Naraharisetty Sri Ram G, Kasyanenko Valeriy M, Zimmermann Jörg, Thielges Megan C, Romesberg Floyd E, Rubtsov Igor V
Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, USA.
J Phys Chem B. 2009 Apr 9;113(14):4940-6. doi: 10.1021/jp8112446.
Perdeuteration of the side chains of amino acids such as leucine results in appearance of reasonably strong absorption peaks around 2050-2220 cm(-1) that belong to the CD stretching modes and exhibit extinction coefficients of up to 120 M(-1) cm(-1). The properties of the CD stretching transitions in leucine-d(10) as structural labels are studied via the methods of two-dimensional infrared (2DIR) spectroscopy. The cross peaks caused by interactions of the CD stretching modes with amide I (Am-I), CO, and amide II (Am-II) modes are obtained by the dual-frequency 2DIR method. The CD stretching peaks in leucine-d(10) are characterized using DFT computational modeling as well as relaxation-assisted 2DIR (RA 2DIR) measurements. The RA 2DIR measurements showed different enhancements and different energy transport times (arrival times) for different CD/Am-II and CD/CO cross peaks; a correlation between the intermode distance, the arrival time, and the amplification factor is reported. We demonstrated that the CD transitions of leucine-d(10) amino acid can serve as convenient structural reporters via the dual-frequency 2DIR methods and discussed the potential of leucine-d(10) and other amino acids with deuterium-labeled side chains as probes of protein structure and dynamics.
对亮氨酸等氨基酸侧链进行全氘代会在2050 - 2220 cm(-1)左右出现相当强的吸收峰，这些峰属于碳氘（CD）伸缩振动模式，消光系数高达120 M(-1) cm(-1)。通过二维红外（2DIR）光谱方法研究了亮氨酸-d(10)中作为结构标记的CD伸缩振动跃迁的性质。利用双频2DIR方法获得了CD伸缩振动模式与酰胺I（Am-I）、羰基（CO）和酰胺II（Am-II）模式相互作用产生的交叉峰。使用密度泛函理论（DFT）计算模型以及弛豫辅助2DIR（RA 2DIR）测量对亮氨酸-d(10)中的CD伸缩峰进行了表征。RA 2DIR测量表明，不同的CD/Am-II和CD/CO交叉峰具有不同的增强效果和不同的能量传输时间（到达时间）；报道了模式间距离、到达时间和放大因子之间的相关性。我们证明，通过双频2DIR方法，亮氨酸-d(10)氨基酸的CD跃迁可以作为方便的结构报告基团，并讨论了亮氨酸-d(10)和其他具有氘标记侧链的氨基酸作为蛋白质结构和动力学探针的潜力。
