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

The study of biomolecules in their native environments is a challenging task because of the vast complexity of cellular systems. Technologies developed in the last few years for the selective modification of biological species in living systems have yielded new insights into cellular processes. Key to these new techniques are bioorthogonal chemical reactions, whose components must react rapidly and selectively with each other under physiological conditions in the presence of the plethora of functionality necessary to sustain life. Herein we describe the bioorthogonal chemical reactions developed to date and how they can be used to study biomolecules.

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Bioorthogonal Chemistry: Fishing for Selectivity in a Sea of Functionality

Since the discovery of organic azides by Peter Griess more than 140 years ago, numerous syntheses of these energy-rich molecules have been developed. In more recent times in particular, completely new perspectives have been developed for their use in peptide chemistry, combinatorial chemistry, and heterocyclic synthesis. Organic azides have assumed an important position at the interface between chemistry, biology, medicine, and materials science. In this Review, the fundamental characteristics of azide chemistry and current developments are presented. The focus will be placed on cycloadditions (Huisgen reaction), aza ylide chemistry, and the synthesis of heterocycles. Further reactions such as the aza-Wittig reaction, the Sundberg rearrangement, the Staudinger ligation, the Boyer and Boyer-Aube rearrangements, the Curtius rearrangement, the Schmidt rearrangement, and the Hemetsberger rearrangement bear witness to the versatility of modern azide chemistry.

Organic Azides: An Exploding Diversity of a Unique Class of Compounds

http://www.chtf.stuba.sk/~szolcsanyi/education/files/Organicka%20chemia%20II/Prednaska%208_Aminokyseliny%20a%20peptidy/Doplnkove%20studijne%20materialy/Amide%20bond%20formation/Amide%20bond%20formation.pdf

Amide bond formation and peptide coupling

Staudinger ligation: a peptide from a thioester and azide.

Proteins have become accessible targets for chemical synthesis. The basic strategy is to use native chemical ligation, Staudinger ligation, or other orthogonal chemical reactions to couple synthetic peptides. The ligation reactions are compatible with a variety of solvents and proceed in solution or on a solid support. Chemical synthesis enables a level of control on protein composition that greatly exceeds that attainable with ribosome-mediated biosynthesis. Accordingly, the chemical synthesis of proteins is providing previously unattainable insight into the structure and function of proteins.

/pdf/chemical-synthesis-of-proteins-54ziyia3np.pdf

Chemical synthesis of proteins.

Instruments. NMR spectra were obtained with Bruker AC-300 and Varian UNITY-500 spectrometers. Mass spectra were obtained with Perkin Elmer Sciex API 365 electrospray ionization (ESI) and Bruker Biflex III matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) instruments at the University of Wisconsin Biotechnology Center. Ultraviolet and visible absorbance was recorded with a Cary Model 3 UV/VIS spectrophotometer from Varian equipped with a Varian temperature controller.

Selenocysteine in Native Chemical Ligation and Expressed Protein Ligation

The Staudinger ligation between an azido-protein and a phosphinothioester-derivatized surface is demonstrated to be an effective means for the site-specific, covalent immobilization of a protein. Immobilization yields of >50% are obtained in 80% of their expected activity. No other method enables more rapid immobilization or a higher yield of active protein. Because azido-peptides and azido-proteins are readily attainable by synthesis, biosynthesis, or semisynthesis, the Staudinger ligation could be of unsurpassed utility in creating microarrays of functional peptides and proteins.

Site-specific protein immobilization by Staudinger ligation.

Self-assembled peptide nanostructures have been increasingly exploited as functional materials for applications in biomedicine and energy. The emergent properties of these nanomaterials determine the applications for which they can be exploited. It has recently been appreciated that nanomaterials composed of multicomponent coassembled peptides often display unique emergent properties that have the potential to dramatically expand the functional utility of peptide-based materials. This review presents recent efforts in the development of multicomponent peptide assemblies. The discussion includes multicomponent assemblies derived from short low molecular weight peptides, peptide amphiphiles, coiled coil peptides, collagen, and β-sheet peptides. The design, structure, emergent properties, and applications for these multicomponent assemblies are presented in order to illustrate the potential of these formulations as sophisticated next-generation bio-inspired materials.

/pdf/multicomponent-peptide-assemblies-1mxig4zs64.pdf

Bradley L. Nilsson

Papers

Staudinger ligation: a peptide from a thioester and azide.

Chemical synthesis of proteins.

Selenocysteine in Native Chemical Ligation and Expressed Protein Ligation

Site-specific protein immobilization by Staudinger ligation.

Multicomponent peptide assemblies