Matching Plasmid Extraction Strategies with Experimental Applications
Matching Plasmid Extraction Strategies with Experimental Applications
Plasmid extraction methods should be selected according to downstream experimental purpose, plasmid copy number, plasmid size, preparation scale, and quality control requirements. Clone verification, sequencing, restriction digestion, cell transfection, viral packaging, and large plasmid preparation have different requirements for plasmid yield, purity, endotoxin level, and conformational integrity.
Keywords: plasmid extraction; alkaline lysis; silica membrane column method; magnetic bead-based plasmid extraction; endotoxin-free plasmid; BAC/PAC plasmid extraction; supercoiled plasmid DNA; transfection-grade plasmid
1 Selection Logic for Plasmid Extraction
1.1 Downstream Application Determines Quality Grade
(1) Routine molecular cloning
For routine clone verification, colony screening, restriction digestion identification, Sanger sequencing, and ordinary PCR template preparation, the main concerns are whether the plasmid is present, whether the insert is correct, and whether the template is compatible with in vitro enzymatic reactions. Such experiments can prioritize routine plasmid extraction or high-purity plasmid miniprep schemes and do not require endotoxin-free grade by default.
(2) Cell- and animal-related experiments
Cell transfection, viral packaging, primary cell experiments, immune cell experiments, and animal administration require higher plasmid purity. Residual salts, organic compounds, protein contamination, endotoxin, and plasmid conformation can all affect cell state, transfection efficiency, viral yield, and in vivo responses. Endotoxin-free or transfection-grade preparation schemes should therefore be prioritized.
1.2 Plasmid Characteristics Affect Extraction Difficulty
(1) High-copy small plasmids
High-copy small plasmids are generally easier to obtain at relatively high yield. Routine rapid extraction or silica membrane column purification can meet the needs of most clone verification, sequencing, and restriction digestion experiments. If yield is low, bacterial strain condition, antibiotic selection, culture time, and bacterial biomass should be checked first rather than directly increasing lysis intensity.
(2) Large plasmids and low-copy plasmids
BACs, PACs, large viral vectors, low-copy plasmids, and vectors containing repetitive sequences are more prone to shearing, rearrangement, low yield, and reduced recovery. Large-plasmid or low-copy-compatible systems should be selected, and mechanical damage should be minimized during lysis, mixing, clarification, and elution.
Table 1 Main factors affecting plasmid extraction quality
Influencing Factor | Effect on Results | Common Problems | Optimization Direction |
Plasmid copy number | Determines baseline yield | Low-copy plasmids give low extraction yield | Increase effective starting amount and select a low-copy-compatible scheme |
Plasmid size | Affects recovery efficiency and integrity | Large plasmids are easily sheared and have low recovery | Mix gently and reduce mechanical damage |
Bacterial biomass | Affects lysis efficiency and impurity load | Excess biomass makes the sample viscous | Control biomass according to purification capacity or reagent ratio |
Lysis time | Affects plasmid release and genomic DNA contamination | Over-lysis causes genomic DNA to enter the supernatant | Strictly control lysis time |
RNase treatment | Affects RNA residue | High A260, gel background tailing | Confirm RNase activity and addition step |
Washing sufficiency | Affects residual salts and organic compounds | Low A260/A230, inhibited enzymatic reactions | Increase washing and drying steps |
Elution conditions | Affect concentration and total recovery | Low concentration or insufficient recovery | Adjust elution volume and elution buffer type |
2 Classification of Plasmid Extraction Methods
2.1 Alkaline Lysis Precipitation Method
(1) Method principle
The alkaline lysis precipitation method uses SDS and alkaline conditions to lyse E. coli, causing plasmid DNA, chromosomal DNA, and proteins to denature. After neutralization, closed circular plasmid DNA more readily renatures and remains in the supernatant, while chromosomal DNA, proteins, and cell debris form precipitates. This method is the basis of most plasmid extraction workflows and is suitable for understanding plasmid extraction principles, low-cost template preparation, and experiments with low purity requirements.
(2) Method characteristics
This method has low cost, but sample purity and reproducibility depend strongly on operational control. Vigorous vortexing after lysis, insufficient neutralization, or incomplete removal of precipitates can easily introduce genomic DNA, protein, RNA, and salt contamination. This approach can be used for ordinary PCR templates or preliminary restriction digestion verification, but it is not suitable as the main preparation method for plasmids used in transfection, viral packaging, or animal experiments.
