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A phosphoramidite monomer bearing an azobenzene is synthesized from D-threoninol. Using this monomer, azobenzene moieties can be introduced into oligodeoxyribonucleotide (DNA) at any position on a conventional DNA synthesizer. With this azobenzene-tethered DNA, formation and dissociation of a DNA duplex can be reversibly photo-regulated by cis-trans isomerization of the azobenzene. When the azobenzene takes a trans-form, a stable duplex is formed. After isomerization of the trans-azobenzene to its cis-form by UV-light irradiation (300 nm < lambda < 400 nm), the duplex can be dissociated into two strands. The duplex is reformed on photo-induced cis-trans isomerization (lambda > 400 nm). The introduction of azobenzenes into the T7 promoter at specific positions also efficiently and reversibly photo-regulates transcription by T7-RNA polymerase. The reversible regulation can be repeated many times without causing damage to the DNA or the azobenzene moiety. These procedures take approximately 10 d to complete.

Contents § 1. Introduction and summary 1.1. Viewpoint of cluster correlations in non-alpha-nuclei 1.2. Interactions between few-nucleon clusters 1.3. Motion of individual nucleons in molecule-like nuclei 1.4. Multi-cluster model for non-alpha-nuclei 1.5. Alpha and three-nucleon cluster states in lightest sd-shell and A=15 nuclei § 2. Interactions between few-nucleon clusters 2.1. Realistic effective nuclear potentials 2.2. N-a interaction 2.3. d-a interaction and distortion effect of deuteron 2.4. Excited states in A=4 system with 3N+N cluster model § 3. Molecular structure in the 8 Be-core region 3.1. Motion of a nucleon around a 8 Be·core 3.2. Molecular orbital model . Structure of 9 Be nucleus 3.4. Structure of 10 B nucleus 3.5. Structure of neutron-rich Be-and B-isotopes § 4. Three-cluster model of the A=lO and 11 nuclei 4.1. Orthogonality condition model § 5. 4.2. 2a + t cluster model of 11 B nucleus 4.3. 2a+d cluster model of 10 B and 10 Be nuclei 4.4. Effect of the complete antisymmetrization Alpha and three-nucleon cluster states in lightest nuclei 5.1. Structure of A=19 nuclei 5.2. Structure of A=l8 nuclei 5.3. Structure of A=l7 nuclei 5.4. Structure of A=l5 nuclei § 1. Introduction and summary sd-shell 1.1. Viewpoint of cluster correlations in non-alpha-nuclei and A=151.1.1. The light nuclei (we consider in this chapter the P-shell and lightest sd-shell nuclei) have a relatively small number of nucleons, and their characters vary remarkably from nucleus to nucleus, showing strong individuality. Even in these light nuclei we see the persistency of saturation property which is considered a fundamental property of overall nuclei. In light nuclei, the saturation property emerges through formation of the acluster as a saturating subunit. This is the fundamental aspect prescribing the characteristics of light nuclei. The basic viewpoint of a-cluster structure in light nuclei has been presented in Ref. 1). As stated in detail in the previous chapter, 2 l recent investigations on light a-nuclei 3 l~el exhibit a remarkable success of the a-cluster model, which provides us with a comprehensive understanding of nuclear structure including quite high excited states, where coexistence of the shell and cluster structures and structure change between them can be understood in a unified way. Now we naturally proceed to an extensive investigation of non-a-nuclei from the cluster-model viewpoint. 1.1.2.The structure of light nuclei has been explained mostly in terms of the intermediate-coupling shell model or the deformed shell model, like the Nilsson model and the deformed Hartree-Fock method. They assume the formation of a static one-center single-particle field. The 9 Be nucleus, on the other hand, has long been considered a prototype of the molecule-like structure of nuclei, in which two a-particles constitute a stable dumbbell-like core and a remaining (valence) neutron moves on a single-particle orbital at NERL on May 26, 2015 http://ptps.oxfordjournals.org/ Downloaded from tion, which is an "elementary interaction...

Studies were made of the 1-70 keV persistent spectra of fifteen magnetars as a complete sample observed with Suzaku from 2006 to 2013. Combined with early NuSTAR observations of four hard X-ray emitters, nine objects showed a hard power-law emission dominating at 10 keV with the 15-60 keV flux of ∼1-11 × 10 −11 ergs s −1 cm −2 . The hard X-ray luminosity L h , relative to that of a soft-thermal surface radiation L s , tends to become higher toward younger and strongly magnetized objects. Updated from the previous study, their hardness ratio, defined as ξ = L h /L s , is correlated with the measured spin-down rateṖ as ξ = 0.62 × (Ṗ /10 −11 s s −1 ) 0.72 , corresponding with positive and negative correlations of the dipole field strength B d (ξ ∝ B d) and the characteristic age τ c (ξ ∝ τ −0.68 c ), respectively. Among our sample, five transients were observed during X-ray outbursts, and the results are compared with their long-term 1-10 keV flux decays monitored with Swift/XRT and RXTE/PCA. Fading curves of three bright outbursts are approximated by an empirical formula used in the seismology, showing a ∼10-40 d plateau phase. Transients show the maximum luminosities of L s ∼1035 erg s −1 , which is comparable to those of the persistently bright ones, and fade back to 10 32 erg s −1 . Spectral properties are discussed in a framework of the magnetar hypothesis.

