Dialyse

Ohne Zusammenfassung     

Exact determination of phagocytic activity of alveolar macrophages toward polymer microspheres by elimination of those attached to the macrophage membrane

A method for exact determination of phagocytic activity of alveolar macrophage (M) cells toward synthetic microspheres (MS) by optical microscopy was developed. We examined the effectiveness of the treatment of M samples with trypsin, acid or xylene to remove the polystyrene latex microspheres (PSL MS) attached to M cell membranes during their phagocytosis by M cells. We found that centrifugation, which was employed to collect M samples after incubation with MS, affected significantly the efficiency of the various treatments. Of the three treatments, xylene treatment without centrifugation was the most effective to determine the phagocytic activity of M cells, as xylene dissolved the PSL MS on the cell surface almost completely. This treatment was also effective in the case of poly(lactic-co-glycolic acid) MS (PLGA MS), which have been commonly used as an efficient vehicle for drug delivery system.     

Conformationally Flexible Biphenyl‐phosphane Ligands for Ru‐Catalyzed Enantioselective Hydrogenation

Stereomutation of a BIPHEP/RuCl ₂ /diamine complex (shown schematically) is possible because of the conformational flexibilty of BIPHEP ligands. The result is an asymmetric activation in the Ru‐catalyzed hydrogenation of carbonyl compounds to optically active alcohols. Whereas a racemic BINAP/RuCl₂ complex with a chiral diamine activator gives a 1:1 mixture of two diastereomers, unequal amounts of the diastereomers can be produced from a BIPHEP/RuCl₂ complex and a chiral diamine. Ar=3,5‐dimethylphenyl, BINAP=2,2′‐bis(diphenylphosphanyl)‐1,1′‐binaphthyl, BIPHEP=2,2′‐bis(diarylphosphanyl)biphenyl.     

Evaluation of efficiency of reference potential spatial warping algorithm in conformational sampling of peptides

Molecular dynamics (MD) simulation using the reference potential spatial warping algorithm (REPSWA) is a promising method for computing the conformational equilibrium of a system with a rugged energy surface. Its effectiveness has previously been demonstrated using only a simplified model system of a hydrocarbon chain omitting nonbonded interaction terms from the potential energy function. To evaluate the applicability of REPSWA MD simulation to more realistic problems, we applied it to small peptide systems in an aqueous environment. Difficulties were encountered, however, forcing us to devise several modifications. We investigated their effectiveness in comparison to conventional constant-temperature and multicanonical MD simulations. We found that the sampling efficiency of the modified REPSWA MD after a careful optimization of its parameters was better than that of the constant-temperature MD and comparable to that of the multicanonical MD in several cases.     

Photoinduced reductive repair of thymine glycol: implications for excess electron transfer through DNA containing modified bases

Photoinduced reduction of thymine glycol in oligodeoxynucleotides was investigated using either a reduced form of flavin adenine dinucleotide (FADH(-)) as an intermolecular electron donor or covalently linked phenothiazine (PTZ) as an intramolecular electron donor. Intermolecular electron donation from photoexcited flavin (FADH(-)) to free thymidine glycol generated thymidine in high yield, along with a small amount of 6-hydroxy-5,6-dihydrothymidine. In the case of photoreduction of 4-mer long single-stranded oligodeoxynucleotides containing thymine glycol by *FADH(-), the restoration yield of thymine was varied depending on the sequence of oligodeoxynucleotides. Time-resolved spectroscopic study on the photoreduction by laser-excited N,N-dimethylaniline (DMA) suggested elimination of a hydroxyl ion from the radical anion of thymidine glycol with a rate constant of approximately 10(4) s(-1) generates 6-hydroxy-5,6-dihydrothymidine (6-HOT(*)) as a key intermediate, followed by further reduction of 6-HOT(*) to thymidine or 6-hydroxy-5,6-dihydrothymdine (6-HOT). On the other hand, an excess electron injected into double-stranded DNA containing thymine glycol was not trapped at the lesion but was further transported along the duplex. Considering redox properties of the nucleobases and PTZ, competitive excess electron trapping at pyrimidine bases (thymine, T and cytosine, C) which leads to protonation of the radical anion (T(-)(*), C(-)(*)) or rapid back electron transfer to the radical cation of PTZ (PTZ(+)(*)), is presumably faster than elimination of the hydroxyl ion from the radical anion of thymine glycol in DNA.     

Synthesis of the putative structure of fistulosin using the ruthenium-catalyzed cycloisomerization of diene

Fistulosin 1, which was isolated from the root of the Welsh onion, is a novel indole alkaloid that has antifungal activity. The first total synthesis of the reported structure of fistulosin using our cycloisomerization of diene is described.