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

One of the fastest moving and most exciting interfaces of nanotechnology is the use of quantum dots (QDs) in biology. The unique optical properties of QDs make them appealing as in vivo and in vitro fluorophores in a variety of biological investigations, in which traditional fluorescent labels based on organic molecules fall short of providing long-term stability and simultaneous detection of multiple signals. The ability to make QDs water soluble and target them to specific biomolecules has led to promising applications in cellular labelling, deep-tissue imaging, assay labelling and as efficient fluorescence resonance energy transfer donors. Despite recent progress, much work still needs to be done to achieve reproducible and robust surface functionalization and develop flexible bioconjugation techniques. In this review, we look at current methods for preparing QD bioconjugates as well as presenting an overview of applications. The potential of QDs in biology has just begun to be realized and new avenues will arise as our ability to manipulate these materials improves.

Quantum dot bioconjugates for imaging, labelling and sensing

Ju Mei,†,‡,∥ Nelson L. C. Leung,†,‡,∥ Ryan T. K. Kwok,†,‡ Jacky W. Y. Lam,†,‡ and Ben Zhong Tang*,†,‡,§ †HKUST-Shenzhen Research Institute, Hi-Tech Park, Nanshan, Shenzhen 518057, China ‡Department of Chemistry, HKUST Jockey Club Institute for Advanced Study, Institute of Molecular Functional Materials, Division of Biomedical Engineering, State Key Laboratory of Molecular Neuroscience, Division of Life Science, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China Guangdong Innovative Research Team, SCUT-HKUST Joint Research Laboratory, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, China

Aggregation-Induced Emission: Together We Shine, United We Soar!

We report that nanoscale carbon particles (carbon dots) upon simple surface passivation are strongly photoluminescent in both solution and the solid state. The luminescence emission of the carbon dots is stable against photobleaching, and there is no blinking effect. These strongly emissive carbon dots may find applications similar to or beyond those of their widely pursued silicon counterparts.

http://www.ecs.umass.edu/ece697mm/Supplement_Clemson_Cbased_Qdots_JAmChemSoc_05_06.pdf

Quantum-sized carbon dots for bright and colorful photoluminescence.

http://light.ece.illinois.edu/ECE564/Research_Projects_files/fPALM_2006.pdf

Ultra-High Resolution Imaging by Fluorescence Photoactivation Localization Microscopy

Research on fluorescent semiconductor nanocrystals (also known as quantum dots or qdots) has evolved over the past two decades from electronic materials science to biological applications. We review current approaches to the synthesis, solubilization, and functionalization of qdots and their applications to cell and animal biology. Recent examples of their experimental use include the observation of diffusion of individual glycine receptors in living neurons and the identification of lymph nodes in live animals by near-infrared emission during surgery. The new generations of qdots have farreaching potential for the study of intracellular processes at the single-molecule level, high-resolution cellular imaging, long-term in vivo observation of cell trafficking, tumor targeting, and diagnostics.

/pdf/quantum-dots-for-live-cells-in-vivo-imaging-and-diagnostics-3y9ayecoh8.pdf

Quantum Dots for Live Cells, in Vivo Imaging, and Diagnostics

We measured the quantum-confined Stark effect (QCSE) of several types of fluorescent colloidal semiconductor quantum dots and nanorods at the single molecule level at room temperature. These measurements demonstrate the possible utility of these nanoparticles for local electric field (voltage) sensing on the nanoscale. Here we show that charge separation across one (or more) heterostructure interface(s) with type-II band alignment (and the associated induced dipole) is crucial for an enhanced QCSE. To further gain insight into the experimental results, we numerically solved the Schrodinger and Poisson equations under self-consistent field approximation, including dielectric inhomogeneities. Both calculations and experiments suggest that the degree of initial charge separation (and the associated exciton binding energy) determines the magnitude of the QCSE in these structures.

https://pubs.acs.org/doi/pdf/10.1021/nn303719m

Single Molecule Quantum-Confined Stark Effect Measurements of Semiconductor Nanoparticles at Room Temperature

Extract: The past few decades have witnessed technical advances that have introduced cell biologists and physicians to a new, dynamic, subcellular world where genes and gene products can be visualized to interact in space and time and in health and disease. The accelerating field of molecular imaging has been critically dependent on indicator probes which show when and where genetically or biochemically defined molecules, signals or processes appear, interact and disappear, with high spatial and temporal resolution in living cells and whole organisms. For example, the use of radionuclide tracers combined with 3-dimensional (3-D) imaging systems such as Positron Emission Tomography (PET) and Single Photon Emission Computed Tomography (SPECT) are now helping clinicians to characterize the molecular status of tumors deep within patients. Other types of imaging probes rely on the bioluminescence and fluorescence of genetically encoded proteins (originally found in fireflies and jellyfish, respectively) or entirely synthetic fluorochromes, or a combination of both. New powerful biological fluorescence microscopes provide the ability to study single molecules within single cells. Multiphoton confocal microscopy has been developed to allow for the capturing of high-resolution, 3-D images of living tissues that have been tagged with highly specific fluorophores.

/pdf/quantum-dots-for-molecular-imaging-and-cancer-medicine-16k53vetiz.pdf

Quantum Dots for Molecular Imaging and Cancer Medicine

We review the concept and the evolution of bandgap and wavefunction engineering, the seminal contributions of Dr. Chemla to the understanding of the rich phenomena displayed in epitaxially grown quantum confined systems, and demonstrate the application of these concepts to the colloidal synthesis of high quality type-II CdTe/CdSe quantum dots using successive ion layer adsorption and reaction chemistry. Transmission electron microscopy reveals that CdTe/CdSe can be synthesized layer by layer, yielding particles of narrow size distribution. Photoluminescence emission and excitation spectra reveal discrete type-II transitions, which correspond to energy lower than the type-I bandgap. The increase in the spatial separation between photoexcited electrons and holes as a function of successive addition of CdSe monolayers was monitored by photoluminescence lifetime measurements. Systematic increase in lifetimes demonstrates the high level of wavefunction engineering and control in these systems.

/pdf/wavefunction-engineering-from-quantum-wells-to-near-infrared-xtjgifv5jz.pdf

Wavefunction engineering: From quantum wells to near-infrared type-II colloidal quantum dots synthesized by layer-by-layer colloidal epitaxy.

We developed a new peptide, natural phytochelatin (PC), which tightly binds to CdSe/ZnS quantum dots’ (QDs) surfaces and renders them water-soluble. Coating QDs with this flexible and all-hydrophilic peptide offers high colloidal stability, adds only 0.8–0.9 nm to the radius of the particles (as compared to their original inorganic radius), preserves very high quantum yield (QY) in water, and affords facile bioconjugation with various functional groups. We demonstrate specific targeting (with minimal nonspecific binding) of such fluorescein-conjugated QDs to ScFv-fused mouse prion protein expressed in live N2A cells. We also demonstrated homogeneous in vivo biodistribution with no significant toxicity in live zebrafish.

J. Jack Li

Papers

Quantum Dots for Live Cells, in Vivo Imaging, and Diagnostics

Single Molecule Quantum-Confined Stark Effect Measurements of Semiconductor Nanoparticles at Room Temperature

Quantum Dots for Molecular Imaging and Cancer Medicine

Wavefunction engineering: From quantum wells to near-infrared type-II colloidal quantum dots synthesized by layer-by-layer colloidal epitaxy.

Stable, Compact, Bright Biofunctional Quantum Dots with Improved Peptide Coating