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

Macromolecular X-ray crystallography is routinely applied to understand biological processes at a molecular level. How­ever, significant time and effort are still required to solve and complete many of these structures because of the need for manual interpretation of complex numerical data using many software packages and the repeated use of interactive three-dimensional graphics. PHENIX has been developed to provide a comprehensive system for macromolecular crystallo­graphic structure solution with an emphasis on the automation of all procedures. This has relied on the development of algorithms that minimize or eliminate subjective input, the development of algorithms that automate procedures that are traditionally performed by hand and, finally, the development of a framework that allows a tight integration between the algorithms.

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PHENIX: a comprehensive Python-based system for macromolecular structure solution

J. Appl. Cryst.の発刊に際して

As the most important skeletal component in plants, the polysaccharide cellulose is an almost inexhaustible polymeric raw material with fascinating structure and properties. Formed by the repeated connection of D-glucose building blocks, the highly functionalized, linear stiff-chain homopolymer is characterized by its hydrophilicity, chirality, biodegradability, broad chemical modifying capacity, and its formation of versatile semicrystalline fiber morphologies. In view of the considerable increase in interdisciplinary cellulose research and product development over the past decade worldwide, this paper assembles the current knowledge in the structure and chemistry of cellulose, and in the development of innovative cellulose esters and ethers for coatings, films, membranes, building materials, drilling techniques, pharmaceuticals, and foodstuffs. New frontiers, including environmentally friendly cellulose fiber technologies, bacterial cellulose biomaterials, and in-vitro syntheses of cellulose are highlighted together with future aims, strategies, and perspectives of cellulose research and its applications.

Cellulose: Fascinating Biopolymer and Sustainable Raw Material

This critical review provides a processing-structure-property perspective on recent advances in cellulose nanoparticles and composites produced from them. It summarizes cellulose nanoparticles in terms of particle morphology, crystal structure, and properties. Also described are the self-assembly and rheological properties of cellulose nanoparticle suspensions. The methodology of composite processing and resulting properties are fully covered, with an emphasis on neat and high fraction cellulose composites. Additionally, advances in predictive modeling from molecular dynamic simulations of crystalline cellulose to the continuum modeling of composites made with such particles are reviewed (392 references).

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Cellulose nanomaterials review: structure, properties and nanocomposites

https://physicstoday.scitation.org/doi/pdf/10.1063/1.1752410

New Facilities Expand Protein Crystallography Opportunities

Synchrotron X-ray and neutron fiber diffraction studies of cellulose polymorphs

We present quantum chemical calculations, through 6-311G**/B3LYP, for the isomerization step in D-Xylose Isomerase, based on truncated models of the 3KCO (linear) and 3KCL (cyclic) X-ray/neutron structures, containing 9 free waters, 2 metals, the sugar and roughly 19 amino acids. Perturbative relaxations upon the experimental framework suggest a possible seven-step mechanism of the isomerzation reaction involving direct ionization of the glucose O2 proton on movement of the mobile magnesium ion (Mg2A ->2B). In this model, we also find a compensating proton shift between the K183/D255 pair, corresponding to a ~10kcal/mol reduction in the cost of the ionization, with a delocalized shift in potential along the reaction plane. We find ~16 kcal/mol reaction barriers in reasonable agreement with experiment (14 kcal/mol), as well as a final, exothermic hydroxide consistent with the 3CWH (product) structure, and possibly explaining observed non-Michaelis behavior of this enzyme.

/pdf/hydroxide-once-or-twice-a-combined-neutron-crystallographic-tuncz9xr06.pdf

Hydroxide Once or Twice? A combined Neutron Crystallographic and Quantum Chemical Study of the Hydride Shift in D-Xylose Isomerase

The form of the transmission factor for sample geometries encountered in X-ray and neutron fibre diffraction studies is considered. Transmission factors obtained by Monte Carlo experiments and a simple first-order approximation are compared and agree to within 1% for studies of the distribution of water and cations around DNA. The first-order approximation has the advantage of being simple and less computationally expensive.

Attenuation corrections for X‐ray and neutron fibre diffraction studies

Before the ILL reactor shutdown in 1991 a group from Keele started neutron diffraction studies of DNA on diffractometer D19. Although neutron diffraction had been used before to investigate the structural properties of fibrous polymers these were the first high-resolution studies. Following the restart in 1995 groups from Cambridge, EMBL Grenoble, ILL, Julich, Keele, Parma and Stockholm began studies using this new technique on a wide variety of systems. This report outlines this trend and the technological and methodological advances which are making it possible.

Paul Langan

Papers

New Facilities Expand Protein Crystallography Opportunities

Synchrotron X-ray and neutron fiber diffraction studies of cellulose polymorphs

Hydroxide Once or Twice? A combined Neutron Crystallographic and Quantum Chemical Study of the Hydride Shift in D-Xylose Isomerase

Attenuation corrections for X‐ray and neutron fibre diffraction studies

Neutron fibre diffraction: Recent advances at the ILL