Uchaneishvili Sophio, Makharadze Maya, Shushanyan Mikhael, van Eldik Rudi, Khoshtariya Dimitri E
Department of Biophysics, I. Beritashvili Center of Experimental Biomedicine, Gotua 14, 0160 Tbilisi, Georgia.
Department of Biophysics, I. Beritashvili Center of Experimental Biomedicine, Gotua 14, 0160 Tbilisi, Georgia; Institute for Biophysics and Bionanosciences at the Department of Physics, I. Javakhishvili Tbilisi State University, I. Chavchavadze Avenue 3, 0128 Tbilisi, Georgia.
Int Sch Res Notices. 2014 Sep 7;2014:834189. doi: 10.1155/2014/834189. eCollection 2014.
An impact of 0.5 to 3 M choline dihydrogen phosphate, [ch][dhp], the biotechnologically relevant ionic substance, on the thermal stability of a model globular protein, α-chymotrypsin (α-CT), has been studied exploiting the highly sensitive differential scanning calorimetry (DSC) technique. The notable overall stabilizing effect of 11 ± 2 K regarding the thermal transition (melting) temperature, T m , has been detected. For this kind of series, for the first time, the calorimetric melting enthalpy (ΔH cal) and transition entropy (ΔS m ) parameters have been determined simultaneously throughout. The first analysis indicated a two-phase impact implying (a) the initial, dramatic drop in both ΔH cal and ΔS m , obviously connected to specific, direct interaction between the [ch][dhp] components and α-CT's charged groups (within 0 to 1 mol/L [ch][dhp]), leading to the essential rearrangement of the interfacial hydrogen-bonded (HB) network; and (b) the follow-up (within 1 to 3.0 mol/L [ch][dhp]), modest changes in ΔH cal and lack of changes in ΔS m , seemingly connected with a subsequent steady strengthening of already reformed HB network, respectively. These changes, presumably, are primarily facilitated by Coulombic interactions between the [dhp] anions and solvent-exposed positively charged amino groups of α-CT.
利用高灵敏度差示扫描量热法（DSC）技术，研究了具有生物技术相关性的离子物质0.5至3M磷酸二氢胆碱（[ch][dhp]）对模型球状蛋白α-胰凝乳蛋白酶（α-CT）热稳定性的影响。已检测到热转变（熔化）温度Tm有11±2K的显著总体稳定作用。对于此类系列，首次同时测定了整个过程中的量热熔化焓（ΔHcal）和转变熵（ΔSm）参数。初步分析表明存在两阶段影响，即（a）初始阶段，ΔHcal和ΔSm均急剧下降，这显然与[ch][dhp]组分与α-CT带电基团之间的特定直接相互作用有关（在0至1mol/L [ch][dhp]范围内），导致界面氢键（HB）网络发生基本重排；（b）后续阶段（在1至3.0mol/L [ch][dhp]范围内），ΔHcal有适度变化，而ΔSm无变化，这似乎分别与已重新形成的HB网络随后的稳定增强有关。据推测，这些变化主要是由[dhp]阴离子与α-CT溶剂暴露的带正电氨基之间的库仑相互作用促成的。
