FURTHER REFINEMENT OF STRUCTURE OF SUCROSE BASED ON NEUTRON-DIFFRACTION DATA
FURTHER REFINEMENT OF STRUCTURE OF SUCROSE BASED ON NEUTRON-DIFFRACTION DATA
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DOI：
10.1107/s0567740873003353
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发表时间：
1973-01-01
期刊：
影响因子：
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通讯作者：
LEVY, HA
中科院分区：
文献类型：
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作者：
BROWN, GM;LEVY, HA
用Brown&Levy[Science(1963)]的中子衍射数据进一步推算了蔗糖C12H220Li的结构。141,921-923]和全矩阵最小二乘法，并进行各向同性消光校正。最终的差异指数R(F)为0-033，拟合标准差为0“997。早些时候报告的参数和结构细节得到了更高精度的确认。键长的标准误差如下：CC和CO，0.0012到0.0019；CH，0-0022到0“0033/~；OH，0-0028到0.0042，~。介绍1963年，我们发表了一份初步报告(Brown&Levy，1963)，根据Beevers，McDonald，Robertson&Stern(1952年)的蔗糖(C12H22Oll)结构的中子微分数据进行了改进。在罗马国际铬研究所描述了后期提炼阶段的结构。1963年的会议(另见Brown&Levy，1964a的简要说明)。应许多感兴趣的人的要求，已经提供了对应于该后期阶段的参数，并且已经将蔗糖的结构特征与在其间已很好地确定其结构的其他糖分子的结构特征进行了比较(例如，参见：Sundaralin-gam，1965,1968；Berman，Chu&Jeffrey，1967；Fries，Rao&Sundalingam，1971；Strahs，1970；Rohrer，1972)。由于最小二乘计算问题的规模(通常涉及45个原子中每个原子的9个参数)相对于1963年使用的计算机的有限能力，结构参数必须分块精化，精化不能继续进行以完成收敛。此外，可用的最小二乘程序没有像今天通常所做的那样，对灭绝影响的观测进行修正。我们曾试图通过使用三个晶体中较小的两个用于较强反射的数据和来自最大晶体的用于较弱反射的数据来最小化消光效应(Brown&Levy，1964a，b)，这些数据构成了大部分数据。然而，尽管我们相信1963年的原子坐标是可靠的，但我们最近一直担心，由于灭绝的残余效应，热参数可能会出现误差。知道一项正在进行的研究(见Hanson，Sieker&Jensen，1973)，使用我们的中子参数与新的X射线数据相结合，比较氢原子的热参数，并研究
The structure of sucrose, C12H22Oli, has been further refined using the neutron-diffraction data of Brown & Levy [Science (1963). 141,921-923] and the full-matrix least-squares method, with an isotropic extinction corrections. The final discrepancy index R (F) is 0-033 and the standard deviation of fit is 0" 997. Parameters and structural details reported earlier are confirmed at a higher level of precision. Standard errors of bond lengths are as follows: CC and CO, 0.0012 to 0.0019.~; CH, 0-0022 to 0" 0033/~.; OH, 0-0028 to 0.0042,~.Introduction In 1963 we published a preliminary report (Brown & Levy, 1963) on a refinement based on neutron-dif-fraction data of the structure of sucrose (C12H22Oll) as reported by Beevers, McDonald, Robertson & Stern (1952). The structure at a later stage of refine-ment was described at the Rome IU Cr. meeting in 1963 (see also the brief description in Brown & Levy, 1964a). Parameters corresponding to this later stage have been made available on request to a number of interested persons, and comparisons have been made of structural features of sucrose with those of other sugar molecules whose structures have been well determined in the intervening time (see for example: Sundaralin-gam, 1965, 1968; Berman, Chu & Jeffrey, 1967; Fries, Rao & Sundaralingam, 1971; Strahs, 1970; Rohrer, 1972). Because of the scale of the least-squares computa-tional problem (involving the usual nine parameters for each of 45 atoms) relative to the limited capability of the computer used in 1963, the structure parameters had to be refined in blocks and the refinement was not continued to complete convergence. Further, the available least-squares program had no provision for correcting the observations for effects of extinction, as is commonly done today. We had attempted to mini-mize extinction effects (Brown & Levy, 1964a, b) by using data from the smaller two of three crystal speci-mens for the stronger reflections and data from the largest crystal for the weaker reflections which make up the bulk of the data. However, although we were confident that the 1963 atomic coordinates were reli-able, we have been concerned lately about possible errors in the thermal parameters arising as residual effects of extinction. Knowing of a study in progress (see the accompanying paper by Hanson, Sieker & Jensen, 1973) using our neutron parameters in con-junction with new X-ray data to compare thermal parameters for the hydrogen atoms and to study the