2.2 Silica Membrane Spin Column Method
(1) Method principle
After alkaline lysis produces a clarified supernatant, the silica membrane spin column method allows plasmid DNA to bind to the silica membrane under high-salt conditions. Proteins, salts, RNA, and small-molecule impurities are removed by washing, and plasmid DNA is finally obtained by elution. This method is highly standardized and is a common core purification route for routine rapid plasmid extraction, high-purity plasmid extraction, and some midi- or maxi-scale preparation schemes.
(2) Method characteristics
The silica membrane spin column method is suitable for clone verification, restriction digestion identification, Sanger sequencing, PCR template preparation, and routine vector construction. Its limitations mainly arise from column capacity and sample load. Excess bacterial biomass, insufficient lysis, or ethanol residue can affect plasmid purity and downstream enzymatic reactions. High-copy small plasmids usually give stable results, while low-copy plasmids, large plasmids, or high-demand cell experiments require a more suitable preparation scale or purification grade.
2.3 Magnetic Bead-Based Plasmid Extraction
(1) Method principle
The magnetic bead method uses reversible adsorption of plasmid DNA to magnetic particles for binding, washing, and elution. Compared with spin column methods, the magnetic bead method reduces centrifugation steps and is more suitable for parallel processing of multiple samples, 96-well plate systems, and automated platforms. Magnetic bead-based plasmid miniprep is suitable for high-throughput clone screening, while magnetic bead-based endotoxin removal systems can further meet low-endotoxin requirements for cell experiments.
(2) Method characteristics
The advantages of the magnetic bead method include high throughput, automation compatibility, and good operational consistency among samples. Key control points include bead ratio, mixing efficiency, magnetic separation time, washing sufficiency, and ethanol residue. Insufficient beads reduce recovery, while inadequate washing or drying affects restriction digestion, sequencing, and transfection. Low- to medium-throughput manual samples can prioritize column methods, while multi-sample and platform-based preparation is more suitable for magnetic bead methods.
2.4 Endotoxin Removal Systems
(1) Method principle
Endotoxin-free plasmid extraction is not a single extraction method independent of lysis and DNA binding. Instead, an endotoxin removal step is incorporated during plasmid purification to reduce residual lipopolysaccharide from Gram-negative bacteria. This system can be combined with column, precipitation, or magnetic bead methods to obtain plasmid DNA more suitable for cell and animal experiments.
(2) Method characteristics
Endotoxin-free systems are suitable for cell transfection, viral packaging, primary cell experiments, immune cell experiments, and animal administration. Ordinary clone verification, restriction digestion, Sanger sequencing, and PCR templates generally do not require endotoxin-free grade. When selecting endotoxin-free products, downstream entry into cell or animal systems should be prioritized rather than judging only by plasmid concentration.
2.5 Anion Exchange or Affinity Chromatography Purification
(1) Method principle
Anion exchange or affinity chromatography purification separates plasmid DNA at higher purity by using charge interactions, conformational differences, or specific binding behavior between plasmid DNA and chromatography media. Supercoiled plasmid DNA affinity chromatography media are more oriented toward process purification and conformational enrichment and can be used to increase the proportion of supercoiled plasmid or further remove impurities.
(2) Method characteristics
Chromatography purification is more suitable for high-purity plasmid preparation, supercoiled plasmid enrichment, process development, and experiments requiring high plasmid conformational consistency. It is not a direct replacement for routine plasmid miniprep and is not suitable for ordinary clone screening. If the experiment only requires restriction digestion, sequencing, or routine template preparation, silica membrane spin columns or magnetic bead methods are usually sufficient.
2.6 Optimized Extraction of Large and Low-Copy Plasmids
(1) Method principle
Large plasmids, BACs, PACs, viral vectors, and low-copy plasmids have low intracellular copy numbers and large molecular sizes and are more prone to shearing, rearrangement, low recovery, and decreased structural integrity during extraction. The core of such methods is not to change the basis of alkaline lysis, but to protect plasmid structure through gentler lysis, larger purification capacity, and more suitable elution conditions.
(2) Method characteristics
BAC/PAC large plasmid extraction systems are suitable for high-molecular-weight vectors or low-copy vectors. Vortexing, harsh pipetting, and excessive bacterial biomass should be avoided during operation. If gel electrophoresis shows tailing, abnormal bands, or obvious degradation, culture conditions, strain stability, lysis intensity, and extraction system capacity should be checked first instead of simply repeating a routine rapid extraction workflow.
