Product Class: Restriction Endonuclease

neb31 recombinant time saver dil_A 37 65 Heat CpG dam reduced star activity

ClaI has been reformulated with Recombinant Albumin (rAlbumin) beginning with Lot #10119493. Learn more.

We are excited to announce that all reaction buffers are now BSA-free. NEB began switching our BSA-containing reaction buffers in April 2021 to buffers containing Recombinant Albumin (rAlbumin) for restriction enzymes and some DNA modifying enzymes. Find more details at

NEB restriction endonuclease that recognizes the sequence AT^CG_AT

Product Introduction

Catalog # Size Concentration
R0197S 1000.0 units 10000 units/ml
R0197L 5000.0 units 10000 units/ml

Product Information


Product Source

An E. coli strain that carries the ClaI gene from Caryophanon latum L (ATCC 49862).
This product is related to the following categories:
Restriction Endonucleases C G Products,
Time-Saver Qualified Restriction Enzymes Products,
This product can be used in the following applications:
Fast Cloning: Accelerate your cloning workflows with reagents from NEB,
Restriction Enzyme Digestion

Reagents Supplied

Reagents Supplied

The following reagents are supplied with this product:

NEB # Component Name Component # Stored at (°C) Amount Concentration

Properties & Usage

Unit Definition

One unit is defined as the amount of enzyme required to digest 1 µg of λ DNA (dam-) in 1 hour at 37°C in a total reaction volume of 50 µl.

Reaction Conditions

1X rCutSmart™ Buffer
Incubate at 37°C

1X rCutSmart™ Buffer
50 mM Potassium Acetate
20 mM Tris-acetate
10 mM Magnesium Acetate
100 µg/ml Recombinant Albumin
(pH 7.9 @ 25°C)

Activity in NEBuffers

NEBuffer™ r1.1: 10%
NEBuffer™ r2.1: 50%
NEBuffer™ r3.1: 50%
rCutSmart™ Buffer: 100%

Diluent Compatibility

Storage Buffer

10 mM Tris-HCl
50 mM KCl
1 mM DTT
0.1 mM EDTA
200 µg/ml Recombinant Albumin
50% Glycerol
pH 7.4 @ 25°C

Heat Inactivation

65°C for 20 minutes

Methylation Sensitivity

dam methylation: Blocked by Overlapping
dcm methylation: Not Sensitive
CpG Methylation: Blocked

Product Notes

  1. ClaI is an isoschizomer of BspDI.
  2. This enzyme has shown to have lower activity on some supercoiled plasmids, with more than 1 unit required to digest 1 μg plasmid DNA. For complete digestion of 1 μg of plasmid DNA please follow our recommended digestion protocol.
  3. Blocked by overlapping dam methylation and CpG methylation.

Protocols, Manuals & Usage


  1. Optimizing Restriction Endonuclease Reactions
  2. Restriction Digest Protocol
  3. Double Digest Protocol with Standard Restriction Enzymes

Usage & Guidelines

Tools & Resources

Selection Charts

Web Tools

FAQs & Troubleshooting


  1. Is ClaI sensitive to methylation?
  2. Does ClaI produce commonly used compatible ends?
  3. What is the activity of ClaI at 25°C?
  4. Do I have to set-up digests with Time-Saver™ qualified enzymes for 5-15 minutes? Can I digest longer?
  5. I tested your restriction enzyme on the substrate DNA recommended by NEB, and it appears to be active, however it does not digest my DNA. What could be the reason?
  6. Which NEB restriction enzymes are supplied with Gel Loading Dye, Purple (6X)?
  7. Does NEB offer any BSA-free and/or animal origin-free restriction enzymes for linearization of plasmids for mRNA vaccine development?
  8. Can you tell me more about the switch from BSA to Recombinant Albumin (rAlbumin) in NEBuffers?


Quality, Safety & Legal

Quality Assurance Statement

Quality Control tests are performed on each new lot of NEB product to meet the specifications designated for it. Specifications and individual lot data from the tests that are performed for this particular product can be found and downloaded on the Product Specification Sheet, Certificate of Analysis, data card or product manual. Further information regarding NEB product quality can be found here.

Specification Change Notifications

ClaI has been reformulated with Recombinant Albumin (rAlbumin) beginning with Lot #10119493. All subsequent (higher number) lots will contain rAlbumin. For additional information, please visit at NEB Restriction Enzyme formulations with Recombinant Albumin rAlbumin


The Specification sheet is a document that includes the storage temperature, shelf life and the specifications designated for the product. The following file naming structure is used to name these document files: [Product Number]_[Size]_[Version]

Certificate Of Analysis

The Certificate of Analysis (COA) is a signed document that includes the storage temperature, expiration date and quality controls for an individual lot. The following file naming structure is used to name these document files: [Product Number]_[Size]_[Version]_[Lot Number]

Safety DataSheets

The following is a list of Safety Data Sheet (SDS) that apply to this product to help you use it safely.

Legal and Disclaimers

Products and content are covered by one or more patents, trademarks and/or copyrights owned or controlled by New England Biolabs, Inc (NEB). The use of trademark symbols does not necessarily indicate that the name is trademarked in the country where it is being read; it indicates where the content was originally developed. The use of this product may require the buyer to obtain additional third-party intellectual property rights for certain applications. For more information, please email [email protected].

This product is intended for research purposes only. This product is not intended to be used for therapeutic or diagnostic purposes in humans or animals.

New England Biolabs (NEB) is committed to practicing ethical science – we believe it is our job as researchers to ask the important questions that when answered will help preserve our quality of life and the world that we live in. However, this research should always be done in safe and ethical manner. Learn more.