Dynamic interaction between oppositely charged vesicles: aggregation, lipid mixing, and disaggregation

We investigated dynamic interactions between oppositely charged small unilamellar vesicles using positively charged vesicles containing 1,2-dioleoyl-3-trimethylammonium-propane or 3beta-[N-(N('),N(')-dimethylaminoethane)-carbamoyl] cholesterol and negatively charged vesicles containing L-alpha-phosphatidyl-DL-glycerol. Aggregation, lipid bilayer mixing, contents mixing and contents leakage were systematically examined using optical density measurements, fluorescence resonance energy transfer assays, fluorescence quenching assays, light-scattering analyses, and freeze-fracture transmission electron microscopy. The oppositely charged vesicles aggregated immediately. Lipid mixing was observed, but there was no mixing of the contents. The vesicle aggregates disaggregated spontaneously after several minutes. The surface potential of the disaggregated vesicles was neutralized. From these results, we infer that the lipids in the external monolayers were exchanged between the oppositely charged vesicles while the internal monolayers remained intact. The two types of cationic lipids used exhibited different speeds of disaggregation.     

New nucleotide pairs for stable DNA triplexes stabilized by stacking interaction

New nucleotide pairs applicable to formation of DNA triplexes were developed. We designed oligonucleotides incorporating 5-aryl deoxycytidine derivatives (dC5Ars) and cyclic deoxycytidine derivatives, dCPPP and dCPPI, having an expanded aromatic area, as the second strand. As pairing partners, two types of abasic residues (C3: propylene linker, phi: abasic base) were chosen. It was concluded that, when the 5-aryl-modified cytosine bases paired with the abasic sites in TFOs in a space-fitting manner, the stability of the resulting triplexes significantly increased. The recognition of C3 toward dC5Ars was selective because of the stacking interactions between their aromatic part and the nucleobases flanking the abasic site. These results indicate the potential utility of new nucleotide triplets for DNA triplex formation, which might expand the variety of structures and sequences and might be useful for biorelated fields such as DNA nanotechnologies.     

Analysis of photo-induced hydration of a photochromic poly(N-isopropylacrylamide) - Spiropyran copolymer thin layer by quartz crystal microbalance

We investigated hydration and swelling behavior of a solid state photoresponsive copolymer in water by using a quartz crystal microbalance technique with dissipation measurement (QCM-D technique). On the gold film electrode of a quartz resonator, we deposited a thin layer of a pNSp-NIPAAm, which is a poly(N-isopropylacrylamide) (pNIPAAm) polymer partially modified with a photochromic chromophore, 6-nitrospiropyran (NSp). Using QCM-D measurements, we found that at a temperature of 19 °C both water adsorption and changes in the viscoelasticity of the solid pNSp-NIPAAm layer were induced when pNSp-NIPAAm was irradiated by 365 nm ultraviolet light, which triggers the photoisomerization of the NSp chromophore and makes the structure of the chromophore hydrophilic. At temperatures between 25 and 35 °C, this photo-induced hydration was not observed. These observations suggest that the photoisomerization of the NSp chromophores triggered the photo-induced hydration only when pNIPAAm component is sufficiently hydrophilic, at a temperature of 19 °C.     

Dendrimer container for anion-responsive lanthanide complexation and "on-off" switchable near-infrared luminescence

A new dendrimer-type ligand dynamically switched the lanthanide complexation and luminescence profiles in response to external anions.     

Synthesis, structures, and properties of meso-phosphorylporphyrins: self-organization through P-oxo-zinc coordination

The synthesis, structures, and optical and electrochemical properties of meso-phosphorylporphyrins are described. The copper-catalyzed carbon-phosphorus cross-coupling reaction of a meso-iodoporphyrin with di-n-butyl phosphite and diphenylphosphane oxide has proved to be an efficient and general method for the synthesis of meso-phosphorylporphyrins. Zinc phosphorylporphyrins thus obtained readily undergo self-organization through P-oxo-Zn coordination to form noncovalently linked, cofacial porphyrin dimers or linear oligomers, which have been characterized by spectroscopic methods and X-ray crystallographic analyses. In toluene, CH(2)Cl(2), and CHCl(3), the zinc phosphorylporphyrins exist mostly as dimers or monomers, depending on their concentrations, the temperature, and the presence of additives. The self-association constants for dimerization in toluene have been determined by UV/Vis absorption titration measurements. The meso-diphenylphosphorylporphyrin dimer displays excitonic coupling of the Soret band with a splitting energy of 940 cm(-1). Fluorescence lifetimes of the zinc phosphorylporphyrins have been found to be affected only slightly by the concentration of the solution, and by the addition of triphenylphosphane oxide, suggesting that the effect of dimerization on their photodynamics in the S(1) state is negligible. On the other hand, the effect of dimerization is clearly reflected in their electrochemical oxidation processes, as the initially produced radical cations are efficiently delocalized over the two porphyrin rings. These findings demonstrate the potential utility of meso-phosphorylporphyrins as new models for the special pair in photosynthesis and as new building blocks for porphyrin-based supramolecular materials.     

