Prepare to Cast Off: A Profile of Precast Acrylamide Gels

Date: July 20, 1998Precast Gels Warning: Neurotoxin. Cancer suspect agent. This product contains a compound known to cause cancer. Wear gloves, eye protection, and dust mask and use in a fume hood. Wash thoroughly after handling. Skin contact, inhalation, or ingestion may cause nervous system disorders. In case of contact, flush with water for 15 minutes. Yuck. The label on your bottle of acrylamide makes itself clear: weighing out acrylamide and pouring your own polyacrylamide gels is a potentially deadly task. Why take the risk when somebody has already done the work for you? That's exactly what the manufacturers of precast gels for polyacrylamide gel electrophoresis (PAGE) are asking. In exchange for a few precious research dollars, they offer convenience and an array of precast gels designed to meet all of your electrophoresis needs. Numerous gradient and single percentage gel configurations, cast in both glass and plastic cassettes, are available with a variety of sample well formats and buffer chemistries. Gels exist for nearly every conceivable electrophoretic application. In this profile, LabConsumer scans the PAGE with an eye on precast gels designed for protein applications and fitting most of the popular minigel boxes currently on the market. Precast polyacrylamide gels have many characteristics. To begin with, precast gels are manufactured in both single percentage and acrylamide gradient formats. Generally, single percentage gels resolve a narrower molecular weight range of proteins than gradient gels. The reproducible nature of manufactured gradient gels, though, has proven to be a strong selling point for these products and goes hand-in-hand with the highly refined casting techniques developed by companies such as Zaxis, Inc. Typically, the range of available acrylamide concentrations runs from 3 to 27%. Any single percentage gel or gradient between these limits can be ordered. Lastly, gel manufacturers frequently include charts in their product information that clarify which single percentage or gradient format to purchase based on the size of the proteins under study. Cassettes are usually 8 x 10 cm or 10 x 10 cm in size and frequently contain a gel 1.0 mm thick. These two cassette sizes fit the majority of minigel devices on the market (see Table 1). Larger format gels, such as 16 x 18 cm and 18.3 x 20 cm, are also manufactured and designed to fit the large gel devices from Bio-Rad and Hoefer. Most gels include poured-in sample wells. Twelve wells are most common, but other formats, ranging from an open cavity for preparative or two-dimensional work to 15 wells, are offered. Most companies offer only one format, but others, such as Bio-Rad and NOVEX, provide as many as 6 sample well configurations. Stacking gels, if they exist at all, consist of a low percentage (usually 4%) layer of acrylamide above the resolving portion of the gel. The historical pH differential between the stacking and separating gel found on handmade gels does not exist on precast gels because simple diffusion eliminates this differential while the gels sit in storage. The single exception is the GELUX PLUSTM line of gels from Biotech Holdings. This company has developed a method to maintain the pH differential on these larger format gels for up to three months. This ability is unique in the industry. Cassettes are constructed of either glass or plastic, with the exception of those from Bio-Rad, which uses a combination glass-and-plastic cassette for its Ready Gels. Generally, gels cast in plastic cost slightly less than gels cast in glass. Prices, however, are dictated by a complicated mixture of factors and therefore do not necessarily reflect the cost of materials and the associated labor. While both types of cassettes work well, glass cassettes may have a slight edge because they contain larger gels than similar sized plastic cassettes, offer improved heat transfer away from the gel, and provide crystal clear visibility. Additionally, some researchers report difficulty with cracking open the plastic cassettes that they haven't experienced with glass. Shelf lives for precast gels span from one month to one year. Prices range from a low of $5.95 (Jule Biotechnologies and FMC BioProducts) to over $30.00 for some of the specialty IEF format gels. The most common buffer system found in precast gels is the Tris-HCl system, which is a modification of the now traditional buffer system first described by Laemmli in 1970 (Nature, 227:680-85, 1970). These gels are cast with or without sodium dodecyl sulfate (SDS). Native or denaturing PAGE applications are determined by the choice of running