Rapid and efficient western blot assay by rotational cyclic draining and replenishing procedure.

Western blot is a principal technique for the detection of specific proteins in various biology disciplines. The antibody incubation is an imperative step in western blot. Antibody incubation by mild shaking on a rocker is generally used to facilitate mixing of antibodies. However, mild shaking is an inefficient process to remove antibody depletion layer on blotting membrane and requires hours of incubation time to achieve antibody binding to target proteins. We propose an alternative method of cyclic draining and replenishing (CDR) incubation of antibody solution using a rotational incubation chamber. The study demonstrated that rotational CDR incubation could shorten antibody incubation time with enhanced sensitivity. Moreover, rotational CDR incubation could achieve a stronger antibody binding with lower antibody concentration when compared with batch incubation. In addition, rotational CDR incubation significantly improved the detection of low abundance proteins. This simple modification in western blot procedure makes it rapid, sensitive, and cost-efficient.

Development of a nanogold slot blot inhibition assay for the detection of antibodies against bovine herpesvirus type 1.

Bovine herpesvirus type 1 (BoHV-1) is recognized as an important pathogen causing respiratory, reproductive, and neurological disorders in cattle and is associated with economic losses to animal industry. Accurate diagnostic methods are needed for prevention of disease transmission. While the virus neutralization test is considered the gold standard method, it requires maintenance of the virus and cell cultures, which is time consuming and expensive. Serological techniques such as enzyme-linked immunosorbent assay (ELISA) are widely applied, as these are easy to perform and provide quick results. In the present study, a nanogold slot blot inhibition assay was developed for the serological diagnosis of BoHV-1 and compared with standard ELISA and horseradish peroxidase (HRP) slot blot assays. Of 42 serum samples tested by ELISA, 32 (76.2%) were positive and 10 (23.8%), were negative. The sensitivity and specificity of the nanogold slot blot inhibition assay was similar to that observed for ELISA and HRP slot blot assays, and a strong correlation was observed between the tests. Thus, the nanogold slot blot inhibition assay may serve as an efficient and rapid alternative to ELISA in settings, where plate-reading equipment is lacking.

Microfluidic Western blotting of low-molecular-mass proteins.

We describe a microfluidic Western blot assay (µWestern) using a Tris tricine discontinuous buffer system suitable for analyses of a wide molecular mass range (6.5-116 kDa). The Tris tricine µWestern is completed in an enclosed, straight glass microfluidic channel housing a photopatterned polyacrylamide gel that incorporates a photoactive benzophenone methacrylamide monomer. Upon brief ultraviolet (UV) light exposure, the hydrogel toggles from molecular sieving for size-based separation to a covalent immobilization scaffold for in situ antibody probing. Electrophoresis controls all assay stages, affording purely electronic operation with no pumps or valves needed for fluid control. Electrophoretic introduction of antibody into and along the molecular sieving gel requires that the probe must traverse through (i) a discontinuous gel interface central to the transient isotachophoresis used to achieve high-performance separations and (ii) the full axial length of the separation gel. In-channel antibody probing of small molecular mass species is especially challenging, since the gel must effectively sieve small proteins while permitting effective probing with large-molecular-mass antibodies. To create a well-controlled gel interface, we introduce a fabrication method that relies on a hydrostatic pressure mismatch between the buffer and polymer precursor solution to eliminate the interfacial pore-size control issues that arise when a polymerizing polymer abuts a nonpolymerizing polymer solution. Combined with a new swept antibody probe plug delivery scheme, the Tris tricine µWestern blot enables 40% higher separation resolution as compared to a Tris glycine system, destacking of proteins down to 6.5 kDa, and a 100-fold better signal-to-noise ratio (SNR) for small pore gels, expanding the range of applicable biological targets.

Western blotting by thin-film direct coating.

