Direct Visualization of Electronic Asymmetry within a Phenyl-Linked Porphyrin Dimer

Asymmetric electronic structures within a single molecule have been investigated by scanning tunneling microscopy and spectroscopy. Inside of a phenyl-linked porphyrin dimer, the asymmetric electronic structures are achieved by the incorporation of a cobalt ion in one porphyrin moiety. We find that a <i>p</i>-<i>n</i> junction between two π-conjugated segments is formed within the porphyrin dimer. The understanding of the local electronic structures of the intramolecular <i>p</i>-<i>n</i> junction should represent a fundamental step to realizing single molecular devices

Two-Step On-Surface Synthesis of One-Dimensional Nanographene Chains

Controllable fabrication of low-dimensional graphene structures is a matter of scientific and technological interest. To date, significant efforts have been devoted to the fabrication of nanographene chains as well as nanographenes and graphene nanoribbons. Here, we present the on-surface synthesis of one-dimensional (1D) nanographene chains composed of hexa-peri-hexabenzocoronene (HBC) which is a common type of nanographene. Using dibromo-substituted hexaphenylbenzene (Br2-HPB) as a precursor, the 1D HBC nanographene chains are achieved through two reaction steps, namely polymerization and cyclodehydrogenation, on a Au(111) surface, which have been investigated by low-temperature scanning tunneling microscopy. The Br2-HPB molecules deposited on Au(111) are formed into a chiral selective self-assembled layer, and the following thermal annealing at 200–300 °C induces debromination and sequential polymerization of Br2-HPB, leading to the formation of long 1D HPB chains. In particular, we find that the same length 1D HPB chains are selectively ordered in a side-by-side arrangement. Finally, by annealing at 400 °C, HBC planar nanographenes are achieved through the cyclodehydrogenation process of HPB within the long 1D chains. The maximum length of the obtained 1D HBC nanographene chains reached is about 30 nm

Transmissibility of H-Type Bovine Spongiform Encephalopathy to Hamster PrP Transgenic Mice

<div><p>Two distinct forms of atypical bovine spongiform encephalopathies (H-BSE and L-BSE) can be distinguished from classical (C-) BSE found in cattle based on biochemical signatures of disease-associated prion protein (PrP^Sc). H-BSE is transmissible to wild-type mice—with infected mice showing a long survival period that is close to their normal lifespan—but not to hamsters. Therefore, rodent-adapted H-BSE with a short survival period would be useful for analyzing H-BSE characteristics. In this study, we investigated the transmissibility of H-BSE to hamster prion protein transgenic (TgHaNSE) mice with long survival periods. Although none of the TgHaNSE mice manifested the disease during their lifespan, PrP^Sc accumulation was observed in some areas of the brain after the first passage. With subsequent passages, TgHaNSE mice developed the disease with a mean survival period of 220 days. The molecular characteristics of proteinase K-resistant PrP^Sc (PrP^res) in the brain were identical to those observed in first-passage mice. The distribution of immunolabeled PrP^Sc in the brains of TgHaNSE mice differed between those infected with H-BSE as compared to C-BSE or L-BSE, and the molecular properties of PrP^res in TgHaNSE mice infected with H-BSE differed from those of the original isolate. The strain-specific electromobility, glycoform profiles, and proteolytic cleavage sites of H-BSE in TgHaNSE mice were indistinguishable from those of C-BSE, in which the diglycosylated form was predominant. These findings indicate that strain-specific pathogenic characteristics and molecular features of PrP^res in the brain are altered during cross-species transmission. Typical H-BSE features were restored after back passage from TgHaNSE to bovinized transgenic mice, indicating that the H-BSE strain was propagated in TgHaNSE mice. This could result from the overexpression of the hamster prion protein.</p></div

PrP^res profiles of H-BSE prions analyzed with mAbs 3F4, 6H4, T2, and SAF84.

<p>(A) Triple bands observed for TgHaNSE mice inoculated with H-BSE were smaller than those of cattle, C57BL/6 mice, and TgBoPrP mice analyzed with mAbs 3F4 and 6H4. TgHaNSE mice infected with H-BSE did not exhibit the 10–12-kDa band detected in cattle, C57BL/6 mice, and TgBoPrP mice infected with H-BSE, which were analyzed with the mAb SAF84. P1, P2, and P3, first, second, and third passage, respectively. TgHaNSE mouse-passaged H-BSE in TgBoPrP mice (H-BSE/TgHa/TgBoPrP) showed the molecular signatures of the H-BSE prion. (B) H-BSE (H), C-BSE (C), and L-BSE (L) strains showed similar molecular features in TgHaNSE mice. Molecular markers are shown to the left (kDa).</p

Molecular typing of PrP^res in brains of third-passage, H-BSE-infected TgHaNSE mice.

