What is a plasmid vector?

A plasmid vector is a small, circular DNA molecule used to carry foreign DNA into a host cell for cloning or expression. Vectors contain essential elements such as an origin of replication, selectable marker (antibiotic resistance), and a multiple cloning site (MCS) with restriction enzyme sites for inserting DNA fragments.

How do I choose the right expression vector?

Consider your host organism (E. coli, yeast, mammalian cells), whether you need constitutive or inducible expression, the desired fusion tag (His, GST, MBP), the selection marker, and the copy number. For bacterial expression, pET vectors with T7 promoter are standard. For mammalian cells, pcDNA3.1 with CMV promoter is widely used.

What is the difference between high-copy and low-copy vectors?

High-copy vectors (like pUC-based, 500–700 copies/cell) produce more plasmid DNA per cell, yielding higher DNA preps but potentially toxic expression of cloned genes. Low-copy vectors (like p15A-based, 10–15 copies/cell) are better for cloning toxic genes and can be co-maintained with high-copy plasmids that have compatible origins.

Can I use two plasmids in the same cell?

Yes, if they have compatible origins of replication. ColE1/pMB1/pUC origins are incompatible with each other but compatible with p15A (pACYC) and CloDF13 (pCDF) origins. The Duet system from Novagen uses four compatible origins for co-expression of up to 8 proteins.

What are lentiviral transfer vectors used for?

Lentiviral transfer vectors (like pLKO.1, pLenti-CMV-GFP) are packaged into lentiviral particles using packaging (psPAX2) and envelope (pMD2.G) plasmids. The resulting virus can transduce both dividing and non-dividing cells, making lentiviruses ideal for stable gene expression in primary cells, neurons, and in vivo applications.

What is the AAV packaging limit?

Adeno-associated virus (AAV) has a strict packaging limit of approximately 4.7 kb between the two ITRs. This includes the promoter, transgene, and polyA signal. Exceeding this limit dramatically reduces viral titer and transduction efficiency. For larger genes, consider dual-AAV or lentiviral delivery.

Does this tool include full vector sequences?

This tool includes partial sequences (first ~200 bp) for display purposes and exports. For full sequences, visit the linked GenBank accession or Addgene page. The feature annotations and maps are based on published vector maps and are suitable for planning cloning strategies.

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Plasmid & Vector Library.

Browse a curated catalog of commonly used plasmid vectors and DNA molecules. View annotated circular maps, compare features, and download FASTA or GenBank files. Filter by category, host organism, or selection marker. All data is client-side.