A novel thin-film direct coating (TDC) technique was developed to markedly reduce the amount of antibody required for Western blotting (WB). Automatic application of the technique for a few seconds easily and homogeneously coats the specific primary antibody on the polyvinylidene fluoride (PVDF) membrane. While conventional WB requires 0.4 µg of the primary antibody, the proposed technique only uses 4 × 10(-2) µg, which can be reduced further to 4 × 10(-5) µg by reducing the coater width. Moreover, the proposed process reduces antibody probing times from 60 to 10 min. The quantification capability of TDC WB showed high linearity within a 4-log2 dynamic range for detecting target antigen glutathione-S-transferase. Furthermore, TDC WB can specifically detect the extrinsic glutathione-S-transferase added in the Escherichia coli or 293T cell lysate with better staining sensitivity than conventional WB. TDC WB can also clearly probe the intrinsic ß-actin, α-tubulin, and glyceraldehyde 3-phosphate dehydrogenase, which are usually used as control proteins in biological experiments. This novel technique has been shown to not only have valuable potential for increasing WB efficiency but also for providing significant material savings for future biomedical applications.

Systems analysis of EGF receptor signaling dynamics with microwestern arrays.

We describe microwestern arrays, which enable quantitative, sensitive and high-throughput assessment of protein abundance and modifications after electrophoretic separation of microarrayed cell lysates. This method allowed us to measure 91 phosphosites on 67 proteins at six time points after stimulation with five epidermal growth factor (EGF) concentrations in A431 human carcinoma cells. We inferred the connectivities among 15 phosphorylation sites in 10 receptor tyrosine kinases (RTKs) and two sites from Src kinase using Bayesian network modeling and two mutual information-based methods; the three inference methods yielded substantial agreement on the network topology. These results imply multiple distinct RTK coactivation mechanisms and support the notion that small amounts of experimental data collected from phenotypically diverse network states may enable network inference.

Microfluidic integration of Western blotting is enabled by electrotransfer-assisted sodium dodecyl sulfate dilution.

We integrate sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) with subsequent antibody probing in a single, monolithic microdevice to realize microfluidic Western blotting. A hurdle to successful on-chip Western blotting lies in restoring antibody recognition of previously sized (denatured, reduced) proteins. To surmount this hurdle, we locally dilute free SDS from SDS-protein complexes using differential electromigration of the species during electrotransfer between SDS-PAGE and blotting regions of a microchamber. Local dilution of SDS minimizes re-association of SDS with proteins offering means to restore antibody binding affinity to proteins after SDS-PAGE. To achieve automated, programmable operation in a single instrument, we utilize a 1 × 2 mm(2) glass microchamber photopatterned with spatially distinct, contiguous polyacrylamide regions for SDS-PAGE, electrotransfer, and antibody blotting. Optimization of both the SDS-PAGE and electrotransfer conditions yields transfer distances of <1 mm (40 s). The Western blot is completed in 180 s, with fully automated assay operation using programmable voltage control. After SDS-PAGE and electrotransfer, we observe ~80% capture of protein band mass on the blotting region for a model protein, C-reactive protein. This novel microfluidic Western blot approach introduces fine transport control for in-transit protein handling to form the basis for an automated, rapid alternative to conventional slab-gel Western blotting.

Surface modification of electrospun polyvinylidene fluoride nanofiber membrane by plasma treatment for protein detection.

Electrospun polyvinylidene fluoride (PVDF) nanofiber membranes have 3-dementional (3-D) open pore channel and hence have excellent application potential in Western blot. In this study we have modified electrospun PVDF nanofiber membrane by argon (Ar) plasma treatment to improve the surface hydrophilic and detection sensitivity. The results showed that the detection sensitivity of the Ar plasma-treated PVDF nanofiber membrane increased with increasing plasma treatment time without the need for a methanol pre-wet step. This suggests that the Ar plasma treated PVDF nanofiber membrane can be useful in Western blot with high sensitivity and without methanol pre-wet step.

Qualitative and quantitative evaluation of Simon™, a new CE-based automated Western blot system as applied to vaccine development.

