Different behavior of Ferguson plot between agarose and polyacrylamide gels.

In this study, we conducted Ferguson plot analyses using both agarose and polyacrylamide gels in native electrophoresis and SDS-PAGE. The results revealed intriguing differences in the behavior of bovine serum albumin (BSA) and other model proteins. Specifically, BSA exhibited Ferguson plot slopes that were dependent on the oligomer size in agarose native gel electrophoresis, while such size-dependent behavior was not observed in native-PAGE or SDS-PAGE. These findings suggest that Ferguson plot analysis is a suitable approach when using agarose gel under the electrophoretic conditions employed in this study. Furthermore, our investigation extended to model proteins with acidic isoelectric points and larger molecular weights, namely Ferritin and caseinolytic peptidase B (ClpB). Notably, these proteins displayed distinct Ferguson plot slopes when subjected to agarose gel electrophoresis. Intriguingly, when polyacrylamide gel was employed, ClpB exhibited multiple bands, each with its unique Ferguson plot slope, deviating from the expected behavior based on molecular size. This divergence in Ferguson plot characteristics between agarose and polyacrylamide gels points to an interesting and complex interplay between protein properties and gel electrophoresis conditions.

Serum protein electrophoresis in European mink (Mustela lutreola): reference intervals and comparison of agarose gel electrophoresis and capillary zone electrophoresis.

BACKGROUND: Knowledge of reference intervals for blood analytes, including serum protein fractions, is of great importance for the identification of infectious and inflammatory diseases and is often lacking in wild animal species. MATERIAL AND METHODS: Serum samples were obtained from European minks enrolled in the breeding program (n = 55). Agarose gel electrophoresis (AGE) and capillary zone electrophoresis (CZE) were used to separate and identify protein fractions. Albumin, α1, α2, ß, and γ-globulins fractions were identified in all mink sera by both electrophoresis methods. Reference intervals (90% CI) were determined following the 2008 guidelines of the Clinical Laboratory Standard Institute. The methods were compared using Passing-Bablok regression, Bland-Altman analysis, and Lin's concordance correlation. RESULTS: A significant bias was found between methods for α1, α2, and γ-globulin. Lin's concordance correlation was considered unacceptable for α1, α2, and ß-globulins. Differences for gender between methods were found for albumin and α2-globuins, which were higher for males than females. γ-globulins were higher for adults than young minks using both methods; however, α1 and α2-globulins were lower. CONCLUSION: Both methods are adequate for identifying serum protein disorders, but the AGE and CZE methods are not equivalent. Therefore, reference intervals for each technique are required.

SURE gel electrophoresis: A method for improved detection and purification of dilute nucleic acid samples.

Agarose gel electrophoresis is performed routinely by molecular biologists as both an analytical and a preparative method for characterization of nucleic acids. Gel analysis of highly dilute DNA solutions is challenging because of the limited sensitivity of detection available with conventional methods. In this study a new approach is described for concentrating samples directly within gels called SURE (successive reloading) electrophoresis. The approach involves loading of dilute samples multiple times into a single well, with each loading followed by a brief pulse of electrical current before the next sample is loaded. The procedure generates single bands created by molecular stacking that exhibit strongly enhanced signal intensities and minimal band broadening. Using optimized voltages and time intervals as many as 20 successive loadings could be performed and up to 800 µL could be loaded into a single well. Gel extraction and fluorescent quantitation demonstrated that approximately 97 % of the DNA from each loading was incorporated into the resultant band. Highly dilute DNA samples (<0.0007 ng per microliter) could be readily detected after six loadings. The method produced good results with either TAE or TBE as electrophoresis buffers, using loading dyes with or without SDS, and in both minigels and large gels.

Isolation of High-Molecular-Weight DNA for Long-Read Sequencing Using a High-Salt Gel Electroelution Trap.

