EXPERIMENTAL-MEASUREMENT OF COULOMB ENERGY AND INTRINSIC DIELECTRIC POLARIZABILITY OF A MULTIPLY PROTONATED PEPTIDE ION USING ELECTROSPRAY-IONIZATION FOURIER-TRANSFORM MASS-SPECTROMETRY
EXPERIMENTAL-MEASUREMENT OF COULOMB ENERGY AND INTRINSIC DIELECTRIC POLARIZABILITY OF A MULTIPLY PROTONATED PEPTIDE ION USING ELECTROSPRAY-IONIZATION FOURIER-TRANSFORM MASS-SPECTROMETRY
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DOI：
10.1021/ja00108a004
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发表时间：
1995-01-25
影响因子：
15
通讯作者：
WILLIAMS, ER
中科院分区：
文献类型：
--
作者：
GROSS, DS;WILLIAMS, ER
演示了一种通过测量气相碱度来定量测量具有两个或多个质子的气相离子库仑能量的方法。根据这些测量和电荷位点之间距离的估计，可以获得分离的肽和蛋白质离子的固有介电极化率(epsilon(r))。该方法通过短杆菌肽 S 进行了验证；对于 (M + 2H)(2+) 离子，我们发现库仑能量 >27.9 kcal/mol。该离子上两个电荷之间的距离 (9.5 埃) 由分子建模获得的最低能量配置确定。所提出的该离子的气相结构与实验确定的单质子化和双质子化分子离子与 D2O 的 H/D 交换速率一致。根据库仑能量和电荷之间的距离，可以获得 epsilon(r) < 1.2 的上限。这明显低于肽和蛋白质预测的 2-4 的理论值。
A method to quantitatively measure the Coulomb energy in gas-phase ions with two or more protons by measuring gas-phase basicity is demonstrated. From these measurements and estimates of distance between charge sites, the intrinsic dielectric polarizability (epsilon(r)) of isolated peptide and protein ions can be obtained. This method is demonstrated with the peptide gramicidin S; for the (M + 2H)(2+) ion, we find the Coulomb energy is >27.9 kcal/mol. The distance between the two charges on this ion (9.5 Angstrom) is determined from the lowest energy configuration obtained by molecular modeling. The proposed gas-phase structure of this ion is consistent with experimentally determined rates of H/D exchange for the singly and doubly protonated molecular ions with D2O. From the Coulomb energy and distance between charges, an upper limit of epsilon(r) < 1.2 is obtained. This is decidedly less than the theoretical value of 2-4 predicted for peptides and proteins.