There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

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

Anion recognition chemistry has grown from its beginnings in the late 1960s with positively charged ammonium cryptand receptors for halide binding to, at the end of the millennium, a plethora of charged and neutral, cyclic and acyclic, inorganic and organic supramolecular host systems for the selective complexation, detection, and separation of anionic guest species. Solvation effects and pH values have been shown to play crucial roles in the overall anion recognition process. More recent developments include exciting advances in anion-templated syntheses and directed self-assembly, ion-pair recognition, and the function of anions in supramolecular catalysis.

Anion Recognition and Sensing: The State of the Art and Future Perspectives

Fluorogenic and chromogenic chemosensors and reagents for anions.

▪ Abstract Proton-coupled electron transfer (PCET) is an important mechanism for charge transfer in a wide variety of systems including biology- and materials-oriented venues. We review several are...

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Proton-Coupled Electron Transfer

Fluorescence Sensing of Anions via Intramolecular Excimer Formation in a Pyrophosphate-Induced Self-Assembly of a Pyrene-Functionalized Guanidinium Receptor

Strong hydrogen bond-mediated complexation of H2PO4− by neutral bis-thiourea hosts

Anion recognition by urea and thiourea groups: Remarkably simple neutral receptors for dihydrogenphosphate

A chloride-selective solvent polymeric membrane electrode based on a neutral hydrogen bond forming ionophore, poly(vinyl chloride) (PVC), the plasticizer 2-nitrophenyl octyl ether (o-NPOE), and cationic sites (50 mol %, relative to the ionophore) is described. At pH 7.0 (HEPES buffer), this electrode responds to chloride in a linear range from 10-5 to 10-2 M with a slope of (−54.0 ± 1.0) mV/decade and a detection limit of (6.5 ± 3.0) × 10-6 M. As compared to conventional anion-exchanger electrodes, the interference of SCN-, Br-, NO3-, I-, and even salicylate is considerably reduced, as shown by the selectivity coefficients determined with the matched potential method (MPM) in the chloride concentration range 10-2.34−10-2.04 M (log (MPM):  Sal-, +1.8; SCN-, +1.6; NO3-, +0.7; I-, +0.5; Br-, +0.4). Because the discrimination of the more hydrophilic anions SO42-, HSO3-/SO32-, OAc-, HCO3-, and H2PO4-/HPO42- is too large for a determination of accurate selectivity coefficients in this high chloride concentratio...

A Chloride Ion-Selective Solvent Polymeric Membrane Electrode Based on a Hydrogen Bond Forming Ionophore

Nucleobase recognition in water is successfully achieved by the use of an abasic site (AP site) as the molecular recognition field. We intentionally construct the AP site in DNA duplex so as to orient the AP site toward a target nucleobase and examine the complexation of 2-amino-7-methylnaphthyridine (AMND) with nucleobases at the AP site. AMND is found to selectively bind to cytosine (C) base with a 1:1 binding constant of >106 M-1, accompanied by remarkable quenching of its fluorescence. In addition to hydrogen bonding, a stacking interaction with nucleobases flanking the AP site seems responsible for the binding properties of AMND at the AP site. Possible use of AMND is also presented for selective and visible detection of a single-base alternation related to the cytosine base.

Seiichi Nishizawa

Papers

Fluorescence Sensing of Anions via Intramolecular Excimer Formation in a Pyrophosphate-Induced Self-Assembly of a Pyrene-Functionalized Guanidinium Receptor

Strong hydrogen bond-mediated complexation of H2PO4− by neutral bis-thiourea hosts

Anion recognition by urea and thiourea groups: Remarkably simple neutral receptors for dihydrogenphosphate

A Chloride Ion-Selective Solvent Polymeric Membrane Electrode Based on a Hydrogen Bond Forming Ionophore

Use of abasic site-containing DNA strands for nucleobase recognition in water