Basic peptides as functional components of non-viral gene transfer vehicles

Improving the performance of non-viral gene-delivery vehicles that consist of synthetic compounds and nucleic acids is a key to successful gene therapy. Supplementing synthetic vehicles with various biological functions by using natural or artificial peptides is a promising approach with which to achieve this goal. One of the obstacles hindering this effort is that some of the potentially useful peptides, especially those with many basic amino acid residues, interfere with the formation of the complex owing to strong electrostatic interactions with the nucleic acid. In this review, we describe our recent work in examining the potential of these peptides in gene delivery, using a recombinant lambda phage particle as the model for the gene-delivery complex. Lambda phage encapsulates large duplex DNA in a rigid polyplex-like shell with a diameter of 55 nm, and can display various peptides on this capsid, independently of particle formation. By examining the expression of marker genes encapsulated in the phage capsid, we have demonstrated that the protein transduction domain of HIV Tat protein and the nuclear localization signal derived from SV40 T antigen can remarkably facilitate the delivery of these marker genes across the two major barriers, the cell membrane and the nuclear membrane, respectively. Our results indicate that these basic peptides can constitute effective components of synthetic gene-transfer complexes, as long as sufficient copies are displayed on the outer surface of the complex.     

Some triplet energy-transfer reactions initiated by photoexcitation of triplet excited state of dibenz[a,h]anthracene to the higher triplet excited states

Some triplet energy-transfer reactions initiated by photoexcitation of the triplet excited state of dibenz[a,h]anthracene to higher triplet excited states (DBA(T_n)) were observed in the presence of the triplet energy quenchers (Q) such as naphthalene, biphenyl, p-dichlorobenzene, and o-dicyanobenzene. In the case of carbon tetrachloride (CCl₄) as Q, DBA(T_n)-sensitized decomposition of CCl₄ occurred.     

Structure–function relationships of the supramolecular assembly of the bacterial photosynthetic antenna complexes in lipid membranes

Appropriate experimental platforms are required to clarify the structure–function relationships of membrane protein assemblies. In photosynthetic bacteria, light-harvesting complex 2 and light-harvesting/reaction center core complex play key roles in capturing and transferring light energy and facilitating subsequent charge separation. These photosynthetic apparatuses form a supramolecular assembly in the photosynthetic membrane. However, the mechanism through which this assembly influences the efficiency of energy conversion remains to be clarified. We review our recent studies that were conducted to evaluate the structure–function relationship of the supramolecular assembly of photosynthetic antenna complexes in various lipid bilayer systems, as well as the construction of novel systems of planar lipid membranes for use as experimental platforms.     

Total Synthesis of cis‐Clavicipitic Acid from Asparagine via Ir‐Catalyzed CH bond Activation as a Key Step

4‐Substituted tryptophan derivatives and the total synthesis of cis‐clavicipitic acid were achieved in reactions in which Ir‐catalyzed C?H bond activation was a key step. The starting material for these reactions is asparagine, which is a cheap natural amino acid. The reductive amination step from the 4‐substituted tryptophan derivative gave cis‐clavicipitic acid with perfect diastereoselectivity.     

Sequence-specific control of azobenzene assemblies by molecular recognition of DNA

We investigated the molecular recognition between the amphiphile AzoAde, which is composed of azobenzene in the hydrophobic and adenine in the hydrophilic portion of the molecule, and oligonucleotides having a homogeneous base (dA30, dT30, dG30, and dC30) at the air-water interface. On the basis of the complementary base-pairing of DNA in the duplex, orderly arrangement of AzoAde on templated dT30 was examined using pi-A isotherm, UV-vis RAS, FT-IR RAS, and XPS measurements. Although there was little interaction between AzoAde and mismatched oligonucleotides (dA30, dG30, and dC30), AzoAde prepared on a dT30 subphase stoichiometrically assembled and interacted with dT30, subsequently forming a J-form assembly at the air-water interface. AFM observation of the LB films revealed the nanostructure of the J-formed AzoAde monolayer on the dT30 subphase as well as the domain structures of the H-formed monolayers on the other oligonucleotide subphases. Therefore, dT30 has a potential application as a template for assembling AzoAde at the air-water interface.     

Photophysical property and photostability of J-aggregate thin films of thiacyanine dyes prepared by the spin-coating method

By use of electrostatic interactions of dye molecules and poly(diallyldimethylammonium chloride) (PDDA), the spin-coating technique has been successfully applied to the preparation of stable J-aggregate thin films of thiacarbocyanine dyes on a polycarbonate or quartz plate. The J-aggregate thin films were prepared by the spin-coating of PDDA aqueous solution on dye thin films prepared on a substrate by the spin-coating of 2,2,3,3-tetrafluoro-1-propanol solution of dyes. Photophysical properties of the dye thin films and J-aggregate thin films were studied by measuring the fluorescence spectra, quantum yields, and lifetimes. Coherent size of the J-aggregates was estimated to be 3-12 by means of the absorption bandwidth (full width at half maximum) or radiative lifetime. Photostability of the J-aggregate thin films was also studied in terms of photodegradation efficiency under argon and oxygen in comparison with the dye thin films, and J-aggregate thin films were found to be more stable than the corresponding dye thin films.     

Rhodium-catalyzed silylation and intramolecular arylation of nitriles via the silicon-assisted cleavage of carbon-cyano bonds

A rhodium-catalyzed silylation reaction of carbon-cyano bonds using disilane has been developed. Under these catalytic conditions, carbon-cyano bonds in aryl, alkenyl, allyl, and benzyl cyanides bearing a variety of functional groups can be silylated. The observation of an enamine side product in the silylation of benzyl cyanides and related stoichiometric studies indicate that the carbon-cyano bond cleavage proceeds through the deinsertion of silyl isocyanide from eta(2)-iminoacyl complex B. Knowledge gained from these studies has led to the development of a new intramolecular biaryl coupling reaction in which aryl cyanides and aryl chlorides are cross-coupled.