Many CE-based technologies such as imaged capillary IEF, CE-SDS, CZE, and MEKC are well established for analyzing proteins, viruses, or other biomolecules such as polysaccharides. For example, imaged capillary isoelectric focusing (charge-based protein separation) and CE-SDS (size-based protein separation) are standard replacement methods in biopharmaceutical industries for tedious and labor intensive IEF and SDS-PAGE methods, respectively. Another important analytical tool for protein characterization is a Western blot, where after size-based separation in SDS-PAGE the proteins are transferred to a membrane and blotted with specific monoclonal or polyclonal antibodies. Western blotting analysis is applied in many areas such as biomarker research, therapeutic target identification, and vaccine development. Currently, the procedure is very manual, laborious, and time consuming. Here, we evaluate a new technology called Simple Western™ (or Simon™) for performing automated Western analysis. This new technology is based on CE-SDS where the separated proteins are attached to the wall of capillary by a proprietary photo activated chemical crosslink. Subsequent blotting is done automatically by incubating and washing the capillary with primary and secondary antibodies conjugated with horseradish peroxidase and detected with chemiluminescence. Typically, Western blots are not quantitative, hence we also evaluated the quantitative aspect of this new technology. We demonstrate that Simon™ can quantitate specific components in one of our vaccine candidates and it provides good reproducibility and intermediate precision with CV <10%.

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.

Identification and validation of rice reference proteins for western blotting.

Studies of rice protein expression have increased considerably with the development of rice functional genomics. In order to obtain reliable expression results in western blotting, information on appropriate reference proteins is necessary for data normalization. To date, no published study has identified and systematically validated reference proteins suitable for the investigation of rice protein expression. In this study, nine candidate proteins were selected and their specific antibodies were obtained through immunization of rabbits with either recombinant proteins expressed in Escherichia coli or synthesized peptides. Western blotting was carried out to detect the expression of target proteins in a set of 10 rice samples representing different rice tissues/organs at different developmental stages. The expression stability of the proteins was analysed using geNorm and Microcal Origin 6.0 software. The results indicated that heat shock protein (HSP) and elongation factor 1-α (eEF-1α) were the most constantly expressed among all rice proteins tested throughout all developmental stages, while the proteins encoded by conventional internal reference genes fluctuated in amount. Comparison among the profiling of translation and transcription [expressed sequence tags (EST) and massively parallel signature sequencing (MPSS)] revealed that a correlation existed. Based on the standard curves derived from the antigen-antibody reaction, the concentrations of HSP and eEF-1α proteins in rice leaves were ∼0.12%. Under the present experimental conditions, the lower limits of detection for HSP and eEF-1α proteins in rice were 0.24 ng and 0.06 ng, respectively. In conclusion, the reference proteins selected in this study, and the corresponding antibodies, can be used in qualitative and quantitative analysis of rice proteins.

Multistrip western blotting to increase quantitative data output.

The qualitative and quantitative measurements of protein abundance and modification states are essential in understanding their functions in diverse cellular processes. Typical western blotting, though sensitive, is prone to produce substantial errors and is not readily adapted to high-throughput technologies. Multistrip western blotting is a modified immunoblotting procedure based on simultaneous electrophoretic transfer of proteins from multiple strips of polyacrylamide gels to a single membrane sheet. In comparison with the conventional technique, Multistrip western blotting increases the data output per single blotting cycle up to tenfold, allows concurrent monitoring of up to nine different proteins from the same loading of the sample, and substantially improves the data accuracy by reducing immunoblotting-derived signal errors. This approach enables statistically reliable comparison of different or repeated sets of data, and therefore is beneficial to apply in biomedical diagnostics, systems biology, and cell signaling research.

Introduction to protein blotting.

Protein blotting is a powerful and important procedure for the immunodetection of proteins following electrophoresis, particularly proteins that are of low abundance. Since the inception of the protocol for protein transfer from an electrophoresed gel to a membrane in 1979, protein blotting has evolved greatly. The scientific community is now confronted with a variety of ways and means to carry out this transfer.