Long-read sequencing technologies require high-molecular-weight (HMW) DNA of sufficient purity and integrity, which can be difficult to obtain from complex biological samples. We propose a method for purifying HMW DNA that takes advantage of the fact that DNA's electrophoretic mobility decreases in a high-ionic-strength environment. The method begins with the separation of HMW DNA from various impurities by electrophoresis in an agarose gel-filled channel. After sufficient separation, a high-salt gel block is placed ahead of the DNA band of interest, leaving a gap between the separating gel and the high-salt gel that serves as a reservoir for sample collection. The DNA is then electroeluted from the separating gel into the reservoir, where its migration slows due to electrostatic shielding of the DNA's negative charge by excess counterions from the high-salt gel. As a result, the reservoir accumulates HMW DNA of high purity and integrity, which can be easily collected and used for long-read sequencing and other demanding applications without additional desalting. The method is simple and inexpensive, yields sequencing-grade HMW DNA even from difficult plant and soil samples, and has the potential for automation and scalability.

Yield Gel via Quantitative Gel Electrophoresis.

Quantitative gel electrophoresis, also referred to as yield gel via gel electrophoresis, is an early quantification method that was developed to provide an estimate of the quality and the quantity of DNA extracted from evidence or reference samples. To conduct quantitative gel electrophoresis, an agarose gel that is combined with a nucleic acid gel stain is prepared. The gel stain intercalates between double-stranded DNA and can be visualized using UV light. DNA extract samples, along with DNA standards (ranging from 250 to 5 ng), and a 1 KB ladder are combined with a 6X loading dye and loaded on the agarose gel. Voltage is applied to facilitate DNA migration through the gel from the negative to the positive electrode, separating DNA fragments by size. After electrophoresis is complete, the results are visualized using UV light, and an image is captured for analysis. High-quality and -quantity DNA should contain a compact band comparable to that of the high molecular weight standards and ladder, with some smearing down the sample well. If a DNA extract sample does not produce a compact band and presents with only a smear, this is an indication that DNA degradation has occurred. This chapter provides instructions on how to successfully prepare an agarose gel, load DNA extract samples and corresponding controls, appropriately set up and run quantitative gel electrophoresis, interpret the results, and ensure comprehension of the method so troubleshooting can be performed if needed.

Appearance of ghost bands in gel electrophoresis depending on agarose concentration.

Standard agarose gel electrophoresis is a widely used method to analyse diversity of nucleic acids. Certain conditions, however, may give rise to artefactual bands. We report on artefactual bands frequently occurring, especially when partially homologous nucleic acids, such as splicing variants of DNA transcripts, are analysed simultaneously. Interestingly, to some extent agarose concentration may influence the occurrence of artefactual bands.

Development of a novel two-dimensional gel electrophoresis protocol with agarose native gel electrophoresis.

A new protocol for conducting two-dimensional (2D) electrophoresis was developed by combining the recently developed agarose native gel electrophoresis with either vertical sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis (PAGE) or flat SDS agarose gel electrophoresis. Our innovative technique utilizes His/MES buffer (pH 6.1) during the first-dimensional (1D) agarose native gel electrophoresis, which allows for the simultaneous and clear visualization of basic and acidic proteins in their native states or complex structures. Our agarose gel electrophoresis is a true native electrophoresis, unlike blue native-PAGE, which relies on the intrinsic charged states of the proteins and their complexes without the need for dye binding. In the 2D, the gel strip from the 1D agarose gel electrophoresis is soaked in SDS and placed on top of the vertical SDS-PAGE gels or the edge of the flat SDS-MetaPhor high-resolution agarose gels. This allows for customized operation using a single electrophoresis device at a low cost. This technique has been successfully applied to analyze various proteins, including five model proteins (BSA, factor Xa, ovotransferrin, IgG, and lysozyme), monoclonal antibodies with slightly different isoelectric points, polyclonal antibodies, and antigen-antibody complexes, as well as complex proteins such as IgM pentamer and ß-galactosidase tetramer. Our protocol can be completed within a day, taking approximately 5-6 h, and can be expanded further into Western blot analysis, mass spectrometry analysis, and other analytical methods.

