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

Inference of macromolecular assemblies from crystalline state.

Chitin and chitosan: Properties and applications

Antimicrobial host defense peptides are produced by all complex organisms as well as some microbes and have diverse and complex antimicrobial activities. Collectively these peptides demonstrate a broad range of antiviral and antibacterial activities and modes of action, and it is important to distinguish between direct microbicidal and indirect activities against such pathogens. The structural requirements of peptides for antiviral and antibacterial activities are evaluated in light of the diverse set of primary and secondary structures described for host defense peptides. Peptides with antifungal and antiparasitic activities are discussed in less detail, although the broad-spectrum activities of such peptides indicate that they are important host defense molecules. Knowledge regarding the relationship between peptide structure and function as well as their mechanism of action is being applied in the design of antimicrobial peptide variants as potential novel therapeutic agents.

Peptide Antimicrobial Agents

Pterocarpus angolensis lectin in complex with sucrose

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Increasing the Hydrophilicity of Cyclic Ketene Acetals Improves the Hydrolytic Degradation of Vinyl Copolymers and the Interaction of Glycopolymer Nanoparticles with Lectins.

Crystals of the disaccharide, (2,3,4,6-tetra- O -acetyl- α - d -glucopyranosyl) (2,3,4,6–tetra- O -acetyl- β - d -glucopyranosyl)amine belong to the space group P2 1 with a =14.848(2), b =21.838(3), c =11.534(2) A, and β =113.72(4)° and Z=4. The crystal structure was solved by direct methods and refined by the full-matrix least squares procedure to an R value of 0.049 ( Rw =0.46) for 4262 observed reflections. This work provides the first crystalline features in the diglycosylamine series and this molecule can be considered as a N -analogue of peracetylated α , β -trehalose. The conformational features of the two independent diglycosylamine molecules do not display any major significant differences. The d –glucopyranose residues have the usual 4 C 1 chair conformations, whereas all the primary and secondary acetate groups display usual orientations. In the crystal structure the hydrogen atom covalently linked to the nitrogen at the glycosidic linkage could be located; its configuration is ( R ) providing the priority is given to the ( R ) carbon neighbor (C-1 β ). The torsional angles at the glycosidic linkages Φα (O-5–C-1 α –N-1–C-1 β ), Φβ (C-1 α –N-1–C-1 β –O-5) of the two molecules have values of (57.6°,−78.8°) and (59.8°,−85.9°), respectively, slightly different from the conformation found in α , β -trehalose monohydrate. These conformations have been rationalized through the use of molecular mechanics calculations. The packing mode is highly anisotropic, with the existence of chains of molecules along the c axis, stabilized by numerous van der Waals contacts and by a strong hydrogen bond, involving the NH group of the glycosidic linkage and the carbonyl group of one acetate.

The Crystal and Molecular Structure of a Diglycosylamine: The N-Analogue of Peracetylated α,β-Trehalose.

Summary The opportunistic pathogen Pseudomonas aeruginosa, a major cause of nosocomial infections, uses carbohydrate-binding proteins (lectins) as part of its binding to host cells. The fucose-binding lectin, LecB, displays a unique carbohydrate-binding site that incorporates two closely located calcium ions bridging between the ligand and protein, providing specificity and unusually high affinity. Here, we investigate the mechanisms involved in binding based on neutron crystallography studies of a fully deuterated LecB/fucose/calcium complex. The neutron structure, which includes the positions of all the hydrogen atoms, reveals that the high affinity of binding may be related to the occurrence of a low barrier hydrogen bond induced by the proximity of the two calcium ions, the presence of coordination rings between the sugar, calcium and LecB, and the dynamic behaviour of bridging water molecules at room temperature. These key structural details may assist in the design of anti-adhesive compounds to combat multi-resistance bacterial infections.

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Neutron crystallography reveals novel mechanisms used by Pseudomonas aeruginosa for host-cell binding

Treatment of methyl 2,3-di-O-benzyl-4,6-O-benzylidene-α(β)- d -glucopyranoside with triethyl phosphite and trimethylsilyl trifluoromethanesulfonate affords the seven-membered phostone arising from the attack of reagents on the acetal protecting group.

Anne Imberty

Papers

Pterocarpus angolensis lectin in complex with sucrose

Increasing the Hydrophilicity of Cyclic Ketene Acetals Improves the Hydrolytic Degradation of Vinyl Copolymers and the Interaction of Glycopolymer Nanoparticles with Lectins.

The Crystal and Molecular Structure of a Diglycosylamine: The N-Analogue of Peracetylated α,β-Trehalose.

Neutron crystallography reveals novel mechanisms used by Pseudomonas aeruginosa for host-cell binding

A Novel Seven‐Membered Carbohydrate Phostone.