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首页> 外文期刊>Acta Crystallographica, Section B. Structural Science >X-ray crystal structures of acetates of 6-s-cis and 6-s-trans astaxanthin and of 78-didehydroastaxanthin and 787'W-tetradehydroastaxanthin:comparison with free and protein-bound astaxanthins
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X-ray crystal structures of acetates of 6-s-cis and 6-s-trans astaxanthin and of 78-didehydroastaxanthin and 787'W-tetradehydroastaxanthin:comparison with free and protein-bound astaxanthins

机译：6-顺式和6-s-反式虾青素，78-二氢虾青素和787'W-四氢虾青素的乙酸盐的X射线晶体结构：与游离和结合蛋白的虾青素的比较

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摘要

The crystal structures of the 6-s-cis [s-cis-(1)] and 6-s-tra_s [s-trans-(1)] conformers of the diacetates of astaxanthin (AXT) and those of (787'W-tetradehydroastaxanthin [(3S,3'S)-3,3'-dihydroxy-7,8-didehydro-,β,β-carotene-4,4'-dione (2)] and (3S,3'S)-7,8,7',8'-tetradehydroastaxanthin [(3S,3'S)-3,3'-dihy-droxy-7,8,7',8'-tetradehydro-β_ β-carotene-4, 4'-dione (3)] are reported. The conformations of these four molecules vary in particular with the angle of twist of the end rings out of the plane of the polyene chain; for s-cis-(1), the end rings are twisted out of the plane of the polyene chain by an angle of _49.0 (5)°, and the conformation is therefore similar to that found for unesterified AXT as well as for the carotenoids, canthaxanthin and β,β-carotene. For s-trans-(1), the end rings are coplanar with the polyene chain and its conformation is much more similar to that of the protein-bound AXT in the blue protein, crustacyanin, which is found in the shell of lobsters, although s-trans-(1) shows much less bowing of the polyene chain. In (2) and (3) the end rings are also almost coplanar with the polyene chain with the end rings in (2) in the s-cis conformation, and in (3) in the s-trans conformation. Thus, an extensive ensemble of the possible ,A end-ring conformations has been determined. These structures are compared with one another as well as unbound, unesterified AXT and protein-bound AXT. Also, the effect of the end-ring conformations on the colour and U__vis spectra of the crystals was established.
机译：虾青素（AXT）和（787'W）双乙酸盐的6-s-顺式[s-顺式（1）]和6-s-tra_s [s-反式（1）]构象的晶体结构-四氢黄花黄素[（3S，3'S）-3,3'-二羟基-7,8-二氢-，β，β-胡萝卜素-4,4'-二酮（2）]和（3S，3'S）-7,8， 7'，8'-四氢黄花黄素[（3S，3'S）-3,3'-二氢-羟基-7,8,7'，8'-四氢-β_β-胡萝卜素-4，4'-二酮（3）]这四个分子的构象尤其随着末端环的扭转角在多烯链平面外的变化而变化;对于s-cis-（1），末端环被扭转在多烯链平面外。多烯链的角度为_49.0（5）°，因此其构象与未酯化AXT以及类胡萝卜素，角黄素和β，β-胡萝卜素的构象相似。对于s-trans-（1），末端环与多烯链共面，并且其构象与蓝色蛋白质Crustacyanin中与蛋白质结合的AXT的构象非常相似，后者在龙虾壳中发现，尽管兰斯（1）显示多烯链的弯曲少得多。在（2）和（3）中，端环也与多烯链几乎共面，其中在（2）中为s-顺式构型，在（3）中为s-反式构型。因此，已经确定了可能的A环构型的广泛组合。将这些结构以及未结合的，未酯化的AXT和蛋白质结合的AXT相互比较。同样，确定了端环构象对晶体的颜色和U_vis光谱的影响。

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