COLLISON-INDUCED ABSORPTION OF OXYGEN MOLECULE AS STUDIED BY HIGH SENSITIVITY SPECTROSCOPY

Oxygen dimol is transiently generated when two oxygen molecules collide. At this short period, the electron clouds of molecules are distorted and some forbidden transition electronic transitions become partially allowed. This transition is called CIA (Collision-induced absorption). There are several CIA bands appearing in the spectral region from UV to near IR. Absorption of solar radiation by oxygen dimol is a small but significant part of the total budget of incoming shortwave radiation. However, a theory predicting the lineshape of CIA is still under developing._x000d_ In this study, we measured CIA band around 630 nm that is assigned to optical transition, a$^{1}$$Delta$$_{g}$(v=0):a$^{1}$$Delta$$_{g}$(v=0)-X$^{3}$$Sigma$$_{g}$$^{-}$(v=0):X$^{3}$$Sigma$$_{g}$$^{-}$(v=0) of oxygen dimol. CRDS(Cavity Ring-down Spectroscopy) was employed to measure weak absorption CIA band of oxygen. Laser beam around 630 nm was generated by a dye laser that was pumped by a YAG Laser. Multiple reflection of the probe light was performed within a vacuum chamber that was equipped with two high reflective mirrors. We discuss the measured line shape of CIA on the basis of collision pair model._x000d

Excited States of Thio-2′-deoxyuridine Bearing an Extended π-Conjugated System: 3′,5′-Di-O-acetyl-5-phenylethynyl-4-thio-2′-deoxyuridine

A new thio-2′-deoxyuridine with an extended π-conjugated group was successfully synthesized: 3′,5′-di-O-acetyl-5-phenylethynyl-4-thio-2′-deoxyuridine. The thio-2′-deoxyuridine derivative has a large red-shifted absorption band in the UVA region and also shows fluorescence, a rare photo-property among thionucleobases/thionucleosides. The triplet–triplet absorption spectrum and the rate constants (the intrinsic decay rate constant of the triplet state, the self-quenching rate constant, and the quenching rate constant of the triplet state by an oxygen molecule) of the thio-2′-deoxyuridine were obtained by transient absorption spectroscopy. The quantum yield of intersystem crossing and the quantum yield of singlet molecular oxygen formation (ϕΔ) under an oxygen atmosphere were also determined. The ϕΔ value of the new thio-2′-deoxyuridine was found to be substantially higher than all reported values of other thio-2′-deoxyribonucleosides in low oxygen concentrations similar to cancer cell environments. The fluorescence quantum yield depended on the excitation wavelength, revealing certain photochemical reactions in the higher excited singlet states. However, when excited into the higher excited state with non-resonant two-photon absorption, the ϕΔ of the thio-2′-deoxyuridine derivative was found to remain sufficiently large. These findings should be very useful for the development of thio-2′-deoxyribonucleoside-based pharmaceuticals as DNA-specific photosensitizers for photochemotherapy

Crucial role of 4-deoxy-L-erythro-5-hexoseulose uronate reductase for alginate utilization revealed by adaptive evolution in engineered Saccharomyces cerevisiae

代謝改変酵母のアルギン酸モノマー代謝能向上メカニズムの解明--国産海洋バイオマス資源から代替ガソリンや合成ゴム原料を生産するための重要な第一歩--. 京都大学プレスリリース. 2017-06-26.In brown macroalgae, alginate and D-mannitol are promising carbohydrates for biorefinery. Saccharomyces cerevisiae is widely used as a microbial cell factory, but this budding yeast is unable to utilize either alginate or D-mannitol. Alginate can be depolymerized by both endo-type and exo-type alginate lyases, yielding a monouronate, 4-deoxy-L-erythro-5-hexoseulose uronate (DEH), a key intermediate in the metabolism of alginate. Here, we constructed engineered two S. cerevisiae strains that are able to utilize both DEH and D-mannitol on two different strain backgrounds, and we also improved their aerobic growth in a DEH liquid medium through adaptive evolution. In both evolved strains, one of the causal mutations was surprisingly identical, a c.50A > G mutation in the codon-optimized NAD(P)H-dependent DEH reductase gene, one of the 4 genes introduced to confer the capacity to utilize DEH. This mutation resulted in an E17G substitution at a loop structure near the coenzyme-binding site of this reductase, and enhanced the reductase activity and aerobic growth in both evolved strains. Thus, the crucial role for this reductase reaction in the metabolism of DEH in the engineered S. cerevisiae is demonstrated, and this finding provides significant information for synthetic construction of a S. cerevisiae strain as a platform for alginate utilization

