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

In the 19th century, Oscar Wilde stated “We live, I regret to say, in an age of surfaces”. Today, we do so even more, and we do not regret it: key advances in the understanding and fabrication of surfaces with controlled wetting properties are about to make the dream of a contamination-free (or 'no-clean') surface come true. Two routes to self-cleaning are emerging, which work by the removal of dirt by either film or droplet flow. Although a detailed understanding of the mechanisms underlying the behaviour of liquids on such surfaces is still a basic research topic, the first commercial products in the household-commodity sector and for applications in biotechnology are coming within reach of the marketplace. This progress report describes the current status of understanding of the underlying mechanisms, the concepts for making such surfaces, and some of their first applications.

Self-cleaning surfaces - virtual realities

Eukaryotic genomes are packaged into nucleosome particles that occlude the DNA from interacting with most DNA binding proteins. Nucleosomes have higher affinity for particular DNA sequences, reflecting the ability of the sequence to bend sharply, as required by the nucleosome structure. However, it is not known whether these sequence preferences have a significant influence on nucleosome position in vivo, and thus regulate the access of other proteins to DNA. Here we isolated nucleosome-bound sequences at high resolution from yeast and used these sequences in a new computational approach to construct and validate experimentally a nucleosome–DNA interaction model, and to predict the genome-wide organization of nucleosomes. Our results demonstrate that genomes encode an intrinsic nucleosome organization and that this intrinsic organization can explain ∼50% of the in vivo nucleosome positions. This nucleosome positioning code may facilitate specific chromosome functions including transcription factor binding, transcription initiation, and even remodelling of the nucleosomes themselves.

http://absimage.aps.org/image/MAR08/MWS_MAR08-2008-020581.pdf

The Genomic Code for Nucleosome Positioning

Superhydrophobic surfaces: From natural to biomimetic to functional

Particle deposit morphologies that resulted from evaporating ink-jetted microdroplets were controlled by varying the ink compositions and concentrations. The ink was a well-dispersed aqueous dispersion of monodisperse silica microspheres. Silica particles suspended in the microdroplet undergo self-assembly upon the evaporation of the solvent. A ringlike deposit of the self-assembled silica particles was produced from the water-based ink, while a uniform two-dimensional monolayer with a well-ordered hexagonal structure was obtained from the mixed-solvent-based inks. Variations in the deposit patterns can be explained in terms of competing effects between the convective and Marangoni flows, which vary with the types of the high-boiling-point solvent added to the ink. The macroscopic shape and microstructure of the silica colloidal deposits were observed by SEM, AFM, and a confocal microscope.

Control of colloidal particle deposit patterns within picoliter droplets ejected by ink-jet printing.

Contact Line Deposits on cDNA Microarrays: A “Twin-Spot Effect”

The paper reports on the preparation of superhydrophobic amorphous silicon oxide nanowires (a-SiONWs) on silicon substrates with a contact angle greater than 150° by means of surface roughness and self-assembly. Nanowires with an average mean diameter in the range 20−150 nm and 15−20 μm in length were obtained by the so-called solid−liquid−solid (SLS) technique. The porous nature and the high roughness of the resulting surfaces were confirmed by AFM imaging. The superhydrophobicity resulted from the combined effects of surface roughness and chemical modification with fluorodecyl trichlorosilane.

Preparation of superhydrophobic silicon oxide nanowire surfaces.

With nucleosomes being tightly associated with the majority of eukaryotic DNA, it is essential that mechanisms are in place that can move nucleosomes 'out of the way'. A focus of current research comprises chromatin remodeling complexes, which are ATP-consuming protein complexes that, for example, pull or push nucleosomes along DNA. The precise mechanisms used by those complexes are not yet understood. Hints for possible mechanisms might be found among the various spontaneous fluctuations that nucleosomes show in the absence of remodelers. Thermal fluctuations induce the partial unwrapping of DNA from the nucleosomes and introduce twist or loop defects in the wrapped DNA, leading to nucleosome sliding along DNA. In this minireview, we discuss nucleosome dynamics from two angles. First, we describe the dynamical modes of nucleosomes in the absence of remodelers that are experimentally fairly well characterized and theoretically understood. Then, we discuss remodelers and describe recent insights about the possible schemes that they might use.

/pdf/the-dynamics-of-the-nucleosome-thermal-effects-external-2r3pfbib5b.pdf

The dynamics of the nucleosome: thermal effects, external forces and ATP.

Performance of DFT/MPWB1K for stacking and H-bonding interactions

The paper reports on wetting, electrowetting (EW), and systematic contact angle hysteresis measurements after electrowetting of superhydrophobic silicon nanowire surfaces (NWs). The surfaces consist of C4F8-coated silicon nanowires grown on Si/SiO2 substrate. Different surfaces modulating (i) the dielectric layer thickness and (ii) the nanotexturation were investigated in this study. It was found that the superhydrophobic NWs display different EW behaviors according to their double nanotexturation with varying droplet impalement levels. Some surfaces exhibited a total reversibility to EW with no impalement (contact angle variation of 35 ± 2° at 190 VTRMS with deionized water), whereas other surfaces showed nonreversible behavior to EW with partial droplet impalement. A scenario is proposed to explain the unique properties of these surfaces.

Ralf Blossey

Papers

Contact Line Deposits on cDNA Microarrays: A “Twin-Spot Effect”

Preparation of superhydrophobic silicon oxide nanowire surfaces.

The dynamics of the nucleosome: thermal effects, external forces and ATP.

Performance of DFT/MPWB1K for stacking and H-bonding interactions

Reversible Electrowetting on Superhydrophobic Double-Nanotextured Surfaces