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人血清白蛋(HSA)在2 96nm的光激发下能发射35 0nm的荧光(即λex=2 96 ,λem =35 0nm)。当HSA中加入适量的维生素B6 (B6 )后,HSA的荧光被部分猝灭,从τ0 (不加B6 时HSA的荧光寿命———分子激发态的寿命)与τi (加入B6 后的寿命)相等(近似)得知这种猝灭是静态猝灭。根据理论,可求出HSA与B6 间的结合常数K =2 6 7×10 4 L·mol- 1 。又从实验上可观察到HSA (它的激发态)可向B6 转移能量,由此可求出HSA和B6 间的临界距离R0 =1 872nm。测定了HSA和(HSA +B6 )的园二色(CD)谱,发现所测得的CD谱都很相似(基本上是一样的)。从测得的[θ]值可以算出各个样品所含的四种结构(α螺旋、β折叠片、β卷角,无规卷曲)的百分含量也大体相同。
Human serum albumin (HSA) emits 350 nm fluorescence (ie, λex = 2 96, λem = 35 0 nm) at 2 96 nm light excitation. The fluorescence of HSA was partially quenched when HSA was supplemented with the appropriate amount of vitamin B6 (B6). The fluorescence intensity of HSA was calculated from τ0 (the fluorescence lifetime of HSA without exon 6 - the lifetime of the excited state of the molecule) and τi (the lifetime after addition of B6) Equivalently (approximately) that this quench is static quenching. According to the theory, the binding constant between HSA and B6 can be calculated as K = 2 6 7 × 10 4 L · mol -1. It has also been experimentally observed that HSA (its excited state) can transfer energy to B6, whereby the critical distance R0 = 1872 nm between HSA and B6 can be found. The dichroism (CD) spectra of HSA and (HSA + B6) were determined and the CD spectra found were similar (essentially identical). From the measured values of [θ], the percentages of the four structures (α-helix, β-sheet, β-roll angle, random coil) contained in each sample were also roughly the same.