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

Worldwide commercial interest in carbon nanotubes (CNTs) is reflected in a production capacity that presently exceeds several thousand tons per year. Currently, bulk CNT powders are incorporated in diverse commercial products ranging from rechargeable batteries, automotive parts, and sporting goods to boat hulls and water filters. Advances in CNT synthesis, purification, and chemical modification are enabling integration of CNTs in thin-film electronics and large-area coatings. Although not yet providing compelling mechanical strength or electrical or thermal conductivities for many applications, CNT yarns and sheets already have promising performance for applications including supercapacitors, actuators, and lightweight electromagnetic shields.

/pdf/carbon-nanotubes-present-and-future-commercial-applications-1nhq3xy4hh.pdf

Carbon Nanotubes: Present and Future Commercial Applications

Detection of chemical and biological agents plays a fundamental role in biomedical, forensic and environmental sciences1–4 as well as in anti bioterrorism applications.5–7 The development of highly sensitive, cost effective, miniature sensors is therefore in high demand which requires advanced technology coupled with fundamental knowledge in chemistry, biology and material sciences.8–13

In general, sensors feature two functional components: a recognition element to provide selective/specific binding with the target analytes and a transducer component for signaling the binding event. An efficient sensor relies heavily on these two essential components for the recognition process in terms of response time, signal to noise (S/N) ratio, selectivity and limits of detection (LOD).14,15 Therefore, designing sensors with higher efficacy depends on the development of novel materials to improve both the recognition and transduction processes. Nanomaterials feature unique physicochemical properties that can be of great utility in creating new recognition and transduction processes for chemical and biological sensors15–27 as well as improving the S/N ratio by miniaturization of the sensor elements.28

Gold nanoparticles (AuNPs) possess distinct physical and chemical attributes that make them excellent scaffolds for the fabrication of novel chemical and biological sensors (Figure 1).29–36 First, AuNPs can be synthesized in a straightforward manner and can be made highly stable. Second, they possess unique optoelectronic properties. Third, they provide high surface-to-volume ratio with excellent biocompatibility using appropriate ligands.30 Fourth, these properties of AuNPs can be readily tuned varying their size, shape and the surrounding chemical environment. For example, the binding event between recognition element and the analyte can alter physicochemical properties of transducer AuNPs, such as plasmon resonance absorption, conductivity, redox behavior, etc. that in turn can generate a detectable response signal. Finally, AuNPs offer a suitable platform for multi-functionalization with a wide range of organic or biological ligands for the selective binding and detection of small molecules and biological targets.30–32,36 Each of these attributes of AuNPs has allowed researchers to develop novel sensing strategies with improved sensitivity, stability and selectivity. In the last decade of research, the advent of AuNP as a sensory element provided us a broad spectrum of innovative approaches for the detection of metal ions, small molecules, proteins, nucleic acids, malignant cells, etc. in a rapid and efficient manner.37



Figure 1

Physical properties of AuNPs and schematic illustration of an AuNP-based detection system.



In this current review, we have highlighted the several synthetic routes and properties of AuNPs that make them excellent probes for different sensing strategies. Furthermore, we will discuss various sensing strategies and major advances in the last two decades of research utilizing AuNPs in the detection of variety of target analytes including metal ions, organic molecules, proteins, nucleic acids, and microorganisms.

/pdf/gold-nanoparticles-in-chemical-and-biological-sensing-5e2qojkdzn.pdf

Gold nanoparticles in chemical and biological sensing.

Suitable labels are at the core of Luminescence and fluorescence imaging and sensing. One of the most exciting, yet also controversial, advances in label technology is the emerging development of quantum dots (QDs)--inorganic nanocrystals with unique optical and chemical properties but complicated surface chemistry--as in vitro and in vivo fluorophores. Here we compare and evaluate the differences in physicochemical properties of common fluorescent labels, focusing on traditional organic dyes and QDs. Our aim is to provide a better understanding of the advantages and limitations of both classes of chromophores, to facilitate label choice and to address future challenges in the rational design and manipulation of QD labels.