Agarose native gel electrophoresis analysis of thermal aggregation controlled by Hofmeister series.

The effects of salting-in and salting-out salts defined by Hofmeister series on the solution state of bovine serum albumin (BSA) in 50 mM Tris-HCl buffer at pH 7.4 before and after thermal unfolding at 80 °C for 5 min were examined using agarose native gel electrophoresis and mass photometry. Gel electrophoresis showed that salting-in MgCl2, CaCl2 and NaSCN resulted in formation of intermediate structures of BSA upon heating on native gel, while heating in buffer alone resulted in aggregated bands. Mass photometry showed large loss of monomer and oligomers when heated in this buffer, but retaining these structures in the presence of 1 M MgCl2 and NaSCN. To our surprise, salting-out MgSO4 also showed a similar effect on gel electrophoresis and mass photometry. Salting-out NaCl and (NH4)2SO4 resulted in smearing and aggregated bands, which were supported by mass photometry. Aggregation-suppressive ArgHCl also showed oligomer aggregates upon gel electrophoresis and mass photometry.

Analysis of Mitochondrial DNA Replication by Two-Dimensional Agarose Gel Electrophoresis.

Two-dimensional neutral/neutral agarose gel electrophoresis (2D-AGE) has been employed for nearly two decades in the analysis of replication and maintenance processes of animal mitochondrial DNA, but the method's potential has not been fully exploited. Here, we describe the various steps involved in this technique, from DNA isolation, to two-dimensional neutral/neutral agarose gel electrophoresis (2D-AGE), Southern hybridization and interpretation. We also provide examples of the applicability of 2D-AGE to investigate the different features of mtDNA maintenance and regulation.

A method for high-concentration agarose gel preparation and its application in high-resolution separation of low-molecular-weight nucleic acids and proteins.

Separation of nucleic acids and proteins using gels has always been a crucial part of molecular biology research. For low-molecular-weight nucleic acids and proteins, low- and medium-concentration agarose gels cannot achieve the high resolution as polyacrylamide gels. We found that 6 %-14 % high-concentration agarose gels (HAGs) could be easily dissolved in an autoclave and the vertical gel cast can be effortlessly filled using an easy-made plastic box. Coupled with the improved buffer condition, HAG electrophoresis resulted in a good resolution of DNA and protein bands. With conventional TBE buffer plus 0.2 % NaCl, DNA fragments that differ by 2-5-bp within the 50-200-bp size range can be resolved on 6 %-8 % HAGs. By using TBE without NaCl, DNA fragments that differ by 2-bp or 2-nt within the 10-100-bp size range can be well resolved on >8 % HAGs. Using a buffer system comprising 1 M Tris-Cl for gel preparation, 0.2 M Tris-Cl/0.2 % SDS as upper tank buffer, and 0.2 M Tris-Cl as the lower tank buffer, HAGs achieved good molecular weight separation of total bacterial and plant proteins in the 10-200 kDa range. In conclusion, we developed a method for HAG preparation and electrophoresis of low-molecular-weight nucleic acids and proteins.

Detection of concentration-dependent conformational changes in SARS-CoV-2 nucleoprotein by agarose native gel electrophoresis.

The nucleoprotein (NP) of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is abundantly expressed during infection, making it a diagnostic target protein. We analyzed the structure of the NP in solution using a recombinant protein produced in E. coli. A codon-optimized Profinity eXact™-tagged NP cDNA was cloned into pET-3d vector and transformed into E. coli T7 Express. The recombinant protein was first purified via chromatographic step using an affinity tag-based system that was followed by tag cleavage with sodium fluoride, resulting in proteolytic removal of the N-terminal tag sequence. The digested sample was then loaded directly onto a size exclusion chromatography run in the presence of L-Arg-HCl, resulting in removal of host nucleic acids and endotoxin. The molecular mass of the main NP fraction was determined by mass photometry as a dimeric form of NP, consistent with the blue native PAGE results. Interestingly, analysis of the purified NP by our newly developed agarose native gel electrophoresis revealed that it behaved like an acidic protein at low concentration despite its alkaline isoelectric point (theoretical pI = 10) and displayed a unique character of concentration-dependent charge and shape changes. This study should shed light into the behavior of NP in the viral life cycle.