<p>(A) PrP^res expression was analyzed with the mAbs 6H4 and SAF84 before or after PNGase F deglycosylation. The unglycosylated fragment from TgHaNSE mice inoculated with H-BSE was similar in size to that of C-BSE and higher than that of L-BSE. Molecular markers are shown to the left (kDa). (B) PrP^res glycoform percentages in C-BSE-, L-BSE-, and H-BSE-infected mice were analyzed with the mAb T2. Glycoform ratios were similar between TgHaNSE mice inoculated with H-BSE and those inoculated with C- or L-BSE. Results are shown as mean ± standard deviation of triplicate experiments. Bar graph shows diglycosylated (white columns), monoglycosylated (gray columns), and unglycosylated (black columns) forms of the protein.</p

Neuroanatomical PrP^Sc distribution patterns in the brains of TgHaNSE mice infected with H-BSE, mouse-passaged C-BSE, or L-BSE.

<p>Representative images of coronal brain sections are shown. From left to right: septal level, hippocampus and thalamic level, midbrain, and medulla with cerebellum. PrP^Sc labeled with the mAb 3F4 was mainly distributed in the brainstem, thalamus, and hippocampus of TgHaNSE mice infected with H-BSE, but was deposited throughout the brain of mice infected with C-BSE. In L-BSE infected mice, PrP^Sc immunoreactivity was dense; the protein formed plaques in the periventricular and subcallosal regions. P1 and P2, first and second passage, respectively.</p

Vacuolar lesion scores and molecular features of TgBoPrP mice inoculated with H-BSE prions passaged in TgHaNSE mice.

<p>(A) Lesion profiles of first-passage TgBoPrP mice inoculated with H-BSE from cattle (H-BSE/cattle; blue), and H-BSE passaged once in TgHaNSE mice (H-BSE/TgHa/TgBo; red). Vacuolation was scored on a scale of 0–5 in the following brain areas: 1, dorsal medulla; 2, cerebellum; 3, midbrain; 4, hypothalamus; 5, thalamus; 6, hippocampus; 7, septal nuclei of the paraterminal body; 8 caudal cerebral cortex; and 9, rostral cerebral cortex. Data represent mean ± standard deviation (<i>n</i> = 6). (B) TgBoPrP mice inoculated with H-BSE passaged in TgHaNSE mice (TgHaNSE/TgBoPrP) yielded an additional fragment representing the traceback when probed with the SAF84 mAb. TgBoPrP mice were subdivided into two groups (<i>n</i> = 5 and 7) and inoculated on different days with the same brain homogenate prepared from first-passage TgHaNSE mice infected with H-BSE. Cattle, cattle infected with H-BSE; TgHaNSE, third-passage TgHaNSE mice infected with H-BSE. Molecular markers are shown to each side (kDa).</p

Characteristics of monoclonal antibodies used in this study.

<p>Characteristics of monoclonal antibodies used in this study.</p

Features and types of PrP^Sc in TgHaNSE mice infected with H-BSE or mouse-passaged C-BSE.

<p>(A, B) Stellate-type PrP^Sc deposits (arrows) were observed in the cerebral cortex of H-BSE-infected mice (A), whereas particulate, punctuate, and stellate-type PrP^Sc were distributed in the cortex of C-BSE-infected mice (B). (C and D) Particulate (C) and fine punctuate (D) PrP^Sc immunoreactivity was observed in the red nuclei of the midbrain. (E–H) In the cerebellum, PrP^Sc immunoreactivity was particulate in the granular layer (E) and streaked in the molecular layer of H-BSE infected mice (G). In contrast, PrP^Sc was less prevalent in the molecular layer of C-BSE-infected mice; however, coarse particulate and stellate-type PrP^Sc accumulation was detected in the granular layer of cerebellar cortex and in the cerebellar medulla, respectively (F and H). P1 and P3, first and third passage, respectively.</p

Western blot analysis of brains from first-passage, H-BSE-infected TgHaNSE mice.

<p>(A) Three of five mice showed positive immunoreactivity using the mAb T2. (B) PrP^res expression in the brains of TgHaNSE or C57BL/6 mice infected with H-BSE, as detected using mAbs 4E10, 3F4, and SAF84. Sc, mouse-adapted Obihiro scrapie control strain. Molecular markers are shown to the left (kDa).</p