Colorimetric Sensors

There is emerging interest in sensitive colorimetric biosensor methods that do not require specialized instruments for signal detection. Nanoparticles, nanovesicles, and optical thin film have been used to transduce complementary hybridization into a color change. Aggregation of probe-labeled nanoparticles in the presence of complementary target is associated with a color shift that can be monitored using a UV-VIS spectrophotometer. This system was coupled in an array format with a chemoresponsive diffraction grating detector to show realtime detection of a synthesized 27-mer DNA target. The experimental detection limit was 0.8 fmol (1 pM in 800 mL), and an extrapolated detection limit of 33 attomol was calculated.[14] In a system using a dye-encapsulated nanovesicle label, Baeumner and colleagues[15] showed that sandwich hybridization in solution could be detected simply and with high sensitivity. Target DNA, capture probe, and labeled probe were mixed for 20 min, sampled with a membrane strip for 10 min, and then read with a reflectometer. This method showed sensitivity to 1 fmol (1 nM in 10 mL). Using an optical thin-film biosensor, Zhong and coworkers1-16-1 printed DNA arrays that detected PCR products with a lower limit less than 5 fmol. The signal is visible to the naked eye, and data can be recorded using a digital camera, a dissecting microscope, and a standard light source. In this system, a 30-40-min oligo sandwich detection method was used, facilitated by a Thermusthermophilus ligase modified to have a 10-fold increase in efficiency. To compare accuracy with standard methods, DNA samples from 100 human subjects were tested for SNPs associated with increased risk of venous thromboembolism, and DNA samples from 50 individuals were tested for SNP genotyping. Results were as good as or better than TaqMan™ or RFLP results.

Getting Started With Dumbbells

Getting Started With Dumbbells

The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.

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