Materials Literature
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Chorismate mutase acts at the first branchpoint of aromatic amino acid biosynthesis and catalyzes the conversion of chorismate to prephenate. Comparison of the x-ray structures of allosteric chorismate mutase from the yeast Saccharomyces cerevisiae with Escherichia coli chorismate mutase/prephenate dehydratase suggest…
The safety of the PEGs has been studied and reported for over fifty years. Despite the fact that PEGS are generally recognized as safe, there is a paucity of recent literature on this topic. In this chapter we review the literature from early studies, and present new information on the safety of two different PEG poly…
The surface force apparatus was used to measure directly the molecular forces between streptavidin and lipid bilayers displaying grafted Mr 2,000 poly(ethylene glycol) (PEG). These measurements provide direct evidence for the formation of relatively strong attractive forces between PEG and protein. At low compressive…
Proceedings of the National Academy of Sciences (PNAS), a peer reviewed journal of the National Academy of Sciences (NAS) - an authoritative source of high-impact, original research that broadly spans the biological, physical, and social sciences.
The chemistry and biological applications of polyethylene glycol (or "PEG") have been the subject of intense study both in academics and in industry. The current volume contains 28 chapters dedicated to providing a review of the major aspects of the topic. In this introductory chapter we highlight recent developments…
The presence of oscillatory structures in the atomic x-ray absorption background is reported for the first time for surface-EXAFS of c N/Cu(100) and N/Cu(110). Systematic analysis of this feature (AXAFS) and comparison to theory yields new information on the electronic structure of the adsorbate - substrate surface bo…
Characterization of amorphous SiO2 surfaces after biasing pretreatments, which induce nucleation of diamond, has been carried out using x-ray photoelectron spectroscopy and Raman spectroscopy. A mixture of silicon carbide, silicon oxycarbide, and diamond are formed upon exposure of biased SiO2 surfaces to a CH4+H2 pla…
We have studied the resonant photoemission of the valence band in V, Cr, Mn and Co transition metals using synchrotron radiation excitation near the 3p ionization thresholds. The effect of the 3p - 3d interaction reaches maximum strength in Cr and Mn. On the other hand, the contribution related to the atomic Fano reso…
The suppression effect of oxygen on Si incorporation in homoepitaxial diamond films grown by microwave assisted chemical vapor deposition is investigated by secondary ion mass spectrometry. The Si depth profile in the multilayered diamond films continuously synthesized with different oxygen addition shows that Si inco…
Protection by shielding—the porphyrinophane complex 1, a functionally active model compound of the cytochrome P-450 isozyme, was prepared in an 18-step convergent synthesis. Porphyrin complex 1 catalyzes the epoxidation of cis-stilbene with iodosylbenzene. The thiolate ligand is shielded from oxidative attack by the c…
An energetically low-lying spin state with S = 5 is observed in the title compound, in which low-spin iron(II) [Fe(bpym)3]2+ and high-spin iron(III) [Fe2(N3)10]4− ions coexist. The magnitude of the ferromagnetic coupling in the dimer (J = + 4.8 cm−1) is twice that reported for a high-spin MnII complex with the same br…
We investigate the switching bistability based on the interaction between dynamic flow and director rotation in twisted nematic liquid crystal cells. Numerical calculation shows that there exists a general type of bistable twisted director configuration. Two specific cases are verified experimentally.
The first modulated structure found in decagonal Al-Ni-Fe quasicrystals [M. Saito, M. Tanaka, A. P. Tsai, A. Inoue, and T. Masumoto, Jpn. J. Appl. Phys. 31, L112 (1992)] is a superstructure in five-dimensional space with a unit cell volume identical to that in the superstructure of decagonal Al-Ni-Co. Peculiar systema…
Ion polarizabilities derived from low-frequency precision measurements of the dielectric constants of single crystals of more than 120 different oxides have recently been published but have proved difficult to interpret in terms of classical theory. The latter predicts that the polarizability of an ion should be propo…
Abstract This article discusses experiments that measure polarizabilities, permanent dipole moments, and absorption spectra of semiconductor clusters such as Si N , Ga N As M , and Ge N Te M isolated in a molecular beam. The experiments show that the transition from the typical optoelectronic properties of macroscopic…
Erbium-doped silica glasses prepared by the sol–gel process are desirable for applications in high-power lasers and integrated optical devices. However, its fluorescence could be quenched due to the high hydroxyl (OH−) content. Although this OH− content can be greatly reduced through special gas treatment [Y. Zhou, S.…
Photoluminescence spectra of porous silicon prepared with electro-chemical etching, were analyzed using a simple model based on a statistical distribution of particle size. It was found that the size of nanoparticles, obeys the logarithmic normal distribution in all the porous silicon investigated here. This model als…
Assembly of units in an alternating disrotatory fashion is a feature of the solid-state structure of an achiral, synthetic cyclic decasaccharide composed of ten α-(1→4)-linked, alternating D- and L-rhamnopyranose residues. The unit cell contains two crystallographically independent, Ci-symmetrical, cylindrical molecul…
We report in this paper optical absorption and electron paramagnetic resonance (EPR) results obtained on -doped phosphate glasses. Optical absorption allowed us to evaluate the crystal-field parameters , B and C. Electron paramagnetic resonance measurements indicate that ions are located in sites with low symmetry and…
The carrier transport of a new calamitic liquid crystal, i.e., 2-(4′-octylphenyl)6-dodecyloxynaphthalene (8-PNP-O12) was investigated by the time-of-flight technique. The fast ambipolar electronic conduction was observed in two smectic phases of 8-PNP-O12. The carrier mobilities were determined to be 1.6×10−3 cm2/V⋅s…