Chandra Observation of the Anomalous X-ray Pulsar 1E 1841-045

We present the results from the {\it Chandra} ACIS CC mode observation of an anomalous X-ray pulsar (AXP) 1E 1841-045. This is the first observation in which the pulsar spectrum in wide energy range is spatially discriminated from the surrounding SNR, Kes 73. Like other AXPs, the phase-integrated spectrum is fitted well with power-law plus blackbody model. The spectral parameters are $\Gamma = 2.0 \pm 0.3$, $kT_{\rm BB} = 0.44 \pm 0.02$ keV, and $N_H = 2.54^{+0.15}_{-0.13} \times 10^{22} {\rm cm}^{-2}$. This photon index is significantly flatter than the other AXPs, and resemble to soft gamma-ray repeaters (SGRs) in the quiescent state. The pulse profile is double-peaked, and we found that the second peak has significantly hard spectrum. The spectra of all phases are consistent with power-law plus blackbody model with constant temperature and photon index. When fitted with two blackbody model, we obtained similarly good fit. These results can be interpreted that there are two emission regions with different energy spectra.Comment: 4 pages, 4 figures, accepted for publication in PASJ Letter

Can the Low-Resolution Structures of Photointermediates of Bacteriorhodopsin Explain Their Crystal Structures?

AbstractTo understand the molecular mechanism of light-driven proton pumps, the structures of the photointermediates of bacteriorhodopsin have been intensively investigated. Low-resolution diffraction techniques have demonstrated substantial conformational changes at the helix level in the M and N intermediates, between which there are noticeable differences. The intermediate structures at atomic resolution have also been solved by x-ray crystallography. Although the crystal structures have demonstrated local structural changes, such as hydrogen bond network rearrangements including water molecules, the large conformational changes at the helix level are not necessarily observed. Furthermore, the two reported crystal structures of an intermediate accumulated using a common method were distinct. To reconcile these apparent discrepancies, low-resolution projection maps were calculated from the crystal structures and compared to the low-resolution intermediate structures obtained using native membranes. The crystal structures can be categorized into three groups, which qualitatively correspond to the low-resolution structures of the M1-type, M2-type, and N-type determined in the native membrane. Based on these results, we conclude that at least three types of intermediate structures play a role during the photocycle

X-ray solution scattering studies of protein folding

Protein folding is a reaction in which an extended polypeptide chain acquires maximal packing through formation of secondary and tertiary structures. Compactness and shape are, therefore, critical properties characterizing the process of protein folding. Because the stability of the native state is determined by the subtle free energy balance between the native and denatured states, the characterization of the denatured state is also essential to understand the conformational stability of the native state. We show that solution X-ray scattering is the best technique available today to address these problems. Although the structural resolution of the unfolded or compact denatured states elucidated from solution X-ray scattering is low, it provides a variety of information complementary to that obtained by NMR or X-ray crystallography

Sarcoidosis and Propionibacterium acnes

Although there have been numerous reports on the isolation of bacteria, fungus, and aetiological agents of chemical substances from specimens of patients with sarcoidosis, none of them have been substantiated. In any event, an understanding of the pathogenesis of pulmonary sarcoid is intimately linked to that of the processes involved in the accumulation of T-cells in the lower respiratory tract of individuals with sarcoidosis. Propionibacterium acnes was isolated at high rates and in high concetrations from lymph nodes in patients with sarcoidosis. However, the precise mechanism of granuloma formation and immunomodulation by P. acnes has not been elucidated yet. In patients with sarcoidosis, it was found that the high levels of interleukin-2 (IL-2) released from alveolar lymphocytes as well as interleukin-1, tumor necrosis factor (TNF) and interleukin-6 (IL-6) released from alveolar macrophages were stimulated by P. acnes. These cytokines (mainly IL-2), released by P. acnes in large quantities, play a major role in the compartmentalization of the T-cell population in the lung and lead to the formation of an alveolitis and granuloma in the lung parenchyma of patients with sarcoidosis. This paper focuses primarily on the role of the cytokine network in the pulmonary mononuclear cells in the lung of patients with sarcoidosis

Arginine remarkably prolongs the lifetime of the M-intermediate in the bacteriorhodopsin photocycle at room temperature

AbstractThe lifetime of the M-intermediate in the bacteriorhodopsin photocycle was remarkably prolonged on drying a suspension of purple membrane, in arginine solution at alkaline pH. The M-intermediate could be completely accumulated under illumination (530 nm) at room temperature. The crystalline structure of purple membranes was retained after this treatment. The lifetime of the M-intermediate was found to be longer than 100 s and depended on the pH of the purple membrane suspension before drying. It was suggested that an interaction between the guanidium group of arginine and an amino acid residue played an important role in the prolongation

