Electronic excitation energy transfer between nucleobases of natural DNA

Transfer of the electronic excitation energy in calf thymus DNA is studied by time-resolved fluorescence spectroscopy. The fluorescence anisotropy, after an initial decay starting on the femtosecond time scale, dwindles down to ca. 0.1. The in-plane depolarized fluorescence decays are described by a stretched exponential law. Our observations are consistent with one-dimensional transfer mediated by charge-transfer excited states.     

Prodrug study of plinabulin using a click strategy focused on the effects of a replaceable water-solubilizing moiety

Plinabulin (1) is a potent anti-microtubule agent, however, its low water solubility has to be improved for the advantage in pharmacokinetics and chemotherapy. In this report, the replaceable water-solubilizing moiety of the water-soluble prodrug of plinabulin (1) was investigated. The properties of the water-soluble prodrugs of plinabulin (1), in which the water-solubilizing part was replaced with a new functionality, were evaluated. The newly introduced water-solubilizing moiety provided interesting effects on the water solubility and half-life of the prodrugs.     

Extended diffusion in a double well potential: Transition from classical to quantum regime

The transition between the classical and quantum regimes in the diffusion of a particle in a 2-4 double-well potential is treated via the strong collision model in the high-temperature limit. Both the classical and semiclassical position correlation functions, their spectra, and correlation times are evaluated using the memory function formalism. It is shown that even in the high temperature limit, marked classical-quantum transition effects appear in the observables when collisions are rare.     

Synthesis of novel anthracene derivatives of isoxazolino-carbocyclic nucleoside analogues

The synthesis of isoxazolino-carbocyclic nor-nucleosides incorporating an anthracene moiety was properly tuned through nitrosocarbonyl intermediates chemistry, and a variety of analogues were attained starting from stereodefined heterocyclic aminols through the linear construction of purine heterocyclic rings. The synthesis hinges on the exo selective 1,3-dipolar cycloaddition of the stable anthracenenitrile oxide to the N-benzoyl-2,3-oxazanorborn-5-ene and simple elaborations of the cycloadducts. A selection of nucleoside derivatives were initially tested for their inhibitory activity against a variety of viruses, including Hepatitis B and C, Human Papilloma virus as well as Influenza viruses of type A and B. Modest anti-viral activities were observed in Hepatitis assays while the activities in the cases of Influenza viruses were almost negligible. Good anti-viral activity was found for compound 11bC with no cellular toxicity at the dose tested in the case of Human Papilloma virus.     

Autoadhesion of Glassy Polymers

Summary: Thick bulk films of linear amorphous polymers with different chain architecture and molecular weight were brought into contact with themselves in a lap-shear joint geometry at bonding temperatures (T) below the glass transition temperatures of their bulk (T), at a small contact pressure, in order to form autoadhesive joints. As-bonded joints were shear-fractured in tension at ambient temperature, and their lap-shear strength was measured as a function of T, bonding time and molecular weight. The kinetics of the process of the development of the lap-shear strength at T < T was investigated, and the molecular mechanisms governing this process were discussed. The quasi-equilibrium surface glass transition temperatures of the investigated polymers were estimated and compared with the corresponding values of T.     

The conversion of phenylpropanedinitrile (phenylmalononitrile) into the carbanion, followed by IR spectra, ab initio and DFT force field calculations

The spectral and structural changes, caused by the conversion of phenylpropanedinitrile (phenylmalononitrile) into the carbanion, have been followed by IR spectra, ab initio HF, MP2 and DFT BLYP force field calculations. In agreement between theory and experiment, the conversion is accompanied with strong frequency decreases (with 114 cm(-1), mean value) of the cyano stretching bands nu(C triple bond N), dramatic increases in the corresponding integrated intensities (136-fold, total value), strong enhancement of the nu(C triple bond N) vibrational coupling and other essential spectral changes. According to the calculations, the strongest structural changes take place at the carbanionic center: (i) shortenings of the Cz-Ph and Cz-CN bonds with 0.064-0.092 A, and increases in the corresponding bond orders with 0.14-0.21 U; (ii) simultaneous enlargements of the bond angles at the same carbon atom with 7.6 degrees -9.7 degrees, as from tetrahedral its configuration becomes trigonal. The carbanionic charge is distributed between the two cyano groups (0.44-0.52 e(-)), phenyl ring (0.31-0.34 e(-)) and carbanionic center (0.14-0.25 e(-)). The formation of moderately strong (CH(3))(2)S=O...H-C(CN)(2)C(6)H(5) hydrogen bonds has been found experimentally.     

Airy plasmons: non‐diffracting optical surface waves

Airy beams represent an important class of non‐diffracting waves which can be realized on a flat surface. Being generated in the form of surface‐plasmon polaritons, such Airy plasmons demonstrate many remarkable properties: they do not diffract while propagating along parabolic trajectories, and they recover their shape after passing through obstacles. This paper reviews the basic physics of Airy plasmons in both paraxial and non‐paraxial cases, and describes the experimental methods for generation of Airy surface waves on metal surfaces, including a control of their trajectories, as well as the interference of Airy plasmons and hot‐spot generation. Many unusual properties of Airy plasmons can be utilized for useful applications, including plasmonic circuitry and surface tweezers. Picture: Observation of two colliding Airy plasmons.     

Nano‐opto‐mechanical effects in plasmonic waveguides

In order to achieve interaction between light beams, a mediating material object is required. Nonlinear materials are commonly used for this purpose. Here a new approach to control light with light, based on a nano‐opto‐mechanical system integrated in a plasmonic waveguide is proposed. Optomechanics of a free‐floating resonant nanoparticle in a subwavelength plasmonic V‐groove waveguide is studied. It is shown that nanoparticle auto‐oscillations in the waveguide induced by a control light result in the periodic modulation of a transmitted plasmonic signal. The modulation depth of 10% per single nanoparticle of 25 nm diameter with the clock frequencies of tens of MHz and the record low energy‐per‐bit energies of 10⁻¹⁸ J is observed. The frequency of auto‐oscillations depends on the intensity of the continuous control light. The efficient modulation and deep‐subwavelength dimensions make this nano‐optomechanical system of significant interest for opto‐electronic and opto‐fluidic technologies.     

Scattering amplitudes of QCD string in the worldline formalism

I review the derivation of large-N QCD meson scattering amplitudes in the Regge regime, where the effective theory of long strings applies in d = 4. A special attention is payed to the reparametrization path integral which plays a crucial role in the consistency of off-shell amplitudes. I show how the linear Reggeon trajectory is obtained for QCD string in the mean-field approximation, which turns out to be exact for the Nambu-Goto string, and discuss the interrelation with perturbative QCD.