Single-microchannel, multistep assay reports protein size and immunoaffinity

We introduce a fully integrated multistep protein assay that reports both protein identity and size. To report these two properties, a microfluidic design strategy integrates pore limit electrophoresis (PLE) with a heterogeneous immunoassay in a single microchannel (PLE-IA). PLE-IA was applied in a study of follistatin, a 31.5 kDa glycoprotein regulating mammalian cell proliferation and differentiation. In a single-channel multistage assay approach, an antibody to follistatin was first immobilized in a polyacrylamide PLE gradient gel, near the origin of the separation axis. Immobilization relies on pore-limit exclusion of the antibody and not on chemical functionalization of either the sieving matrix or the antibody, making assay customization by an end-user straightforward. Subsequently, target and ladder protein species were electrophoretically introduced into the antibody-patterned PLE channel. Species having an affinity for the immobilized antibody were detected via heterogeneous immunoassay. Noninteracting and, thus, unbound species electromigrated past the patterned antibodies, along the separation axis, and finally separated according to the pore-size limit of each, yielding a log-linear dependence of molecular weight on migration distance. Separations of 10 min yielded an average peak capacity of 18 ± 1.3 (separation resolution (SR) = 1) in a 10 mm separation distance. Comparison of the separated peaks in two parallel PLE channels in the presence or absence of capture antibody with a protein size ladder revealed good agreement of the target molecular weight with reported values. In addition, a more than 50-fold decrease in the detection limit (0.078 vs 5 nM) was achieved using an electrophoretic "continuous injection" technique in which sample material was continuously loaded for 40 min. On the basis of this proof-of-principle demonstration with follistatin, PLE-IA should find application in study of cell signaling, including questions related to aging and regeneration.     

Multianalyte on-chip native Western blotting

We introduce and characterize multiplexed native Western blotting in an automated and unified microfluidic format. While slab gel Western blotting is slow and laborious, conventional multiplexed blotting ("reblotting": probing one sample with multiple antibodies) requires even more resources. Here we detail three key advances that enable an automated and rapid microfluidic alternative to slab gel reblotting. First, we introduce both assay and microdevice designs that integrate protein blotting against multiple antibody blotting regions with native polyacrylamide gel electrophoresis. This microfluidic integration strategy overcomes nonspecific material losses inherent to harsh antibody stripping steps typically needed for conventional reblotting; said conditions can severely limit analyte quantitation. Second, to inform rational design of the multiplexed microfluidic device we develop an analytical model for analyte capture on the blotting regions. Comparison to empirical observations is reported, with capture efficiencies of >85%. Third, we introduce label free detection that makes simultaneous and quantitative multiplexed measurements possible without the need for prelabeling of sample. Assay linear dynamic range spans 8-800 nM with assay completion in 5 min. Owing to the speed, automation, enhanced quantitation capability, and the difficulty of conventional slab gel Western reblotting, microfluidic multiplexed native Western blotting should find use in systems biology, in particular in analyses of protein isoforms and multimeric protein complexes.     

触摸屏的光学增强与EMI屏蔽

对触摸屏技术的期待已经渗透到每个配置有显示器的电子设备上,其结果是要求工程师使用触摸屏来扩展每个设备的应用范围和适用环境。通常成功的项目是易读性与电磁兼容性的平衡。     

Biomass assessment and small scale biomass fired electricity generation in the Green Triangle, Australia

Coal fired electricity is a major factor in Australia’s greenhouse gas emissions (GHG) emissions. The country has adopted a mandatory renewable energy target (MRET) to ensure that 20% of electricity comes from renewable sources by 2020. In order to support the MRET, a market scheme of tradable Renewable Energy Certificates (RECs) has been implemented since 2001. Generators using biomass from eligible sources are able to contribute to GHG emission reduction through the substitution of coal for electricity production and are eligible to create and trade RECs. This paper quantifies the potential biomass resources available for energy generation from forestry and agriculture in the Green Triangle, one of the most promising Australian Regions for biomass production. We analyse the cost of electricity generation using direct firing of biomass, and estimate the required REC prices to make it competitive with coal fired electricity generation. Major findings suggest that more than 2.6 million tonnes of biomass are produced every year within 200 km of the regional hub of Mount Gambier and biomass fired electricity is viable using feedstock with a plant gate cost of 46 Australian Dollars (AUD) per tonne under the current REC price of 34 AUD per MWh. These findings are then discussed in the context of regional energy security and existing targets and incentives for renewable energies.     

