C18 sep pak cartridgeswere

Oligonucleotides were synthesized via
standard automated DNA synthesis on an Applied Biosystems Inc. model
394 instrument. DNA synthesis reagents were obtained from Glen Research.
Oligonucleotides were purified by 20% denaturing gel electrophoresis
and desalted using C18-Sep-Pak cartridges. Oligonucleotides were characterized
by ESI (Thermoquest LCQ Deca) or MALDI-TOF (Bruker Autoflex III) mass
spectrometry.
Radiolabeling was carried out using standard protocols
and is briefly described below.³⁴ T4 polynucleotide
kinase (PNK) was purchased from New England Biolabs. γ-³²P-ATP was purchased form PerkinElmer. C18-Sep-Pak cartridges
were obtained from Waters. Quantification of radiolabeled oligonucleotides
was carried out using a Molecular Dynamics phosphorimager equipped
with ImageQuant TL software. Radiolabeled samples were counted using
a Beckman Coulter LS 6500 scintillation counter. Photolyses were carried
out in a Rayonet RPR-100 photoreactor (Southern New England Ultraviolet)
equipped with 16 lamps with maximum emission at 350 nm. BME and piperidine
solutions were freshly prepared.

Oligonucleotides were purchased from Integrated
DNA Technologies (Coralville, IA). Hydralazine hydrochloride, 2-deoxy-d-ribose, sodium hydroxide, and other chemicals were purchased
from Sigma-Aldrich (St. Louis, Mo) and used without further purification.
The enzyme uracil DNA glycosylase (UDG) was purchased from New England
Biolabs (Ipswich, MA). [γ-³²P]-ATP (6000 Ci/mmol)
was purchased from PerkinElmer (Waltham, MA). C18 Sep-Pak cartridges
were purchased from Waters (Milford, MA), and BS Polyprep columns
were obtained from BioRad (Hercules, CA). Measurement of radioactivity
in polyacrylamide gels was carried out using a Personal Molecular
Imager (Bio-Rad) with Quantity One software (v.4.6.5).