buffer, either Tris-glycine or Tris-glycine-SDS, respectively. Novel buffer systems are also available. In particular, NOVEX's NuPAGE gels use Tris-Bis and Tris-acetate buffer systems that, among other benefits, contribute to the gels' one-year shelf life. Several companies manufacture gels that use the Tris-Tricine buffer system of Schagger and von Jagow (Analytical Biochemistry, 166:369, 1987). This system has strong applications for the resolution of small proteins and peptides with molecular weights as low as 1,000 daltons, and almost always includes a 10-20% gradient gel. Here, the buffer system enables the separation of small protein-SDS complexes from SDS-micelles. In other buffer systems, the SDS-micelles often interfere with the resolution of small, fast-moving proteins. A few companies manufacture gels for isoelectric focusing applications. These gels are cast with a pH gradient that enables the separation of proteins based on their net overall charges, often resolving proteins not separated by other methods. Most IEF gels are manufactured with either a wide or narrow pH gradient. IEF tube gels for 2D electrophoresis systems are also sold. Finally, Bio-Rad, NOVEX, and Owl Separation Systems manufacture zymogram gels. These gels are cast with casein or gelatin uniformly mixed within the gel matrix and have application for the detection of proteases that use either of the two proteins as a substrate. COMPANIES SELLING PRECAST GELS FOR NUCLEIC ACID ANALYSIS Amersham Pharmacia Biotech800-526-3593 AMRESCO, Inc.800-829-2805 Bio-Rad Laboratories800-4-BIORAD Biotech Holdings 330-655-5644 Crescent Chemical Company800-877-3225 Embi Tec800-255-1777 ESA, Inc.800-959-5095 FMC Corporation 800-341-1574 Hitachi Software800-624-6176 ICN 800-854-0530 Intermountain Scientific 800-999-2901 Jule, Inc. 800-648-1772 NOVEX 800-403-5024 Sigma Chemical Company 800-325-3010 Stratagene 800-424-5444 Zaxis800-435-2633 Bio-Rad Laboratories Bio-Rad's Ready Gels consist of a battery of precast gels designed to meet the requirements of commonly used protein electrophoresis techniques. Built to fit into Bio-Rad's convenient Ready Gel Cell, Ready Gels offer fast set up times and often run to completion in the time usually required to pour a gel from scratch. Formulated without SDS, Bio-Rad's Tris-HCl Ready Gels are suitable for either native PAGE or SDS PAGE applications. Six single percentage gels and four gradient compositions are available; the single percentage gels also include a 4% stacking layer. Designed for the accurate separation of peptides and proteins with molecular weights as low as 1,000 daltons, Bio-Rad casts its Tris-Tricine Ready Gels in a 10-20% gradient format and as a 16.5% straight percentage gel. These gels have also proven useful for resolving mixtures of lipopolysaccharides and lipooligosaccharides. The IEF Ready Gels for pI Determination come in two pH ranges. Cast in 5% acrylamide gels without denaturing agents, the wide range covers from pH 3 to pH 10 and the narrow range spans pH 5 to pH 8. IEF Ready Gels are recommended for simple isoelectric point (pI) determination, for use as the first dimension of a 2D electrophoresis procedure, and for blotting in immunodetection and protein sequencing protocols. Designed for the detection of proteolytic activity, the Zymogram Ready Gels for Protease Analysis contain casein or gelatin for use as a substrate by many different proteases. After separation by denaturing electrophoresis, the proteases are renatured and then allowed to digest the substrate. Subsequent staining reveals the proteases as light bands against a blue background. A 10% gel prepared with gelatin and a 12% gel cast with casein are available. Tris-Borate-EDTA (TBE) gels and TBE-Urea gels are available for high-resolution separations of nucleic acids. They are available in single percentage acrylamide concentrations of 5%, 10%, and 15%, with a 4-20% gradient gel also available for TBE gels. All of Bio-Rad's Ready Gels are 1.0 mm thick and are offered with a choice of 6 sample well formats. These include two 10-well combs with different volume wells, a 12- and a 15-well comb, a 2D/Prep well comb for samples up to 450 µl or an IEF tube gel, and a 9-well comb designed for the Octapette pipet that leaves one lane open for a standard. Biotech Holdings, Inc. (BHI) As a small company, Biotech Holdings, Inc. prides itself on its ability to offer custom services and strives to diligently optimize each customer's electrophoresis needs. In fact, the company's mission is to offer only customized products and services for research, industry, and educational markets. Specializing in larger format gels designed to fit the Hoefer SE 