Utility of serum indices in a particular case of serum protein electrophoresis.

Screening and measurement of monoclonal (M) proteins are commonly performed using capillary zone electrophoresis (CZE). The identification of M-protein or monoclonal component (CM) is an essential requirement for diagnosis and monitoring of monoclonal gammopathies. The detection of CM has been largely improved by CZE. Capillary electrophoresis estimates CM more accurately, because absence of variation due to different dye binding affinities of proteins as instead seen with agarose gel electrophoresis. However, interferences can be present in CZE. This occurs because all substances absorbing at 200 nm can be identified. Recognition and handling of specimens exhibiting such interferences is essential to ensure accurate diagnostic and patient safety. We herein report on an unusual case of serum protein electrophoresis, to highlight that laboratory staff must be aware of and familiarise with the information provided by laboratory instruments. For example, in the case of serum indices, about specimen quality.

Noise-Activated Fast Locomotion of DNA through the Frictional Landscape of Nanoporous Gels.

It is hypothesized that nonlinear solid friction between the gel matrix and DNA molecules inhibits the motion of DNA through the nanopores of the gel during electrophoresis. In this article, it is demonstrated that external noise can alleviate the effect of solid friction, thus enhancing the mobility of DNA in an electrophoretic setting. In the presence of noise, the mobility of DNA increases by more than ∼113% compared to conventional electrophoresis. Although at a high power of noise, DNA exhibits Arrhenius kinetics, at a low power of noise, super-Arrhenius kinetics suggests the collective behavior of the activated motion of DNA molecules. A stochastic simulation following modified Langevin dynamics with the asymmetric pore size distribution of the agarose gel successfully predicts the mobility of DNA molecules and reveals the salient features of the overall dynamics. This "noise lubricity" may have a broader applicability from molecular to macroscopic locomotion.

Ladder observation of bovine serum albumin by high resolution agarose native gel electrophoresis.

A commercially available bovine serum albumin (BSA) was examined by agarose native gel electrophoresis using two different agarose sources, UltraPure and MetaPhor agarose. While UltraPure agarose up to 5 % showed no clear separation of BSA oligomers, MetaPhor agarose clearly demonstrated oligomer bands above 4 %, indicating that the latter agarose has greater molecular sieving effects and is hence characterized to have high resolution for size differences, as probed by a greater slope of Ferguson plot. Physical properties are different between two agaroses. In general, UltraPure agarose has physical strength, while MetaPhor agarose is considerably fragile, but MetaPhor agarose solution is less viscous so that even 10 % gel can be made. Cause of oligomers was shown to be not associated with inter-chain disulfide bonds, but is due to association of native or native-like molecules.

Western blotting of native proteins from agarose gels.

We have developed a new Western blotting method of native proteins from agarose-based gel electrophoresis using a buffer at pH 6.1 containing basic histidine and acidic 2-(N-morpholino)ethanesulfonic acid. This gel electrophoresis successfully provided native structures for a variety of proteins and macromolecular complexes. This paper is focused on the Western blotting of native protein bands separated on agarose gels. Two blotting methods from agarose gel to PVDF membrane are introduced here, one by contact (diffusion) blotting and another by electroblotting after pre-treating the agarose gels with SDS. The contact blotting resulted in the transfer of native GFP, native human plexin domain containing protein 2 (PLXDC2) and native SARS-CoV-2 spike protein, which were detected by conformation-specific antibodies generated in-house.

Circular RNA migration in agarose gel electrophoresis.

