Effects of lysozyme and bovine serum albumin on membrane characteristics of dipalmitoylphosphatidylglycerol liposomes

The effects of adsorption of two kinds of proteins on the membrane characteristics of liposomes were examined at pH 7.4 in terms of adsorption amounts of proteins on liposomes, penetrations of proteins into liposomal bilayer membranes, phase transition temperature, microviscosity and permeability of liposomal bilayer membranes, using positively charged lysozyme (LSZ) and negatively charged bovine serum albumin (BSA) as proteins and negatively charged L-alpha-dipalmitoylphosphatidylglycerol (DPPG) liposomes. The saturated adsorption amount of LSZ was 720 g per mol of liposomal DPPG, while that of BSA was 44 g per mol of liposomal DPPG. The penetration of LSZ into DPPG lipid membranes was greater than that of BSA. The microviscosity in the hydrophobic region of liposomal bilayer membranes increased due to adsorption (penetration) of LSZ or BSA, while the permeability of liposomal bilayer membranes increased. The gel-liquid crystalline phase transition temperature of liposomal bilayer membranes was not affected by adsorption of LSZ or BSA, while the DSC peak area (heat of phase transition) decreased with increasing adsorption amount of LSZ or BSA. It is suggested that boundary DPPG makes no contribution to the phase transition and that boundary DPPG and bulk DPPG are in the phase-separated state, thereby increasing the permeability of liposomal bilayer membranes through adsorption of LSZ or BSA. A possible schematic model for the adsorption of LSZ or BSA on DPPG liposomes was proposed.     

Diffusion Approximations for Queues with Markovian Bases

Consider a base family of state-dependent queues whose queue-length process can be formulated by a continuous-time Markov process. In this paper, we develop a piecewise-constant diffusion model for an enlarged family of queues, each of whose members has arrival and service distributions generalized from those of the associated queue in the base. The enlarged family covers many standard queueing systems with finite waiting spaces, finite sources and so on. We provide a unifying explicit expression for the steady-state distribution, which is consistent with the exact result when the arrival and service distributions are those of the base. The model is an extension as well as a refinement of the M/M/s-consistent diffusion model for the GI/G/s queue developed by Kimura [13] where the base was a birth-and-death process. As a typical base, we still focus on birth-and-death processes, but we also consider a class of continuous-time Markov processes with lower-triangular infinitesimal generators.     

A consistent diffusion approximation for finite-capacity multiserver queues

A diffusion approximation is developed for general multiserver queues with finite waiting spaces, which are typical models of manufacturing systems as well as computer and communication systems. The model is the standard GI/G/s/s + r queue with s identical servers in parallel, r extra waiting spaces, and the first-come, first-served discipline. The main focus is on the steady-state distribution of the number of customers in the system. The process of the number of customers is approximated by a time-homogeneous diffusion process on a closed interval in the nonnegative real line. A conservation law plus some heuristics standing on solid theoretical ground generate approximation formulas for the steady-state distribution and other congestion measures. These formulas are consistent with the exact results for the M/G/s/s and M/M/s/s + r queues. The accuracy of approximations for principal congestion measures are numerically examined for some particular cases.     

Transmission positron microscopes

Immediate and near-future plans for transmission positron microscopes being built at KEK, Tsukuba, Japan, are described. The characteristic feature of this project is remolding a commercial electron microscope to a positron microscope. A point source of electrons kept at a negative high voltage is changed to a point source of positrons kept at a high positive voltage. Positional resolution of transmission microscopes should be theoretically the same as electron microscopes. Positron microscopes utilizing trapping of positrons have always positional ambiguity due to the diffusion of positrons.     

Design and synthesis of chiral poly(binaphthyl salen zinc complex) and application of the asymmetric field based on its helical conformation to a catalytic asymmetric reaction

According to a rational design of helices (i.e., fusing C₂ chiral binaphthyl units and metallosalen complexes inevitably results in the formation of helical polymers), chiral poly(binaphthyl salen zinc complex)es ( 3 -Zn) were synthesized from an (R)-3,3′-diformylbinaphthol derivative, α,ω-diamines, and zinc acetate or diethylzinc. Their helical structures were well supported by their infrared, ultraviolet, and circular dichroism spectra, in addition to MM calculations and a CPK model study. The catalysis of 3 -Zn during the asymmetric addition of diethylzinc to aldehydes was investigated. In the presence of 5 unit mol % 3 -Zn, diethylzinc reacted with benzaldehyde to yield 1-phenyl-1-propanol in high yields (∼100%) and with high enantioselectivity (∼95%). The asymmetric yield of 1-phenyl-1-propanol increased significantly as the temperature was lowered, whereas both the asymmetric yield and the absolute configuration were drastically changed as the structure of the diamine unit of 3 -Zn was varied. Several aromatic aldehydes were converted into their corresponding alcohols with high enantioselectivity. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4693–4703, 2004     

