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Key Points Pulling of VWF A1 domain that is engaged to GPIb-IX induces unfolding of a hitherto unidentified mechanosensitive domain in GPIbα. The spatial proximity of the mechanosensitive domain to GPIbβ and GPIX suggests a novel mechanism of platelet mechanosensing.

Cationic poly(amidoamine) (PAMAM) dendrimers were widely used as nonviral gene carriers. PAMAM dendrimer-based products such as Superfect and Priofect were already commercially available gene transfection reagents. However, these products are based on high generation dendrimers with high cost and serious cytotoxicity. In this study, we prepared high efficient gene carriers using disulfide cross-linked low generation (generation 2, G2) PAMAM dendrimers. These synthesized materials can effectively condense DNA into ~200 nm polyplexes and degrade into G2 dendrimers after cellular uptake. Confocal laser scanning microscope studies revealed high cellular uptake behavior of disulfide cross-linked G2 PAMAM dendrimers. Compared to G2 and G5 PAMAM dendrimers, disulfide cross-linked G2 PAMAM dendrimers showed much improved gene transfection efficacy (both EGFP and luciferase gene) and low cytotoxicity on both HEK293 and HeLa cell lines. The disulfide cross-linked G2 dendrimer prepared at a linker/dendrimer molar ratio of 1:1 showed the highest gene transfection efficacy and exhibited comparable efficacy to branched PEI with a molecular weight of 25 kD, a commercially available nonviral gene vector. Our study demonstrated that disulfide cross-linked low generation PAMAM dendrimers with high transfection efficacy, low cytotoxicity, and low cost are efficient alternatives to high generation PAMAM dendrimers in gene delivery.

Platelet GPIb-IX receptor complex has 3 subunits GPIb␣, GPIb␤, and GPIX, which assemble with a ratio of 1:2:1. Dysfunction in surface expression of the complex leads to Bernard-Soulier syndrome. We have crystallized the GPIb␤ ectodomain (GPIb␤ E ) and determined the structure to show a single leucine-rich repeat with Nand C-terminal disulphide-bonded capping regions. The structure of a chimera of GPIb␤ E and 3 loops (a,b,c) taken from the GPIX ectodomain sequence was also determined. The chimera (GPIb␤ Eabc ), but not GPIb␤ E , forms a tetramer in the crystal, showing a quaternary interface between GPIb␤ and GPIX. Central to this interface is residue Tyr106 from GPIb␤, which inserts into a pocket generated by 2 loops (b,c) from GPIX. Mutagenesis studies confirmed this interface as a valid representation of interactions between GPIb␤ and GPIX in the full-length complex. Eight GPIb␤ missense mutations identified from patients with BernardSoulier syndrome were examined for changes to GPIb-IX complex surface expression. Two mutations, A108P and P74R, were found to maintain normal secretion/folding of GPIb␤ E but were unable to support GPIX surface expression. The close structural proximity of these mutations to Tyr106 and the GPIb␤ E interface with GPIX indicates they disrupt the quaternary organization of the GPIb-IX complex. (Blood. 2011;118(19):5292-5301) IntroductionGPIb-IX-V complex is an abundant membrane receptor complex on the platelet surface that plays a critical role in mediating platelet adhesion to the damaged vessel wall under conditions of high shear stress. 1 Platelets adhere, and integrins are subsequently activated by interactions of GPIb-IX-V with VWF bound to the subendothelium. How GPIb-IX-V transmits the VWF-binding signal across the membrane is not clear, partly because the structure and organization of this complex receptor remain to be elucidated. Because GPV is only weakly associated with the receptor complex and is not essential for complex expression, assembly, VWF binding, or signal transduction, 2,3 we focus on the GPIb-IX complex here.The GPIb-IX complex contains 3 subunits, GPIb␣, GPIb␤, and GPIX, with a 1:2:1 stoichiometry. 4 Each subunit is a type I transmembrane (TM) protein, containing an ectodomain with leucine-rich repeats (LRRs), 5 a single TM helix, and a relatively short cytoplasmic tail. The GPIb␣ ectodomain contains binding sites for a growing list of hemostatically important ligands, including VWF and thrombin. 6-8 Covalent and noncovalent interactions are important to the quaternary stabilization of the receptor. GPIb␣ links to 2 GPIb␤ subunits through membrane-proximal disulfide bonds to constitute the GPIb complex. 4 GPIX tightly associates with GPIb through noncovalent interactions. 9 Assembly of these subunits into a tightly integrated complex is also supported by genetic evidence. Bernard-Soulier syndrome (BSS) is a hereditary bleeding disorder that is characterized in most cases by giant platelets, low platelet counts, and little or no expression of GPIb-IX on the p...

Experimental realizations of cold 85 Rb atom interferometers in Wuhan are reviewed in this paper. The application of atom interferometers in local gravity measurement are reported. The resolutions of gravity measurement are 2.0 × 10 −7 g for 1 s and 4.5 × 10 −9 g for 1,888 s. The absolute g value was derived with a difference of 1.6 × 10 −7 g compared to the gravity reference value. The tidal phenomenon was observed by continuously monitoring the local gravity over 123 h. A 10-meter atom interferometer designed for precision gravity measurement and the equivalence principle test is under construction, the latest status is reported for the first time.

Aims. The phase scintillation of the European Space Agency's Venus Express (VEX) spacecraft telemetry signal was observed at X-band (λ = 3.6 cm) with a number of radio telescopes of the European Very Long Baseline Interferometry (VLBI) Network in the period 2009-2013. Methods. We found a phase fluctuation spectrum along the Venus orbit with a nearly constant spectral index of −2.42 ± 0.25 over the full range of solar elongation angles from 0 • to 45 • , which is consistent with Kolmogorov turbulence. Radio astronomical observations of spacecraft signals within the solar system give a unique opportunity to study the temporal behaviour of the signal's phase fluctuations caused by its propagation through the interplanetary plasma and the Earth's ionosphere. This gives complementary data to the classical interplanetary scintillation (IPS) study based on observations of the flux variability of distant natural radio sources. Results. We present here our technique and the results on IPS. We compare these with the total electron content for the line of sight through the solar wind. Finally, we evaluate the applicability of the presented technique to phase-referencing VLBI and Doppler observations of currently operational and prospective space missions.

Context. The closest ever fly-by of the Martian moon Phobos, performed by the European Space Agency's Mars Express spacecraft, gives a unique opportunity to sharpen and test the Planetary Radio Interferometry and Doppler Experiments (PRIDE) technique in the interest of studying planet-satellite systems. Aims. The aim of this work is to demonstrate a technique of providing high precision positional and Doppler measurements of planetary spacecraft using the Mars Express spacecraft. The technique will be used in the framework of Planetary Radio Interferometry and Doppler Experiments in various planetary missions, in particular in fly-by mode. Methods. We advanced a novel approach to spacecraft data processing using the techniques of Doppler and phase-referenced very long baseline interferometry spacecraft tracking. Results. We achieved, on average, mHz precision (30 µm/s at a 10 s integration time) for radial three-way Doppler estimates and sub-nanoradian precision for lateral position measurements, which in a linear measure (at a distance of 1.4 AU) corresponds to ∼50 m.

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