Cryoprotectants Severely Exacerbate X-ray-Induced Photoreduction,The Journal of Physical Chemistry Letters

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Cryoprotectants Severely Exacerbate X-ray-Induced Photoreduction
The Journal of Physical Chemistry Letters ( IF 4.8 ) Pub Date : 2018-01-19 00:00:00 , DOI: 10.1021/acs.jpclett.7b03111
Kurt H. Nienaber ₁ , M. Jake Pushie ₂ , Julien J. H. Cotelesage ₁ , Ingrid J. Pickering _{1,

3} , Graham N. George _{1,

3}

Affiliation

Approximately 11% of enzymes contain a transition metal ion that is essential for catalytic function. Such metalloenzymes catalyze much of the most chemically challenging and biologically essential chemistry carried out by life. X-ray-based methods, predominantly macromolecular crystallography (MX) and also X-ray absorption spectroscopy (XAS), have proved essential for determining structures of transition metal ion-containing active sites in order to deduce enzyme catalytic mechanisms. However, X-ray irradiation can induce change in both the oxidation state and structure of the metal, which is problematic in structure determination. We present an XAS study of whether cryoprotectants such as polyethylene glycol (PEG) or glycerol, routinely added to MX or XAS samples to improve data quality, affect photoreduction. Our data demonstrate a remarkable 10-fold exacerbation in rate of photoreduction of Cu(II) to Cu(I) when alcohol or ether cryoprotectants are present. Our results suggest that widespread use of cryoprotectants may increase the potential for erroneous structures.

中文翻译：

低温保护剂严重加剧了X射线诱导的光还原

大约11％的酶包含对催化功能至关重要的过渡金属离子。此类金属酶催化了生命中进行的许多最具化学挑战性和生物学必不可少的化学反应。基于X射线的方法，主要是大分子晶体学（MX）以及X射线吸收光谱法（XAS），已被证明对于确定含过渡金属离子的活性位点的结构以推断酶催化机理至关重要。然而，X射线照射可引起金属的氧化态和结构的变化，这在结构确定中是有问题的。我们提供了一项XAS研究，该研究是常规地添加到MX或XAS样品中以提高数据质量的防冻剂（例如聚乙二醇（PEG）或甘油）是否会影响光还原。我们的数据表明，当存在酒精或乙醚防冻剂时，Cu（II）还原为Cu（I）的速率显着增加10倍。我们的结果表明，防冻剂的广泛使用可能会增加错误结构的可能性。

更新日期：2018-01-19

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