Geometrical factors suitable for use in Mie–Gans theory are derived from discrete dipole aproximation generated spectra for a number of pseudonanorods permitting the rapid calculation of extinction spectra. It is shown that the rod width, rod end-cap geometry (flat, oblate spheroid, and sphere) and the rod size distribution all have a significant effect on the position of the peak absorbance. Moreover, it is shown that spectrometric characterization of nanorods is possible given an independent measure of rod width and suitable assumptions regarding the end-cap geometry and the form of the rod-length distribution; under such conditions the full width half maximum and the extinction peak uniquely determine the average rod length and the breadth of the distribution.

Reversible addition−fragmentation chain transfer (RAFT) polymerization techniques are successfully used to control molecular weight and polydispersity in the seeded emulsion polymerization of styrene. A novel technique was used to assist the transport into the seed particles of a RAFT agent that is of very low water solubility, ensuring the RAFT agent was localized in the particle phase. The polymer produced in these experiments was seen to have low molecular weight polydispersity (1.1 < M̄ w/M̄ n < 1.4), and the molecular weight could be controlled by the amount of RAFT agent used. The procedure permitted living polymerization to be performed in an emulsion polymerization system. Importantly, the RAFT agent had no adverse effect on latex stability, and unusual amounts of coagulum were not observed. Reductions in the rate of polymerization (measured by dilatometry) were observed along with significant inhibition periods, for which possible explanations and remedies are discussed. This appears to be the first instance where good living character has been demonstrated in a true emulsion polymerization of styrene while maintaining good colloidal stability.

Surface protrusions of Plasmodium falciparum-infected erythrocytes, called knobs, display focal aggregates of P falciparum erythrocyte membrane protein 1 (PfEMP1), the adhesion ligand binding endothelial-cell receptors. The resulting sequestration of infected erythrocytes in tissues represents an important factor in the course of fatalities in patients with malaria. The main component of knobs is the knob-associated histidine-rich protein (KAHRP), and it contributes to altered mechanical properties of parasiteinfected erythrocytes. The role of KAHRP domains in these processes is still elusive. We generated stable transgenic P falciparum-infected erythrocytes expressing mutant versions of KAHRP. Using atomic force and electron microscopy we show that the C-terminal repeat region is critical for the formation of functional knobs. Elasticity of the membrane differs dramatically between cells with different KAHRP mutations. We propose that the 5 repeat region of KAHRP is important in cross-linking to the host-cell cytoskeleton and this is required for knob protrusion and efficient adhesion under physi- IntroductionPlasmodium falciparum is the most lethal malaria parasite of humans. 1 An important aspect in virulence of P falciparum is the ability of infected erythrocytes to sequester in and obstruct the microvasculature of different organs. 2 These abnormal circulatory properties of erythrocytes involve parasite-induced alterations in their biomechanical and adhesive properties and are important for survival and pathogenicity of P falciparum. 3 Cytoadhesion is mediated by the antigenically variant P falciparum erythrocyte membrane protein-1 (PfEMP1), which can bind to host receptors including CD36 and chondroitin sulfate A (CSA). 4 PfEMP1 is concentrated on electron-dense elevations of the membrane referred to as knobs, 5-7 providing a platform for adherence under physiologic flow conditions. 8 Increased erythrocyte rigidity and adhesiveness result in dramatically augmented hemodynamic resistance observed in microvasculature perfused with P falciparum-infected erythrocytes. 9 Knobs consist predominantly of the knob-associated histidine-rich protein (KAHRP), 10,11 assembling on the cytoplasmic face of the membrane. KAHRP is required for knob formation. 8 KAHRP has a signal sequence with a recessed hydrophobic core that directs the protein into the parasitophorous vacuole via the endomembrane system. 12 A second signal, we termed the "Plasmodium export element" (PEXEL), 13 is required for transfer across the parasitophorous vacuole membrane to the erythrocyte cytosol. 13,14 The PEXEL is followed by a histidine-rich region containing sequences responsible for interaction with Maurer clefts, 15 structures assembled in the P falciparum-infected erythrocyte cytosol important in protein sorting and trafficking. 12 There are also 2 blocks of highly charged repeats, designated the 5Ј and 3Ј repeats according to their location. 10,11 Current evidence suggests KAHRP interacts with various cytoskeletal components of the erythr...