600, for example, Biotech Holdings' gels are cast in patented plastic cassettes with unique built-in combs that form 13, 20, or 27 wells. Ultrasonically welded to prevent leaking, the cassettes also feature GelBond film which serves as a plastic gel support and offers easy gel-handling properties. The same sizes are offered in glass cassettes, too. Biotech Holdings will also prepare custom gels in glass tubes, including both regular acrylamide and IEF formats. The two basic gel lines, the GELUXTM and GELUX PLUSTM precast gels, differ only in the choice of a prepoured stacking gel. On the GELUX PLUS gels, the pH of the stacking gel is lower than the pH of the separating gel. Stable for three months, the pH differential across the stacking and separating gels is unique in the precast gel industry. In keeping with the company's philosophy of offering only the highest quality customized products and services, GELUX gels are available in any single percentage or gradient composition between 3 and 27 percent acrylamide. Tris-borate-EDTA (TBE), SDS, or Tris-Tricine buffer systems are available. Finally, Biotech Holdings prefers to sell fresh gels rather than gels that have been sitting in storage awaiting buyers. Crescent Chemical Co., Inc. A recent addition to the U.S. precast gel market, Crescent Chemical Company's precast gels are a product of SERVA/Electrophoresis GmbH (formerly Boehringer Ingelheim Bioproducts Partnership) of Europe. Cast in a 10 x 10 cm format to fit the SERVA BlueVertical 101 system, among others, the SERVA Vertical Gels feature Tris-glycine chemistry in 10, 12.5, and 15 percent concentrations. Gels with Tris-tricine chemistry are available in 10 and 16.5 percent acrylamide concentrations, along with two IEF formats. These gels cover a wide pH range from 3 to 8.5 and a narrow pH range from 4 to 6. The SERVA Vertical gels are cast in unbreakable plastic cassettes with numerous features. These include an integral key for cassette opening, numbered wells from 1 to 12, centimeter markings to monitor dye front migration, and a slanted corner to mark gel orientation. Gradient gels will soon be available from Crescent Chemical. The company also sells a complete line of electrophoresis buffers, markers, stains, blotting supplies, and instrumentation. ESA, Inc. Boasting a one-year shelf life, the precast minigels from ESA, Inc. consist of two types. Both are based on a novel Tris-tricine chemistry (W.F. Patton et. al., Anal. Biochem, 197:25-33, 1991) that offers improved resolution of low molecular weight proteins. Cast in glass cassettes for enhanced cooling and heat transfer for sharper bands, these gels fit most of the commercially available minigel devices. ESA's Standard Acrylamide Mini-Gels are poured in an 8 cm x 10 cm x 1 mm format. Five straight percentage and two gradient gels with 4% stacking gels are offered. Made with ESA's proprietary high tensile strength DuracrylTM acrylamide, the High Resolution Duracyl Mini-Gels are supplied in a 10 cm x 10 cm x 0.5 mm format. The thin format provides enhanced band resolution and faster staining, while Duracryl confers increased tensile strength for improved gel handling characteristics. Both types of gels are sold in 10-packs that also include premixed buffers. Designed primarily for the Investigator 2-D Electrophoresis System, the Investigator Pre-Cast Large Format Gels are made with Duracryl and feature ESA's Tris-tricine chemistry. Designed as the second dimension slab gel in the 2D system, these gels are comprised of an 8-18% gradient gel and a 10% single percentage gel, but ESA will also accommodate custom orders. Two-dimensional electrophoresis is nothing without the first dimension, so ESA manufactures IEF tube gels in both analytical and preparative formats. The Pre-cast IEF Carrier Ampholyte Tube Gel s have two pH gradients, 3-10 and 4-8. The Pre-cast Immobilized Isoelectric Focusing Tube Gels consist of a 3-10 pH gradient in the analytical-sized tube. The analytical gels are 1 mm inside diameter (ID) x 18 cm and accept up to 100 µg of protein, whereas the preparative gels are 3 mm ID x 18 cm and run up to 1 mg of protein. ESA's tube gels are made to order to take full advantage of the gels' six-week shelf lives. Fisher Scientific Fisher's Tris-Glycine Precast Gels are compatible with Bio-Rad's Ready Gel Cell and Mini-Protean II systems, the FisherBiotech MiniVertical Electrophoresis System and the E-C Apparatus Mini Vertical Gel System. Formulated for both native PAGE and SDS-PAGE, Fisher's gels are 1 mm thick and include 10 wells. The sample comb also doubles as an opener for the plastic cassette. Choose from 7.5, 10, or 12 percent single concentration gels