Physical Chemistry Department, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032, India.
Chemphyschem. 2011 Mar 14;12(4):814-22. doi: 10.1002/cphc.201000912. Epub 2011 Feb 21.
The deuterium isotopic effect on the structure and solvation dynamics of the protein, human serum albumin (HSA), has been studied by using circular dichroism (CD), femtosecond up-conversion, FRET, and single-molecule spectroscopy. The CD spectra suggest that D(2)O affects the structure of HSA, leading to a 20% decrease in the helical structure. The FRET study indicates that the distance of C153 from the lone tryptophan residue of HSA is quite similar (≈21 Å) in H(2)O and D(2)O, and hence, the location of the probe in the protein remains the same in the two solvents. The single-molecule study suggests that coumarin 153 (C153) binds almost exclusively (>96%) to one site of HSA. Solvation dynamics of C153 in HSA is found to be markedly retarded in D(2)O compared with H(2)O. In H(2)O, the solvation of C153 bound to HSA is found to be biexponential with one component of 7 ps (30%) and a long component of 350 ps (70%). In D(2)O, we detected a short component of 4 ps (41%) and a long component of 950 ps (59%). Thus, the ultraslow component of the solvation dynamics of C153 bound to HSA in D(2)O (950 ps) is 2.5-fold slower than that in H(2)O (350 ps). The marked deuterium isotope effect has been ascribed to water molecules confined in the protein environment and to a lesser extent to the structural modification of protein by D(2)O.
氘同位素对蛋白质（人血清白蛋白，HSA）结构和溶剂化动力学的影响已通过圆二色性（CD）、飞秒上转换、FRET 和单分子光谱学进行了研究。CD 光谱表明 D2O 会影响 HSA 的结构，导致其螺旋结构减少 20%。FRET 研究表明，C153 与 HSA 中游离色氨酸残基的距离在 H2O 和 D2O 中非常相似（≈21 Å），因此探针在蛋白质中的位置在两种溶剂中保持不变。单分子研究表明，香豆素 153（C153）几乎仅（>96%）结合到 HSA 的一个位点上。与 H2O 相比，C153 在 HSA 中的溶剂化动力学在 D2O 中明显减慢。在 H2O 中，与 HSA 结合的 C153 的溶剂化被发现是双指数的，其中一个成分是 7 ps（30%），长成分是 350 ps（70%）。在 D2O 中，我们检测到一个 4 ps（41%）的短成分和一个 950 ps（59%）的长成分。因此，C153 与 HSA 结合的溶剂化动力学的超慢成分在 D2O 中（950 ps）比在 H2O 中（350 ps）慢 2.5 倍。明显的氘同位素效应归因于蛋白质环境中受限的水分子，以及在较小程度上归因于 D2O 对蛋白质结构的修饰。
