Hu D D, Eftink M R
Department of Chemistry, University of Mississippi, University 38677.
Biophys Chem. 1994 Apr;49(3):233-9. doi: 10.1016/0301-4622(93)e0073-e.
The association of L-tryptophan and some of its analogs, including three conformationally restricted analogs, with trp aporepressor (apo trpR) was studied by isothermal titration microcalorimetry. Contributions of the functional groups of a ligand to the free energy change, delta G degrees', and enthalpy change, delta H degree', of the interaction were evaluated on a molecular basis. Analogs without the alpha-amino group (i.e. desamino analogs) bind with a slightly higher affinity to the protein. On the other hand, descarboxy analogs show weaker binding to the apo trpR. In addition, it is found that there exists enthalpy-entropy compensation for the association of the congener series of ligands with the protein. The entropy change, delta S degree', appears to play a more important role in the binding of the conformationally restricted analogs than in the binding of L-tryptophan and the unlocked ligands.
采用等温滴定量热法研究了L-色氨酸及其一些类似物（包括三种构象受限类似物）与色氨酸脱辅基阻遏蛋白（apo trpR）的结合情况。从分子层面评估了配体官能团对相互作用的自由能变化（ΔG°′）和焓变（ΔH°′）的贡献。没有α-氨基的类似物（即脱氨基类似物）与该蛋白的结合亲和力略高。另一方面，脱羧类似物与apo trpR的结合较弱。此外，还发现配体同系物与该蛋白结合存在焓-熵补偿。熵变（ΔS°′）在构象受限类似物的结合中似乎比在L-色氨酸和非受限配体的结合中发挥更重要的作用。
