Proteomics and structural genomics require protein extraction methods that allow the simultaneous screening of hundreds of proteins on different combinations of vectors and hosts (Stevensetal., 2001). The best combinations identified in this multiparallelscreen that are correctly folded with high expression levels are scaled up to the milligram scale to produce pure products for functional and structural analysis. This high-throughout (HT) protein expression and purification strategy has accelerated the development and optimization of reagents and instrumentation capable of efficiently lysing cells and extracting proteins on both micro- and bulk scales.
Operation method
Experiments on the preparation of biological extracts required for protein purification Move I. Chemical and enzymatic cell lysis Microscopic cell lysis is often accomplished chemically or enzymatically or both. For example, ultrasound and Frenchpress homogenizers are not easy to use in the collection of cultures less than or equal to 5 mL, and the application of these mechanical methods often encounters problems such as excessive heat generation and sample oxidation. A major advance in the simplification of microcell lysis has been the development of descaler-based reagents such as frPer (Chuetal., 1998) and BUgBUSter (GrabSkietaL, 1999). These reagents do not require expensive equipment for their use and are very fast acting and easy to use. They are very convenient and effective methods for the high throughput preparation of cell extracts. Highly active enzymes and enzyme mixtures have been used to improve lysis efficiency and to reduce the high viscosity of extracts due to incomplete digestion of genomic DNA. These commercially available lysis reagents and enzymes (Table 18.1), alone or in combination, are effective in lysing cells of bacteria, yeast, plants, insects, and higher eukaryotes and extracting proteins from them. Descaler-based methods for obtaining extracts and protein enrichments as well as subcellular tissues and organelles from eukaryotic cells and tissues are described in detail by Michelsen and vonHagen in Chapter 19 of this book. Another aspect of advances in chemical methods for lysing cells is their application to high-throughput automated processing of samples. Improved reagents and methods allow recombinant proteins to be extracted directly from E. coli cultures without collecting cells. (Grabskietal., 2001;2003;StevensandKobs,2004). Traditional protein purification methods first require the collection of cells, a step that concentrates the cells and removes residual medium components from them (Burgess, 1987;Deutscher, 1990;Scopes, 1994). This step is as difficult to automate and scale down and perform small extractions of multiple proteins at the same time as some of the mechanical method lysing cell steps. Concentrated descaler-based reagents (Table 18.1), such as PopCulture, FaStBreakTMffiB~PER are capable of overcoming these bioprocessing hurdles to automation by being applied directly in conjunction with high-activity lysozyme and nuclease. High-throughput extraction and purification reagents have the advantage of eliminating the need for multiple centrifugations to isolate cells and clarify crude extracts from the culture medium, as well as the need for mechanical lysis (Nguyenetal., 2004). These innovations allow for affinity adsorption of target proteins from all media extracts, enabling cell culture, protein extraction, and purification to be accomplished all in one tube. The active ingredients in some bacterial lysis reagents are non-ionic detergents or zwitterionicdetergent, which function to cleave cell membranes and cell wall structures and weaken the cell structure to facilitate lysis of the cell by osmotic shock, freeze-thawing, and enzymatic degradation by phage lysozyme or chicken egg white lysozyme. With very few exceptions, Gram-positive bacteria can be readily lysed by lysozyme treatment alone (Cull and McHenry, 1990). Gram-negative bacteria are difficult to lyse by lysozyme alone because the outer lipidbilayer must first be permeabilized to expose its peptidoglycans before the cell wall can be degraded by enzymes. The addition of EDTA to Tris buffer exposed approximately 50% of the polyanionic lipopolysaccharide in the bilayer (Lieve, 1974). However, EDTA interferes with immobilized metal affinity chromatography (immo bilizedmetalaffinitychromatography (IMAC), which is the most commonly used step in the downstream purification of recombinant proteins. Descaler-based lysis reagents are very effective in permeabilizing extracellular membranes and do not interfere with IMAC. However descaler-based cell lysis reagents have several drawbacks, and the solubility of some proteins extracted with descalers may be enhanced due to the interaction of the descaler with the protein. The solubility of these proteins depends on the ratio of descaler to protein. The solubility of some specific proteins extracted with these descaling agents may not match the solubility of proteins extracted by amplified mechanical methods. Descaling agents and impurities in the descaling agent can interfere with the downstream purification process and final structural identification (Swidereketal., 1997), and chromatographic separation methods based on hydrophobic interactions should be avoided (Marshaketal., 1996). Despite these drawbacks, descaling agent-based lysis reagents are still widely used in modern genomics. The structure of the cells to be lysed determines the chemical nature and concentration of the descaling agent required for the work, and the exact type and concentration of descaling agent in these lysis reagents are protected by patents. Several papers mentioned in this chapter (Neugebauer, 1990; Chu and Mallia, 2001; EshaghietaL, 2005; Kashino, 2003) provide valuable information on protein extraction and solubilization, which can be easily accomplished by formulating the extraction reagents according to the recipe. Yeasts are more difficult to lyse than bacteria. Their dense and complex cell walls account for 25% of the dry weight of the cell. Typical components are glucans, cellulose, mannoproteins and chitosan, which are cross-linked by covalent, disulfide, hydrogen and hydrophobic forces. For more efficient cell lysis, yeasts should be collected in late logarithmic growth and early stable growth because the longer the yeast is in the stable growth phase, the thicker the cell wall, and the denser the buddingyeast's cell wall, the more dense the buddingscar or aggregate appears. Protease inhibitors should be added to the lysis buffer or commercial lysis reagents, and protease-deficient strains can be used to express the protein. Reagents such as Y-Per and YeastBuster (Table 18.1) can also be used to lyse yeast. The new approach of lysing yeast by controlled manipulation of genes that play a role in cell wall synthesis (biogenesis) complements the previously established mechanical and enzymatic methods of lysing yeast (Drottetal., 2002). Compared to mechanical and chemical methods, enzymatic treatment of microbial cells to lyse and reduce the viscosity of the lysate has several significant advantages: hydrolytic enzymes are highly specific for the cell wall components of the target cells, they are gentle and do not generate shear forces; they do not lead to damage by heat or oxidation; and they do not require special specialized equipment for their operation. Enzymatic treatment of cells and extraction of proteins can be combined with mechanical lysis to improve the selectivity of target protein release, increase the yield and rate of acquisition of extracts, minimize damage to the product, and reduce viscosity for downstream manipulation (Andrewsand Yasuraya, 1987;0 Dazzling Dagger 31^&1&1., 1999). Modified bioengineered enzymes and enzyme preparations (Table 18.1) include phage lysozymes with highly specific activity, e.g., rLysozyme, Ready-Lyse; recombinant lysozymes and nonspecific nuclease enzymes, e.g., Benzonase and OmniCleave; and lysozyme-nuclease blends (cocktails), e.g., Liquisonic, Lysonic, Lysonase, and Lysonase. Liquisonic, Lysonase, and EasyLyse; recombinant lysozyme Ready-Lyse and rLysozyme building block lytic enzymes with highly specific activities more than 200-fold higher than chicken egg white lysozyme. The nuclease from Serraiiamarc-esem, available as the highly pure recombinant enzyme Benzonase, is the least specific (promiscuous) nuclease known. This enzyme is capable of digesting all forms of DNA and RNA (Meissetal., 1995; NestleandRoberts, 1969). Benzonase attacks the various substrates more equally than bovine pancreatic deoxyribonuclease (KbovinepancreaticDNaseI), which gives it excellent selectivity for reducing the viscosity of extracts due to DNA. zymolase and lyticaseglucanase are