was assembled using GM building blocks, having a guluronic acid acceptor part and a mannuronic acid donor side to allow the fully stereoselective construction of the cis‐glycosidic linkages. It was found that the nature of the reducing‐end anomeric center, which is ten atoms away from the reacting alcohol group in the key disaccharide acceptor, had a tremendous effect on the efficiency with which the building blocks were united. This chiral center determines the overall shape of the acceptor and it is revealed that the conformational flexibility of the acceptor is an all‐important factor in determining the outcome of a glycosylation reaction.     

Flows on the nozzle plate of an inkjet printhead

Flow patterns of ink layers on the nozzle plate of a piezo-driven printhead are investigated. Two different flow types are identified. First, a jet of droplets induces a radial airflow in the direction of the jet, which in turn causes a liquid flow towards the nozzle. Second, the movement of the meniscus in the nozzle causes an equally strong flow, but completely different flow patterns. The results are presented in a phase diagram with pulse amplitude and firing frequency as parameters.     

A Luminescent Nitrogen‐Containing Polycyclic Aromatic Hydrocarbon Synthesized by Photocyclodehydrogenation with Unprecedented Regioselectivity

We present a nitrogen‐containing polycyclic aromatic hydrocarbon (N‐PAH), namely 12‐methoxy‐9‐(4‐methoxyphenyl)‐5,8‐diphenyl‐4‐(pyridin‐4‐yl)pyreno[1,10,9‐h,i,j]isoquinoline (c‐TPE‐ON), which exhibits high quantum‐yield emission both in solution (blue) and in the solid state (yellow). This molecule was unexpectedly obtained by a three‐fold, highly regioselective photocyclodehydrogenation of a tetraphenylethylene‐derived AIEgen. Based on manifold approaches involving UV/Vis, photoluminescence, and NMR spectroscopy as well as HRMS, we propose a reasonable mechanism for the formation of the disk‐like N‐PAH that is supported by density functional theory calculations. In contrast to most PAHs that are commonly used, our system does not suffer from entire fluorescence quenching in the solid state due to the peripheral aromatic rings preventing π–π stacking interactions, as evidenced by single‐crystal X‐ray analysis. Moreover, its rod‐like microcrystals exhibit excellent optical waveguide properties. Hence, c‐TPE‐ON comprises a N‐PAH with unprecedented luminescent properties and as such is a promising candidate for fabricating organic optoelectronic devices. Our design and synthetic strategy might lead to a more general approach to the preparation of solution‐ and solid‐state luminescent PAHs.     

Oscillation of a Punch Moving on the Free Surface of an Elastic Half Space

The contact problem concerning oscillation of a circular rigid punch, moving uniformly at sub-Rayleigh speed along the surface of an elastic half space, is investigated using a three-dimensional formulation. Slow motion of the punch is considered, which implies that the characteristic time for the external loading is much larger than the time interval necessary for shear waves to propagate across the punch. An asymptotic solution for the vertical oscillation of the punch is given. It is shown that the vertical displacement of the punch can approximately be described by the equation of dynamics for a system of one degree of freedom with viscous friction. The dependence of the coefficients for effective viscosity and stiffness, occurring in this equation, on the speed of the punch and Poisson ratio of the half space, is investigated. The solution for the non-stationary problem concerning a suddenly applied moving point load is also obtained, correcting and extending the result known so far. Mathematics Subject Classifications (2000) 74H10, 74J05, 74M15.     

The vibrational spectra of E-1,2-bis(3-methoxy-2-thienyl)ethene in the crystalline phase

Density functional theoretical (DFT) calculations using the 6-311+G* basis set were carried out to study the vibrational spectrum of E-1,2-bis(3-methoxy-2-thienyl)ethene in the solid state. Based on the calculated frequencies, infrared intensities and potential energy distributions (PED), the experimental IR and Raman spectra of the solid phase were assigned.     

SESAME site selected in Jordan

Fundamental studies on the effects of pressure on biosystems emerged in the 1960s and 1970s while remaining confined to a small community. This situation has changed gradually in the past few years. First, specific interests in high pressure (HP) for the study of macromolecules have been clarified. Second, instrumentation has made progress, extending the range of measurements and relaxing constraints of the HP environment. Third, high-resolution structural methods, NMR, and macromolecular crystallography (MX) have been adapted to HP. These powerful newcomers complete low-resolution methods such as small-angle neutron and X-ray scattering (SANS and SAXS) and spectroscopic techniques such as infrared (IR) and Raman. Accordingly, there is now a toolbox for integrated pressure-perturbed biophysics, including structural and dynamical aspects. It was an opportune moment for HPMB 2008, an international meeting focused on fundamental research in HP molecular biophysics, held near Paris from December 10–12, 2008. As SR is crucial, in particular for MX, SAXS and IR, HPMB2008 was held at a third-generation SR facility, SOLEIL. Organizing labs were SOLEIL, IBS (Grenoble) and CBM (Orléans). More than 70 participants, including a number of PhD students and postdocs, from nine countries including European Union countries, Japan, Russia, and the USA, attended the meeting. The format of the conference allowed extensive formal and informal discussions.