Table 2 Comparison of plasmid extraction methods
Method Type | Core Principle | Main Advantages | Main Limitations | Applicable Scenarios |
Alkaline lysis precipitation | Removes impurities by precipitation and centrifugation after alkaline lysis | Low cost, clear principle | Purity and reproducibility depend on operation | Teaching, low-requirement templates, preliminary validation |
Silica membrane spin column | Plasmid DNA binds to silica membrane under high-salt conditions | Standardized workflow, suitable for routine experiments | Limited by column capacity and sample load | Clone verification, restriction digestion, sequencing, routine preparation |
Magnetic bead method | Reversible binding between plasmid DNA and magnetic particles | High throughput, automation-friendly | Requires control of bead ratio and ethanol residue | Multi-sample screening, automated plasmid extraction |
Endotoxin removal system | Reduces LPS residue during purification | Suitable for cell and animal experiments | Higher cost, more complex workflow | Transfection, viral packaging, primary cells, animal experiments |
Anion exchange/affinity chromatography | Purifies plasmids by charge, conformation, or specific binding differences | Stronger purity and conformation control | More oriented toward process purification | Supercoiled plasmid enrichment, high-purity preparation |
Optimized extraction for large/low-copy plasmids | Gentle lysis and capacity adaptation | Helps protect large plasmid integrity | Yield and stability are more condition-dependent | BACs, PACs, large viral vectors, low-copy plasmids |
3 Selecting Methods by Experimental Application
3.1 Clone Verification, Sequencing, and Restriction Digestion
(1) Colony screening
Colony screening can use silica membrane spin columns or magnetic bead methods. The former is suitable for low- to medium-throughput manual operation, while the latter is suitable for parallel processing of multiple samples. The core purpose of this type of experiment is to rapidly determine whether the clone is correct, and endotoxin-free systems are not required by default.
(2) Sequencing and restriction digestion
Sanger sequencing and restriction digestion are better suited to templates prepared by routine column extraction or high-purity column extraction. Salt, ethanol, RNA, and protein contamination should be controlled. If restriction digestion is incomplete or sequencing chromatograms are unstable, A260/A230, gel bands, and template concentration should be evaluated together.
3.2 Cell Transfection, Viral Packaging, and In Vivo Experiments
(1) Cell transfection
Small-scale cell transfection can use endotoxin-free miniprep, while medium-scale or highly reproducible transfection experiments are more suitable for endotoxin-free midiprep. Plasmid endotoxin, salt residue, conformational ratio, and cell state can all affect transfection efficiency.
(2) Viral packaging
Lentiviral packaging, AAV-related experiments, and high-dose transfection should prioritize endotoxin-free maxiprep or high-purity endotoxin-free maxiprep. These applications require attention to total DNA amount, purity, endotoxin level, and batch consistency.
(3) Animal experiments
Animal administration or in vivo functional studies are more sensitive to endotoxin and residual impurities. Endotoxin-free plasmid preparation systems should be used, and plasmid concentration, absorbance ratios, conformational integrity, and storage conditions should be confirmed according to experimental requirements.
3.3 High-Throughput and Special Plasmid Scenarios
(1) High-throughput clone screening
Multi-clone screening, 96-well plasmid template preparation, and automated platforms are more suitable for magnetic bead methods. The bacterial culture volume, lysis time, bead addition amount, mixing method, magnetic separation time, and washing/drying conditions should be standardized in the workflow to reduce well-to-well variation.
(2) Automated low-endotoxin preparation
When sample number is large and plasmids will enter cell systems, magnetic bead-based endotoxin removal plasmid extraction systems can be considered to meet low-endotoxin requirements while maintaining sample throughput and workflow standardization.
(3) Low-copy and large plasmids
Low-copy plasmids, BACs/PACs, large viral vectors, and plasmids containing repetitive sequences should not directly follow ordinary high-copy small plasmid workflows. Large-plasmid or low-copy-compatible schemes should be selected, and culture conditions, lysis intensity, and mechanical shearing should be controlled.