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Validated2026-04-07

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Vector Catalog

Name	Category	Size	Markers	Promoter	Copy #
Cloning	Cloning	2,686 bp	Ampicillin	lac	high
Cloning	Cloning	4,361 bp	AmpicillinTetracycline	bla, tet	medium
Cloning	Cloning	2,961 bp	Ampicillin	T7, T3, lac	high
Cloning	Cloning	2,743 bp	Ampicillin	T7, SP6, lac	high
Bacterial Expression	Bacterial Expression	5,369 bp	Kanamycin	T7, T7lac	medium
Bacterial Expression	Bacterial Expression	5,900 bp	Ampicillin	T7	medium
Bacterial Expression	Bacterial Expression	4,969 bp	Ampicillin	tac	medium
Bacterial Expression	Bacterial Expression	6,721 bp	Ampicillin	tac	medium
Bacterial Expression	Bacterial Expression	2,897 bp	Ampicillin	T7	high
Mammalian Expression	Mammalian Expression	5,428 bp	AmpicillinNeomycin (G418)	CMV	high
Mammalian Expression	Mammalian Expression	5,427 bp	AmpicillinNeomycin (G418)	CMV	high
Mammalian Expression	Mammalian Expression	4,300 bp	AmpicillinNeomycin (G418)	CMV	high
Mammalian Expression	Mammalian Expression	7,032 bp	AmpicillinPuromycin	U6 (shRNA), hPGK (puromycin)	high
Mammalian Expression	Mammalian Expression	8,500 bp	AmpicillinPuromycin	CMV	high
Mammalian Expression	Mammalian Expression	4,675 bp	Ampicillin	CMV	high
Yeast	Yeast	5,856 bp	AmpicillinURA3	GAL1	high
Yeast	Yeast	6,077 bp	AmpicillinLEU2	lac (E. coli)	low
Yeast	Yeast	6,849 bp	AmpicillinLEU2	lac (E. coli)	high
Reporter	Reporter	4,242 bp	Ampicillin	(none — promoterless)	high
Reporter	Reporter	4,850 bp	Ampicillin	SV40	high
Reporter	Reporter	4,733 bp	KanamycinNeomycin (G418)	CMV	high
Reporter	Reporter	4,731 bp	KanamycinNeomycin (G418)	CMV	high
Reporter	Reporter	4,723 bp	KanamycinNeomycin (G418)	CMV	high
Viral Transfer	Viral Transfer	10,703 bp	Ampicillin	CMV, CAG	high
Viral Transfer	Viral Transfer	5,822 bp	Ampicillin	CMV	high
Viral Transfer	Viral Transfer	9,200 bp	Kanamycin	CMV (transgene), CMV (GFP)	medium
Standard DNA	Standard DNA	48,502 bp		PL, PR	low
Standard DNA	Standard DNA	5,386 bp		—	low
Standard DNA	Standard DNA	7,249 bp		lac	low
Bacterial Expression	Bacterial Expression	4,176 bp	Ampicillin	trc	medium
Cloning	Cloning	4,245 bp	ChloramphenicolTetracycline	—	low
Bacterial Expression	Bacterial Expression	4,407 bp	Ampicillin	cspA	high
Bacterial Expression	Bacterial Expression	6,354 bp	AmpicillinChloramphenicol (ccdB cassette)	T7	medium
Mammalian Expression	Mammalian Expression	5,800 bp	Ampicillin	CAG	high
Mammalian Expression	Mammalian Expression	5,308 bp	KanamycinNeomycin (G418)	CMV	high
Mammalian Expression	Mammalian Expression	4,700 bp	AmpicillinNeomycin (G418)	CMV	high
Cloning	Cloning	2,870 bp	Ampicillin	T7, lac	high
Bacterial Expression	Bacterial Expression	5,443 bp	Ampicillin	T7	medium
Bacterial Expression	Bacterial Expression	5,708 bp	Ampicillin	T7	medium
Bacterial Expression	Bacterial Expression	4,102 bp	Ampicillin	araBAD	medium
Bacterial Expression	Bacterial Expression	5,420 bp	Ampicillin	T7 (x2)	medium
Reporter	Reporter	4,728 bp	KanamycinNeomycin (G418)	CMV	high
Reporter	Reporter	4,091 bp	Ampicillin	HSV-TK	high
Mammalian Expression	Mammalian Expression	5,070 bp	AmpicillinHygromycin B	CMV	high
Viral Transfer	Viral Transfer	6,300 bp	AmpicillinPuromycin	MSCV LTR	high
Viral Transfer	Viral Transfer	10,826 bp	Ampicillin	EF1α	high

When to use

Look up vector features, selection markers, and promoters when planning a cloning experiment
Compare vectors across categories to choose the best backbone for your expression system
Download FASTA or GenBank format files for sequence analysis and primer design
Export an annotated SVG plasmid map for publications or lab notebooks
Browse the catalog to find vectors compatible with your host organism

Do not use for

Full-length vector sequences — use GenBank or Addgene for complete sequences
In silico cloning and sequence editing — use SnapGene, Benchling, or ApE
Ordering vectors — use Addgene for obtaining physical plasmids

Check origin compatibility before co-transformation

Two plasmids with the same origin of replication cannot be stably maintained in the same cell. ColE1, pMB1, and pUC origins are in the same incompatibility group. Use p15A (pACYC) or CloDF13 (pCDF) for the second plasmid.

Match your expression system to the promoter

T7 promoter vectors (pET) require a host with T7 RNA polymerase (like BL21(DE3)). Using them in standard E. coli strains will give no expression. Similarly, CMV promoter vectors are designed for mammalian cells and will not work in bacteria.

Consider fusion tag removal

If your downstream application requires native protein (crystallography, activity assays), choose a vector with a protease cleavage site (thrombin, TEV, Factor Xa) between the tag and your insert. Test cleavage efficiency early.

