HOLIDAY HOURS
In observance of the U.S. Thanksgiving holiday, Scarab Genomics will be closed Thursday and Friday, November 22-23. Normal business hours will resume Monday, November 26th. In observance of Christmas and New Year's holiday, Scarab Genomics will be closed December 24-25, Dec 31, 2018 and January 1, 2019. The last INTERNATIONAL shipping day of 2018 is Friday, December 14th. The last DOMESTIC shipping day of 2018 is December 19th.

Frequently Asked Questions

General Questions

Q. Do the Clean Genome® E. coli strains express the Dam or Dcm methylases?
A. Yes, they are dam+ and dcm+.

Q. What host restriction systems do the Clean Genome® E. coli strains contain?
A. They are ΔhsdR, ΔhsdM and ΔhsdS.

Q. What host modification systems do the Clean Genome® E. coli strains contain?
A. They are ΔmcrA, ΔmcrB, ΔmcrC, and Δmrr.

Insertion Elements (IS)

Q. How to I determine if my DNA of interest contain IS elements?
A. Use the White Glove Kit to test your DNA. If it tests, positive, then follow Scarab’s Isolation of IS-Free Plasmid Protocol to isolate IS-free DNA.

Q. How do I Isolate IS-Free Plasmid DNA?
A. If your plasmid was NOT grown in a Clean Genome Strain (many commercial vectors are grown in wild-type E. coli), it will likely contain IS elements. To isolate IS-free plasmid DNA, follow Scarab’s Isolation of IS-Free Plasmid Protocol to isolate IS-free DNA. This protocol uses the White Glove IS Detection Kit .

Protein Expression

Q. What is the ScarabXpress Systems composed of?
A. The ScarabXpress Systems are composed of a Host strain + Expression vector.

Q. What is the difference between ScarabXpress1 and ScarabXpress2?
A. ScarabXpress1 consists of the ScarabXpress® T7 lac host + a vector containing a T7 promoter vectors such as the pET vectors. ScarabXpress2 consists of Scarab’s pSX2 expression vector + ANY Clean Genome® E. coli host strain.

Q. How do the two Scarab Protein Expression Systems compare?
A. ScarabXpress2 generally provides higher expression levels of any given target protein. It enables tighter expression control, which is very useful for periplasmic expressed targets and “toxic” targets that are detrimental to the host. In a side by side comparison using a test protein, ScarabXpress2 produced 29- 36x more test protein than BL21(DE3), where as ScarabXpress1 only produced 12x more test protein than BL21(DE3). Learn More

Q. What concentration of IPTG should I use for inducing my protein expression?
A. The optimum concentration of IPTG will vary with the target protein. The Scarab Express-2 expression system shows a graded increase in protein expression with increasing induction level, allowing for a 3000-fold induction range. We recommend testing a series of IPTG levels ranging from 5 uM to 500 uM IPTG for each of your protein targets. Learn More

Plasmid DNA

Q. How to I determine if my DNA of interest contain IS elements?
A. Use the White Glove Kit to test your DNA. If it tests, positive, then follow Scarab’s Isolation of IS-Free Plasmid Protocol to isolate IS-free DNA.

Q. How do I Isolate IS-Free Plasmid DNA?
A. If your plasmid was NOT grown in a Clean Genome Strain (many commercial vectors are grown in wild-type E. coli), it will likely contain IS elements. To isolate IS-free plasmid DNA, follow Scarab’s Isolation of IS-Free Plasmid Protocol to isolate IS-free DNA. This protocol uses the White Glove IS Detection Kit .

Q. Do the Clean Genome® strains work well with plasmids that contain secondary structure such as viral Long Terminal Repeats (LTR) or short-hairpin RNA (shRNA) etc?
A. Yes, they work well with plasmids that contain challenging secondary structure. Learn More

Retroviral, Lentiviral and shRNA Vectors

Q. Do the Clean Genome® E. coli strains work well with Lentiviral vectors?
A. Yes, Chakiath & Esposito (2007) showed that “Lentiviral expression clones, which contain long direct repeats, often show dramatic instability in Escherichia coli.” Even hosts such as Stbl3™ that are specifically designed for cloning lentiviral direct repeats have proven inadequate. Chakiath & Esposito showed that Clean Genome® E. coli strain MDS42, the foundation strain of the reduced genome platform, stabilizes lentiviral expression clones containing these repeats. In over 100 cloning reactions using MDS42, these authors picked just two transformant colonies for analysis, and in >95% of the cases both clones chosen had the correct restriction maps, saving substantial time and effort in recombinant plasmid preparation. Learn More

Q. Do the Clean Genome® E. coli strains work well for Retrovirial vectors such as adenoassociated virus (AAV) vectors?
A. Yes, in fact it has been shown to work on pT-ITR-IL2, an adenoassociated virus (AAV) vector which contains particularly extensive secondary structure.

Structure of the ITR "hammerheads" in wild-type AAV2

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