Circular RNAs are garnering increasing interest as potential regulatory RNAs and a format for gene expression. The characterization of circular RNA using analytical techniques commonly employed in the literature, such as gel electrophoresis, can, under differing conditions, yield different results when attempting to distinguish circular RNA from linear RNA of similar molecular weights. Here, we describe circular RNA migration in different conditions, analyzed by gel electrophoresis and high-performance liquid chromatography (HPLC). We characterize key parameters that affect the migration pattern of circular RNA in gel electrophoresis systems, which include gel type, electrophoresis time, sample buffer composition, and voltage. Finally, we demonstrate the utility of orthogonal analytical tests for circular RNA that take advantage of its covalently closed structure to further distinguish circular RNA from linear RNA following in vitro synthesis.

A platform method for plasmid isoforms analysis by capillary gel electrophoresis.

In the production of novel biological products, plasmids are often engineered into delivery vectors for target genes, which can be used directly as vaccines or as intermediate products for gene/cell therapy. Plasmid DNA exists in several topological forms such as supercoiled, linear, and open circular. As supercoiled plasmid shows the highest efficiency in transfecting eukaryotic cells, the content of supercoiled plasmids becomes an important indicator of plasmid quality. CGE is an effective analysis method for separating different topological structures of plasmids. For the purpose of providing plasmid manufacturers and regulatory agencies with an efficient and readily used tool for monitoring the quality of plasmids, this article identifies the optimal separation and detection conditions of CGE, presents a platform-based plasmid analytical method, and uses plasmid of different sizes to verify the feasibility of this method. In terms of detector, the LIF detector has obvious advantages over the ultraviolet detector in sensitivity and resolution. Using the optimal CE condition (10× gel buffer), baseline separation of different topological forms and impurities can be achieved for different plasmid sizes (5.9, 7.8, 15.4 kb). In addition, 6.5 kb plasmid was used to compare the different separation technologies such as CGE-LIF, ion exchange chromatography and agarose gel electrophoresis. The result shows that CGE-LIF can provide better resolution and quantitation accuracy than ion exchange chromatography and agarose gel electrophoresis. CGE-LIF, as a quick and convenient method to separate and quantify plasmids, has the advantages of high sensitivity, high resolution, and high quantitative accuracy. Therefore, it is ideal for analysis of plasmids with different sizes, and it can also be used as a platform method for manufacturers and regulatory agencies to monitor the purity and stability of plasmids.

Agarose gel electrophoresis to assess PCR product yield: comparison with spectrophotometry, fluorometry and qPCR.

Agarose gel electrophoresis is a relatively easy to use method, commonly applied to evaluate PCR reaction success. Intercalating agents or dyes are used to visualize the amplified fragments. However, it is uncertain to what extent the brightness of bands is informative about the concentration of the amplicons. To more closely examine the suitability of agarose gel electrophoresis to assess PCR product yield, we quantified the brightness of bands on a gel and compared these data with the results from spectrophotometry, fluorometry and qPCR. Evaluation of the results suggests that assessment of the relative quantity of amplicons by band brightness is precise enough even for post-PCR analysis steps requiring PCR product concentrations within a certain range to function properly.

Separation of RNA according to Size: Electrophoresis of RNA through Agarose Gels Containing Formaldehyde.

Samples of RNA may be denatured by treatment with formamide and separated by electrophoresis through agarose gels containing formaldehyde. In this method, RNA is fractionated by electrophoresis through an agarose gel containing 2.2 m formaldehyde.

Transfer and Fixation of Denatured RNA in Agarose Gels to Membranes by Capillary Transfer.

In most cases, fractionation of RNA by agarose gel electrophoresis is but a prelude to hybridization of the fractionated population to specific labeled probes that detect particular target mRNAs. RNA is first transferred from an agarose gel to a 2D support, usually a nylon membrane. This protocol presents the steps involved in the transfer of RNA from an agarose gel to a membranous support, facilitated by the upward flow of buffer, followed by various methods for fixation of the RNA to the membrane in preparation for hybridization. An alternative method for transfer by downward capillary flow is also given.