Excited state properties of 5‐fluoro‐4‐thiouridine derivative^†

The excited state properties of thionated 5- fluorouridine (2′,3′,5′- tri- O- acetyl- 5- fluoro- 4- thiouridine; ta5F4TUrd), synthesized with Lawesson's reagent, have been intensively investigated with nanosecond transient absorption spectroscopy, time- resolved thermal lensing, near- infrared emission, and quantum chemical calculation. The intrinsic triplet lifetime of ta5F4TUrd was determined to be 4.2±0.7μs in acetonitrile, and the formation quantum yield of the excited tri-plet state was as large as 0.79±0.01. The quenching rate constants of the triplet ta5F4TUrd by the dissolved oxygen molecule and by the self- quenching process were found to be nearly equal to the diffusion- controlled rate of acetonitrile. The quantum yield of the singlet molecular oxygen produced through energy transfer between the triplet ta5F4TUrd and the dissolved oxygen, ΦΔ, was successfully de-termined to be 0.61±0.02 under the oxygen- saturated condition. From the oxy-gen concentration dependence of the ΦΔ value, the fraction of triplet ta5F4TUrd quenched by dissolved oxygen which gives rise to the 1O2* formation, SΔ, was successfully obtained to be 0.78±0.01, which was the largest among the thionu-cleobases and the thionucleosides reported so far. This could be due to the lower energy and/or the ππ* character of the triplet state

Treatment planning comparison of high-dose-rate brachytherapy vs. robotic and conventional stereotactic body radiotherapy for ultrahypofractionated treatment of prostate cancer

Background and purpose: Ultrahypofractionated radiation therapy is increasingly used in the treatment of prostate cancer. High-dose-rate brachytherapy (HDR-BT) and stereotactic body radiotherapy (SBRT) are representative methods of ultrahypofractionation. This study was performed to compare clinically applied treatment plans for patients who had been treated using HDR-BT vs. conventional or robotic SBRT. Materials and methods: Calculated dose-volume indices between HDR-BT without a perirectal spacer (n = 20), robotic SBRT without a spacer (n = 40), and conventional (non-robotic) SBRT with a spacer (n = 40) were compared. Percentages against the prescription dose regarding the planning target volume (PTV), bladder, rectum, and urethra were statistically compared. Results: The D50% of the PTV with HDR-BT (140.5% ± 4.9%) was significantly higher than that with robotic or conventional SBRT (116.2% ± 1.6%, 101.0% ± 0.4%, p < 0.01). The D2cm3 of the bladder with HDR-BT (65.6% ± 6.4%) was significantly lower than those with SBRT (105.3% ± 2.9%, 98.0% ± 1.3%, p < 0.01). The D2cm3 of the rectum with HDR-BT (60.6% ± 6.2%) was also significantly lower than those with SBRT (85.1% ± 8.8%, 70.4% ± 9.6%, p < 0.01). By contrast, the D0.1cm3 of the urethra with HDR-BT (117.1% ± 3.6%) was significantly higher than those with SBRT (100.2% ± 0.7%, 104.5% ± 0.6%, p < 0.01). Conclusions: HDR-BT could administer a higher dose to the PTV and a lower dose to the bladder and rectum, at the cost of a slightly higher dose to the urethra compared with SBRT

Case reports of pregnancies complicated with kidney disease and their fetal prognosis

　The number of patients with chronic kidney disease (CKD) has been increasing every year, with a current prevalence of one in eight adults. Although the frequency of complications due to kidney disease before pregnancy is not high (0.02–0.12%), frequency of pregnancy with CKD, including cases receiving continuous dialysis therapy is expected to increase in the future. The fertility and birth rates among dialysis patients are low, and perinatal management in these patients is currently difficult. However, even under such circumstances, the probability of having a live-born baby in pregnant women on dialysis has increased due to improvements in dialysis technology, perinatal management, and neonatal care. There are some case reports written about them, and I think that it is possible to approach term delivery with careful care through the cases experienced this time.　In this study, we examined the pregnant patients, on dialysis or requiring postpartum dialysis, at Kawasaki Medical School Hospital between January 2005 and March 2018. Six patients (86%) had a live-born baby, while one had a miscarriage. One patient underwent two pregnancies on dialysis; one case gave a full-term birth, while the rest had a premature delivery. The modes of delivery were vaginal delivery (n = 1), elective cesarean section (n = 3), and emergency cesarean section (n = 2). Five patients delivered successfully and had a good prognosis, while in one case, the neonate died.　Over the years, owing to continuous improvement at our hospital, we have achieved better pregnancy prognosis and longer gestation periods in the patients. In particular, one case, which had a natural second pregnancy, 9 years after the beginning of dialysis, was worthy of note; we were able to manage her second pregnancy using the process followed during her first pregnancy as reference