/pdf/quantum-dots-versus-organic-dyes-as-fluorescent-labels-50cbzj94q6.pdf

Quantum dots versus organic dyes as fluorescent labels

Colloidal metal nanoparticles are emerging as key materials for catalysis, plasmonics, sensing, and spectroscopy. Within these applications, control of nanoparticle shape lends increasing functionality and selectivity. Shape-controlled nanocrystals possess well-defined surfaces and morphologies because their nucleation and growth are controlled at the atomic level. An overall picture of shaped metal particles is presented, with a particular focus on solution-based syntheses for the noble metals. General strategies for synthetic control are discussed, emphasizing key factors that result in anisotropic, nonspherical growth such as crystallographically selective adsorbates and seeding processes.

/pdf/shape-control-of-colloidal-metal-nanocrystals-33lclmees7.pdf

Shape Control of Colloidal Metal Nanocrystals

The creation of nanoscale materials for advanced structures has led to a growing interest in the area of biomineralization. Numerous microorganisms are capable of synthesizing inorganic-based structures. For example, diatoms use amorphous silica as a structural material, bacteria synthesize magnetite (Fe3O4) particles and form silver nanoparticles, and yeast cells synthesize cadmium sulphide nanoparticles. The process of biomineralization and assembly of nanostructured inorganic components into hierarchical structures has led to the development of a variety of approaches that mimic the recognition and nucleation capabilities found in biomolecules for inorganic material synthesis. In this report, we describe the in vitro biosynthesis of silver nanoparticles using silver-binding peptides identified from a combinatorial phage display peptide library.

Biomimetic synthesis and patterning of silver nanoparticles

The ability of gecko lizards to adhere to a vertical solid surface comes from their remarkable feet with aligned microscopic elastic hairs. By using carbon nanotube arrays that are dominated by a straight body segment but with curly entangled top, we have created gecko-foot-mimetic dry adhesives that show macroscopic adhesive forces of approximately 100 newtons per square centimeter, almost 10 times that of a gecko foot, and a much stronger shear adhesion force than the normal adhesion force, to ensure strong binding along the shear direction and easy lifting in the normal direction. This anisotropic force distribution is due to the shear-induced alignments of the curly segments of the nanotubes. The mimetic adhesives can be alternatively binding-on and lifting-off over various substrates for simulating the walking of a living gecko.

https://science.sciencemag.org/content/sci/322/5899/238.full.pdf

Carbon nanotube arrays with strong shear binding-on and easy normal lifting-off.

Robust immobilization techniques that preserve the activity of biomolecules have many potential applications. Silicates, primarily in the form of sol-gel composites or functionalized mesoporous silica, have been used to encapsulate a wide variety of biomolecules but the harsh conditions required for chemical synthesis limit their applicability. Silaffin polypeptides from diatoms catalyze the formation of silica in vitro at neutral pH and ambient temperature and pressure. Here we show that butyrylcholinesterase entrapped during the precipitation of silica nanospheres retained all of its activity. Ninety percent of the soluble enzyme was immobilized, and the immobilized enzyme was substantially more stable than the free enzyme. The mechanical properties of silica nanospheres facilitated application in a flow-through reactor. The use of biosilica for enzyme immobilization combines the excellent support properties of a silica matrix with a benign immobilization method that retains enzyme activity.

Enzyme immobilization in a biomimetic silica support.

In this work, the suitability of imidazolium-based ionic liquid solvents is investigated for the dissolution and regeneration of silkworm (Bombyx mori) silk. Within an ionic liquid the anion plays a larger role in dictating the ultimate solubility of the silk. The dissolution of the silk in the ionic liquid is confirmed using wide-angle X-ray scattering. The dissolved silk is also processed into 100 μm-thick, two-dimensional films, and the structure of these films is examined. The rinse solvent, acetonitrile or methanol, has a profound impact on both the topography of the films and the secondary structure of the silk protein. The image depicts a silkworm cocoon dissolved in 1-butyl-3-methylimidazolium chloride and then regenerated as a film with birefringence.

Morley O. Stone

Papers

Biomimetic synthesis and patterning of silver nanoparticles

Carbon nanotube arrays with strong shear binding-on and easy normal lifting-off.

Enzyme immobilization in a biomimetic silica support.

Dissolution and Regeneration of Bombyx mori Silk Fibroin Using Ionic Liquids

Synthesis of Gold Nanoparticles Using Multifunctional Peptides