二维分子形状和定量手性程度的研究

Studies on 2D molecular shape and chiral quantitation

以二进制编码描述苯环型化合物分子在二维空间的形状,所得到的编码能够区分二维平面上一对苯环型化合物对映体。由于对映体的二进制编码不同,基于化合物和其镜像的编码计算得到了海明距离,并以其表征1对对映体的定量手性程度。以28对周长为22的手性苯环型化合物对映体为实例,计算苯环型化合物的定量手性程度,其结果仅仅有2个数值,分别为海明距离4和6。具有不同形状的该类化合物很多,为了提高分辨率,分别计算了窗口宽度从1～16时的海明距离,并分别以其来代表定量手性程度。结果显示全部16个窗口的海明距离的加和具有最大的区分能力,共得到17种海明距离。如果将每一窗口的细节引入到计算中,并采用类似的方法计算,则实例中所有的28个苯环型化合物实现了完全的区分,所得到的定量手性程度的区分能力是令人满意的。本研究证明如果用适当的编码来描述二维空间中分子的边界,能够解决分子形状的定量表征。尽管本文的二进制编码衍生于平面系统的苯环型化合物,并以其描述分子的边界来进行手性程度的测量,但是,原则上同样的方法可以应用到所有二维平面上的形状描述。

The two - dimensional shape of molecular periphery of benzenoid was described by the binary code, which is able to distinguish between a pair of enantiomers. Since enantiomers have distinct codes, the quantitative measure of chirality based on Hamming distance between the codes for a structure and its mirror image was obtained. The quantitative measure of chirality was implemented to 28 pairs of enantiomers of benzenoids, which have constant perimeter 22, and the benzenoids can only be grouped into two classes - Hamming distance 4 and 6. It is hard to imagine that so many molecules would have the same chirality measure. To increase the resolution, the Hamming distance of different widths of windows from 1 to 16 was calculated to represent degree of chirality, individually, and the sum of Hamming distance of 16 windows has the most discrimination - 17 classes. When the detail of each window was involved and similar methods were adopted in the calculation, all 28 benzenoids were able to be distinguished. The distinction of degree of chirality was satisfactory. The present work has demonstrated that molecular shapes can be tackled quantitatively using appropriate codes to describe the molecular periphery. We considered the use of binary codes for benzenoid - like planar systems that represent molecular boundary for deriving a chirality measure. The same approach in principle can apply to all 2D shapes.