We demonstrate that the use of wormlike nonionic micelles as drag-tags in end-labeled free-solution electrophoresis (“micelle-ELFSE”) provides single-base resolution of Sanger sequencing products up to 502 bases in length, a nearly 2-fold improvement over reported ELFSE separations. “CiEj” running buffers containing 48 mM C12E5, 6 mM C10E5, and 3 M urea (32.5 °C) form wormlike micelles that provide a drag equivalent to an uncharged DNA fragment with a length (α) of 509 bases (effective Rh = 27 nm). Runtime in a 40 cm capillary (30 kV) was 35 min for elution of all products down to the 26-base primer. We also show that smaller Triton X-100 micelles give a read length of 103 bases in a 4 min run, so that a combined analysis of the Sanger products using the two buffers in separate capillaries could be completed in 14 min for the full range of lengths. A van Deemter analysis shows that resolution is limited by diffusion-based peak broadening and wall adsorption. Effects of drag-tag polydispersity are not observed, despite the inherent polydispersity of the wormlike micelles. We ascribe this to a stochastic size-sampling process that occurs as micelle size fluctuates rapidly during the runtime. A theoretical model of the process suggests that fluctuations occur with a time scale less than 10 ms, consistent with the monomer exchange process in nonionic micelles. The CiEj buffer has a low viscosity (2.7 cP) and appears to be semidilute in micelle concentration. The large drag-tag size of the CiEj buffers leads to steric segregation of the DNA and tag for short fragments and attendant mobility shifts.

Hybridization analysis of short DNA and RNA targets presents many challenges for detection. The commonly employed sandwich hybridization approach cannot be implemented for these short targets due to insufficient probe-target binding strengths for unmodified DNA probes. Here, we present a method capable of rapid and stable sandwich hybridization detection for 22 nucleotide DNA and RNA targets. Stable hybridization is achieved using an n-alkylated, polyethylene glycol γ-carbon modified peptide nucleic acid (γPNA) amphiphile. The γPNA’s exceptionally high affinity enables stable hybridization of a second DNA-based probe to the remaining bases of the short target. Upon hybridization of both probes, an electrophoretic mobility shift is measured via interaction of the n-alkane modification on the γPNA with capillary electrophoresis running buffer containing nonionic surfactant micelles. We find that sandwich hybridization of both probes is stable under multiple binding configurations and demonstrate single base mismatch discrimination. The binding strength of both probes is also stabilized via coaxial stacking on adjacent hybridization to targets. We conclude with a discussion on the implementation of the proposed sandwich hybridization assay as a high-throughput microRNA detection method.

Atomic force microscopy (AFM) was used to measure the disjoining pressures of perfluoropolyether lubricant films (0.8−4.3 nm of Fomblin Z03) on both silicon wafers and hard drive disks coated with a diamondlike carbon overcoat. Differences in the disjoining pressure between the two systems were expected to be due to variations in the strength of van der Waals interactions. Lifshitz theory calculations suggest that this substrate switch will lead to relatively small changes in disjoining pressure as compared to the more pronounced effects reported due to changes in lubricant chemistry. We demonstrate the sensitivity of our AFM method by distinguishing between these similar systems.

The stability and passivity of poly(ethylene glycol)–polyethylenimine (PEG–PEI) graft films are important for their use as antifouling coatings in a variety of biotechnology applications. We have used AFM colloidal-probe force measurements combined with optical reflectometry to characterize the surface properties and stability of PEI and dense PEG–PEI graft films on silica. Initial contact between bare silica probes and PEI-modified surfaces yields force curves that exhibit a long-range electrostatic repulsion and short-range attraction between the surfaces, indicating spontaneous desorption of PEI in the aqueous medium. Further transfer of PEI molecules to the probe occurs with subsequent application of forces between FR=300 and 500 μN/m. The presence of PEG reduces the adhesive properties of the PEI surface and prevents transfer of PEI molecules to the probe with continuous contact, though an initial desorption of PEI still occurs. Glutaraldehyde crosslinking of the graft films prevents both the initial desorption and subsequent transfer of the PEI, resulting in sustained attractive interaction forces of electrostatic origin between the negatively charged probe and the positively charged copolymer graft films.

A run-of-mine (ROM) ore milling circuit poses many difficulties in terms of measuring process variables and determining accurate models. Control of the ROM circuit is therefore not a trivial task to achieve. An example of a ROM circuit model with reduced complexity that works well for control purposes is discussed. The mill model is discussed in detail, as this model is used for state estimation. A neural network is trained with three disturbance parameters and used to estimate the internal states of the mill, and the results are compared with those of particle filter implementation. A novel combined neural network and particle filter state estimator is presented. The estimation performance of the neural network is promising when the disturbance magnitude used is smaller than that used to train the network.

DNA separation is required to be rapid to be a useful component in DNA analysis devices. Different microfluidic device structures can be exploited to separate DNA with high throughput. We presents a framework for determining the optimal microfluidic device structure for rapid DNA separation through solving a nonlinear programming problem. Optimally designed spiral and serpentine microfluidic device configurations are shown to give comparable results for separating up to 425 bases of DNA using the micelle end-labeled free solution electrophoresis technique. The minimum run time for the serpentine microfluidic device configuration separating up to 425 bases of DNA is 5.1 minutes.