Diffusion blotting for rapid production of multiple identical imprints from sodium dodecyl sulfate polyacrylamide gel electrophoresis on a solid support.

A very simple and fast method for diffusion blotting of proteins from precast SDS-PAGE gels on a solid plastic support was developed. Diffusion blotting for 3 min gave a quantitative transfer of 10% compared with 1-h electroblotting. For each subsequent blot from the same gel a doubling of transfer time is necessary to obtain the same amount of protein onto each blot. The relative transfer of low and high molecular weight components was similar in diffusion and electroblotting. However, both methods do give a higher total transfer of the low molecular weight proteins compared with the large proteins. The greatest advantage of diffusion blotting is that several blots can be made from each lane, thus enabling testing of multiple antisera on virtually identical blots. The gel remains on the plastic support, which prevents it from stretching or shrinking. This ensures identical blots and facilitates more reliable molecular weight determination. Furthermore, the proteins remaining in the gel can be stained with Coomassie Brilliant Blue or other methods for exact and easy comparison with the developed blots. These advantages make diffusion blotting the method of choice when quantitative protein transfer is not required.

Blotting from PhastGel to membranes by ultrasound.

Ultrasound-based approach for enhanced protein blotting is proposed. Three minutes of ultrasound exposure (1 MHz, 2.5 W/cm(2)) was sufficient for a clear transfer of proteins from a polyacrylamide gel (PhastGel) to nitrocellulose or Nylon 66 Biotrans membrane. The proteins evaluated were prestained sodium dodecyl sulfate-polyacrylamide standards (18,500-106,000 Da) and (14)C-labeled Rainbow protein molecular weight markers (14,300-200,000 Da).

Western blot analysis of adhesive interactions under fluid shear conditions: the blot rolling assay.

Western blotting has proven to be an important technique in analysis of receptor-ligand interactions (i.e., by ligand blotting) and for identifying molecules mediating cell attachment (i.e., by cell blotting). Conventional ligand blotting and cell blotting methods employ nondynamic (static) incubation conditions, whereby molecules or cells of interest are placed in suspension and overlaid on membranes. However, many cell-cell and cell-matrix adhesive interactions occur under fluid shear conditions, and shear stress itself mediates and/or facilitates the engagement of these physiologically appropriate receptors and ligands. Notably, shear forces critically influence the adhesion of circulating cells and platelets to vessel walls in physiologic cell migration and hemostasis, as well as in inflammatory and thrombotic disorders, cancer metastasis, and atherosclerosis. Use of nondynamic blotting conditions to analyze such interactions can introduce bias, overtly missing relevant effectors and/or exaggerating the relative role(s) of nonphysiologic adhesion molecules. To address this shortfall, we have developed a new technique for identifying binding interactions under fluid shear conditions, the "blot rolling assay." Using this method, molecules in a complex mixture are resolved by gel electrophoresis, transferred to a membrane that is rendered semi-transparent, and the membrane is then incorporated into a parallel-plate flow chamber apparatus. Under controlled flow conditions, cells or particles bearing adhesion proteins of interest are then introduced into the chamber and interactions with individual immobilized molecules (bands) can be visualized in real-time. The substrate molecule(s) supporting adhesion under fluid shear can then be identified by staining with specific antibodies or by excising the relevant band(s) and performing mass spectrometry or microsequencing of the isolated material. This method thus allows for the identification, within a complex mixture and without prior isolation or purification, of both known and previously uncharacterized adhesion molecules operational under dynamic conditions.

Phosphoprotein detection on protein electroblot using a phosphate-specific fluorophore.

