The slowly relaxing local structure (SRLS) approach is applied to ¹⁵N–H relaxation from the major urinary protein I (MUP-I), and its complex with pheromone 2-sec-butyl-4,5-dihydrothiazol. The objective is to elucidate dynamics, and binding-induced changes in conformational entropy. Experimental data acquired previously in the 283–308 K temperature range are used. The N–H bond is found to reorient globally with correlation time, τ_1,0, and locally with correlation time, τ_2,0, where τ_1,0 ≫ τ_2,0. The local motion is restricted by the potential u = −c₀²D₀₀², where D₀₀² is the Wigner rotation matrix element for L = 2, K = 0, and c₀² evaluates the strength of the potential. u yields straightforwardly the order parameter, ⟨D₀₀²⟩, and the conformational entropy, S_k, both given by P_eq = exp(−u). The deviation of the local ordering/local diffusion axis from the N–H bond, given by the angle β, is also determined. We find that c₀² ≅ 18 ± 4 and τ_2,0 = 0–170 ps for ligand-free MUP-I, whereas c₀² ≅ 15 ± 4 and τ_2,0 = 20–270 ps for ligand-bound MUP-I. β is in the 0–10° range. c₀² and τ_2,0 decrease, whereas β increases, when the temperature is increased from 283 to 308 K. Thus, SRLS provides physically well-defined structure-related (c₀² and ⟨D₀₀²⟩), motion-related (τ_2,0), geometry-related (β), and binding-related (S_k) local parameters, and their temperature-dependences. Intriguingly, upon pheromone binding the conformational entropy of MUP-I decreases at high temperature and increases at low temperature. The very same experimental data were analyzed previously with the model-free (MF) method which yielded “global” (in this context, “relating to the entire 283–308 K range”) amplitude (S²) and rate (τ_e) of the local motion, and a phenomenological exchange term (R_ex). S² is found to decrease (implying implicitly “global” increase in S_k) upon pheromone binding.

中文翻译：

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蛋白质在¹⁵ N–H弛豫中缓慢弛豫的局部结构分析引起的构象熵：在283–308 K温度范围内信息素与MUP-I结合的应用

缓慢松弛局部结构（SRLS）方法可用于从主要尿蛋白I（MUP-1）及其与信息素2 - sec -butyl-4,5-dihydrothiazol的复合体中释放¹⁵ N–H 。目的是阐明动力学和结合诱导的构象熵变化。使用先前在283–308 K温度范围内获取的实验数据。的N-H键被发现重新定向与全局相关时间，τ _1,0，并在本地与相关时间，τ _2,0，其中τ _1,0 »τ _2,0。局部运动受电势u = − c ₀ ² D ₀₀ ^2的限制，其中D ₀₀ ²是维格纳旋转矩阵元素，其中L = 2，K = 0，并且c ₀ ²评估电势的强度。ü直截了当产生的有序参数，⟨ d ₀₀ ² ⟩，和构象熵，小号_ķ，由两个给定P_当量= EXP（ - Ú）。还确定了局部有序/局部扩散轴与N–H键的偏离，由角度β给出。我们发现，c ^ ₀ ² ≅18±4和τ _2,0 = 0 -170个皮秒为无配体的MUP-I，而c ^ ₀ ² ≅15±4和τ _2,0 = 20 - 270皮秒为配体-结合的MUP-I。β在0 – 10°的范围内。c ^ ₀ ²和τ _2,0降低，而β的增加，当温度从283增加至308 K.因此，SRLS提供物理良好定义的结构相关的（C ^ ₀ ²和⟨ d ₀₀ ² ⟩），MOTION-相关（_τ2,0），几何相关（β）和绑定相关（S _k）局部参数及其温度依赖性。有趣的是，信息素结合后，MUP-1的构象熵在高温下降低，而在低温下升高。非常相同的实验数据（“与整个283-308 K范围之外”在此上下文中，）振幅（用其产生“全局”的无模型（MF）方法之前分析的小号²）和率（τ _ë）局部运动和现象交换术语（R _ex）。发现在信息素结合后，S ²降低（暗示S _k隐式“整体”增加）。