Table 3 Selection pathway for plasmid extraction schemes
Experimental Goal | Recommended Method | Selection Rationale |
Colony screening | Silica membrane spin column or magnetic bead method | Fast operation, suitable for multi-clone verification |
Sanger sequencing | High-purity column extraction | Stable purity, suitable as sequencing template |
Restriction digestion identification | Routine column extraction or high-purity column extraction | Low salt and impurity content, good compatibility with enzymatic reactions |
High-throughput clone screening | Magnetic bead-based plasmid extraction | Suitable for multiwell plates and automated workflows |
Small-scale cell transfection | Endotoxin-free miniprep | Reduces the effects of LPS and impurities on cell state |
Medium-scale transfection | Endotoxin-free midiprep | Balances total DNA amount and low-endotoxin requirement |
Viral packaging | Endotoxin-free maxiprep | Requires high purity and larger DNA quantity |
Automated low-endotoxin preparation | Magnetic bead-based endotoxin removal plasmid extraction | Balances low endotoxin and workflow standardization |
BAC/PAC large plasmids | Optimized large plasmid extraction | Reduces the risk of shearing and structural disruption |
Supercoiled plasmid enrichment | Affinity chromatography purification | Suitable for purification scenarios requiring high plasmid conformational quality |
4 Plasmid Quality Evaluation
4.1 Absorbance Indicators
(1) Concentration
Plasmid concentration should be interpreted together with elution volume and total recovery. RNA, salts, and protein residues can cause falsely high absorbance values, so Nanodrop concentration alone should not be used as the only quality evaluation criterion.
(2) A260/A280
A260/A280 is mainly used to roughly assess protein contamination, and plasmid DNA is usually close to 1.8. If this value is significantly low, A260/A230 and agarose gel electrophoresis should be used together to evaluate residual proteins, phenolic compounds, or other absorbance-interfering contaminants.
(3) A260/A230
A260/A230 is more sensitive to residual salts, guanidine salts, ethanol, and small molecules. When this value is low, restriction digestion, PCR, ligation, sequencing, and transfection may all be affected. Common optimization approaches include additional washing, extended drying time, repurification, or changing the extraction workflow.
4.2 Gel Electrophoresis and Downstream Performance
(1) Gel conformation
On agarose gels, plasmids commonly appear as supercoiled, open circular, and linear conformations, which migrate at different speeds. High-quality samples usually show a clear dominant supercoiled band with a small amount of other conformations. Multiple conformational bands should not be directly interpreted as contamination.
(2) Abnormal bands
Obvious tailing, high-molecular-weight viscous material, low-molecular-weight RNA background, or genomic DNA contamination suggests problems in lysis, neutralization, RNase treatment, or clarification steps. Large plasmid samples also require attention to shearing, rearrangement, or abnormal conformational ratios.
(3) Abnormal downstream experiments
Incomplete restriction digestion is often related to salts, ethanol residues, or DNA conformation. Messy sequencing chromatograms may result from template contamination, unsuitable concentration, mixed clones, or abnormal plasmid structure. Low transfection efficiency requires simultaneous investigation of endotoxin, plasmid conformation, salt residues, and cell state.
Table 4 Plasmid quality abnormalities and optimization directions
Abnormal Phenomenon | Possible Cause | Priority Optimization Direction |
Low yield | Low-copy plasmid, insufficient bacterial biomass, incomplete lysis | Optimize culture conditions and select a low-copy-compatible scheme |
Viscous sample | Chromosomal DNA contamination, vigorous shaking after lysis | Mix gently and fully clarify by centrifugation |
Low A260/A280 | Protein or phenolic contamination | Improve clarification and washing |
Low A260/A230 | Residual salts, guanidine salts, or ethanol | Increase washing and drying steps |
Obvious RNA background | RNase failure or insufficient treatment | Replace RNase or extend treatment |
Incomplete restriction digestion | Salt/ethanol residue, DNA conformation, or unsuitable digestion conditions | Repurify and adjust the digestion system |
Low transfection efficiency | Endotoxin, salts, cell state, or plasmid conformation problems | Use endotoxin-free plasmid and recheck cell state |
Large plasmid tailing | Plasmid shearing, genomic DNA contamination, or rearrangement | Operate gently and select a large-plasmid extraction scheme |
5 Key Control Points in Experimental Operation
5.1 Culture and Lysis
(1) Bacterial culture
Bacterial state directly affects plasmid yield and integrity. Over-culturing increases the proportion of dead bacteria, lysis byproducts, and risk of plasmid rearrangement. Low-copy plasmids, toxic gene plasmids, and large vectors are more sensitive to culture temperature, culture time, antibiotic effectiveness, and strain selection.