or a 4-20% gradient gel. Shelf lives range between 10 and 16 weeks, with 8 weeks guaranteed to the customer. FMC BioProducts One of the newer lines of precast gels on the market, FMC's PAGE TM gels are available in four straight and two gradient concentrations, and FMC will offer custom configurations in the near future. Cast in easy-to-open 8 x 10 cm or 10 x 10 cm plastic cassettes (the cassette is opened with the included well comb), PAGEr gels feature a 4% stacking gel and fit most of the available vertical gel boxes. Well markings embedded in the cassette facilitate easier sample loading, and FMC has optimized the tape removal process. The Tris-Glycine chemistry of the PAGEr gels permits both native and denaturing PAGE. FMC offers its gels in a "PAGEr scouting kit," which contains one each of the six different gel concentrations. The gels are available in packs of two or more, and FMC also provides a "Mix-and-Match" option that allows researchers to select a combination of 10 gels to meet specific needs. FMC plans to offer additional comb sizes and buffer systems in the near future. Gradipore, LTD Australia-based Gradipore, LTD, has been a precast gel manufacturer for nearly 30 years. In fact, the company's founder, Joel Margolis, obtained the first patent for gradient gel technology. While not currently active in North America, Gradipore plans to introduce its precast gels here in early 1999. ICN Biomedical Research Products Touting 2.5 times better resolution than other standard gradient minigels, ICN places a heavier emphasis on its gradient gels than most of the other companies in the profile. ICN CAPTM-Gels, as they are called, are manufactured using a Controlled Acrylamide Polymerization technique called CAPTM technology. By avoiding traditional gravity-pour methods and incorporating computerized gel casting control, CAP technology results in gradient gels with extremely narrow regions that contain very discrete pore sizes. The resolution ultimately produced by these gels frequently leads to a 50 percent reduction of sample amount compared to the sample loads needed by other gradient gels. Cast in two cassette sizes, 8 x 10 cm and 10 x 10 cm, ICN CAP-Gels fit into all of the existing minigel devices and feature a unique, corrugated plastic comb preinserted in the gel cassette. Unlike gels with poured-in combs where the wells are formed in acrylamide, this comb itself creates 12 clearly defined sample wells and prevents cross-contamination. CAP-Gels are manufactured with a Tris-SDS buffer system. Five gradient compositions and three single percentage gels are available in the CAP-Gel family. The next generation of precast gels from ICN is the CAP-Gel Plus line of precast polyacrylamide gels. Using the same CAP technology as the CAP-Gels, the CAP-Gel Plus gels feature a poured-in comb that provides 12 uniform sample wells. Additionally, these gels include a thin, low-concentration acrylamide stacking layer. Both Tris-HCl and Tris-Tricine buffer systems are used in the CAP-Gel Plus gels. Jule Biotechnologies, Inc. With prices starting at $5.95 per gel, Jule Biotechnologies, Inc., offers one of the lowest prices in the profile while giving its customers high flexibility when ordering. Jule's Precast Gels in Glass Cassettes are designed to fit both the large and small gel apparatuses from Hoefer and Bio-Rad. These gels are available from a selection of two gradients, two thicknesses, and any single concentration and in nondenaturing, denaturing, and tricine chemistries. Custom gradients are also available and easily specified with Jule's ordering system. Jule's minigels, known as SNAP-A-GELTM Precast Gels, are some of the most economical minigels on the market. Cast in patented, specially designed plastic cassettes, these gels are available in 0.75 or 1.5 mm thicknesses, with 0, 10, or 15 sample wells, and include a choice of three gradients or any single acrylamide concentration. Compatible with the minigel instruments from Bio-Rad, Hoefer, NOVEX, Owl Separation Systems, and E-C Apparatus. The SNAP-A-GELTM Precast Gels run from $5.95 to $8.95 apiece when ordered in packs of 10. Finally, Jule sells empty SNAP-A-GELTM cassettes to researchers who prefer to cast their own gels. NOVEX: Novel Experimental Technology Established in 1987 with the goal of making electrophoresis faster, easier, and reproducible, NOVEX has grown into the leader of the precast gel industry. NOVEX provides a complete line of precast gels designed exclusively to fit its convenient and simple-to-use XCell II Mini-Cell, in addition to all the necessary equipment, reagents, and supplies required to perform electrophoresis simply and easily. The newest