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

https://www.seas.upenn.edu/%7Edischer/pdfs/Cell_on_Gel-CELLpaper.pdf

Matrix elasticity directs stem cell lineage specification.

Microarrays can measure the expression of thousands of genes to identify changes in expression between different biological states. Methods are needed to determine the significance of these changes while accounting for the enormous number of genes. We describe a method, Significance Analysis of Microarrays (SAM), that assigns a score to each gene on the basis of change in gene expression relative to the standard deviation of repeated measurements. For genes with scores greater than an adjustable threshold, SAM uses permutations of the repeated measurements to estimate the percentage of genes identified by chance, the false discovery rate (FDR). When the transcriptional response of human cells to ionizing radiation was measured by microarrays, SAM identified 34 genes that changed at least 1.5-fold with an estimated FDR of 12%, compared with FDRs of 60 and 84% by using conventional methods of analysis. Of the 34 genes, 19 were involved in cell cycle regulation and 3 in apoptosis. Surprisingly, four nucleotide excision repair genes were induced, suggesting that this repair pathway for UV-damaged DNA might play a previously unrecognized role in repairing DNA damaged by ionizing radiation.

/pdf/significance-analysis-of-microarrays-applied-to-the-ionizing-10j4beasgw.pdf

Significance analysis of microarrays applied to the ionizing radiation response

Although gold is the subject of one of the most ancient themes of investigation in science, its renaissance now leads to an exponentially increasing number of publications, especially in the context of emerging nanoscience and nanotechnology with nanoparticles and self-assembled monolayers (SAMs). We will limit the present review to gold nanoparticles (AuNPs), also called gold colloids. AuNPs are the most stable metal nanoparticles, and they present fascinating aspects such as their assembly of multiple types involving materials science, the behavior of the individual particles, size-related electronic, magnetic and optical properties (quantum size effect), and their applications to catalysis and biology. Their promises are in these fields as well as in the bottom-up approach of nanotechnology, and they will be key materials and building block in the 21st century. Whereas the extraction of gold started in the 5th millennium B.C. near Varna (Bulgaria) and reached 10 tons per year in Egypt around 1200-1300 B.C. when the marvelous statue of Touthankamon was constructed, it is probable that “soluble” gold appeared around the 5th or 4th century B.C. in Egypt and China. In antiquity, materials were used in an ecological sense for both aesthetic and curative purposes. Colloidal gold was used to make ruby glass 293 Chem. Rev. 2004, 104, 293−346

Gold nanoparticles: assembly, supramolecular chemistry, quantum-size-related properties, and applications toward biology, catalysis, and nanotechnology.

Semiconductor nanocrystals were prepared for use as fluorescent probes in biological staining and diagnostics. Compared with conventional fluorophores, the nanocrystals have a narrow, tunable, symmetric emission spectrum and are photochemically stable. The advantages of the broad, continuous excitation spectrum were demonstrated in a dual-emission, single-excitation labeling experiment on mouse fibroblasts. These nanocrystal probes are thus complementary and in some cases may be superior to existing fluorophores.

https://science.sciencemag.org/content/sci/281/5385/2013.full.pdf

Semiconductor Nanocrystals as Fluorescent Biological Labels

Potential applications of stem cells in medicine range from their inclusion in disease modeling and drug discovery to cell transplantation and regenerative therapies. However, before this promise can be realized several obstacles must be overcome, including the control of stem cell differentiation, allogeneic rejection and limited cell availability. This will require an improved understanding of the mechanisms that govern stem cell potential and the development of robust methods to efficiently control their fate. Recently, a number of small molecules have been identified that can be used both in vitro and in vivo as tools to expand stem cells, direct their differentiation, or reprogram somatic cells to a more naive state. These molecules have provided a wealth of insights into the signaling and epigenetic mechanisms that regulate stem cell biology, and are already beginning to contribute to the development of effective treatments for tissue repair and regeneration.

Chemical Control of Stem Cell Fate and Developmental Potential

Antibody catalysis of difficult chemical transformations

We report here the isolation and characterization of a 35-nucleotide (nt) RNA that catalyzes the related Cu(II) insertion into mesoporphyrin IX with a k{sub cat}/K{sub m} value of 2100 M{sup -1} s{sup -1}, close to the value for the metalation of mesoporphyrin with Fe(II) catalyzed by recombinant human ferrochelatase. This work demonstrates the ability of RNA to catalyze a reaction closely related to that required for the biosynthesis of the essential cofactor, heme. The small size of the catalytic sequence motif found here should facilitate structural studies. Moreover, mutants of this RNA may be selected to display other porphyrin-based activities: ferrochelatase activity, reversible oxygen binding with RNA-bound heme, peroxidase activity, or complementation of ferrochelatase-deficient (heme H{sup -}) auxotrophs which could ultimately lead to in vivo complementation of ferrochelatase deficiency using gene transfer techniques. 25 refs., 2 figs., 1 tab.

Porphyrin metalation catalyzed by a small RNA molecule

Construction of a light-activated protein by unnatural amino acid mutagenesis

An unnatural amino acid, l-3-(2-naphthyl)alanine, has been site-specifically incorporated into proteins in Escherichia coli. An orthogonal aminoacyl-tRNA synthetase was evolved that uniquely aminoacylates the unnatural amino acid onto an orthogonal amber suppressor tRNA, which delivers the acylated amino acid in response to an amber nonsense codon with translational fidelity greater than 99%. This result, together with the in vivo site-specific incorporation of O-methyl-l-tyrosine reported previously, demonstrate that this methodology may be applicable to a host of amino acids. The expansion of the genetic code to include amino acids beyond the common 20 would provide an opportunity to better understand and possibly enhance protein (and perhaps organismal) function.

Peter G. Schultz

Papers

Chemical Control of Stem Cell Fate and Developmental Potential

Antibody catalysis of difficult chemical transformations

Porphyrin metalation catalyzed by a small RNA molecule

Construction of a light-activated protein by unnatural amino acid mutagenesis

Adding l-3-(2-Naphthyl)alanine to the Genetic Code of E. coli