Lateral transport of domains in anionic lipid bilayer membranes under DC electric fields: A coarse-grained molecular dynamics study

Dynamic lateral transport of lipids, proteins, and self-assembled structures in biomembranes plays crucial roles in diverse cellular processes. In this study, we perform a coarse-grained molecular dynamics simulation on a vesicle composed of a binary mixture of neutral and anionic lipids to investigate the lateral transport of individual lipid molecules and the self-assembled lipid domains upon an applied direct current (DC) electric field. Under the potential force of the electric field, a phase-separated domain rich in the anionic lipids is trapped in the opposite direction of the electric field. The subsequent reversal of the electric field induces the unidirectional domain motion. During the domain motion, the domain size remains constant, but a considerable amount of the anionic lipids is exchanged between the anionic-lipid-rich domain and the surrounding bulk. While the speed of the domain motion (collective lipid motion) shows a significant positive correlation with the electric field strength, the exchange of anionic lipids between the domain and bulk (individual lipid motion) exhibits no clear correlation with the field strength. The mean velocity field of the lipids surrounding the domain displays a two-dimensional (2D) source dipole. We revealed that the balance between the potential force of the applied electric field and the quasi-2D hydrodynamic frictional force well explains the dependence of the domain motions on the electric-field strengths. The present results provide insight into the hierarchical dynamic responses of self-assembled lipid domains to the applied electric field and contribute to controlling the lateral transportation of lipids and membrane inclusions.Comment: 9 pages, 6 figure

Coupling between pore formation and phase separation in charged lipid membranes

We investigated the effect of charge on the membrane morphology of giant unilamellar vesicles (GUVs) composed of various mixtures containing charged lipids. We observed the membrane morphologies by fluorescent and confocal laser microscopy in lipid mixtures consisting of a neutral unsaturated lipid [dioleoylphosphatidylcholine (DOPC)], a neutral saturated lipid [dipalmitoylphosphatidylcholine (DPPC)], a charged unsaturated lipid [dioleoylphosphatidylglycerol (DOPG$^{\scriptsize{(-)}}$)], a charged saturated lipid [dipalmitoylphosphatidylglycerol (DPPG$^{\scriptsize{(-)}}$)], and cholesterol (Chol). In binary mixtures of neutral DOPC/DPPC and charged DOPC/DPPG$^{\scriptsize{(-)}}$, spherical vesicles were formed. On the other hand, pore formation was often observed with GUVs consisting of DOPG$^{\scriptsize{(-)}}$ and DPPC. In a DPPC/DPPG$^{\scriptsize{(-)}}$/Chol ternary mixture, pore-formed vesicles were also frequently observed. The percentage of pore-formed vesicles increased with the DPPG$^{\scriptsize{(-)}}$ concentration. Moreover, when the head group charges of charged lipids were screened by the addition of salt, pore-formed vesicles were suppressed in both the binary and ternary charged lipid mixtures. We discuss the mechanisms of pore formation in charged lipid mixtures and the relationship between phase separation and the membrane morphology. Finally, we reproduce the results seen in experimental systems by using coarse-grained molecular dynamics simulations.Comment: 34 pages, 10 figure

マイクロレオロジー計測手法の開発と超高精度流体物性測定に関する研究

学位の種別:課程博士University of Tokyo(東京大学

Demonstration of unconditional one-way quantum computations for continuous variables

Quantum computing promises to exploit the laws of quantum mechanics for processing information in ways fundamentally different from today's classical computers, leading to unprecedented efficiency. One-way quantum computation, sometimes referred to as the cluster model of quantum computation, is a very promising approach to fulfil the capabilities of quantum information processing. The cluster model is realizable through measurements on a highly entangled cluster state with no need for controlled unitary evolutions. Here we demonstrate unconditional one-way quantum computation experiments for continuous variables using a linear cluster state of four entangled optical modes. We implement an important set of quantum operations, linear transformations, in the optical phase space through one-way computation. Though not sufficient, these are necessary for universal quantum computation over continuous variables, and in our scheme, in principle, any such linear transformation can be unconditionally and deterministically applied to arbitrary single-mode quantum states.Comment: 9 pages, 3 figure

Delayed enhancement on cardiac magnetic resonance imaging is a poor prognostic factor in patients with cardiac sarcoidosis

AbstractBackgroundPredictors of ventricular arrhythmias (VA) in patients with cardiac sarcoidosis (CS) remain unclear.Methods and resultsWe examined 61 consecutive CS patients who were admitted to our hospital from April 2002 to March 2012 with a mean follow-up period of 45±31 months for the relationship between delayed enhancement on cardiac magnetic resonance imaging (DE-MRI) and VA or a composite endpoint, including VA, heart failure hospitalization, and cardiovascular mortality. Although there was no significant difference in baseline clinical characteristics between patients with VA and those without it, the former group was characterized as compared with the latter by lower left ventricular (LV) ejection fraction (p<0.05), larger LV systolic/diastolic dimensions (both p<0.05), and a significant association with DE-MRI (p<0.05). Furthermore, the patients with DE-MRI (n=26), as compared with those without it (n=11), had a significantly higher composite endpoint event rate (41% vs. 0%, p<0.05) and a trend toward higher VA (29% vs. 0%, p=0.12). Univariate analysis also showed that impaired LV systolic function was significantly associated with composite events on follow-up.ConclusionsThese results indicate that the presence of DE-MRI is a significant predictor of VA events and poor outcome in CS patients

Adamantinoma of the Tibia. - Report of a Case with Findings of Ultrastructural and Immunohistochemical Studies,

A case of tibial adamantinoma in a one-year and ten-month old girl is reported. She had gait disturbance and her roentogenogram showed a well circumscribed radiolucent area in the tibia. Light microscopic examination showed the epithelial component of nests and pseudoglandular arrays in the loose fibrous connective tissue. We finally diagnsed the tumor as adamantinoma of the tibia based on roentogenographical and histological findings. Moreover, the nature of the neoplastic cells was studied by the immunohistochemical and electron microscopic methods. The adamantinoma is regarded as a unique neoplasm capable of differen - tiating into epithelial elements as well as mesenchymal ones . Detection of epithelial component is important to differentiate from similar disorders. The fibrous dysplasia- like lesion in stroma is interpreted as a part of the spectrum of mesenchymal differentiation

Papillary Adenoma of Type 2 Pneumocytes in the Lung

Recent developments in radiologic imaging and thoracoscopic excision techniques have increased the possibility of encountering small, benign or premalignant tumors in the lung. In this report, we describe a rare case of papillary adenoma of type 2 pneumocytes. A 51-year-old Japanese woman was hospitalized following a traffic accident. Helical CT scan of the chest incidentally detected a nodular ground-glass opacity measuring 8 mm in diameter at the subpleural region of left lung. The nodule was thoracoscopically resected out. Light microscopic examination demonstrated a noninfiltrative tumor consisting of cuboidal cells covering fibrovascular cores; thus, the tumor exhibited a branching papillary appearance. The cuboidal cells showed little nuclear atypia. Mitotic figures, necrosis, and intercellular mucin were absent. The cytoplasm was immunohistochemically stained for surfactant apoprotein A and cytokeratin, though not for carcinoembryonic antigen (CEA), epithelial membrane antigen (EMA), or S100 protein. The morphologic and immunohistochemical findings fulfilled the criteria of papillary adenoma of type 2 pneumocytes