members of the NOVEX family of precast gels are found in the NuPAGE Gel System. Packing year-long shelf lives, these gels feature unique buffering chemistries that create a much lower pH environment than traditional SDS-PAGE systems. These chemistries enable run times as low as 35 minutes and offer improved band resolution and transfer efficiencies when compared to other buffer systems. The NuPAGE Bis-Tris Gels are designed for the separation of small and midsize proteins under denaturing conditions. These separations are facilitated by the choice of a 4-Morpholine ethanesulfonic acid (MES) or 4-Morpholinepropanesulfonic acid (MOPS) running buffer, respectively. For the separation of large molecular weight proteins under native or denaturing conditions, NOVEX offers its NuPAGE Tris-Acetate Gels. Both NuPAGE gel types feature 10, 12, 15 and 2D well configurations. A one-well cavity is also available on the Bis-Tris gels. NOVEX's line of Tris-Glycine Gels includes one of the broadest ranges of standard, single percentage gels in the profile. Spanning from 4 to 18 percent acrylamide, these gels also include a choice of four gradient compositions; all include a 4% stacking gel. Cast without SDS, the Tris-Glycine gels accurately separate native and denatured proteins, depending on the choice of running buffer. These gels are offered with a choice of two thicknesses and six sample well arrangements. A recent addition to NOVEX's line, the NOVEX 8x10 Pre-cast Gels feature Tris-Glycine chemistry and have 10 sample wells. Available in 7.5, 10, and 12 percent straight percentage gels and a 4-20% gradient gel, the 8x10 gels are 1.0 mm thick. The gels are compatible with electrophoresis units that accommodate 8x10 cm gel cassettes. For the resolution of low molecular weight proteins and peptides, NOVEX manufactures Tricine Gels. Cast with a 4% stacking gel and without SDS, these gels consist of 10 and 16 percent straight percentage gels and a 10-20% gradient gel. All gels include a 10, 12, 15, or 2D sample well format. NOVEX offers two types of Isoelectric Focusing Gels. Both are cast with 5% acrylamide and 2% ampholytes and cover two pH ranges, 3-7 and 3-10. The pH 3-10 gels also use NOVEX's reverse IEF method for the resolution of basic proteins with pI's above 8. The Zymogram Gels manufactured by NOVEX are sold as a tool for the detection and characterization of proteases that use casein or gelatin as a substrate. Analyzed under SDS conditions on gels incorporating one of the two substrates, the proteases are easily visualized as clear bands against a dark background following a simple renaturing and staining procedure. The gels feature Tris-glycine chemistry and consist of a 10% gel with gelatin, a 12% gel with casein, and a unique 4-16% prestained gradient gel incorporating blue stained casein as the substrate. Owl Separation Systems, Inc. Offering an impressive grouping of precast gels, Owl Separation Systems manufactures and sells both stock and custom gels in mini and large size formats. Owl casts all of its gels in glass cassettes for improved thermal conductivity and clarity; the mini gel cassettes also feature a silk-screened centimeter measuring scale and premarked lanes. With the exception of Owl's larger format gels, the gels are cast with 12 wells and are 1 mm thick. The mini format gels are compatible with Daiichi's Mini 2-Gel and Mini 6-Gel systems, Owl's Puffin and Penguin systems, and other devices on the market. A collaborative product of Owl and Daiichi Pure Chemical Company, the original manufacturer of precast gels, Owl's PAGE-ONETM gels are available in both the 8 x 10 cm and 10 x 10 cm formats. Three single percentage gels (7.5, 10, and 12.5 %) and two gradient formats (4-20% and 10-20%) are cast in both sizes of cassettes. A 2-15% gradient is available in the 10 x 10 cm cassette only. PAGE-ONE gels are manufactured in Owl's GMP FDA approved facility and are compatible with native gel, SDS-PAGE, and tricine gel protocols. Owl's Mini and MiniPlus TG SepraGelsTM (8 x 10 and 10 x 10 cm formats) are cast with Tris-HCl buffer at pH 8.8 and are suitable for denaturing and native PAGE. Both gel types also feature a low percentage stacking layer. Single percentage gels from 5 to 15% and gradients from 2-15% to 17-27% are available, along with custom formulations. Available in four sizes (see table), Owl's Tricine compatible TC SepraGels are manufactured for the resolution of small molecular weight proteins and peptides using a Tris-Tricine running buffer. Additionally, these gels may be run in Tris-glycine and Tris-glycine-SDS buffers for added versatility. All four sizes are sold as a standard 10-20% gradient, but custom