sequence-specific hybridization and forms a highly regular double-helical structure with suitable flexibility. [1][2][3][4] DNA is probably one of the most promising biomolecules for future applications in nanotechnology and materials science.[5] Many 2D and 3D nanostructures with determined shapes and geometries have been reported recently in which DNA is used as the building blocks and mortar. [3,6,7] More excitingly, several types of DNA nanomachines, fuelled with DNA oligonucleotides [8] or other molecules such as intercalators [9] and metal ions, [10] have been constructed. [4,5] During these 10 years of development, substantial progress has been made in the design of DNA-based devices such as tweezers, walkers, and gears, which can perform mechanical functions such as scission, directional motion, or rolling. [11][12][13] The prospects of this field are extraordinarily promising, and several valuable applications of DNA nanomachines as sensors, transporters, and drug-delivery systems have also been reported. [5] For most of the DNA nanomachines constructed so far, oligonucleotides have been generally used as the fuel. In many of these systems, the mechanical motion was usually carried out by hybridization of one DNA fuel molecule to target sequences followed by its removal with another DNA sequence that is completely or partially complementary to the first. [5] Yurke et al. demonstrated the first DNA machine that functioned as "tweezers" fuelled by two strands of DNA with tailored complementarity.[8a] As the energy for operating these DNA nanomachines is produced by a strand-exchange strategy, a DNA duplex is produced as a waste product in every working cycle. Thus, the operating efficiency decreases gradually with the accumulation of "wastes". A new strategy is therefore required to overcome this problem for the further development of DNA nanotechnology.Over the past decade, we have developed a series of photoresponsive DNAs by covalently tethering azobenzene moieties onto the DNA strand. [14][15][16][17][18][19] Hybridization of these photoresponsive DNAs to single-stranded DNA (to form duplexes), RNA (to form DNA-RNA hybrids), or double-stranded DNA (to form triplexes) can be efficiently switched "on" and "off" by simply irradiating with UV and visible light. This is based on the following mechanism: the planar trans-azobenzene intercalates between adjacent base pairs and stabilizes the duplex or triplex structure by stacking interactions, whereas the nonplanar cisazobenzene destabilizes it by steric hindrance.[19] The successful photoregulation of primer elongation, transcription, and RNase H activity have also been demonstrated with photoresponsive DNAs. [20][21][22] Photoregulation efficiency can be amplified by the introduction of multiple azobenzene residues onto the DNA.[23] For example, nine azobenzene groups were introduced onto a DNA strand 20 nucleotides (nt) in length, and the clearcut photoswitching of DNA duplex formation was observed without loss of sequence specificity. Photoregulation of ...

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The introduction of methyl groups into two ortho positions (2' and 6' positions) of the same benzene ring in an azobenzene remarkably raised both its photoregulation ability and the thermal stability of the cis-form.

We synthesized various azobenzenes methylated at their ortho positions with respect to the azo bond for more effective photoregulation of DNA hybridization. Photoregulatory efficiency, evaluated from the change of T(m) (DeltaT(m)) induced by trans-cis isomerization, was significantly improved for all ortho-modified azobenzenes compared with non-modified azobenzene due to the more stabilized trans form and the more destabilized cis form. Among the synthesized azobenzenes, 4-carboxy-2',6'-dimethylazobenzene (2',6'-Me-Azo), in which two ortho positions of the distal benzene ring with respect to carboxyl group were methylated, exhibited the largest DeltaT(m), whereas the newly synthesized 2,6-Me-Azo (4-carboxy-2,6-dimethylazobenzene), which possesses two methyl groups on the two ortho positions of the other benzene ring, showed moderate improvement of DeltaT(m). Both NMR spectroscopic analysis and computer modeling revealed that the two methyl groups on 2',6'-Me-Azo were located near the imino protons of adjacent base pairs; these stabilized the DNA duplex by stacking interactions in the trans form and destabilized the DNA duplex by steric hindrance in the cis form. In addition, the thermal stability of cis-2',6'-Me-Azo was also greatly improved, but not that of cis-2,6-Me-Azo. Solvent effects on the half-life of the cis form demonstrated that cis-to-trans isomerization of all the modified azobenzenes proceeded through an inversion route. Improved thermal stability of 2',6'-Me-Azo but not 2,6-Me-Azo in the cis form was attributed to the retardation of the inversion process due to steric hindrance between lone pair electrons of the pi orbital of the nitrogen atom and the methyl group on the distal benzene ring.