Verify insert orientation after cloning

When using a single restriction enzyme for cloning, the insert can ligate in either orientation. Always verify by colony PCR with one vector primer and one insert primer, or by diagnostic restriction digest.

AAV cargo must stay under 4.7 kb

The space between AAV ITRs is strictly limited. Exceeding the packaging limit does not cause an error — it silently reduces titer. Always calculate: promoter + transgene + polyA + any tags must fit within ~4.5 kb to be safe.

Method

The vector database is curated from published vector maps, GenBank records, and Addgene depositions. Feature annotations (origins, promoters, resistance genes, tags) are mapped to their approximate genomic coordinates. Circular SVG maps are rendered client-side using pure SVG path calculations — no D3 or external library dependency. Partial sequences (first ~200 bp) are included for display; full sequences should be obtained from GenBank accession links.

Validated

Last validated 2026-04-07. Calculations are designed for planning and documentation support; verify procurement decisions against manufacturer specifications or institutional SOPs.

How to cite

How to Cite

ConductScience Plasmid & Vector Library (v1.25.0). ConductScience, Inc. 2026. Available at: https://conductscience.com/tools/plasmid-vector-library

Sambrook J, Russell DW. Molecular Cloning: A Laboratory Manual. Cold Spring Harbor Laboratory Press. 2001.

Gibson DG et al. Enzymatic assembly of DNA molecules up to several hundred kilobases. Nature Methods. 2009;6:343-345. doi:10.1038/nmeth.1318

Studier FW, Moffatt BA. Use of bacteriophage T7 RNA polymerase to direct selective high-level expression of cloned genes. J Mol Biol. 1986;189:113-130. doi:10.1016/0022-2836(86)90385-2

Anatomy of a plasmid vector

Every functional cloning vector requires several core elements:

Origin of replication (ori): Determines the host range and copy number. Common origins include pMB1/ColE1 (E. coli, high copy), p15A (E. coli, low copy), 2μ (yeast, high copy), CEN/ARS (yeast, low copy), and SV40 (mammalian, for episomal replication in COS cells).

Selectable marker: Usually an antibiotic resistance gene that allows selection of cells containing the plasmid. Ampicillin (bla), kanamycin (kan), and chloramphenicol (cat) are standard for bacteria. Neomycin (G418), puromycin, and hygromycin are used for mammalian stable selection.

Multiple cloning site (MCS): A short region containing unique restriction enzyme sites for inserting foreign DNA. The MCS is typically positioned downstream of the promoter and upstream of a terminator.

Promoter: Drives transcription of the cloned gene. T7, tac, and araBAD are common bacterial promoters. CMV, EF1α, and CAG are used in mammalian cells. GAL1 is a galactose-inducible yeast promoter.

Choosing an expression system

E. coli expression is the fastest and cheapest option. Use pET vectors with BL21(DE3) for T7-based expression, or pBAD for tightly regulated arabinose induction. Add solubility tags (MBP, Trx, GST) for difficult proteins.

Yeast expression (S. cerevisiae or Pichia pastoris) adds eukaryotic post-translational modifications while maintaining simple culture. pYES2 (GAL1 promoter, 2μ) is standard for S. cerevisiae.

Mammalian expression is required for proteins needing mammalian-specific modifications. pcDNA3.1 (CMV) is the workhorse for transient transfection. Lentiviral vectors enable stable expression in hard-to-transfect cells.

Viral vectors (AAV, lentivirus, adenovirus) are used for in vivo gene delivery. AAV is preferred for gene therapy due to low immunogenicity but has a 4.7 kb packaging limit.

Modern cloning strategies

Traditional restriction enzyme cloning has been largely supplemented by:

Gibson Assembly: Seamlessly joins 2–15 DNA fragments with overlapping ends using a one-step isothermal reaction. Ideal for multi-fragment assemblies and gene synthesis.
Golden Gate Assembly: Uses Type IIS restriction enzymes for scarless, directional, multi-part assembly in a single reaction.
Gateway Cloning: att-site recombination moves inserts between compatible vectors without re-cloning. Useful for high-throughput expression screening.
TOPO Cloning: Topoisomerase-mediated ligation for quick cloning of PCR products.
In-Fusion Cloning: Recombination-based method similar to Gibson but enzyme-free.

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