percentages also available. Developed for protease analysis, the Substrate SepraGel Precast Gels contain uniformly dispersed casein or gelatin for use as a substrate. Unlike other companies that sell similar gels from stock configurations, Owl has the customer specify gel percentage, substrate concentration, and sample well formation. Designed for the Daiichi Mini 2-Gel system, the Vertical MiniPlus IEF SepraGel consists of a pH 3-10 gradient in a 6% acrylamide gel. Available only in a 10 x 10 cm format, the gels feature 12 wells that hold up to 20 µl each. Developed with larger sample capacity and greater protein separation length in mind, Owl's Standard and Notched SepraGels are provided with a 2.5 cm headspace. Here, the user pours the stacking gel following instructions supplied with each gel and therefore selects the desired sample well comb. Both the standard and notched gels are 1.5 mm thick. The Standard gels are 14 x 18 cm and are designed to fit top-loading electrophoresis systems. The 18 x 18 cm Notched plates fit systems that use the notched plate to from the upper buffer reservoir. Both types are cast with Tris-HCl buffer. DEVICE8 X 10 CM10 X 10 CM Bio-Rad Mini-PROTEAN II, Ready Gel CellX CBS ScientificXX Daiichi Mini 2-Cell & Mini 6-CellXX FisherBiotech MiniVerticalX E-C Apparatus Mini VerticalX Hoefer Mighty Small (SE260) X Hoefer Mighty Small (SE250)X ISSXX Life Technologies MiniVX NOVEX Xcell I & II X Owl Scientific Penguin & Puffin X SERVA BlueVertical 101 X Sigma Aldrich Mini TechwareXX Zaxis System 2000XX Owl also sells precast gels manufactured by Daiichi. Called Multigels, they include two single percentage and five gradient compositions. Multigels are also cast in glass cassettes, have 12 wells, and come with a low percentage acrylamide stacking layer. Finally, Owl offers its precast gels in a variety of formats on a custom basis. Single percentage gels are available between 5 and 15% acrylamide, and custom gradients fall between 3 and 27% acrylamide. Sigma Chemical Company Sold in either 8 x 10 cm or 10 x 10 cm formats in both glass and plastic cassettes, Sigma's Precast Mini-Polyacrylamide Gels are available with Tris-HCl and Tris-Tricine buffer systems. Sigma also sells a gel for isoelectric focusing. Compatible with Tris-glycine buffer for native proteins and Tris-glycine-SDS for denatured proteins, the Tris-HCl gels are available in 5, 7.5, 10, 12.5, and 15% concentrations and gradient ranges of 2 to 15, 4 to 20, and 10 to 27%. Recommended for the analysis of low molecular weight proteins and peptides, the Tris-Tricine gels are sold in a 10-20% acrylamide gradient format. Sigma's IEF gel format is prepared with a pH range of 3 to 10. All gels are available singularly and in packs of 5 and 10. Zaxis, Inc. Using a proprietary, computer-controlled gradient gel casting technology, Zaxis (pronounced "Zee-axis") consistently produces some of the highest resolution gradient gels on the market. All of the Zaxis Tris-Glycine Gels offer high resolution and straight sample lanes across the entire gel, including the end lanes, so that all 12 poured-in sample wells may be used with confidence. Zaxis manufactures a wide variety of straight percentage gels, ranging from 4 to 18%, and precise gradient gels, such as 4-12%, 4-20%, 10-20%, and 17-27%. Cast in glass cassettes to improve heat transfer away from the gel, each gel also includes a 4% stacking layer. Zaxis prepares custom gels and manufactures cassettes of unique sizes upon request with minimum quantity orders and also operates on an original equipment manufacturer (OEM) basis. By manufacturing gels in both 8 x 10 cm and 10 x 10 cm formats, Zaxis provides gels that fit into all of the commercially available minigel boxes. Zaxis exercises stringent quality control from raw materials to finished products to ensure optimum results for all of its customers. Planning is perhaps the most important consideration when purchasing precast gels. For instance, the shelf lives of these products begin with the date of manufacture. If a manufacturer prepares gels ahead of time, part of that shelf live period transpires while the gels sit in storage awaiting buyers. While that may not appear to be a problem for the gels with one-year shelf lives, many users and manufacturers would argue, and rightly so, that fresher is better. So plan accordingly. Convenience comes at a stiff price when it ends up expired and in the trash. Precast Gels Michael Brush is an Associate Scientist at Hitachi Chemical Company in Irvine, California. He can be reached at mdbrush@compuserve.com

Prepare to Cast Off: A Profile of Precast Acrylamide Gels

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