useful for yeast cell lysis.) Zymolase and lyticaseglucanase are very useful enzymes for cell lysis in yeast and for obtaining yeast protoplasts. Potential problems with enzymatic processing limit its application, especially in cell lysis on an industrial scale. This problem includes downstream purification complicated by the addition of the hydrolase itself and other components contained in the enzyme preparation; degradation of the recovered product during lysis; and the optimal temperature and pH of the hydrolase may not be compatible with the target product. The limited application and high cost of most hydrolytic enzymes have prevented their use on an industrial scale (Hopkins, 1991). Ultrasound and high-pressure lysis have been efficiently applied to the lysis of microbial, plant and animal cells. These methods have been employed for decades and their equipment and principles have been elucidated in detail (Harrison, 1991; Hopkins, 1991; Mid-delberg, 1995). Ultrasonic cleavage works by shear forces generated by high-frequency ultrasonic oscillations triggered by the resonance (15-25 kHz) of a tuned probe or arm. The pressure wave at the speed of sound generates tiny bubbles in the liquid and subsequently collapses, and the implosion resulting from this process produces a shock wave with sufficient energy to lyse the cell wall and shear the nucleic acids to reduce the viscosity of the sample. High-pressure homogenizers and pressureextruders work by forcing the pressurized cell suspension through a narrow orifice valve. Such a valve may be as simple as a flow-restricting needle-orifice valve (restrictingneedlevalve) (e.g., the Fuchs cell crusher), or it may be a more complex design with a combination of valve seats and impact rings (e.g., in the APVManton-Gaulin homogenizer). The mechanism of lysis is to lyse the cells with the aid of differential pressure and shear forces at the pressure extruding nozzle. Various mechanisms for cell lysis by pressure homogenizers have been proposed, including turbulence, cavitation, viscous shear, and impingement (Kleinig and Middelberg, 1998; Pandolfe, 1999). It is widely recognized that there is no completely single mechanism of action in the fragmentation process. However, cavitation and collision are considered to be the major contributors to cell lysis (Shirgaonkaretal‖ 1998; SPXCorp., 2009). Cell lysis by grinding cells in suspension with glass beads is a common procedure at both laboratory scale and production scale, such as the glass bead milling (ball milling) and bead homogenization methods mentioned above, which can be carried out in the laboratory using simple equipment such as electromagnetic stirrers, vortex mixers or stirrers. The glass bead mill method can be performed in the laboratory using simple equipment such as electromagnetic stirrers, vortex mixers, or agitators, or it can be accomplished using commercially available specialized high-speed mills, oscillators, and stirrers. The degree of cell lysis is related to the cell concentration, the diameter and material of the beads, the proportion of beads in the suspension, the treatment time and the force applied (Ramananetal., 2008). This method is very efficient for some difficult to lyse cells such as yeasts, spores, microalgae (microalgae), and has been successfully applied to the lysis of bacterial, plant, and animal cells, and has also been preferentially employed in the large-scale lysis of fungi (Hopkins, 1991). The process and principles of the ball mill method have been reviewed (Harrison, 1991; Middelberg, 1995). In general, the cells are squeezed through contact with the abrasive and the reaction cell itself, and the grinding, resulting shear forces cause the cells to be lysed. The specialized machines required for the mechanical lysis of cells technique have undergone functional innovation and many new devices have emerged. Most mechanical methods are not easy to apply to the processing of cells recovered in 5 mL or less of medium, and excessive heat production and oxidation are common problems with mechanical cell lysis. Although in some cases the descaling agents left behind during purification may interfere with the biochemical or crystallographic properties of proteins, multi-head ultrasonic probes (96-wellsonicatorheadandmicroplatehorn) specific to 96-well plates and other types of microplates have been used (Misonix, Inc., Farmingdale, NY, USA). Farmingdale, NY; www.misonix.com). This physical, high-throughput approach to cell lysis is well established.The SonicMan high-throughput sonication system (MatriCal, Inc. Spokane, WA; www.matrical.com) is divided into individual or combined system units of % wells, ferruginous 4 wells, or 1536 wells. The system features touch-screen controls, a disposablegasketedpinlid to prevent well-to-well cross-contamination, and a microplate chute that allows direct access to the automated operator station. Other new ultrasonographs, such as BioSpec's wireless, handheld Sonozap ultrasonic homogenizer. The 1/8-inch-diameter, self-tuning probe is ideal for small volumes of samples ranging from 0.3 to 5 mL. PressureBioscience (www.pressurebiosciences.com) has developed a benchtop Barocycler. PressureBioscience () has developed the benchtop Barocycler and handheld PCTShredder sample preparation systems. These devices are capable of creating fast, high pressure (up to 35kpsi) circulations in specialized PULSE tubes. These 1.2 to I.5 mL tubes contain rammed (ram) perforated disks (lysisdisks) that generate high pressures in the fluid, making it easy to lyse plant, animal, insect, and microbial cells (Garrettetal_, 2002).FastPrep (Fast Nucleic Acid Extractor) ( MPBiomedicals, Irvine, CA; www.mpbio,com), Geno/Grinder (SPEXCertiprep, Inc., Metuchen, NJ; www.spexcsp.com), Mag-NALyser (RocheDiagnostics. Penzberg, Germany www.roche.com), Mikro-Dismem-brator (SartoriusStedimBiotech, Aubagne, France; www.sartorius-stedim.com)^ MiniBeadBeaterCBioSpecProducts,Bartlesville,OK;http: //www.biospec.com)RetschMixerMill(RetschGmbH,Haan,Germany;www.retsch.com) and others contain All types of ball mills for processing samples of a few milliliter volume are included. These devices are not really high throughput, but can efficiently process very recalcitrant cells in 1-5 mL systems. The microfluidicsmicrofluidizer (Newton, MA; www.microfluidicscorp.com) differs from other types of high-pressure homogenizers. This device pressurizes, accelerates, and diverts the cell suspension through micro-orifices of fixed geometry by means of pneumatic pumping. Later, when leaving the outlet of the device, the two high-speed moving fluids collide directly with each other generating high shear forces and differential pressure to lyse the cells. Microfluidic homogenizer models range from the M-110P, which is suitable for laboratory use and capable of handling small sample volumes of 25 mL, to the biopharmaceutical industry-scale M-700, which is capable of handling volumes of up to 900 L/h, with full process control monitors and support for CIP, and which has been validated for use with products such as 21 CFR and cyclic guanosine mononucleotide (cGMP). ConstantSystemsLtd. (LowMarchDaventry, Northants, England; www.constantsystems.com) has designed a hydraulically driven cracking unit that functions similarly to the original Fritz cell crusher by applying disruptiveforce to move the material through the cell. The ConstantSystems line of equipment ranges from single-sample (1-20 mL per sample) benches to continuous processing (405-565 mL/min) modes and includes touch-screen monitoring and control, a cooling jacket, and an on-site control panel. Avestin, Inc. (www.avestin.com) offers EmulsiFlex high-pressure homogenizers for processing volumes from I.0 to I.0 mL. These homogenizers use air chestnuts or electric piston pumps to produce lysis pressures from 500 to 30,000 psi. These units are equipped with heat exchangers to cool cell extracts and are capable of SIP in-situ sterilization in order to comply with the manufacturer's Good Manufacturing Practices (GMP) requirements. IN; www. Glas-Col, LLC's (TerreHaute, IN; www. glascol.com) BioNeb Cell Lysis System uses pneumatic atomization at 10-250 psi to breakopen cells, which has the advantage of not generating heat. Laminar flow in the atomization orifice creates a shear force that lyses the cells, and the magnitude of this force is dependent on factors such as the pressure used, the type of gas (argon<nitrogen<helium), and the viscosity of the fluid. The smaller the atomized droplets, the higher the viscosity of the material, and the higher the gas pressure used, the greater the shear force generated (Surzyckietal., 1996). The methods, reagents, and equipment for cell lysis described in this chapter are all usable and efficient if properly adapted to the