WAVELENGTH DEPENDENCE OF THE FORMATION OF SINGLE-STRAND BREAKS AND BASE CHANGES IN DNA BY THE ULTRAVIOLET RADIATION ABOVE 150 nm

The wavelength dependence of the formation of two types of DNA damage, single-strand breaks and base changes, was investigated in the UV region from 150 nm to 254 nm using superhelical closed circular (form I) colicin El DNA with synchrotron radiation. Single-strand breaks were measured by agarose gel electrophoresis as a direct conversion of form I DNA to form II DNA (open circular). Base damages were defined as sensitive sites to a crude extract of endonuclease from Micrococcus luteus. They also were estimated using the same conversion, from form I to form II after the DNA was treated with endonuclease. The fluence-effect relationship could be fitted by a simple exponential function for both types of damage. Action spectra were constructed based on the reciprocal of the 37% fluence. The action spectrum for strand breaks increased rather monotonically over three decades from 254 nm to 150 nm in a logarithmic scale, while that for base damages showed a breaking point at 190 nm, being relatively flat above 190 nm. The characteristics of the action spectra are compared with the absorption spectra of the DNA and its main chain moiety calculated on the basis of data on calf thymus DNA and synthetic polynucleotides. Our main conclusions are (1) that the majority of single-strand breaks were induced by the absorption of photon in the sugar-phosphate group in the vacuum-UV region and (2) that the base changes were induced equally well by absorption in the vacuum-UV and in the far-UV region.     

FORMATION OF AGGREGATES OF TRYPTIC FRAGMENTS DERIVED FROM THE CARBOXYL- TERMINAL HALF OF PEA PHYTOCHROME and LOCALIZATION OF THE SITE OF CONTACT BETWEEN THE FRAGMENTS BY AMINO-TERMINAL AMINO ACID SEQUENCE ANALYSIS*

Limited trypsinization of large pea (Pisum sativum cv. Alaska) phytochrome and subsequent size-exclusion chromatography (SEC) in 0.1 M Na phosphate, pH 7.8, yielded a high-molecular-mass aggregate of tryptic fragments of phytochrome. Further SEC in 0.1 M Tris-HCl, pH 7.5, plus various concentrations of NaSCN, indicated that the tryptic-fragment complex contained an aggregate of 7 fragments of molecular mass from 38 to 55 kDa. The amino-terminal sequence of each fragment was determined from the samples electroblotted from sodium dodecylsulfate polyacrylamide gels onto polyvinylidene difluoride membranes, in order to localize the various fragments on the phytochrome polypeptide chain. All of the 7 fragments in the aggregate were found to be derived from the carboxyl-terminal half of phytochrome. A portion of the polypeptide chain (from Ala-752 to Arg-1000) common to all the tryptic fragments has been assigned as the site(s) of contact of the fragments. The tryptic-fragment complex, as well as large phytochrome itself, has been shown by SEC to dissociate to monomers in 2 M NaSCN. The result indicates that the main force involved in maintaining the complex and in contacts between monomers of phytochrome is non-ionic in nature. Relationship between the contact site(s) of the tryptic-fragment complex and large phytochrome monomer is discussed.     

INACTIVATION ACTION SPECTRA OF BACILLUS SUBTILIS SPORES IN EXTENDED ULTRAVIOLET WAVELENGTHS (50–300nm) OBTAINED WITH SYNCHROTRON RADIATION

Five types of Bacillus subtilis spores (UVR, UVS, UVP, RCE, and RCF) differing in repair and/or recombinational capabilities were exposed to monochromatic radiations at 13 wavelengths from 50 to 300 nm in vacuum. An improved biological irradiation system connected to a synchrotron radiation source was used to produce monochromatic UV radiation in this extended wavelength range with sufficient fluence to inactivate bacterial spores. From the survival curves obtained, the action spectra for the inactivation of the spores were depicted. Recombination-deficient RCE (recE) and RCF (recF) spores were more sensitive than the wild-type UVR spores in the entire range of wavelengths. This was considered to mean that DNA was the major target for the inactivation of the spores. Vacuum-UV radiations of 125-175 nm were effective in killing the spores, and distinct peaks of the sensitivity were seen with all types of the spores. Insensitivities at 190 and 100 nm were common to all five types of spores, indicating that these wavelengths were particularly impenetrant and absorbed by the outer layer materials. The vacuum-UV peaks centering at 150 nm were prominent in the spores defective in recombinational repair, while the far-UV peaks at around 235 and 270 nm were prominent in the UVS (uvrA ssp) and UVP (uvrA ssp polA) spores deficient in removal mechanisms of spore photoproducts. Thus, the profiles of the action spectra were explained by three factors; the penetration depth of each radiation in a spore, the efficiency of producing DNA damage that could cause inactivation, and the repair capacity of each type of spore.     

