Block copolymer micelles with dye loaded on their shells or cores

We prepared reversible micelles with dye loaded on the shells or cores by ion exchange. A poly(4-styrylmethyl triphenylphosphonium chloride)-block-polystyrene diblock copolymer prepared from poly(4-vinylbenzylchloride)-block-polystyrene and triphenylphosphine was reacted with methyl orange in a mixed solvent of benzene and acetonitrile to produce poly[4-styrylmethyl triphenylphosphonium 4-(4-dimethylamino)phenylazobenzenesulfonate]-block-polystyrene. The loading of the methyl orange on the micellar shells or cores was dependent on the composition of the mixed solvents. Dynamic light scattering demonstrated that the loading of the dye on the cores significantly expanded the micelles when compared to that on the shells. The loading of the dye on the cores shifted the UV wavelength of the methyl orange, whereas that on the shells produced no changes in the UV wavelength. Transmission electron microscopy confirmed the formation of the spherical micelles.     

Matrix-assisted laser desorption/ionization quadrupole ion trap time-of-flight (MALDI-QIT-TOF)-based imaging mass spectrometry reveals a layered distribution of phospholipid molecular species in the mouse retina

We recently developed a matrix-assisted laser desorption/ionization quadrupole ion trap time-of-flight (MALDI-QIT-TOF)-based imaging mass spectrometry (IMS) system. This system enables us to perform structural analyses using tandem mass spectrometry (MS/MS), as well as to visualize phospholipids and peptides in frozen sections. In the retina, phototransduction is regulated by the light-sensitive interaction between visual pigment-coupled receptor proteins, such as rhodopsin, and G proteins, such as transducin. There are some reports that the conformation of rhodopsin is influenced by the composition of phospholipids in the lipid bilayer membrane. However, these results were based on in vitro experiments and have not been analyzed in vivo. In this study, we visualized and identified phospholipids in mouse retinal sections with the MALDI-QIT-TOF-based IMS system. From a spectrum obtained by raster-scanned analysis of the sections, ions with high signal intensities were selected and analyzed by MS/MS. As a result, sixteen ions were identified as being from four diacyl-phosphatidylcholine (PC) species, i.e., PC (16:0/16:0), PC (16:0/18:1), PC (16:0/22:6), and PC (18:0/22:6), with different ion forms. The ion images revealed different distributions on the retinal sections: PC (16:0/18:1) was distributed in the inner nuclear layer and outer plexiform layer, PC (16:0/16:0) in the outer nuclear layer and inner segment, and both PC (16:0/22:6) and PC (18:0/22:6) in the outer segment and pigment epithelium. In conclusion, our in vivo IMS analyses demonstrated a three-zone distribution of PC species on the retinal sections. This approach may be useful for analyzing lipid changes and their contribution to phototransduction in the retina.     

Characterizations of linear Volterra integral equations with nonnegative kernels

We first introduce the notion of positive linear Volterra integral equations. Then, we offer a criterion for positive equations in terms of the resolvent. In particular, equations with nonnegative kernels are positive. Next, we obtain a variant of the Paley-Wiener theorem for equations of this class and its extension to perturbed equations. Furthermore, we get a Perron-Frobenius type theorem for linear Volterra integral equations with nonnegative kernels. Finally, we give a criterion for positivity of the initial function semigroup of linear Volterra integral equations and provide a necessary and sufficient condition for exponential stability of the semigroups.     