type and size of the cells. However, the question must be asked: which method is best for a specific application? In response to this question, the relationship between the mode of cell lysis and the protein content of the resulting extract has been studied (BenovandAl-Ibraheem, 2002; DeMeyetal., 2008; Guerlavaetal., 1998; HoetaL, 2008). Physical methods such as high-pressure homogenizers and ball mills are optimal for large-scale cracking because of the high efficiency and low cost of these methods and their ability to process different volumes of material quickly. Ultrasonication, chemical reagent methods (including descalers, enzymatic treatments), freeze-thaw methods, and enzymatic cleavage methods combined with chemical or physical methods are also very efficient and are often used in the laboratory, especially for small volumes. The uniqueness of each protein and the differences in the structure of different host cells make the selection and optimization of cell lysis and extract preparation techniques highly dependent on experience. However, tools and methods for successful extraction and preparation of biologics can always be found, and these methods are always evolving in parallel with the needs of modern structural and functional proteomics. The various strategies and guidelines described below with the quality of the cell extract product as the starting point are applicable to most downstream purification and analytical processes. Although the focus of the presentation is on small or larger laboratory-scale E. coli lysis, some techniques can be used and scaled up for cell lysis and intracellular protein extraction from other sources. The extensive literature on protein purification provides additional information on some of the guidelines for protein extract preparation and protein purification and characterization listed here (Burgess, 1987; Deutscher, 1990; HarrisandAngal, 1989; Hopkins, 1991; Marshaketal. Scopes, 1994). The composition and volume of the cell lysis buffer is not only critical for efficient cell lysis, but will also affect the subsequent purification process and the stability and recovery of the target protein once it is released from the cells. Each extracted protein is unique and theoretically a buffer for extraction and purification should exist that is compatible with both its own biochemical properties and the intended purification process. In most cases, most common extraction buffers give good results if several basic conditions are met. These basic conditions include pH, ionic strength, additives to prevent degradation and improve stability, and buffer-to-cell ratio. An excellent reference for maintaining enzyme activity through buffer composition and other methods is ProteinPurification by Scopes (1994). Technical information on pH and buffers can be found in Dawson et al. (1986), which includes a table for preparing buffers from pH 1 to 13, buffer properties and the effect of salts, temperature, dilution and other factors. These include tables for preparing buffers from pH 1 to 13, buffer properties and effects of salt, temperature, and dilution. The pH of the extraction buffer should be chosen to be at least one unit above or below the isoelectric point of the protein. This pH, which is different from Pl, prevents isoelectric precipitation by maintaining a positive or negative charge on the surface of the protein and also facilitates ion exchange as a purification step. In order to maintain buffering capacity and minimal increase in conductivity, the ionic strength of the buffer should be 20 to 50 mmol/L, and the pKa of the buffer salts employed should be within 0.5 units of the pH employed. Typical cell cytoplasm has an ionic strength of 150-200 mmol/L, which contains a high concentration of charged bioactive molecules that interact with ionized proteins. The lysis buffer should contain at least 50-100_ol/L NaCl. Increasing the ionic strength of the lysis buffer will decrease the interaction force of these ions and reduce the precipitation of charged particles. These precipitates adsorb proteins, which can be removed by centrifugation or filtration, but thus result in the loss of target proteins. Finally, substances that prevent protein degradation and improve protein stability should be added to the buffer as essential components. This includes protease inhibitors (Table 18.2), reducing agents [e.g., dithiothreitol (DTT)], tris(P-chloroethyl)phosphine [tris(2-carboxyethyl)phosphine, TCEP], tris(3-lightly propyl)phosphine [tris(hydroxyprophl)phosphine, THP], and other substances. phosphine, THP], divalent cations, cofactors, kosmotropes (e.g., glycerol, sorbitol, or alginate). The water-soluble, odorless phosphine analogs of TCEP and THP are both very stable and more effective at maintaining disulfide bonds in the reduced state than most commonly used thihydrogen-based reductants/9■ mercaptoethanol (Chan mercaptoethanol) and DTT, for example (Clineetal., 2004; Getzetal., 1999; HanandHan, 1994). Nonionic and amphoteric detergents can be added to increase the solubility of hydrophobic proteins. Reducing agents, protease inhibitors, and descaling agents can interfere with some purification processes and the results of test assays and analytical methods. The potential interference of these components must be considered when selecting the chemicals to be used in the buffer and their concentrations. For lysis of E. coli cells, the following buffers are used: 50 mmol/L Tris-HCl or sodium mercaptan pH 7.5-8.0, 50 mmol/L NaCl, 5% glycerol, 0.5 mmol/LEDTA and 0.5 mmol/LDTT. The recommended lysis buffers are lysis buffer Y for yeast and lysis buffer Y for insect cells. Recommended lysis buffers for yeast (bufferY) and insect cells (bufferI) are given below. Since the insoluble material adsorbs about 50% of its own volume, a buffer of at least 3 times the volume should be used to ensure a recovery of up to 85% of the liquid. Proteins are more stable at higher concentrations, but extracts at higher concentrations are difficult to manipulate and protein aggregation can occur. Although a 3:1 ratio of lysis buffer to cell volume can result in a more concentrated extract, 5-10 times the volume of the buffer is preferred and results in more soluble proteins and lower viscosity of the extract. Note: In these buffers, protease inhibitors may be added or omitted (Table 18.2), depending on the sensitivity of the target protein to protease hydrolysis and the amount and type of inhibitor required. If the initial protein separation step is ion-exchange chromatography, the ionic strength of Buffer I and Buffer Y can be reduced or diluted after the extraction is complete. Formulation of 10 mL lysis reagent solution: 10 mLB-Per or BugBuster,20/iLLysonaseBioprocessingReagent. If needed to reduce protein hydrolysis and increase the solubility and stability of target proteins can be added, such as EDTA, protease inhibitors, 5% to 10% glycerol, and reducing agents and other additives. The composition of the buffer and its concentration should be chosen with the subsequent purification and assay in mind. (1) Add ImL of medium to a 2 mL X 96-well plate, or add 5 mL of medium to a 24-well plate and seal with a breathable sealing film or BugStopperTM sealing cap (capmat) to incubate the organism and express the target protein. (2) Centrifuge to collect the organisms. (3) Aspirate and discard the medium. (4) Resuspend the organisms in 100~200yL lysis buffer with a pipette. (5) Mix and shake on a shaker for 10 min to carry out the reaction. (6) Aspirate 10 of the mixture for whole bacterial lysate analysis. (7) Centrifuge for 5 min and remove 10 of the supernatant for analysis of soluble proteins. The remaining supernatant can be used for other isolation or analytical operations. (8) The amount of target protein present in the insoluble fraction can be indirectly estimated by comparing the difference between the total bacterial extract in step (6) and the soluble protein in step (7). Typical methods of sample comparison are electrophoresis, enzyme-linked immunosorbent assay (ELISA) or enzymatic analysis. Direct detection of the insoluble fraction can be obtained by electrophoresis after aspirating the soluble supernatant and dissolving the remaining precipitated fraction in SD^PAGE sample buffer. Note: Procedures and techniques for preparing protein samples for SDS^PAGE are available in Grabski and Burgess (2001). This article provides SD&PAGE sample buffer formulations, protein sample preparation, gel loading recommendations, and alternative methods for analyzing difficult samples. 