Pouwels P J, Hartman R F, Rose S D, Kaptein R
Bijvoet Center for Biomolecular Research, Utrecht University, The Netherlands.
Photochem Photobiol. 1995 Jun;61(6):563-74. doi: 10.1111/j.1751-1097.1995.tb09871.x.
The light-induced splitting of pyrimidine dimers was studied using the electron acceptor anthraquinone-2-sulfonate (AQS) as a photosensitizer. To this end, photochemically induced dynamic nuclear polarization (photo-CIDNP) experiments were performed on a series of pyrimidine monomers and dimers. The CIDNP spectra demonstrate the existence of both the dimer radical cation, which is formed by electron transfer from the dimer to the photoexcited sensitizer AQS*, and its dissociation product, the monomer radical cation. In spectra of 1,1'-trimethylene bridged cis, syn pyrimidine dimers, polarization is observed that originates from a spin-sorting process in the dimer radical pair. This points to a relatively long lifetime of the dimer radical cation involved, which is presumably due to stabilization by the trimethylene bridge. Polarization originating from a dimer radical pair is detected in the spectrum of trans,anti (1,3-dimethyluracil) dimer as well. The spectra of the bridged pyrimidines also demonstrate the reversibility of the dissociation of dimer radical cation into monomer radical cation, which is concluded from the observation of polarization in the dimer as a result of spin sorting in the monomer radical pair.
使用电子受体蒽醌 - 2 - 磺酸盐（AQS）作为光敏剂研究了嘧啶二聚体的光诱导分裂。为此，对一系列嘧啶单体和二聚体进行了光化学诱导动态核极化（photo - CIDNP）实验。CIDNP光谱证明了二聚体自由基阳离子及其解离产物单体自由基阳离子的存在，二聚体自由基阳离子是通过电子从二聚体转移到光激发的敏化剂AQS*而形成的。在1,1'-三亚甲基桥连的顺式、反式嘧啶二聚体的光谱中，观察到极化现象，其源于二聚体自由基对中的自旋分选过程。这表明所涉及的二聚体自由基阳离子具有相对较长的寿命，这可能是由于三亚甲基桥的稳定作用。在反式、反式（1,3 - 二甲基尿嘧啶）二聚体的光谱中也检测到了源于二聚体自由基对的极化。桥连嘧啶的光谱还证明了二聚体自由基阳离子解离为单体自由基阳离子的可逆性，这是根据单体自由基对中的自旋分选导致二聚体中出现极化现象而得出的结论。
