Sequence-Dependent Fluorescence of Cyanine Dyes on Microarrays

Cy3 and Cy5 are among the most commonly used oligonucleotide labeling molecules. Studies of nucleic acid structure and dynamics use these dyes, and they are ubiquitous in microarray experiments. They are sensitive to their environment and have higher quantum yield when bound to DNA. The fluorescent intensity of terminal cyanine dyes is also known to be significantly dependent on the base sequence of the oligonucleotide. We have developed a very precise and high-throughput method to evaluate the sequence dependence of oligonucleotide labeling dyes using microarrays and have applied the method to Cy3 and Cy5. We used light-directed in-situ synthesis of terminally-labeled microarrays to determine the fluorescence intensity of each dye on all 1024 possible 5′-labeled 5-mers. Their intensity is sensitive to all five bases. Their fluorescence is higher with 5′ guanines, and adenines in subsequent positions. Cytosine suppresses fluorescence. Intensity falls by half over the range of all 5-mers for Cy3, and two-thirds for Cy5. Labeling with 5′-biotin-streptavidin-Cy3/-Cy5 gives a completely different sequence dependence and greatly reduces fluorescence compared with direct terminal labeling

Factors Associated with Revision Surgery after Internal Fixation of Hip Fractures

Background: Femoral neck fractures are associated with high rates of revision surgery after management with internal fixation. Using data from the Fixation using Alternative Implants for the Treatment of Hip fractures (FAITH) trial evaluating methods of internal fixation in patients with femoral neck fractures, we investigated associations between baseline and surgical factors and the need for revision surgery to promote healing, relieve pain, treat infection or improve function over 24 months postsurgery. Additionally, we investigated factors associated with (1) hardware removal and (2) implant exchange from cancellous screws (CS) or sliding hip screw (SHS) to total hip arthroplasty, hemiarthroplasty, or another internal fixation device. Methods: We identified 15 potential factors a priori that may be associated with revision surgery, 7 with hardware removal, and 14 with implant exchange. We used multivariable Cox proportional hazards analyses in our investigation. Results: Factors associated with increased risk of revision surgery included: female sex, [hazard ratio (HR) 1.79, 95% confidence interval (CI) 1.25-2.50; P = 0.001], higher body mass index (fo

Good Enough Yet? A Preliminary Evaluation Of Human-Surrogate Interaction

Research exploring the implementation of surrogates has included areas such as training (Chuah et al., 2013), education (Yamashita, Kuzuoka, Fujimon, & Hirose, 2007), and entertainment (Boberg, Piippo, & Ollila, 2008). Determining the characteristics of the surrogate that could potentially influence the human\u27s behavioral responses during human-surrogate interactions is of importance. The present work will draw on the literature about human-robot interaction (HRI), social psychology literature regarding the impact that the presence of a surrogate has on another human, and communications literature about human-human interpersonal interaction. The review will result in an experimental design to evaluate various dimensions of the space of human-surrogate characteristics influence on interaction. © 2014 Springer International Publishing

Mechanical Properties of End-Linked PEG/PDMS Hydrogels

Poly­(ethylene glycol) (PEG)/polydimethylsiloxane (PDMS) hydrogels were synthesized by cross-linking norbornene end-functionalized polymers with a tetrafunctional thiol using thiol–norbornene chemistry. The swelling capacity and mechanical properties, including the Young’s modulus (<i>E</i>) and fracture toughness (<i>G</i>_c), of the hydrogels were characterized and quantified as a function of the volume fractions of PEG and PDMS. <i>E</i> and <i>G</i>_c increased simultaneously with the volume fraction of PDMS. The moduli of the hydrogels were quantitatively described and predicted as a function of the volume fraction ratio of PEG to PDMS using the Voigt and Reuss models. The fracture toughness was well described by the Lake–Thomas theory at low volume fractions of PDMS. As the volume fraction of PDMS increased, PDMS not only controlled the swelling capacity of the hydrogels but also contributed to hydrogel toughness

Synthetically Simple, Highly Resilient Hydrogels

Highly resilient synthetic hydrogels were synthesized by using the efficient thiol-norbornene chemistry to cross-link hydrophilic poly­(ethylene glycol) (PEG) and hydrophobic polydimethylsiloxane (PDMS) polymer chains. The swelling and mechanical properties of the hydrogels were controlled by the relative amounts of PEG and PDMS. The fracture toughness (<i>G</i>_c) was increased to 80 J/m² as the water content of the hydrogel decreased from 95% to 82%. In addition, the mechanical energy storage efficiency (resilience) was more than 97% at strains up to 300%. This is comparable with one of the most resilient materials known: natural resilin, an elastic protein found in many insects, such as in the tendons of fleas and the wings of dragonflies. The high resilience of these hydrogels can be attributed to the well-defined network structure provided by the versatile chemistry, low cross-link density, and lack of secondary structure in the polymer chains

Synthetically Simple, Highly Resilient Hydrogels

Highly resilient synthetic hydrogels were synthesized by using the efficient thiol-norbornene chemistry to cross-link hydrophilic poly­(ethylene glycol) (PEG) and hydrophobic polydimethylsiloxane (PDMS) polymer chains. The swelling and mechanical properties of the hydrogels were controlled by the relative amounts of PEG and PDMS. The fracture toughness (<i>G</i>_c) was increased to 80 J/m² as the water content of the hydrogel decreased from 95% to 82%. In addition, the mechanical energy storage efficiency (resilience) was more than 97% at strains up to 300%. This is comparable with one of the most resilient materials known: natural resilin, an elastic protein found in many insects, such as in the tendons of fleas and the wings of dragonflies. The high resilience of these hydrogels can be attributed to the well-defined network structure provided by the versatile chemistry, low cross-link density, and lack of secondary structure in the polymer chains