The reversible phosphorylation of phosphoproteins is a vital regulatory process for many cellular pathways. A reliable and simple fluorescent detection technique for phosphoproteins has been developed using a small-molecule organic fluorophore, Pro-Q Diamond dye. This was originally developed for use in gel staining, but a new formulation has allowed for its use in protein blotting. The dye binds noncovalently and selectively to the phosphate moiety, so proteins lacking phosphate groups and other macromolecules such as DNA or RNA are not detected. It uses a standard electrophoresis and electroblotting technique, which can blot the sample onto nitrocellulose membranes or polyvinylidene fluoride (PVDF). The electroblotting is followed by staining with the dye and destaining. The blot can then be read by multiple types of imaging devices such as a laser-based gel scanner. This process is compatible with matrix-assisted laser desorption time-of-flight mass spectrometry (MALDI-TOF-MS) and Edman sequencing. It can also be followed by standard chemiluminescent, colorimetric, and fluorogenic detection techniques used in immunoblotting.

"Rainbow" western blotting.

The ''Rainbow western'' method permits detection of multiple antigens on a single protein blot. The procedure utilizes horseradish peroxidase (HRPase)-based detection with both a chemiluminescent and colorimetric substrate. In the ''Rainbow western'' procedure four different HRPase-colorimetric substrates that produce black, brown, red, and green colors are employed sequentially for detection and simultaneous display of four different antigens on the same blot. The Rainbow western methods have the potential to consolidate the work to analyze the expression levels of several proteins in studies of signaling pathways within biological samples. This technique could be particularly valuable for analysis of comigrating proteins, isoforms, and/or facilitating studies on phosphorylation, acetylation, and oligomerization of proteins tagged by the same epitope.

Nonelectrophoretic bidirectional transfer of a single SDS-PAGE gel with multiple antigens to obtain 12 immunoblots.

Protein blotting is an invaluable technique in immunology to detect and characterize proteins of low abundance. Proteins resolved on sodium dodecyl sulfate (SDS) polyacrylamide gels are normally transferred electrophoretically to adsorbent membranes such as nitrocellulose or polyvinylidene diflouride membranes. Here, we describe the nonelectrophroretic transfer of the Ro 60 (or SSA) autoantigen, 220- and 240-kD spectrin antigens, and prestained molecular weight standards from SDS polyacrylamide gels to obtain up to 12 immunoblots from a single gel and multiple sera.

Ultrarapid electrophoretic transfer of high and low molecular weight proteins using heat.

An ultrarapid method for the electrophoretic transfer of high and low molecular weight proteins to nitrocellulose membranes following sodium dodecyl sulfate (SDS) polyacrylamide gel is described here. The transfer was performed with heated (70-75 degrees C) normal transfer buffer from which methanol had been omitted. Complete transfer of high and low molecular weight antigens (molecular weight protein standards, a purified protein, and proteins from a human tissue extract) could be carried out in 10 min for a 7% (0.75 mm) SDS polyacrylamide gel. For 10 and 12.5% gels (0.75 mm) the corresponding time was 15 min. A complete transfer could be carried out in 20 min for 7, 10, and 12.5% gels (1.5 mm gels). The permeability of the gel is increased by heat, such that the proteins trapped in the polyacrylamide gel matrix can be easily transferred to the membrane. The heat mediated transfer method was compared with a conventional transfer protocol, under similar conditions. The conventional method transferred minimal low molecular weight proteins while retaining most of the high molecular weight proteins in the gel. In summary, this procedure is particularly useful for the transfer of high molecular weight proteins, very rapid, and avoids the use of methanol.

Efficient electroblotting of very large proteins using a vertical agarose electrophoresis system.

Very large proteins (subunit sizes >200 kDa) are difficult to electrophoretically separate, and they are also challenging to analyze by western blotting because of their incomplete transfer out of polyacrylamide gels. An SDS vertical agarose gel system has been developed that has vastly improved resolving power for very large proteins. The large pores of the agarose also allow full transfer of proteins as large as titin (Mr =3,000-3,700 kDa) onto blots. Inclusion of a reducing agent in the upper reservoir buffer and transfer buffer has been found to be a key technical procedure in blotting large proteins.