Surface and dynamic structures of bacteriorhodopsin in a 2D crystal, a distorted or disrupted lattice, as revealed by site-directed solid-state 13C NMR

The 3D structure of bacteriorhodopsin (bR) obtained by X-ray diffraction or cryo-electron microscope studies is not always sufficient for a picture at ambient temperature where dynamic behavior is exhibited. For this reason, a site-directed solid-state 13C NMR study of fully hydrated bR from purple membrane (PM), or a distorted or disrupted lattice, is very valuable in order to gain insight into the dynamic picture. This includes the surface structure, at the physiologically important ambient temperature. Almost all of the 13C NMR signals are available from [3-13C]Ala or [1-13C]Val-labeled bR from PM, although the 13C NMR signals from the surface areas, including loops and transmembrane alpha-helices near the surface (8.7 angstroms depth), are suppressed for preparations labeled with [1-13C]Gly, Ala, Leu, Phe, Tyr, etc. due to a failure of the attempted peak-narrowing by making use of the interfered frequency of the frequency of fluctuation motions with the frequency of magic angle spinning. In particular, the C-terminal residues, 226-235, are present as the C-terminal alpha-helix which is held together with the nearby loops to form a surface complex, although the remaining C-terminal residues undergo isotropic motion even in a 2D crystalline lattice (PM) under physiological conditions. Surprisingly, the 13C NMR signals could be further suppressed even from [3-13C]Ala- or [1-13C]Val-bR, due to the acquired fluctuation motions with correlation times in the order of 10(-4) to 10(-5) s, when the 2D lattice structure is instantaneously distorted or completely disrupted, either in photo-intermediate, removed retinal or when embedded in the lipid bilayers.     

Synthesis of oligomeric poly[(1, 2-propanediamine)-alt-(oxalic acid)] and anomalous proton conductivities of the thin films

New proton-conductive polyamide oligomers, oligomeric poly[(1, 2-propanediamine)-alt-(oxalic acid)], were synthesized to investigate the proton transport properties of bulk and thin films. The obtained oligomers were characterized by the X-ray diffraction, FT-IR spectra, ¹H NMR, Matrix Assisted Laser Desorption/Ionization Time of Flight (MALDI-TOF) mass spectrum, and electrical conductivity measurements. The bulk proton conductivity is 3.0 × 10^? 4 S cm^? 1 at the relative humidity (RH) of 80%. The proton conductivity of thin film is relatively higher than that of bulk sample. Thickness dependence of the proton conductivity was observed in these thin films. The maximum proton conductivity of the thin film is 4.0 × 10^? 3 S cm^? 1 at the relative humidity (RH) of 80%, which is higher one order magnitude than that of the bulk sample. The activation energies of bulk and 200 nm thick film are 1.0 and 0.69 eV at the RH of 60%, respectively.     

Total Synthesis and Biological Evaluation of (+)‐Neopeltolide and Its Analogues

The stereocontrolled total synthesis of the originally proposed ( 1 ) and correct ( 2 ) structures of (+)‐neopeltolide, a novel marine macrolide natural product with highly potent antiproliferative activity against several cancer cell lines as well as potent antifungal activity, has been achieved by exploiting a newly developed Suzuki–Miyaura coupling/ring‐closing metathesis strategy. Alkylborate 44 , which was generated in situ from iodide 34 , was coupled with enol phosphate 8 by a Suzuki–Miyaura coupling. Ring‐closing metathesis of the derived diene 45 followed by stereoselective hydrogenation afforded tetrahydropyran 47 as a single stereoisomer in high overall yield from 34 . Our convergent strategy enabled us to construct the 14‐membered macrolactone core structure of 2 in a rapid and efficient manner. Total synthesis and biological evaluation of synthetic intermediates and designed synthetic analogues, performed to establish the structure–activity relationships of 2 , led to the discovery of a structurally simple yet potent cytotoxic analogue, 9‐demethylneopeltolide ( 54 ).     

On the Lp–Lq maximal regularity for the linear thermoelastic plate equation in a bounded domain

This paper is concerned with the thermoelastic plate equations in a domain Ω: subject to the boundary condition: u|=D_νu|=θ|=0 and initial condition: (u, u_t, θ)|_t=0=(u₀, v₀, θ₀). Here, Ω is a bounded domain in ?ⁿ(n≧2). We assume that the boundary ?Ω of Ω is a C⁴ hypersurface. We obtain an L_p–L_q maximal regularity theorem. Copyright © 2008 John Wiley & Sons, Ltd.