Mitsunori Araki

Antimicrobial effect of blue light using Porphyromonas gingivalis pigment

The development of antibiotics cannot keep up with the speed of resistance acquired by microorganisms. Recently, the development of antimicrobial photodynamic therapy (aPDT) has been a necessary antimicrobial strategy against antibiotic resistance. Among the wide variety of bacteria found in the oral flora, Porphyromonas gingivalis (P. gingivalis) is one of the etiological agents of periodontal disease. aPDT has been studied for periodontal disease, but has risks of cytotoxicity to normal stained tissue. In this study, we performed aPDT using protoporphyrin IX (PpIX), an intracellular pigment of P. gingivalis, without an external photosensitizer. We confirmed singlet oxygen generation by PpIX in a blue-light irradiation intensity-dependent manner. We discovered that blue-light irradiation on P. gingivalis is potentially bactericidal. The sterilization mechanism seems to be oxidative DNA damage in bacterial cells. Although it is said that no resistant bacteria will emerge using aPDT, the conventional method relies on an added photosensitizer dye. PpIX in P. gingivalis is used in energy production, so aPDT applied to PpIX of P. gingivalis should limit the appearance of resistant bacteria. This approach not only has potential as an effective treatment for new periodontal diseases, but also offers potential antibacterial treatment for multiple drug resistant bacteria.

Radio Search for H2CCC toward HD 183143 as a Candidate for a Diffuse Interstellar Band Carrier

To clarify the authenticity of a recently proposed identification of H2CCC (linear-C3H2) as a diffuse interstellar band (DIB) carrier, we searched for the rotational transition of H2CCC at a frequency of 103 GHz toward HD 183143 using the 45 m telescope at the Nobeyama Radio Observatory. Although rms noise levels of 32 mK in the antenna temperature were achieved, detection of H2CCC was unsuccessful, producing a 3σ upper limit corresponding to a column density of 2.0 × 1013 cm–2. The upper limit indicates that the contribution of H2CCC to the DIB at 5450 A is less than 1/25; thus, it is unlikely that the laboratory bands of the B 1 B 1-X 1 A 1 transition of H2CCC and the DIBs at 5450 A (and also 4881 A) toward HD 183143 are related.

Laboratory optical spectroscopy of the thiophenoxy radical and its profile simulation as a diffuse interstellar band based on rotational distribution by radiation and collisions

The gas-phase optical absorption spectrum of the thiophenoxy radical (C{sub 6}H{sub 5}S), a diffuse interstellar band (DIB) candidate molecule, was observed in the discharge of thiophenol using a cavity ringdown spectrometer. The ground-state rotational constants of the thiophenoxy radical were theoretically calculated, and the excited-state rotational constants were determined from the observed rotational profile. The rotational profile of a near prolate molecule having C {sub 2v} symmetry was simulated on the basis of a rotational distribution model by radiation and collisions. Although the simulated profile did not agree with the observed DIBs, the upper limit of the column density for the thiophenoxy radical in the diffuse clouds toward HD 204827 was evaluated to be 2 × 10{sup 13} cm{sup –2}. The profile simulation indicates that rotational distribution by radiation and collisions is important to reproduce a rotational profile for a DIB candidate and that the near prolate C {sub 2v} molecule is a possible candidate for DIB with a band width variation dependent on the line of sight.