Integrated preconcentration SDS-PAGE of proteins in microchips using photopatterned cross-linked polyacrylamide gels

The potential of integration of functions in microfluidic chips is demonstrated by implementing on-chip preconcentration of proteins prior to on-chip protein sizing by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Two polymeric elements-a thin (approximately 50 microm) size exclusion membrane for preconcentration and a longer (approximately cm) porous monolith for protein sizing-were fabricated in situ using photopolymerization. Contiguous placement of the two polymeric elements in the channels of a microchip enabled simple and zero dead volume integration of the preconcentration with SDS-PAGE. The size exclusion membrane was polymerized in the injection channel using a shaped laser beam, and the sizing monolith was cast by photolithography using a mask and UV lamp. Proteins injected electrophoretically were trapped on the upstream side of the size exclusion membrane (MW cutoff approximately 10 kDa) and eluted off the membrane by reversing the electric field. Subsequently, the concentrated proteins were separated in a cross-linked polyacrylamide monolith that was patterned contiguous to the size exclusion membrane. The extent of protein preconcentration is easily tuned by varying the voltage during injection or by controlling the sample volume loaded. Electric fields applied across the nanoporous membrane resulted in a concentration polarization effect evidenced by decreasing current over time and irreproducible migration of proteins during sizing. To minimize the concentration polarization effect, sieving gels were polymerized only on the separation side of the membrane, and an alternate electrical current path was employed, bypassing the membrane, for most of the elution and separation steps. Electrophoretically sweeping a fixed sample volume against the membrane yields preconcentration factors that are independent of protein mobility. The volume sweeping method also avoids biased protein loading from concentration polarization and sample matrix variations. Mobilities of the concentrated proteins were log-linear with respect to molecular weight, demonstrating the suitability of this approach for protein sizing. Proteins were concentrated rapidly (<5 min) over 1000-fold followed by high-resolution separation in the sieving monolith. Proteins with concentrations as low as 50 fM were detectable with 30 min of preconcentration time. The integrated preconcentration-sizing approach facilitates analysis of low-abundant proteins that cannot be otherwise detected. Moreover, the integrated preconcentration-analysis approach employing in situ formation of photopatterned polymeric elements provides a generic, inexpensive, and versatile method to integrate functions at chip level and can be extended to lowering of detection limits for other applications such as DNA analysis and clinical diagnostics.     

Augmented solar energy collection using different types of planar reflective surfaces; theoretical calculations and experimental results

The use of planar reflective surfaces can substantially improve the performance of both active and passive solar collectors. In this paper the results of theoretical calculations and experimental tests are presented on the use of different types of flat reflective surfaces to increase the collection of solar energy by flat collectors. Specular, diffuse, and combination specular/diffuse reflective surfaces are discussed. This present work differs from that of other investigators principally in that an attempt has been made to describe the reflective properties of surfaces in more generalized terms than simple specular or simple diffuse. Most real surfaces possess a combination of specular- and diffuse-like reflectivities. The reflectivity properties of a given surface can be measured in the laboratory as a function of incident and reflected angles, and these measured reflective properties can be used in the computer model to predict the increase in collector performance with such a reflector. Thus outdoor tests of a given reflector can be avoided if desired, and yet it is possible to make an estimate of the reflector's contribution to the collector's overall performance. Theoretical calculations of collector energy inputs were done for several distinct types of reflecting surfaces. These calculations based on indoor laboratory measurements of the reflective properties of the surfaces, were compared with experimental results obtained from an outdoor simulation apparatus. Predictions of system performance were made for various collector/reflector configurations, and compared with the performance of an optimally oriented collector without a reflector.     

Optimization of human-powered elastic mechanisms for endurance amplification

Throughout the human body hundreds of muscles exert forces to stiffen and move the limbs and torso. During heavy exercise, only a small portion of these muscles fatigue. We report here a new kind of human-powered mechanism which amplifies endurance by altering the distribution of work output between fatiguing and nonfatiguing muscles. During heavy exercise, springs within the mechanism are stretched by muscles which would not fatigue if the exercise were conducted without the mechanism. This stored energy is then used to assist those muscles which typically would fatigue, resulting in an increase in endurance. A mathematical model is used to predict the efficiency with which the body can perform mechanical work at various spring stiffnesses for a particular heavy-exercise activity and mechanism. The model results support the hypothesis that the spring stiffnesses which maximize endurance also maximize the efficiency with which the human body can perform work.     

Current and past depression as predictors of family functioning: A comparison of men and women in a community sample.

The association between family functioning and parental depression has primarily been studied in samples of women. In particular, very little research exists that examines how parent gender and past diagnoses of depression are related to family functioning. The family relationships of 469 couples from a community sample were examined using self- and partner report measures of the marital relationship and youth report and interviewer-rated measures of the parent-youth relationship. Both currently and formerly depressed men and women were shown to have poorer family functioning than nondepressed and never depressed individuals, respectively. Interactions of gender and depression status indicated that depression and poorer marital functioning were more strongly related for women than for men, but there were few gender differences in the parent-youth relationship. The results highlight the need for further research on men's family functioning and suggest that targeting current depressive symptoms in treatment may not be sufficient to resolve marital and parent-youth difficulties that endure after depressive episodes remit. (PsycINFO Database Record (c) 2010 APA, all rights reserved)