<Regular Article>Reactions of 10-Alkyl- and 10-Aryl-9-phenylthioxanthenium Salts with Various Bases : 1,4-Sigmatropic Rearrangement of 10-Alkyl- and 10-Aryl-9-phenyl-9-thiaanthracenes

A 1,4-sigmatropic rearrangement of 10-alkyl and 10-aryl-9-phenyl-10-thiaanthracenes is described. 10-(4-Methoxyphenyl)-9-phenyl-10-thiaanthracene generated by proton abstraction of 10-(4-methoxyphenyl)-9-phenylthioxanthenium perchlorate (1a) with bases such as sodium dimsylate, sodium methoxide, sodium hydride, and Grignard reagent underwent 1,4-rearrangement to afford 9-(4-methoxyphenyl)-9-phenylthioxanthene (2a) in high yield. The deprotonation of 1a with organolithiums such as phenyllithium or methyllithium afforded 9,9-diphenylthioxanthene ( 3 ) or 9-methyl-9-phenylthioxanthene (2d) via ligand-exchanged thiaanthracene intermediates generated in situ, along with 2a. Other 10-alkyl or 10-aryl-9-phenylthiaanthracenes generated from the corresponding thioxanthenium salts (1b-g) by treatment with base also decomposed thermally to give 1,4-rearranged products 2b-g in good yield. These 1,4-rearrangements were found to be intramolecular 1,4-sigmatropic rearrangements by cross over experiments

Experimental Pulmonary Granuloma Mimicking Sarcoidosis Induced by Propionibacterium acnes in Mice

Propionibacterium acnes has been implicated as an etiologic agent of sarcoidosis since the isolation of this bacterium from sarcoid lesions. We experimentally produced a murine pulmonary granuloma model using P. acnes with several features that simulate sarcoidosis. Mice were sensitized with heat-killed P. acnes and complete Freund's adjuvant and were subsequently challenged with heat-killed P. acnes at 2-week intervals. P. acnes-challenged mice developed epitheloid cell granulomas in the lungs. These mice showed a pulmonary immune response characterized by an increased number of T-lymphocytes, especially CD4 cells, and the ratio of CD4/CD8 in bronchoalveolar lavage (BAL) fluid also increased. Furthermore, significant elevations in both angiotensin-converting enzyme (ACE) serum levels and antibody titers against P. acnes were observed. Mice sensitized with P. acnes without complete Freund's adjuvant were capable of forming pulmonary granulomas, which appeared to be caused by indigenous P. acnes. The genome of P. acnes was found in the lungs, BAL cells, hilar lymph nodes, liver, and spleen in non-sensitized mice, which were thought to be germ-free. These results suggest that the immune response against indigenous P. acnes may play an important role in the pathogenesis of granuloma formation in a murine model.</p

<Regular Article>Reactions of 10-Alkyl- and 10-Aryl-9-phenylthioxanthenium Salts with Various Bases : 1,4-Sigmatropic Rearrangement of 10-Alkyl- and 10-Aryl-9-phenyl-9-thiaanthracenes

A 1,4-sigmatropic rearrangement of 10-alkyl and 10-aryl-9-phenyl-10-thiaanthracenes is described. 10-(4-Methoxyphenyl)-9-phenyl-10-thiaanthracene generated by proton abstraction of 10-(4-methoxyphenyl)-9-phenylthioxanthenium perchlorate (1a) with bases such as sodium dimsylate, sodium methoxide, sodium hydride, and Grignard reagent underwent 1,4-rearrangement to afford 9-(4-methoxyphenyl)-9-phenylthioxanthene (2a) in high yield. The deprotonation of 1a with organolithiums such as phenyllithium or methyllithium afforded 9,9-diphenylthioxanthene ( 3 ) or 9-methyl-9-phenylthioxanthene (2d) via ligand-exchanged thiaanthracene intermediates generated in situ, along with 2a. Other 10-alkyl or 10-aryl-9-phenylthiaanthracenes generated from the corresponding thioxanthenium salts (1b-g) by treatment with base also decomposed thermally to give 1,4-rearranged products 2b-g in good yield. These 1,4-rearrangements were found to be intramolecular 1,4-sigmatropic rearrangements by cross over experiments

Trimeric mutant bacteriorhodopsin, D85N, shows a monophasic CD spectrum

AbstractThe structure of mutant bacteriorhodopsin (bR), D85N, was examined by CD and X-ray diffraction at pH 7. The absorption maximum of D85N at pH 7 is located at 605 nm, which is similar to the acid-blue form of wild-type bR. D85N shows a monophasic CD band, the maximum of which is at 575 nm, although the crystalline arrangement and the trimeric structure is maintained. The acid-blue form of wild-type bR shows a biphasic CD despite the similarity in absorption spectra