A SEARCH FOR INTERSTELLAR CARBON-CHAIN ALCOHOL HC4OH IN STAR-FORMING REGION L1527 AND DARK CLOUD TMC-1

We report a sensitive search for the rotational transitions of the carbon-chain alcohol HC{sub 4}OH in the frequency range 21.2-46.7 GHz in the star-forming region L1527 and the dark cloud TMC-1. The motivation was laboratory detection of HC{sub 4}OH by microwave spectroscopy. Despite achieving rms noise levels of several millikelvin in the antenna temperature using the 45 m telescope at Nobeyama Radio Observatory, the detection was not successful, leading to 3{sigma} upper limits corresponding to the column densities of 2.0 Multiplication-Sign 10{sup 12} and 5.6 Multiplication-Sign 10{sup 12} cm{sup -2} in L1527 and TMC-1, respectively. These upper limits indicate that [HC{sub 4}OH]/[HC{sub 5}N] ratios are less than 0.3 and 0.1 in L1527 and TMC-1, respectively, where HC{sub 5}N is an HC{sub 4}-chain cyanide and HC{sub 4}OH is a hydroxide. These ratios suggest that the cyano carbon-chain molecule dominates the hydroxyl carbon-chain molecule in L1527 and TMC-1. This is contrary to the case of saturated compounds in hot cores, e.g., CH{sub 3}OH and CH{sub 3}CN, and can be a chemical feature of carbon-chain molecules in L1527 and TMC-1. In addition, the column densities of the unsubstituted carbon-chain molecule C{sub 4}H and the sulfur-bearing molecules SO and HCS{sup +} were determined frommorexa0» detected lines in L1527.«xa0less

Infrared radiative decay dynamics from the γ 1u (3P2), H 1u (3P1), and 1u (1D2) ion-pair states of I2 observed by a perturbation facilitated optical-optical double resonance technique

We report the spectroscopic and temporal analyses on the amplified spontaneous emission (ASE) from the single rovibrational levels of the Ω = 1u ion-pair series, γu20091u ((3)P2), Hu20091u ((3)P1), and 1u ((1)D2), of I2 by using a perturbation facilitated optical-optical double resonance technique through the c (1)Πg ∼ B (3)Π(0u (+)) hyperfine mixed valence state as the intermediate state. The ASE detected in the infrared region was assigned to the parallel transitions from the Ω = 1u ion-pair states down to the nearby Ω = 1g ion-pair states. The subsequent ultraviolet (UV) fluorescence from the Ω = 1g states was also observed and the relative vibrational populations in the Ω = 1g states were derived through the Franck-Condon simulation of the intensity pattern of the vibrational progression. In the temporal profiles of the UV fluorescence, an obvious delay in the onset of the fluorescence was recognized after the excitation laser pulse. These results revealed that ASE is a dominant energy relaxation process between the Ω = 1u and 1g ion-pair states of I2. Finally, the lifetimes of the relevant ion-pair states were evaluated by temporal analyses of the UV fluorescence. The propensity was found which was the longer lifetime in the upper level of the ASE transitions tends to give intense ASE.

Developments of Optical Spectrometers as Approaches to Diffuse Interstellar Bands

DEVELOPMENTS OF OPTICAL SPECTROMETERS AS APPROACHES TO DIFFUSE INTERSTELLAR BANDS Tokyo University of Science Mitsunori Araki, Satoshi Uchida, Norihisa Kondo, Yuki Matsushita, Kyoko Abe, Kunio Ito and Koichi Tsukiyama To be able to solve the diffuse interstellar bands (DIBs) problem, we have developed a discharge-emission spectrometer and a cavity ringdown spectrometer. Hollow cathode discharge cell was installed in the spectrometers to generate molecular ions, which are probable DIBs candidates. Recently the electronic transition of the butatriene cation H2CCCCH2 + was observed in the discharge emission. The observed frequency of the transition enables the comparison of the absorption feature of H2CCCCH2 + with DIBs. Diffuse Interstellar Bands Diffuse Interstellar Bands (DIBs) are absorption bands of optical stellar light by unknown interstellar matters. DIBs were first discovered in the optical absorption spectra on stars in about 1920. Although several hundreds DIBs were detected already, DIBs still remain the longest standing unsolved problem in spectroscopy and astrochemistry. To identify the carriers of DIBs, candidate molecules need to be generated in the laboratory for evaluating the frequencies of electronic transitions, which can be eventually compared with astronomical DIB spectra. Introduction Discharge-Emission Spectrometer Ar Discharge Cavity Ringdown Spectrometer [4,5] The bands at 20381 cm-1 (4905A) was assigned to the B3u – X B2g transition of H2CCCCH2 based on the reported photoelectron spectrum [1]. Butatriene cation H2CCCCH2 + Discharge Emission Spectra Summary Torsional Vibrational Levels and Potential Curve Comparison with DIBs PMT Mirror Mirror Pulse laser Cavity