Observation of a Single-Stranded DNA/Pyrrolobenzodiazepine Adduct

TY - JOUR

T1 - Observation of a Single-Stranded DNA/Pyrrolobenzodiazepine Adduct

AU - Rahman, Khondaker

AU - James, CH

AU - Bui, TTT

AU - Drake, AF

AU - Thurston, DE

PY - 2011/12/7

Y1 - 2011/12/7

N2 - Pyrrolobenzodiazepine (PBD) antitumor agents have, to date, only been observed to bind to duplex DNA, apparently requiring a minor groove environment for covalent bond formation between their C11-position and the C2-NH2 functionality of a guanine base. Using an HPLC/MS assay we have now observed and isolated for the first time PBD adducts with single-stranded DNA fragments. Surprisingly, these adducts could only be formed through dissociation of duplex DNA adducts and not by direct interaction of PBDs with single-stranded DNA. They were sufficiently stable for characterization by MALDI-TOF-MS and remained intact after storing at −20 °C for at least 20 days, although the PBD became detached from the DNA within 7 days if stored at room temperature. Furthermore, addition of a complementary strand allowed the duplex adduct to reform. The relative stability of single-stranded PBD/DNA adducts despite a complete loss of minor groove structure was further confirmed by CD spectroscopic analysis. The CD signal induced by the presence of a PBD molecule in the single-stranded adducts remained prominent despite heating for 2 h at 50–60 °C, thus indicating their relatively robust nature.

AB - Pyrrolobenzodiazepine (PBD) antitumor agents have, to date, only been observed to bind to duplex DNA, apparently requiring a minor groove environment for covalent bond formation between their C11-position and the C2-NH2 functionality of a guanine base. Using an HPLC/MS assay we have now observed and isolated for the first time PBD adducts with single-stranded DNA fragments. Surprisingly, these adducts could only be formed through dissociation of duplex DNA adducts and not by direct interaction of PBDs with single-stranded DNA. They were sufficiently stable for characterization by MALDI-TOF-MS and remained intact after storing at −20 °C for at least 20 days, although the PBD became detached from the DNA within 7 days if stored at room temperature. Furthermore, addition of a complementary strand allowed the duplex adduct to reform. The relative stability of single-stranded PBD/DNA adducts despite a complete loss of minor groove structure was further confirmed by CD spectroscopic analysis. The CD signal induced by the presence of a PBD molecule in the single-stranded adducts remained prominent despite heating for 2 h at 50–60 °C, thus indicating their relatively robust nature.

U2 - 10.1021/ja205395r

DO - 10.1021/ja205395r

M3 - Article

SN - 1520-5126

SN - 1520-5126

VL - 133

SP - 19376

EP - 19385

JO - Journal of the American Chemical Society

JF - Journal of the American Chemical Society

IS - 48

ER -