FREQUENTLY ASKED TECHNICAL QUESTION
QUESTION: Which should I use - psoralen C2 or psoralen C6?
RESPONSE:Psoralen C2 is designed to crosslink to a T residue adjacent to the 3'-terminus of the opposite strand of double stranded DNA. Psoralen C6 is intended to fulfill the same purpose but, with the longer spacer, crosslinks to the triple strand of triplex DNA.
Max excitation=330nm, observed at max 395nm
QUESTION: What is the sequence requirement for psoralen mediated cross-linking in double stranded DNA?
RESPONSE:Psoralens are a class of naturally occurring heterocyclic compounds which intercalates between bases in double-stranded or triple stranded DNA. Upon exposure to long wavelength light (350 nm) Psoralen forms covalent linkages to Thymidine (cyclobutane linkage). Psoralen is a bifunctional reagent and can form either a monoadduct, linking one adjacent thymidine on the same or complimentary strand, or a diadduct, linking adjacent thymidines on the same or complimentary strands. Diadducts formed between adjacent thymidines are photoreversable with short wavelength UV light (254 nm).
|
Type of Adduct
|
Optimal Sequence
|
Cross-linking
|
Reversing
|
|
|
Wavelength
|
Wavelength
|
|
Monoadduct
|
5’-Psoralen-XAX-XXX-
|
350 nm
|
NA
|
|
Diadduct
|
5’-Psoralen-TAX-XXX-
|
350 nm
|
254 nm
|
Note: For adducts between double-stranded DNA use Psoralen C210-1982.
For adducts between triple-stranded DNA use Psoralen C6 which has a longer linker arm 10-1983.
REFERENCE(S):
1. U. Pieles and U. Englisch, Nucleic Acids Res., 1989, 17, 285.
QUESTION: What are the relative extinction coefficients of 5'-Fluorescein, Hex and Tet etc.. at 260 nm and their Lambda max?
RESPONSE:Please see http://www.glenresearch.com/Technical/Extinctions.html
REFERENCE(S):
Oligonucleotide Properties Calculator; http://www.basic.northwestern.edu/biotools/oligocalc.html
If you cannot find the answer to your problem then please contact us or telephone +44 (0)1954 210 200