抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Synthesis and surface engineering of iron oxide nanoparticles for biomedical applications

1. Introduction 20642. Synthesis of Magnetic Nanoparticles 20662.1. Classical Synthesis by Coprecipitation 20662.2. Reactions in Constrained Environments 20682.3. Hydrothermal and High-TemperatureReactions20692.4. Sol-Gel Reactions 20702.5. Polyol Methods 20712.6. Flow Injection Syntheses 20712.7. Electrochemical Methods 20712.8. Aerosol/Vapor Methods 20712.9. Sonolysis 20723. Stabilization of Magnetic Particles 20723.1. Monomeric Stabilizers 20723.1.1. Carboxylates 20733.1.2. Phosphates 20733.2. Inorganic Materials 20733.2.1. Silica 20733.2.2. Gold 20743.3. Polymer Stabilizers 20743.3.1. Dextran 20743.3.2. Polyethylene Glycol (PEG) 20753.3.3. Polyvinyl Alcohol (PVA) 20753.3.4. Alginate 20753.3.5. Chitosan 20753.3.6. Other Polymers 20753.4. Other Strategies for Stabilization 20764. Methods of Vectorization of the Particles 20765. Structural and Physicochemical Characterization 20785.1. Size, Polydispersity, Shape, and SurfaceCharacterization20795.2. Structure of Ferro- or FerrimagneticNanoparticles20805.2.1. Ferro- and Ferrimagnetic Nanoparticles 20805.3. Use of Nanoparticles as Contrast Agents forMRI20825.3.1. High Anisotropy Model 20845.3.2. Small Crystal and Low Anisotropy EnergyLimit20855.3.3. Practical Interests of Magnetic NuclearRelaxation for the Characterization ofSuperparamagnetic Colloid20855.3.4. Relaxation of Agglomerated Systems 20856. Applications 20866.1. MRI: Cellular Labeling, Molecular Imaging(Inﬂammation, Apoptose, etc.)20866.2.

Magnetic Iron Oxide Nanoparticles: Synthesis, Stabilization, Vectorization, Physicochemical Characterizations, and Biological Applications

Core/Shell Nanoparticles: Classes, Properties, Synthesis Mechanisms, Characterization, and Applications

In this chapter, we will restrict our attention to the ferrites and a few other closely related materials. The great interest in ferrites stems from their unique combination of a spontaneous magnetization and a high electrical resistivity. The observed magnetization results from the difference in the magnetizations of two non-equivalent sub-lattices of the magnetic ions in the crystal structure. Materials of this type should strictly be designated as “ferrimagnetic” and in some respects are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present. We shall not adhere to this special nomenclature except to emphasize effects, which are due to the existence of the sub-lattices.

Ferromagnetic materials

The first experimental evidence of a ``negative-viscosity'' effect in a magnetic fluid is presented here. In a Poiseuille flow, a constant magnetic field balances vorticity and impedes the rotation of individual magnetic particles. Conversely, an alternating magnetic field helps vorticity and favors this rotation: The magnetic energy is partially transformed into the angular momentum of the particles, which in turn is converted into a hydrodynamic motion of the fluid. It manifests itself in a decrease of the total viscosity: Its rotational part becomes negative. The theory developed here corroborates the experimental results.

"Negative-viscosity" effect in a magnetic fluid.

Novel magnetic nanocomposites (see Figure) are obtained by the self-assembly in water of polypeptide-based diblock copolymers of polybutadiene-block-poly(glutamic acid) combined with hydrophobically modified gamma-Fe2O3 nanoparticles. These hybrid supramolecular objects are either filled micelles (three dimensional) or hollow vesicles with a magnetic membrane (two dimensional), the deformation of which, under an applied magnetic field, has been evidenced.

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Magnetic Nanocomposite Micelles and Vesicles

In this paper, we compare the structure and the phase behavior of two kinds of magnetic fluids, also called ferrofluids. They are constituted of the same maghemite particles, the diameters of which lie around 8 nm, dispersed either in water or in cyclohexane. Both systems are constructed to get the same interparticle interactions and differ only through the nature of the repulsion. Repulsion is either electrostatic, due to the charges of citrate molecules adsorbed on the particles surface in water, or steric, due to the alkyl chains of adsorbed surfactants in cyclohexane. Small angle neutron scattering (SANS) experiments show that both systems are highly repulsive and that the structure factors are very similar. This is confirmed by stability measurements: the samples are stable if temperature is decreased and if a magnetic field is applied. If the repulsion is decreased by the addition of electrolyte in water or bad solvent in cyclohexane, a gas–liquid-like transition is observed in both systems. However, the standard electrostatic potential (Derjaguin–Landau–Verwey–Overbeek potential) fails to describe the electrostatic repulsion in the aqueous ferrofluid while the behavior of this system is very similar to the behavior of the sterically stabilized ferrofluid. This underestimate of the electrostatic repulsion is probably due to the finite size effects of the trivalent ions. The striking similarities in the structure and the behavior of both kinds of dispersions, despite their chemical differences, seems to be related to the presence, in both cases, of the adsorbed surface species which ensure the repulsion between particles. Moreover, this repulsion may be described by an effective Yukawa potential very similar in range and intensity in both systems.

Structural analogy between aqueous and oily magnetic fluids

In this paper we investigate the superspin glass behavior of a concentrated assembly of interacting maghemite nanoparticles and compare it to that of canonical atomic spin glass systems ac versus temperature and frequency measurements show evidence of a superspin glass transition taking place at low temperature In order to fully characterize the superspin glass phase, the aging behavior of both the thermo-remanent magnetization (TRM) and ac susceptibility has been investigated It is shown that the scaling laws obeyed by superspin glasses and atomic spin glasses are essentially the same, after subtraction of a superparamagnetic contribution from the superspin glass response functions Finally, we discuss a possible origin of this superparamagnetic contribution in terms of dilute spin glass models

Régine Perzynski

Papers

"Negative-viscosity" effect in a magnetic fluid.

Magnetic Nanocomposite Micelles and Vesicles

Structural analogy between aqueous and oily magnetic fluids

Spin-glass behavior in an interacting γ -Fe 2 O 3 nanoparticle system

Magnetization temperature dependence and freezing of surface spins in magnetic fluids based on ferrite nanoparticles