Turn‐On Fluorogenic and Chromogenic Detection of Small Aromatic Hydrocarbon Vapors by a Porous Supramolecular Host

Benzene, toluene, ethylbenzene, the isomers of xylene, and trimethylbenzene are harmful volatile organic compounds and pose risks to human health and the environment. However, there are currently no effective chemosensors for vapors of these compounds. A porous supramolecular host for turn‐on fluorogenic and chromogenic detection of the vapors of small aromatic hydrocarbons is presented. The host was constructed from a naphthalenediimide derivative that was supramolecularly connected to tris(pentafluorophenyl)borane. The amorphous powder form of the host allowed for effective accommodation of vapors of small aromatic hydrocarbons, resulting in a guest‐dependent fluorescence emission. Increases in the fluorescence yield of 76‐, 46‐, and 37‐fold were observed with toluene, benzene, and m‐xylene, respectively. Negligible responses were obtained with common organic solvents. This simple supramolecular host could be applied as a useful sensor of small aromatic hydrocarbon vapors.     

Selective Targeting of the KRAS Codon 12 Mutation Sequence by Pyrrole–Imidazole Polyamide seco‐CBI Conjugates

Mutation of KRAS is a key step in many cancers. Mutations occur most frequently at codon 12, but the targeting of KRAS is notoriously difficult. We recently demonstrated selective reduction in the volume of tumors harboring the KRAS codon 12 mutation in a mouse model by using an alkylating hairpin N‐methylpyrrole–N‐methylimidazole polyamide seco‐1,2,9,9a‐tetrahydrocyclopropa[1,2‐c]benz[1,2‐e]indol‐4‐one conjugate (conjugate 4 ) designed to target the KRAS codon 12 mutation sequence. Herein, we have compared the alkylating activity of 4 against three other conjugates that were also designed to target the KRAS codon 12 mutation sequence. Conjugate 4 displayed greater affinity for the G12D mutation sequence than for the G12V sequence. A computer‐minimized model suggested that conjugate 4 could bind more efficiently to the G12D match sequence than to a one‐base‐pair mismatch sequence. Conjugate 4 was modified for next‐generation sequencing. Bind‐n‐Seq analysis supported the evidence showing that conjugate 4 could target the G12D mutation sequence with exceptionally high affinity and the G12V mutation sequence with much higher affinity than that for the wild‐type sequence.     

Global stability of nonresident computer virus models

In this paper, applying Lyapunov functional techniques to nonresident computer virus models, we establish global dynamics of the model whose threshold parameter is the basic reproduction number R₀ such that the virus‐free equilibrium is globally asymptotically stable when R₀ ≤ 1, and the infected equilibrium is globally asymptotically stable when R₀ > 1 under the same restricted condition on a parameter, which appeared in the literature on delayed susceptible‐infected‐recovered‐susceptible (SIRS) epidemic models. We use new techniques on permanence and global stability of this model for R₀ > 1. Copyright © 2014 John Wiley & Sons, Ltd.     

9,9‐Diaryl‐4,5‐diazafluorene‐based Cardo polymer; Synthesis and characteristic properties

To open out new aspects of 9,9‐diarylfluorene (DAF)‐based polymers with high performances, 9,9‐(4‐hydroxyphenyl)‐4,5‐diazafluorene ( N‐BPF ) was designed as a new cardo structure and the properties of poly(ether ketone)s ( N‐PEKs ) containing N‐BPF skeletons were examined in detail. N‐PEKs were synthesized in high yields via polycondensation of N‐BPF with difluoroarenes. N‐PEKs showed cardo polymer‐specific properties such as high thermal stability and high solubility in organic solvents. The addition of p‐toluenesulfonic acid (TsOH) to N‐PEK resulted in the formation of network polymer based on interchain hydrogen bonds. It turned out that the films of network polymer are flexible and transparent and exhibit high refractive index and low birefringence. The effects of feed ratio of TsOH to N‐PEK were also evaluated on the mechanical properties of network polymer. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4541–4549