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

Perylene Bisimide Dye Assemblies as Archetype Functional Supramolecular Materials

Helicenes: synthesis and applications.

The spectroscopic analysis of large biomolecules is important in applications such as biomedical diagnostics and pathogen detection, and spectroscopic techniques can detect such molecules at the nanogram level or lower. However, spectroscopic techniques have not been able to probe the structure of large biomolecules with similar levels of sensitivity. Here, we show that superchiral electromagnetic fields, generated by the optical excitation of plasmonic planar chiral metamaterials, are highly sensitive probes of chiral supramolecular structure. The differences in the effective refractive indices of chiral samples exposed to left- and right-handed superchiral fields are found to be up to 10(6) times greater than those observed in optical polarimetry measurements, thus allowing picogram quantities of adsorbed molecules to be characterized. The largest differences are observed for biomolecules that have chiral planar sheets, such as proteins with high β-sheet content, which suggests that this approach could form the basis for assaying technologies capable of detecting amyloid diseases and certain types of viruses.

/pdf/ultrasensitive-detection-and-characterization-of-4vm2e080ni.pdf

Ultrasensitive detection and characterization of biomolecules using superchiral fields

We introduce a measure of the local density of chirality of the electromagnetic field. This optical chirality determines the asymmetry in the rates of excitation between a small chiral molecule and its mirror image, and applies to molecules in electromagnetic fields with arbitrary spatial dependence. A continuity equation for optical chirality in the presence of material currents describes the flow of chirality, in a manner analogous to the Poynting theorem for electromagnetic energy. ``Superchiral'' solutions to Maxwell's equations show larger chiral asymmetry, in some regions of space, than is found in circularly polarized plane waves.

/pdf/optical-chirality-and-its-interaction-with-matter-4w9nb3y2se.pdf

Optical chirality and its interaction with matter.

A molecule or larger body is chiral if it cannot be superimposed on its mirror image (enantiomer). Electromagnetic fields may be chiral, too, with circularly polarized light (CPL) as the paradigmatic example. A recently introduced measure of the local degree of chiral dissymmetry in electromagnetic fields suggested the existence of optical modes more selective than circularly polarized plane waves in preferentially exciting single enantiomers in certain regions of space. By probing induced fluorescence intensity, we demonstrated experimentally an 11-fold enhancement over CPL in discrimination of the enantiomers of a biperylene derivative by precisely sculpted electromagnetic fields. This result, which agrees to within 15% with theoretical predictions, establishes that optical chirality is a fundamental and tunable property of light, with possible applications ranging from plasmonic sensors to absolute asymmetric synthesis.

/pdf/enhanced-enantioselectivity-in-excitation-of-chiral-z8yw4wfr2a.pdf

Enhanced Enantioselectivity in Excitation of Chiral Molecules by Superchiral Light

http://cohenweb.rc.fas.harvard.edu/Publications/Yang_Tang_Cohen_NanoToday.pdf

Spectroscopy in sculpted fields

Fluorescent imaging of single helicene molecules is applied to study the optical activity of chiral fluorophores. In contrast to the previous report by Hassey et al. (Science 2006, 314, 1437), the dissymmetry factors of single chiral fluorophores are found not to differ significantly from the bulk value of |g| < 10(-4) at 457 nm. Linear dichroism and birefringence of the dichroic mirror inside the fluorescence microscope change the polarization state of the incoming laser beam significantly; i.e., circular polarized light sent into the microscope becomes highly elliptically polarized after reflection from the dichroic mirror. Compensation for this effect should be made to avoid artifacts brought by linear dichroism in single immobilized molecules.

/pdf/limits-on-fluorescence-detected-circular-dichroism-of-single-2cakkxur7x.pdf

Limits on fluorescence detected circular dichroism of single helicene molecules.

The circular photogalvanic effect (CPGE) of the two-dimensional electron gas (2DEG) in Al025Ga075N/GaN heterostructures induced by infrared radiation has been investigated under uniaxial strain The observed photocurrent consists of the superposition of the CPGE and the linear photogalvanic effect currents, both of which are up to 10(-2) nA The amplitude of the CPGE current increases linearly with additional strain and is enhanced by 186% with a strain of 22x10(-3) Based on the experimental results, the contribution of bulk-inversion asymmetry (BIA) and structure-inversion asymmetry (SIA) spin splitting of the 2DEG to the CPGE current in the heterostructures is separated, and the ratio of SIA and BIA terms is estimated to be about 132, indicating that the SIA is the dominant mechanism to induce the k-linear spin splitting of the subbands in the triangular quantum well at AlxGa1-xN/GaN heterointerfaces (C) 2007 American Institute of Physics

Yiqiao Tang

Papers

Optical chirality and its interaction with matter.

Enhanced Enantioselectivity in Excitation of Chiral Molecules by Superchiral Light

Spectroscopy in sculpted fields

Limits on fluorescence detected circular dichroism of single helicene molecules.

Circular photogalvanic effect of the two-dimensional electron gas in AlxGa1−xN∕GaN heterostructures under uniaxial strain