Harada K, Ogawa K, Matsuura K, Murata H, Suzuki M, Watanabe M F, Itezono Y, Nakayama N
Faculty of Pharmacy, Meijo University, Nagoya, Japan.
Chem Res Toxicol. 1990 Sep-Oct;3(5):473-81. doi: 10.1021/tx00017a014.
A nondestructive method using a combination of three 2D NMR techniques, DQF-COSY (double quantum filter correlation spectroscopy), HMQC (1H-detected multiple quantum coherence), and HMBC (heteronuclear multiple bond correlation), were developed for structural determination of microcystins, toxic heptapeptides produced by cyanobacteria. With this procedure we were able to assign all carbons and protons of microcystins LR (1) and RR (2), thus determining the constituent amino acid sequences. The procedure was also applied to the microcystin-associated nontoxic minor components, which have molecular weights and amino acid compositions similar to those of 1 and 2 and toxicities different from those of 1 and 2. From detailed analysis of these spectra we rapidly deduced that the minor components are geometrical isomers with respect to C-7 of the diene in Adda of the parent toxins. The structures were finally confirmed to be 3 and 4 by ROESY (rotating frame nuclear Overhauser and exchange spectroscopy) technique.
开发了一种结合三种二维核磁共振技术（双量子滤波相关光谱法（DQF-COSY）、氢检测多量子相干法（HMQC）和异核多键相关法（HMBC））的无损方法，用于微囊藻毒素（蓝藻产生的有毒七肽）的结构测定。通过该方法，我们能够确定微囊藻毒素LR（1）和RR（2）的所有碳和质子，从而确定其组成氨基酸序列。该方法还应用于与微囊藻毒素相关的无毒次要成分，这些成分的分子量和氨基酸组成与1和2相似，但毒性与1和2不同。通过对这些光谱的详细分析，我们迅速推断出次要成分是母体毒素Adda中二烯C-7的几何异构体。最终通过旋转框架核Overhauser和交换光谱法（ROESY）技术确认结构为3和4。