(2) Lysis and neutralization
Lysis should be sufficient but not excessive. After P2 is added, gentle inversion should be used for mixing, and vortexing should be avoided. After neutralization, obvious flocculent precipitates should form, and cell debris, chromosomal DNA, and protein complexes should be removed by sufficient centrifugation. Turbid or viscous supernatant should not be directly loaded onto a column or used in the magnetic bead binding step.
5.2 Purification and Storage
(1) Binding and washing
Both column and magnetic bead methods rely on efficient binding of plasmid DNA to a solid-phase carrier. Turbid samples, mismatched salt conditions, or loading beyond capacity can reduce binding efficiency and increase impurity carryover. Insufficient washing causes residual salts, organic compounds, and protein contamination, while incomplete removal of ethanol inhibits restriction digestion, ligation, PCR, sequencing, and transfection.
(2) Elution and storage
Small-volume elution increases plasmid concentration, while a second elution helps improve total recovery. Nuclease-free water is suitable for direct PCR, restriction digestion, or sequencing. TE buffer or plasmid DNA storage solution is more suitable for storage. Plasmids used for transfection and viral packaging should avoid repeated freeze-thaw cycles and maintain low-salt and low-endotoxin status.
Table 5 Key steps and control points in plasmid extraction
Step | Control Goal | Common Error | Recommendation |
Bacterial culture | Obtain a stable plasmid source | Overlong overnight culture, expired antibiotic | Control culture time and use fresh antibiotic |
Bacterial harvest | Control sample load | Excess bacterial biomass | Control biomass according to kit or column capacity |
Resuspension | Fully disperse bacterial cells | Bacterial pellet not fully dispersed | Completely resuspend before lysis |
Alkaline lysis | Release plasmid DNA | Over-lysis or vortexing | Invert gently and control time |
Neutralization and clarification | Remove chromosomal DNA and proteins | Precipitate not removed | Centrifuge sufficiently and avoid carrying precipitate |
Binding/column loading | Capture plasmid DNA | Turbid sample or column overload | Clarify sample first and control loading amount |
Washing | Remove salts and impurities | Insufficient washing | Wash thoroughly according to the workflow |
Drying | Remove ethanol | Ethanol residue | Extend column drying or air-drying time |
Elution | Obtain plasmid DNA | Low concentration or insufficient recovery | Adjust elution volume and elution conditions |
6 Related Product and Material Selection
Table 6 Products and materials related to plasmid extraction
Catalog | Product Name | Grade & Purity | Method Category | Preparation Positioning |
Rapid Plasmid Mini Kit | BioReagent, Molecular Biology Grade | Routine rapid extraction/column purification | Miniprep; suitable for clone verification, restriction digestion identification, Sanger sequencing, and ordinary PCR template preparation | |
High Purity Rapid Plasmid Mini Kit | BioReagent, Molecular Biology Grade | High-purity column purification | High-purity miniprep; suitable for high-quality sequencing, restriction digestion, ligation, and routine molecular cloning | |
Endo-Free High Purity Rapid Plasmid Mini Kit | BioReagent, Molecular Biology Grade | Endotoxin removal system | Small-scale low-endotoxin preparation; suitable before small-scale transfection and cell experiments | |
Endo-free Plasmid Mini Kit | BioReagent, for DNA and RNA applications | Endotoxin removal system | Medium-scale low-endotoxin preparation; suitable before cell transfection and viral packaging | |
Endo-free Plasmid Maxi Kit | BioReagent, for DNA and RNA applications | Endotoxin removal system | Large-scale low-endotoxin preparation; suitable before transfection, viral packaging, and animal experiments | |
Endo-Free High Purity Rapid Plasmid Maxi Kit | BioReagent, Molecular Biology Grade | High-purity endotoxin-free system | Large-scale high-purity low-endotoxin preparation; suitable for high-requirement cell- or virus-related experiments | |
BAC/PAC Large Plasmid Extraction Kit | BioReagent, Molecular Biology Grade | Large-plasmid optimized extraction + endotoxin-free system | Large-scale low-endotoxin preparation for BACs, PACs, and other large plasmids or low-copy vectors | |
Magnetic Plasmid Mini Kit | BioReagent, for DNA and RNA applications, Suitable for molecular biology | Magnetic bead method | Small-scale high-throughput preparation; suitable for multi-sample, automated, or high-throughput plasmid extraction | |
Magnetic Endo-free Plasmid Mini Kit | BioReagent, for DNA and RNA applications | Magnetic bead method + endotoxin-free system | Small-scale low-endotoxin preparation; suitable for plasmid preparation before multi-sample cell experiments | |
