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Speciation of Transition-Metal-Substituted Keggin-Type Silicotungstates Affected by the Co-crystallization Conditions with Proteinase K
Inorganic Chemistry ( IF 4.6 ) Pub Date : 2021-09-16 , DOI: 10.1021/acs.inorgchem.1c02005
Joscha Breibeck 1 , Elias Tanuhadi 1 , Nadiia I Gumerova 1 , Gerald Giester 2 , Alexander Prado-Roller 3 , Annette Rompel 1
Affiliation  

We report on the synthesis of the tetrasubstituted sandwich-type Keggin silicotungstates as the pure Na salts Na14[(A-α-SiW10O37)2{Co4(OH)2(H2O)2}]·37H2O (Na{SiW10Co2}2) and Na14[(A-α-SiW10O37)2{Ni4(OH)2(H2O)2}]·77.5H2O (Na{SiW10Ni2}2), which were prepared by applying a new synthesis protocol and characterized thoroughly in the solid state by single-crystal and powder X-ray diffraction, IR spectroscopy, thermogravimetric analysis, and elemental analysis. Proteinase K was applied as a model protein and the polyoxotungstate (POT)–protein interactions of Na{SiW10Co2}2 and Na{SiW10Ni2}2 were studied side by side with the literature-known K5Na3[A-α-SiW9O34(OH)3{Co4(OAc)3}]·28.5H2O ({SiW9Co4}) featuring the same number of transition metals. Testing the solution behavior of applied POTs under the crystallization conditions (sodium acetate buffer, pH 5.5) by time-dependent UV/vis spectroscopy and electrospray ionization mass spectrometry speciation studies revealed an initial dissociation of the sandwich POTs to the disubstituted Keggin anions HxNa5–x[SiW10Co2O38]3– and HxNa5–x[SiW10Ni2O38]3– ({SiW10M2}, M = CoII and NiII) followed by partial rearrangement to the monosubstituted compounds (α-{SiW11Co} and α-{SiW11Ni}) after 1 week of aging. The protein crystal structure analysis revealed monosubstituted α-Keggin POTs in two conserved binding positions for all three investigated compounds, with one of these positions featuring a covalent attachment of the POT anion to an aspartate carboxylate. Despite the presence of both mono- and disubstituted anions in a crystallization mixture, proteinase K selectively binds to monosubstituted anions because of their preferred charge density for POT–protein interaction.

中文翻译:

受蛋白酶 K 共结晶条件影响的过渡金属取代 Keggin 型硅钨酸盐的形态

我们报道了四取代夹心型 Keggin 硅钨酸盐的合成为纯 Na 盐 Na 14 [(A-α-SiW 10 O 37 ) 2 {Co 4 (OH) 2 (H 2 O) 2 }]·37H 2 O ( Na{SiW 10 Co 2 } 2 ) 和 Na 14 [(A-α-SiW 10 O 37 ) 2 {Ni 4 (OH) 2 (H 2 O) 2 }]·77.5H 2 O ( Na{SiW 102} 2 ),它们是通过应用新的合成方案制备的,并通过单晶和粉末 X 射线衍射、红外光谱、热重分析和元素分析在固态下进行了彻底的表征。蛋白酶 K 被用作模型蛋白,同时研究了Na{SiW 10 Co 2 } 2Na{SiW 10 Ni 2 } 2的多氧钨酸盐 (POT)-蛋白质相互作用与文献中已知的 K 5 Na 3 [ A-α-SiW 9 O 34 (OH) 3 {Co 4 (OAc) 3 }]·28.5H2 O ( {SiW 9 Co 4 } ) 具有相同数量的过渡金属。通过时间相关的紫外/可见光谱和电喷雾电离质谱形态研究在结晶条件(乙酸钠缓冲液,pH 5.5)下测试应用 POT 的溶液行为,揭示了夹层 POT 与二取代 Keggin 阴离子 H x Na的初始解离5– x [SiW 10 Co 2 O 38 ] 3–和 H x Na 5– x [SiW 10 Ni 2 O 38 ] 3–( {SiW 10 M 2 } , M = Co II和 Ni II ) 然后部分重排成单取代化合物 ( α-{SiW 11 Co}α-{SiW 11 Ni}) 老化 1 周后。蛋白质晶体结构分析显示单取代的 α-Keggin POT 在所有三种研究化合物的两个保守结合位置,其中一个位置具有 POT 阴离子与天冬氨酸羧酸盐的共价连接。尽管结晶混合物中同时存在单取代和双取代阴离子,但蛋白酶 K 选择性地结合单取代阴离子,因为它们对 POT-蛋白质相互作用具有优选的电荷密度。
更新日期:2021-10-18
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