We developed a chemical route to produce graphene nanoribbons (GNR) with width below 10 nanometers, as well as single ribbons with varying widths along their lengths or containing lattice-defined graphene junctions for potential molecular electronics. The GNRs were solution-phase-derived, stably suspended in solvents with noncovalent polymer functionalization, and exhibited ultrasmooth edges with possibly well-defined zigzag or armchair-edge structures. Electrical transport experiments showed that, unlike single-walled carbon nanotubes, all of the sub-10-nanometer GNRs produced were semiconductors and afforded graphene field effect transistors with on-off ratios of about 10(7) at room temperature.

the overall write performance of flash memory. In order to solve this "erase-before-write" problem, the flash memory controller can be integrated with a software module, called "flash translation layer (FTL)." Among many FTL schemes available, the log block buffer scheme is considered to be optimum. With this scheme, a small number of log blocks, a kind of write buffer, can improve the performance of write operations by reducing the number of erase operations. However, this scheme can suffer from low space utilization of log blocks. In this paper, we show that there is much room for performance improvement in the log buffer block scheme, and propose an enhanced log block buffer scheme, called FAST (full associative sector translation). Our FAST scheme improves the space utilization of log blocks using fully-associative sector translations for the log block sectors. We also show empirically that our FAST scheme outperforms the pure log block buffer scheme. . 2007. A log bufferbased flash translation layer using fully-associative sector translation. ACM Trans. Embedd.

The design of proteins that bind to a specific site on the surface of a target protein using no information other than the three-dimensional structure of the target remains a challenge1–5. Here we describe a general solution to this problem that starts with a broad exploration of the vast space of possible binding modes to a selected region of a protein surface, and then intensifies the search in the vicinity of the most promising binding modes. We demonstrate the broad applicability of this approach through the de novo design of binding proteins to 12 diverse protein targets with different shapes and surface properties. Biophysical characterization shows that the binders, which are all smaller than 65 amino acids, are hyperstable and, following experimental optimization, bind their targets with nanomolar to picomolar affinities. We succeeded in solving crystal structures of five of the binder–target complexes, and all five closely match the corresponding computational design models. Experimental data on nearly half a million computational designs and hundreds of thousands of point mutants provide detailed feedback on the strengths and limitations of the method and of our current understanding of protein–protein interactions, and should guide improvements of both. Our approach enables the targeted design of binders to sites of interest on a wide variety of proteins for therapeutic and diagnostic applications.

This paper investigates the sampling behavior of the quasi-maximum likelihood estimator of the Gaussian GARCH(1,1) model. The rescaled variable (the ratio of the disturbance to the conditional standard deviation) is not required to be Gaussian nor independent over time, in contrast to the current literature. The GARCH process may be integrated (α + β = 1), or even mildly explosive (α + β > 1). A bounded conditional fourth moment of the rescaled variable is sufficient for the results. Consistent estimation and asymptotic normality are demonstrated, as well as consistent estimation of the asymptotic covariance matrix.

Solvent evaporation from extensively hydrated peptides and selected model compounds formed by electrospray ionization has been examined using an external ion source Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. Water evaporation from the clusters, formed at room temperature by appropriate operation of an electrospray ion source, is initially rapid and results in evaporative cooling of the clusters to a temperature around 130−150 K, determined by the balance between evaporative cooling and heating by background blackbody radiation. In this “freeze-drying” process, it is observed that the kinetics of solvent evaporation and the cluster size distributions are highly dependent on the nature of the core ion in the cluster. In agreement with earlier studies of the hydrated proton, pure water clusters exhibit special stability characteristic of clathrate formation where, for example, a hydronium ion is encapsulated by a pentagonal dodecahedron of twenty water molecules. Similar clustering of water occurs around protonated primary alkylamines where the protonated amine replaces one of the water molecules in the clathrate structures, which encapsulate one or more neutral water molecules. This observation supports the conjecture that the doubly protonated cyclic decapeptide gramicidin S with 40 water molecules attached, the most significant magic number observed in mass spectra at various delay times, has both protonated ornithine residues solvated by pentagonal dodecahedron clathrate structures. Other peptides such as doubly protonated bradykinin do not exhibit any specific solvation during the freeze-drying process. Studies of model compounds are presented which reveal other interesting aspects of water structure around singly and multiply charged ions with low extents of hydration, including the observation of neutral clathrates attached to a “spectator” ion.

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1Background: Medial meniscus posterior root tear (MMPRT) have a different

Salt bridge chemistry has recently been realized as a determining factor in the structures and reaction dynamics of biological molecules in the gas phase. In this paper, we further investigate salt bridge chemistry in studies of the low-energy collision-induced dissociation (CID) of sodiated peptides. MALDI and electrospray ionization are used to generate singly and multiply charged sodiated peptides which are analyzed by using an external ion source Fourier transform ion cyclotron resonance mass spectrometer. Of particular interest is the observation that sodiated peptides exhibit highly selective cleavage at aspartic acid residues. Sodiated peptides that lack acidic residues, however, undergo sequential cleavages from the C-terminus on low-energy CID. We propose a mechanism for cleavage at aspartic acid residues that involves a salt bridge intermediate in which the sodium ion stabilizes the ion pair formed by proton transfer from aspartic acid to the adjacent amide nitrogen. This proposal is supported by ab initio calculations to quantify the reaction energetics. In several instances the less selective low-energy fragmentation processes of the protonated peptides have also been investigated for comparison.