Mizutani Y, Kitagawa T
Institute for Molecular Science, Okazaki National Research Institutes, Myodaiji, Okazaki 444, Japan.
Science. 1997 Oct 17;278(5337):443-6. doi: 10.1126/science.278.5337.443.
The formation of vibrationally excited heme upon photodissociation of carbonmonoxy myoglobin and its subsequent vibrational energy relaxation was monitored by picosecond anti-Stokes resonance Raman spectroscopy. The anti-Stokes intensity of the nu4 band showed immediate generation of vibrationally excited hemes and biphasic decay of the excited populations. The best fit to double exponentials gave time constants of 1.9 +/- 0.6 and 16 +/- 9 picoseconds for vibrational population decay and 3.0 +/- 1.0 and 25 +/- 14 picoseconds for temperature relaxation of the photolyzed heme when a Boltzmann distribution was assumed. The decay of the nu4 anti-Stokes intensity was accompanied by narrowing and frequency upshift of the Stokes counterpart. This direct monitoring of the cooling dynamics of the heme cofactor within the globin matrix allows the characterization of the vibrational energy flow through the protein moiety and to the water bath.
通过皮秒反斯托克斯共振拉曼光谱监测一氧化碳肌红蛋白光解离时振动激发血红素的形成及其随后的振动能量弛豫。ν4带的反斯托克斯强度显示出振动激发血红素的立即产生以及激发态群体的双相衰减。当假设为玻尔兹曼分布时，对双指数的最佳拟合给出了振动群体衰减的时间常数为1.9±0.6和16±9皮秒，以及光解血红素温度弛豫的时间常数为3.0±1.0和25±14皮秒。ν4反斯托克斯强度的衰减伴随着斯托克斯对应物的变窄和频率上移。对球蛋白基质中血红素辅因子冷却动力学的这种直接监测使得能够表征通过蛋白质部分并传递到水浴中的振动能量流。
