Mechanism of Olefin Hydrogenation Catalysis Driven by Palladium-Dissolved Hydrogen

The Pd-catalyzed hydrogenation of CC double bonds is one of the most important synthetic routes in organic chemistry. This catalytic surface reaction is known to require hydrogen in the interior of the Pd catalyst, but the mechanistic role of the Pd-dissolved H has remained elusive. To shed new light into this fundamental problem, we visualized the H distribution near a Pd single crystal surface charged with absorbed hydrogen during a typical catalytic conversion of butene (C₄H₈) to butane (C₄H₁₀), using H depth profiling via nuclear reaction analysis. This has revealed that the catalytic butene hydrogenation (1) occurs between 160 and 250 K on a H-saturated Pd surface, (2) is triggered by the emergence of Pd bulk-dissolved hydrogen onto this surface, but (3) does not necessarily require large stationary H concentrations in subsurface sites. Even deeply bulk-absorbed hydrogen proves to be reactive, suggesting that Pd-dissolved hydrogen chiefly acts by directly providing reactive H species to the surface after bulk diffusion rather than by indirectly activating surface H through modifying the surface electronic structure. The chemisorbed surface hydrogen is found to promote hydrogenation reactivity by weakening the butene-Pd interaction and by significantly reducing the decomposition of the olefin

Site-Specific Attachment of a Protein to a Carbon Nanotube End without Loss of Protein Function

Establishing a nanobiohybrid device largely relies on the availability of various bioconjugation procedures which allow coupling of biomolecules and inorganic materials. Especially, site-specific coupling of a protein to nanomaterials is highly useful and significant, since it can avoid adversely affecting the protein’s function. In this study, we demonstrated a covalent coupling of a protein of interest to the end of carbon nanotubes without affecting protein’s function. A modified Staudinger-Bertozzi ligation was utilized to couple a carbon nanotube end with an azide group which is site-specifically incorporated into a protein of interest. We demonstrated that Ca²⁺-sensor protein, calmodulin, can be attached to the end of the nanotubes without affecting the ability to bind to the substrate in a calcium-dependent manner. This procedure can be applied not only to nanotubes, but also to other nanomaterials, and therefore provides a fundamental technique for well-controlled protein conjugation

Peak picking and statistical analysis of mass spectra in case 1.

<p>Peak picking and statistical analysis of mass spectra in case 1.</p

HE-stained section of case 1.

<p>(A) Thyroid papillary cancer tissue was localized on the left, and normal thyroid tissue was localized on the right (original magnification 40×). The stromal region was excluded. The ROI was determined from the corresponding HE-staining results. The black boxes indicate the representative region of cancer and normal thyroid tissue. (B) Magnified representative regions of cancer and normal tissue (original magnification 200×). The cancer cells had a high cytoplasmic ratio and displayed nuclear features characteristic of papillary thyroid cancer. Histologic findings of thyroid papillary cancer consisted of columnar thyroidal epithelium set in papillary projection. The normal thyroid tissue is composed of many spherical hollow sacs called thyroid follicles.</p

Visualization of molecular distribution of <i>m/z</i> values that were expressed to higher levels in cancer tissue from all cases.

<p>The ROI of each case is defined by a dashed line in HE-staining images. The intensity of all values in the cancer region was higher than in normal regions. The distribution of intensity in <i>m/z</i> 741.5 was different from the distribution of intensity in the other <i>m/z</i> values.</p

Overview of the <i>m/z</i> values that had higher expression levels in cancer regions of all cases.

<p>Overview of the <i>m/z</i> values that had higher expression levels in cancer regions of all cases.</p

Averaged spectrum for case 1.

<p>(A) Spectrum of the cancer region and (B) spectrum of normal region. Each spectrum was averaged from the ROI of cancer and normal tissue in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0048873#pone-0048873-g001" target="_blank">Figure 1</a>. Each number shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0048873#pone-0048873-t001" target="_blank">Table 1</a> was assigned using these spectra.</p

Visualization of molecular distribution in case 1.

<p>We visualized ion images corresponding to the results shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0048873#pone-0048873-t001" target="_blank">Table 1</a>. In all images, the cancer tissue is on the left and normal tissue is on the right. The distribution of the intensity for each <i>m/z</i> value was not constant in the cancer and normal thyroid tissue.</p

Additional file 1: of Escherichia coli-based production of recombinant ovine angiotensinogen and its characterization as a renin substrate

Purification of recombinant oANG using Ni-affinity column chromatography. (PDF 64 kb