Barthwal R, Agarwal A, Kukreti S, Mujeeb A
Department of Biosciences and Biotechnology, University of Roorkee, India.
Physiol Chem Phys Med NMR. 1987;19(2):125-39.
The binding of tetrapeptide Lys-Trp-Gly-Lys OtBu to d-CpGpCpG has been studied by proton NMR at 90 MHz and 400 MHz. Changes in chemical shift have been observed in the temperature range 275-335 K. Interaction with tetrapeptide Lys-Ala-Ala-Lys NHEt has been studied in order to ascertain the contribution to changes in chemical shift due to the electrostatic interactions alone. On addition of Lys-Trp-Gly-Lys OtBu to d-CGCG, the H-5 and H-6 resonances of internal cytosine shift upfield about 0.04-0.07 ppm at 275 K. The upfield shift in external Cytosine are relatively small about 0.01 ppm. Changes in chemical shifts of internal and external Guanine (H-8) are indistinguishable being in the range 0.02-0.11 ppm. The changes in chemical shift of Tryptophan ring protons on binding to oligonucleotide are considerably large, it being typically an upfield shift to 0.18-0.53 ppm at 275 K. The changes in chemical shift of all resonances decrease with temperature. The observations suggest intercalation of Tryptophan ring in d-CGCG. Using the magnetic anisotropy ring current shifts, overlap geometries of Tryptophan ring in d(C-G) and d(G-C) sites of d-CGCG have been proposed. The same has been verified by using Corey-Pauling-Koltun models.
已通过90 MHz和400 MHz的质子核磁共振研究了四肽Lys-Trp-Gly-Lys OtBu与d-CpGpCpG的结合。在275-335 K的温度范围内观察到了化学位移的变化。为了确定仅由于静电相互作用对化学位移变化的贡献，研究了与四肽Lys-Ala-Ala-Lys NHEt的相互作用。向d-CGCG中加入Lys-Trp-Gly-Lys OtBu后，内部胞嘧啶的H-5和H-6共振在275 K时向上位移约0.04-0.07 ppm。外部胞嘧啶的向上位移相对较小，约为0.01 ppm。内部和外部鸟嘌呤（H-8）的化学位移变化在0.02-0.11 ppm范围内难以区分。色氨酸环质子与寡核苷酸结合时的化学位移变化相当大，在275 K时通常向上位移至0.18-0.53 ppm。所有共振的化学位移变化均随温度降低。这些观察结果表明色氨酸环插入了d-CGCG中。利用磁各向异性环电流位移，提出了d-CGCG的d（C-G）和d（G-C）位点中色氨酸环的重叠几何结构。这已通过使用Corey-Pauling-Koltun模型得到验证。