Magnetic Endo-Free Plasmid Med Kit | BioReagent, for DNA and RNA applications, Suitable for molecular biology | Magnetic bead method + endotoxin-free system | Medium-scale low-endotoxin preparation; suitable for platform-based or automated workflows | |
Magnetic Endo-Free Plasmid Maxi Kit | BioReagent, for DNA and RNA applications, Suitable for molecular biology | Magnetic bead method + endotoxin-free system | Large-scale low-endotoxin preparation; suitable for scaled preparation scenarios | |
plasmid medium preparation kit |
| Routine plasmid purification | Medium-scale preparation; suitable for routine experiments requiring increased total DNA amount | |
plasmid mass preparation kit |
| Routine plasmid purification | Large-scale preparation; suitable for high-input templates or preparation before downstream purification | |
GoldHi EndoFree Plasmid Midi Kit |
| Endotoxin removal system | Ultra-yield medium-scale preparation; suitable for high-yield low-endotoxin plasmid requirements | |
GoldHi EndoFree Plasmid Maxi Kit |
| Endotoxin removal system | Ultra-yield large-scale preparation; suitable for high-yield low-endotoxin plasmid requirements | |
GoldVac EndoFree Plasmid Maxi Kit |
| Endotoxin removal system/vacuum method | Large-scale preparation by vacuum method; suitable for scaled or high-throughput maxiprep workflows | |
Plasmid Agarose Resin | BioReagent, endotoxin tested, 70% v/v | Affinity chromatography purification | Supercoiled plasmid DNA enrichment, high-purity plasmid purification, or process purification | |
Plasmid DNA Preservation Solution | BioReagent, ready-to-use, RNase free, sterile | Storage supporting material | Storage and stability maintenance after plasmid DNA extraction |
7 Frequently Asked Questions
7.1 Is plasmid miniprep suitable for transfection?
Plasmids prepared by ordinary miniprep can be used for some low-requirement preliminary experiments, but they are not suitable as the main plasmid source for high-requirement transfection, primary cell transfection, or viral packaging. Such experiments should prioritize endotoxin-free or transfection-grade plasmid extraction systems.
7.2 Nanodrop concentration is high, but restriction digestion is poor. What are possible reasons?
Common reasons include salts, ethanol, guanidine salts, or protein contamination, which can falsely increase absorbance readings and inhibit enzymatic reactions. A260/A230, A260/A280, and agarose gel electrophoresis should be evaluated together. Repurification or optimization of washing and drying steps may be needed.
7.3 Why does RNA contamination appear after plasmid extraction?
RNase failure, improper addition step, or insufficient post-lysis processing can all cause RNA residue. RNA contamination increases A260 readings and forms a low-molecular-weight background on gels. RNase storage conditions and reagent validity should be checked.
7.4 Why does large plasmid extraction fail easily?
Large plasmids are more susceptible to mechanical shearing and structural instability and are also more likely to show low recovery when the purification capacity is not matched. Gentle mixing should be used, vortexing should be avoided, and extraction systems suitable for large plasmids, BACs/PACs, or low-copy vectors should be selected.
7.5 What is the difference between magnetic bead-based plasmid extraction and column-based extraction?
Column-based methods are more suitable for low- to medium-throughput sample processing, with intuitive workflows and controllable costs. Magnetic bead-based methods are more suitable for multi-sample, high-throughput, and automated workflows. Magnetic bead-based methods require careful control of bead ratio, washing sufficiency, and ethanol residue.
7.6 When is endotoxin-free plasmid required?
Endotoxin-free plasmids are recommended for cell transfection, viral packaging, primary cell experiments, animal experiments, and immune functional experiments. Ordinary restriction digestion, sequencing, PCR, and clone verification generally do not require endotoxin-free grade.
7.7 Can plasmids with low A260/A230 still be used?
Usability depends on the downstream experiment. Ordinary PCR or preliminary restriction digestion may still be attempted, but sequencing, ligation, transfection, and in vitro transcription are more likely to be affected. If A260/A230 is significantly low, repurification or a different extraction workflow is recommended.
Plasmid extraction methods should be selected according to downstream application, plasmid characteristics, and preparation scale. Clone verification and sequencing can use silica membrane spin column or magnetic bead methods. Cell transfection and viral packaging should use endotoxin-free systems. BACs/PACs, large plasmids, and low-copy vectors require gentler optimized extraction schemes with better-matched capacity.