Structural variety of membrane permeable peptides

Peptide-mediated protein delivery into living cells has been attracting our attention. Among the peptides that have been reported to have carrier activity, the one from the human immunodeficient virus (HIV)-1 Tat has been most often used for the introduction of exogenous macromolecules into cells. We have shown that not only the Tat peptide, but also various arginine-rich peptides showed very similar characteristics in translocation, and the possible presence of ubiquitous internalization mechanisms among the arginine-rich peptides has also been suggested. These arginine-rich peptides includes ones derived from HIV-1 Rev and flock house virus coat proteins. The linear- and branched-chain peptides containing approximately 8 residues of arginine also show a similar ability. In this review, we present the structural variety of membrane permeable peptides and provide a survey of the findings on the translocation of these peptides through the cell membranes.     

Total synthesis of (+)-tubelactomicin A. 2. Synthesis of the upper-half segment and completion of the total synthesis

[reaction: see text]. We have completed the total synthesis of natural (+)-tubelactomicin A (1), a 16-membered macrolide antibiotic. This Letter presents a highly efficient synthesis of the upper-half segment (C14-C24) and the completion of the total synthesis featuring a high-yielding Stille coupling for the connection of the upper-half and lower-half segments and Mukaiyama macrolactonization for the construction of the entire structure of 1.     

DNA-bleomycin interaction: Nucleotide sequence-specific binding and cleavage of DNA by bleomycin

Biosynthetic intermediates and synthetic analogues of bleomycin (BLM) have been investigated for their metal binding, dioxygen activation, and DNA cleavage. Molecular O₂ was activated by the Fe(II) complex of a synthetic model ligand. Nucleotide sequence specificities in DNA cleavage by the BLM-Fe(II) and deglyco-BLM-Fe(II) complexes were almost identical. It has been shown that (1) the β-aminoalanine-pyrimidine-β-hydroxyhistidine portion of BLM is essential for the metal binding and dioxygen activation and (2) the bithiazole moiety contributes to the specific binding to guanine base of DNA.     

alpha-Aminoallylation of aldehydes with ammonia: stereoselective synthesis of homoallylic primary amines

Three-component reactions of aldehydes, ammonia, and allylboronates were found to provide homoallylic primary amines in high yields with high chemo- and stereoselectivities. A two-step, one-pot, stereoselective synthesis of an uncommon alpha-amino acid, alloisoleucine, was achieved utilizing this reaction.     

Selective wet air oxidation of diluted aqueous ammonia solutions over co-precipitated transition metal-aluminium catalysts

Catalytic wet air oxidation of ammonia over a co-precipitated transition metal-aluminium catalyst was investigated. Copper-aluminium (Cu-Al-O) catalyst exhibited the highest activity and N₂ selectivity among those prepared from Co, Fe, Mn, and Ni. 50% of 1500 ppm of ammonia could be removed from wastewater of pH 12 at 503 K under 2.0 MPa of air by using 4.0 g of catalyst without formation of toxic nitrogen containing compounds. Cu and Al ions were not found in solution after the reaction. It has been found that the catalytic performance of Cu-Al-O catalyst was strongly dependent on the preparation methods. The co-precipitated Cu-Al-O catalysts showed high N₂ selectivity. The presence of CuO is concluded to promote the reaction and CuAl₂O₄ in bulk phase is needed to stabilize the catalyst.     

Effect of polymer on electron-donating character of polymer donor. II. Formation of charge-transfer complex between polymers containing N-dimethylaniline group and trinitrotoluene

Formation of charge-transfer complexes with trinitrotoluene (TNT) as a common acceptor was studied in detail by using dimethyltoluidine (DMT), poly-N-dimethyl-p-aminostyrene (poly-ASt), and also copolymers of aminostyrene (ASt) and styrene (St) as donors. A smooth bathochromic shift in λ_max was observed with increasing ASt unit content in copolymers. Values of the constant for charge transfer complex formation K_CT were found to increase smoothly with ASt unit content. However, the K_CT value with DMT did not coincide with the value extrapolated from the plot of K_CT value versus ASt unit content to zero ASt unit content, but was found to be much higher than the limiting value, in contradiction to the results obtained with maleic anhydride (MAnh). The entropy of complex formation with DMT was found to be exceptionally small; this small value may be responsible for the high K_CT value with DMT.     

Zooxanthellamide Cs: vasoconstrictive polyhydroxylated macrolides with the largest lactone ring size from a marine dinoflagellate of Symbiodinium sp

Zooxanthellamide Cs (ZAD-Cs), C(128)H(220)N(2)O(53)S(2) (ca. 2.7 kDa), was obtained from a cultured marine dinoflagellate of the genus Symbiodinium as an inseparable isomeric mixture of polyhydroxylated 61- to 66-membered macrolides. The chemical structures of the components were clarified by detailed 2D NMR analysis to be the macrolactonized analogues of zooxanthellamide A (ZAD-A), which had been previously isolated from the same microalgae. Chemical lability of ZAD-Cs suggests that ZAD-A is an artifact derived from ZAD-Cs during the isolation steps. Three of the components possess the largest (63-, 64-, and 66-membered) ring sizes found to date among the natural macrolides. ZAD-Cs exhibited higher vasoconstrictive activity than that of the zooxanthellatoxins, the first vasoconstrictive macrolides from Symbiodinium sp. The structure-activity relationship suggests that the huge macrolactone structure is important for biological activity. The relationship between the structures of the polyol metabolites and the phylogenetic systematics of Symbiodinium sp. is also discussed.     

Kinetics and mechanism of the reduction of 1,10-phenanthroline—copper(II) complex

The cyclic voltammetric study of 1,10-phenanthroline—copper(II) complex was carried out in acidic buffer solution. It was found from the current—mole ratio (copper (II): 1,10-phenanthroline) relationship that the maximum coordination number of 1,10-phenanthroline—copper(II) complex was four under the present experimental condition. The reduction mechanism and kinetics of copper(II) was studied in the presence of various concentrations of 1,10-phenanthroline.