Ding Fei, Peng Wei, Peng Yu-Kui
College of Agriculture and Plant Protection, Qingdao Agricultural University, Qingdao 266109, China.
Center for Food Quality Supervision & Testing, Ministry of Agriculture, College of Food Science & Engineering, Northwest A&F University, Yangling 712100, China.
Phys Chem Chem Phys. 2016 Apr 28;18(17):11959-71. doi: 10.1039/c5cp07754k.
The current work explores the biomolecular recognition of a series of flavonols by a protein and then uncovers the influences of the structural features of flavonols and the protein's own characteristics, e.g. the dynamics and flexibility, on the bioavailability of flavonols by using the pivotal biomacromolecule hemoglobin as a model. The experimental results revealed that flavonol may lead to a notable decrease in the steady-state fluorescence intensity of the β-37 Trp residue, and in the meantime the R-T transition of the protein transpired. Such noncovalent recognition forms the ground-state adduct, with an association intensity of 3.991 × 10(4) M(-1) in the reaction process, which has already been authenticated by the detailed analysis of time-resolved fluorescence and UV/vis absorption spectra. Furthermore, flavonol can form hydrogen bonds and π-conjugation effects with several amino acid residues on the polypeptide chain, for example, Trp-37, Arg-40, Asp-99 and Asn-102, and this event would induce self-regulation of the compact, regular conformation of the protein to a certain extent, which explicitly corroborates the results of circular dichroism. According to the study of molecular docking and structure-activity relationships, we could see that the recognition capacities of the protein-flavonols are inversely interrelated with the C log P values of the flavonol molecules. Moreover, the properties of the substituents in the structural B-ring unit of flavonols, i.e. polarity, position and number, will also prominently affect the degree of affinity and bioavailability of the protein-flavonol complexes. The analytical results of molecular dynamics (MD) simulation testified that the discussions of the structure-activity relationships are entirely logical, and the conformations of the amino acid residues forming noncovalent interactions tend to be stable in the MD simulation, as further elucidated from the dynamics data. Plainly, molecular recognition of the protein-flavonols might noticeably cause relatively large changes in protein flexibility, and then manifest different recognition strengths and corresponding biological activities. This issue will be carefully validated by the interpretation of root-mean-square fluctuation.
当前的工作研究了一系列黄酮醇与一种蛋白质的生物分子识别，然后以关键生物大分子血红蛋白为模型，揭示了黄酮醇的结构特征以及蛋白质自身特性（如动力学和柔韧性）对黄酮醇生物利用度的影响。实验结果表明，黄酮醇可能导致β-37色氨酸残基的稳态荧光强度显著降低，同时蛋白质发生R-T转变。这种非共价识别形成了基态加合物，反应过程中的缔合强度为3.991×10⁴ M⁻¹，这已通过时间分辨荧光和紫外/可见吸收光谱的详细分析得到证实。此外，黄酮醇可与多肽链上的几个氨基酸残基形成氢键和π共轭效应，例如色氨酸-37、精氨酸-40、天冬氨酸-99和天冬酰胺-102，这一过程将在一定程度上诱导蛋白质紧密、规则构象的自我调节，这明确证实了圆二色性的结果。根据分子对接和构效关系的研究，我们可以看出蛋白质-黄酮醇的识别能力与黄酮醇分子的C log P值呈负相关。此外，黄酮醇结构B环单元中取代基的性质，即极性、位置和数量，也将显著影响蛋白质-黄酮醇复合物的亲和力和生物利用度。分子动力学（MD）模拟的分析结果证明了构效关系的讨论是完全合理的，在MD模拟中形成非共价相互作用的氨基酸残基构象趋于稳定，动力学数据进一步阐明了这一点。显然，蛋白质-黄酮醇的分子识别可能会显著引起蛋白质柔韧性的较大变化，进而表现出不同的识别强度和相应的生物活性。这个问题将通过均方根波动的解释进行仔细验证。