Lipase-catalyzed asymmetric synthesis of desprenyl-carquinostatin A and descycloavandulyl-lavanduquinocin

An asymmetric synthesis of the core carbazole structure, 6-desprenyl-carquinostatin 3 and 6-descycloavandulyl-lavanduquinocin 3, toward a total synthesis of carquinostatin A (1) and lavanduquinocin (2), has been established. Lipase QLM (Meito) catalyzed enantioselective acetylation of the racemic alcohol 6 gave the (-)-acetate 7 and the (+)-alcohol 6 with high enantioselectivity. The absolute stereochemistry of the (-)- and (+)-alcohol 6 have been determined to be R- and S-configurations, respectively, by the advanced Mosher method. In the same manner, the (-)-acetate 13 and the (+)-alcohol 12 have been obtained from the racemic alcohol 12. The (R)-(-)-acetate 13, derived from the (R)-(-)-acetate 7, was the same as the (-)-acetate 13, which has been determined to be (R)-configuration. Oxidation of the (R)-(-)-acetate 13 followed by hydrolysis afforded (R)-(-)-6-desprenyl-carquinostatin [and (R)-(-)-6-descycloavandulyl-lavanduquinocin] 3. In addition, oxidation of the (S)-(+)-alcohol 12 provided (S)-(+)-3, which is the enantiomer of 6-desprenyl-carquinostatin A (R)-(-)-3.     

Molecular complex consisting of two typical external medicines: intermolecular interaction between indomethacin and lidocaine

The molecular complex formed between indomethacin (IDM) and lidocaine (LDC), which are typical external medicines, was studied. A thermal analysis, microscopic study and phase solubility technique suggested intermolecular interaction between IDM and LDC. The phase solubility profiles with IDM and LDC were classified as A(L)-type, indicating the formation of a 1 : 1 stoichiometric molecular complex. The apparent stability constant (K(S)), calculated from the slope and the intercept, was 4478.9 M(-1). A molecular ion peak was detected at 592.2 (m/z) from fast-atom bombardment-MS measurements, which was in accordance with the sum of the molecular weight for IDM (M(W): 357.81) and LDC (M(W): 234.38). The changes of IR spectra in the C=O stretching region showed that each intact hydrogen bond network was collapsed in the IDM-LDC system and strong interaction between IDM and LDC formed after their kneading. From the (1)H-NMR analyses, it was estimated that the dominant interactive site was the IDM carboxylic acid group which associated with the LDC diethyl amino group non-covalently.     

Synthesis and characterization of partially fluorinated stearolic acid analogs: Effect of their fluorine content on the monolayer at the air-water interface

Novel stearolic acid analogs (i.e., 9-octadecynoic acid analogs: 1a-d) containing the shorter perfluoroalkyl groups, CF₃, C₂F₅, n-C₃F₇ or n-C₄F₉ group were synthesized. Equilibrium spreading pressures (π_es) of their monolayers at the air-water interface were measured in order to demonstrate how the fluorine content has an effect on the stability of the fatty acid monolayers. As the fluorine content in stearolic acid molecule increased, its melting points was lowered indicating the solid bulk phase of stearolic acid became thermally unstable, while its monolayer stability evaluated by π_e at 25 °C, dramatically increased and subsequently leveled off above a certain fluorine content. Under this condition, the replacement of at least five hydrogen atoms at the terminal hydrophobic segment in stearolic acid molecule by fluorine atoms (CF₃CF₂ group) was required to alter the bulk property of stearolic acid and exhibit the stabilization of monolayers, whereas further fluorination of stearolic acid had a minor effect on the monolayer stability. This behavior suggests the terminal fluorinated hydrophobic segment exclusively controls the interfacial stability of fatty acid monolayers.     

Analysis on heat stress-induced hyperphosphorylation of stathmin at serine 37 in Jurkat cells by means of two-dimensional gel electrophoresis and tandem mass spectrometry

Two-dimensional gel electrophoresis (2-DE) and tandem mass spectrometry were successfully used for determination of a phosphorylation site of stathmin induced by heat stress to Jurkat cells of a human T lymphoblastic cell line. The cells were incubated for 30 min at 41 degrees C up to 45 degrees C in a serum free 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) buffered culture medium. The intracellular soluble proteins were separated by 2-DE, and some of the proteins increased their abundance by heat stress. Those proteins were identified to be calmodulin, protein kinase C substrate, thymosin beta-4 and F-actin capping protein beta-subunit by peptide mass fingerprinting (PMF) with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). On the contrary, protein phosphatase 2C gamma-isoform, nucleophosmin, translationally controlled tumor protein, Rho GDP-dissociation inhibitor-1, eukaryotic translation initiation factors 5A and 3A subunit 2, ubiquitin-like protein SMT 3B and chloride intracellular channel protein-1 were decreased their abundance. A protein spot of M(r) 18,000 and pI 5.9 was markedly increased at temperatures higher than 43 degrees C at which the cells were led to apoptosis. The spot was identified to be stathmin of a signal relay protein which has a function of sequestering microtubule. MALDI-quadrupole ion trap (QIT)-TOF-MS/MS and immunoblotting with a monoclonal antibody specific for a phosphorylation site of stathmin showed that the spot was a phosphorylated stathmin at serine 37 (Ser 37). The phosphorylation was suppressed by treatment of cells with olomoucine of an inhibitor specific for cyclin dependent kinase (Cdk-1). These results strongly suggest that heat stress activates Cdk-1 which phosphorylates Ser 37 on the stathmin molecule. The phosphorylation may cause the functional loss of stathmin for dynamic microtubule assembly and leads Jurkat cells to cell cycle arrest and apoptosis.