10 mL lysis reagent formulation: 10 mLPopCulture, FastBreak, or B-PerDirect, 200yLLysonaseBioprocessingReagent Subsequent protocols can be accomplished in multiwell plates using an automated hydraulic drive platform, and multi-channel pipettes can be used to perform multiple culture operations simultaneously on a single plate. Multiple pipettes can be used to manipulate multiple cultures simultaneously on a single plate. Porous filter plates for separating affinity resins from culture extracts and treated solutions are available from multiple manufacturers. Successful separation of magnetic beads has been achieved using specialized magneticpinplates or platforms. (1) Add ImL to a 2 mLX96-well plate or 5 mL of medium to a 10 mLX24-well plate to culture cells and express target proteins and seal with a breathable sealing film or BugStopperTM sealing cap. (2) Add 1/10 volume of lysis reagent to the medium. (3) Mix with a pipette and shake for 10miri on a shaker to get the reaction going. (4) Remove 50yL of whole cell lysate mixture for analysis. Samples may be analyzed by electrophoresis, ELISA, or enzymatic methods. Direct SD^PAGE analysis and Caulobacter staining require high expression levels and large sample volumes or the detection of diluted protein samples by precipitation. Special filter plates (Pall, Millipore, 3M) can be used to remove protein aggregates and inclusion bodies from the protein solution, allowing easy detection of the soluble expression level of the protein in this step. (5) Add equilibrated affinity capture resin (affinitycaptureresin) or affinity magnetic beads directly to untreated cell lysates. Typical addition amounts are 50~100 ML of gel slurry (50% gel slurry in capture buffer VmL starting medium volume, depending on the gel's ability to capture recombinant proteins and the expression level of target proteins to determine the exact amount to be added. (6) Use 10~30 times the gel volume of rinsing buffer to remove impurities. (7) Elute the target protein with 3 times the volume of elution buffer. 10 mL of lysis reagent: 10 niL of lysis buffer at a concentration of 50-100_ol/L (one of glycine, sodium acetate, Tris-HCK sodium phosphate, or HEPES, depending on the desired pH), 50-100_ol/L of lysis buffer, 50-100_ol/L of lysis buffer, and 50-100_ol/L of lysis buffer. 300 mrnol/L NaCl, 30 jixLLysonaseBioprocessingReagent. e.g., EDTA, detergents, protease inhibitors, 5%-10% glycerol, and reducing agents can be added to the lysis buffer as needed to reduce hydrolysis of the target protein and increase its solubility and stability. When selecting lysis buffer components and their concentrations, it is important to consider the requirements of downstream purification and analytical processes. The efficiency of cell lysis by freeze-thaw method depends on the density of cell suspension, the number of freeze-thaw cycles, and the rate of freezing. However, it has been experimentally shown to be less efficient for protein release from E. coli than the bead vortexing method (beadvortexing), the Fuchs crusher, or sonication (BenovandAl-Ibraheem, 2002). However, when combined with lysozyme cleavage, its a gentle release method for unstable proteins and does not require special devices. A slow freeze-thaw cycle ruptures the cell membrane, exposing the cell wall to contact with the enzyme and degradation. (1) Place ImL of medium in 2 mLX96-well plates or 5 mL of medium in 10 mLX24 deep-well plates and seal with breathable sealing film or BugStcwerTM sealing caps to culture cells and express target proteins. (2) Centrifuge to allow the bacteria to form a precipitate. (3) Aspirate and discard the residual medium. (4) Place the organisms at _20°C until completely frozen. (5) Add 100-200 lysis reagent by pipette and resuspend the organisms. (6) Place on a shaker and shake for 10 min at room temperature. (7) Place the suspension again at 20°C until completely frozen. (8) Lysed at room temperature, mixed, and 10fxL of whole cell lysis mixture removed for analysis. (9) Centrifuge for 5 min, remove 10juL of supernatant for analysis of soluble proteins, and use the remaining clarified supernatant for other purification or assay processes. "The remaining supernatant, which has been clarified, can be For more product details, please visit Aladdin Scientific website
In order to efficiently lyse the organisms and to ensure the recovery efficiency of the extracts after removal of the precipitated material from the insoluble cell fractions by centrifugation and filtration, the volume of the buffer used to resuspend the cells should be at least three times the volume of the original cells.