In the originally published version of this article, the label for the vertical axis at the bottom of Figure 7H mistakenly referred to the state where D core < D IDR . The correct label should read D core R D IDR . The corrected Figure 7 is shown here and this error has now been corrected in the article online. We apologize for any confusion this error may have caused.

We report the application of a set of twin optical tweezers to trap and oscillate a ConA (lectin)- coated polystyrene particle and to measure its interaction with glycoprotein receptors at the cellular plasma membrane of a Chinese hamster ovary (CHO) cell. The particle was trapped between two quadratic potential wells defined by a set of twin optical tweezers and was forced to oscillate by chopping on and off one of the trapping beams. We tracked the oscillatory motion of the particle via a quadrant photodiode and measured with a lock-in amplifier the amplitude of the oscillation as a function of frequency at the fundamental component of the driving frequency over a frequency range from 10Hz to 600Hz. By analyzing the amplitude as a function of frequency for a free particle suspended in buffer solution without the presence of the CHO cell and compared with the corresponding data when the particle was interacting with the CHO cell, we deduced the transverse force constant associated with the optical trap and that associated with the interaction by treating both the optical trap and the interaction as linear springs. The force constants were determined to be approximately 2.15pN/mum for the trap and 2.53pN/mum for the lectin-glycoprotein interaction. When the CHO cell was treated with lantrunculin A, a drug that is known to destroy the cytoskeleton of the cell, the oscillation amplitude increased with time, indicating the softening of the cellular membrane, until a steady state with a smaller force constant was reached. The steady state value of the force constant depended on the drug concentration.

share similarities in composition and properties with the so-called lipid rafts and with the liquid-ordered phase (Lo) of model membranes. Here we use optical and fluorescence microscopy to study the solubilization process of giant unilamellar vesicles (GUVs) made of erythrocyte lipid extracts (erythro-GUVs) by the commonly used detergent Triton X-100. For comparison, ternary lipid mixtures of POPC, sphingomyelin (SM) and cholesterol are also investigated. Erythro-GUVs do not exhibit macroscopic phase separation, as seen by the homogenous distribution of a fluorescence probe that preferentially partition into the fluid (Ld) phase. However, contact with Triton X-100 immediately causes formation of micrometer-sized bright domains, typical of Lo/Ld phase separation. Then, at Triton X-100 concentrations above its cmc, the fluid part is first detached from the original vesicle and then completely solubilized by Triton X-100. The insoluble vesicle left is only faintly fluorescent and appears to be in the Lo phase. Typically, one third of the erythro-GUV surface area is solubilized. Solubilization of POPC:SM:chol GUVs in a certain composition range follow the same sequence of events. Our results show that Triton X-100 promotes formation of macroscopic domains in both biological and biomimetic membranes, and that the partial solubilization occurs after phase separation, suggesting that the composition of the insoluble membrane fraction is modulated by the choice of the detergent used. Financial support: CNPq, FAPESP and INCT-FCx.

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the target sites and formation of a DNA quadruplex. As a result, target sequences are accessible for the next round of priming and DNA amplification proceeds under isothermal conditions. QPA can proceed in either a linear or an exponential amplification mode. Experiments here demonstrate that linear QPA has a potential to be highly specific. We have combined linear QPA with nicking enzymes to reach the level of exponential signal amplification. In our assays we use specifically designed probes that are complementary to both pathogen and QPA template. When the probe is annealed to the pathogen DNA and the nicking site is folded, the enzyme nicks the pathogen strand and creates the 5'-overhang or primer/template complex, which is elongated by polymerase. At this point the nicking enzyme and polymerase initiate QPA template production, which later binds to QPA primers and produces signal. We will discuss thermodynamic and kinetic bases of these multi-step reaction, which can be conducted isothermally between 55 and 65 C. Genome instability is an underlying factor of all cancers. Defects in DNA repair mechanisms contribute significantly to this factor. Recent reports indicate the mechanical properties of cells change as they advance through different stages of neoplastic transformation. The main goal of this study is to investigate how changes in the intracellular environment and changes in DNA repair protein distribution are altered in cells undergoing neoplastic transformation. For this study we have chosen to use human mammary epithelial (HME) cells from the Weinberg line. Lipofection was used to transiently transfect enhanced green fluorescent protein (egfp) fusions to MSH2 mismatch repair proteins. We have measured the localization and diffusion of these fusions using fluorescence recovery after photobleaching (FRAP) and raster image correlation spectroscopy (RICS) on live cells maintained under appropriate environmental conditions. We have tested normal, immortal, and tumorigenic cells in this study. The acquired data was analyzed using custom written Matlab programs as well as commercially available software. Preliminary results show localization of the fusions to the nucleolus in all cell types tested. The surrounding nucleus generally has the weakest localization signal. We have also observed smaller diffusion coefficients in the nucleus of tumorigenic cells compared to normal cells. A nanostructured polystyrene based inorganic-organic composite membrane has been synthesized by sol-gel method under acidic conditions. Investigation on the electrochemical properties showed that higher membrane potential was observed in case of LiCl than other electrolytes used such as NH 4 Cl, KCl and NaCl for the nanocomposite membrane. Effective fixed charge densities were evaluated from the measured potential and were found to follow the order Li þ > NH 4 þ > K þ > Na þ . The permselectivity, ionic mobility ratio and counter-ion transport number of the composite membrane have also been calculated which suggest that the inor...