Achievement of ring inversion of myo-inositol derivatives due to silyloxy/silyloxy repulsion enhanced by the trans-substituents on both sides

The introduction of quite bulky trialkyl or diarylalkylsilyl groups into vicinal trans-hydroxy groups induced a conformational flip of certain multifunctionalized cyclohexane rings from the usual chair form possessing more equatorial substituents (equatorial-rich chair form) into another chair-form that has more axial substituents (axial-rich chair form). This realization was experimentally revealed by the conformational study of the synthetic myo-inositol derivatives possessing two tert-butyldimethylsilyl (TBS), two triisopropylsilyl (TIPS), or two tert-butyldiphenylsilyl (TBDPS) groups on an adjacent trans-diol. Among them, the cyclohexane rings of the 4,5-bis-O-TIPS-myo-inositol, 4,5-bis-O-TBDPS-myo-inositol, and 1,2,3,6-tetra-O-benzyl-4,5-bis-O-TBDPS-myo-inositol were in the axial-rich chair form. Comparison of the ring conformations also revealed that the order of the repulsion was OTBDPS/OTBDPS>OTIPS/OTIPS>OTBS/OTBS, and the silyloxy/silyloxy repulsion was enhanced when the two silyloxy groups were placed in the center of the contiguous four equatorial substituents.     

Anodic stripping voltammetry of hexavalent molybdate

The anodic stripping voltammetry of hexavalent molybdate was investigated with a hanging mercury drop electrode in phosphate-borate buffer solution of pH 5.8–6.7. It was found that the deposition reaction was limited by the diffusion of the protonated molybdate ion, and the anodic stripping reaction was kinetically controlled by the dissolution of the deposited molybdate. A calibration curve for the anodic peak current versus Mo(VI) concentration was linear when Mo(VI) was within the range of 7×10^?6M and 2×10^?4M at pH 5.80. Various effects for the calibration curve were studied, and its application for the determination of Mo(VI) was discussed.     

Effect of surface layering time of lactose carrier particles on dry powder inhalation properties of salbutamol sulfate

The effect of the surface layering time of lactose carrier particles on the dry powder inhalation properties of salbutamol sulfate was investigated. Lactose carrier particles were layered with vegetable magnesium stearate by physical mixing. In the present study, drug/carrier powder mixtures were designed consisting of micronized salbutamol sulfate and lactose carriers with various particle surface conditions prepared by surface layering. These powder mixtures were aerosolized by a Jethaler, and the in vitro deposition properties of salbutamol sulfate were evaluated by a twin impinger. Compared with the powder mixed with unlayered lactose carrier, the in vitro inhalation properties of the powder mixture prepared using the surface layering lactose carrier were significantly different, showing that the in vitro inhalation properties of the drug/carrier powder mixtures were improved. In vitro deposition properties (RP) increased with surface layering time. Using this surface layering system would thus be valuable for increasing the inhalation properties of dry powder inhalation.     

Total Synthesis of Mallotusinin

The total synthesis of mallotusinin, which bears a tetrahydroxydibenzofuranoyl (THDBF) bridge between the 2-oxygen and 4-oxygen of glucose on corilagin with a 3,6-O-(R)-hexahydroxydiphenoyl (HHDP) bridge, is described. The key features of the total synthesis are: 1) improvements of our previously reported method to synthesize corilagin; 2) establishment of the THDBF skeleton via an unusual intramolecular S_NAr reaction of an HHDP analogue, and 3) the application of a two-step bislactonization strategy for a HHDP bridge construction into the 2,4-O-THDBF bridge. Oxidative phenol coupling of 1,2,4-orthoacetyl-3,6-di-(4-O-benzylgalloyl)-α-d -glucopyranose and the orthoester cleavage of the coupling product without the pyranose-furanose ring transformation are key reactions for the improved synthesis of corilagin, which enabled the adequate supply of a corilagin precursor that was required to develop the mallotusinin synthesis. These established methods are expected to help develop the synthesis of other ellagitannins with a bridge between the two oxygens of corilagin.     

Multi-scale theoretical study of support effect on sintering dynamics of Pt

The capability of theoretical durability studies to offer an efficient alternative methodology for predicting the potential performance of catalysts has improved in recent years. In this regard, multi-scale theoretical methods for predicting sintering behavior of Pt on various catalyst supports are being developed. Various types of Pt diffusions depending on support were confirmed by the micro-scale ultra accelerated quantum chemical molecular dynamics (UA-QCMD) method. Moreover, macro-scale sintering behavior of Pt/γ-Al₂O₃, Pt/ZrO₂ and Pt/CeO₂ catalysts were studied using a developed 3D sintering simulator. Experimental results were well reproduced. While Pt on γ-Al₂O₃ sintered significantly, Pt on ZrO₂ sintered slightly and Pt on CeO₂ demonstrated the highest stability against sintering.