Monteserín María, Burrows Hugh D, Valente Artur J M, Mallavia Ricardo, Di Paolo Roberto E, Maçanita Antonio L, Tapia María J
Departamento de Química, Universidad de Burgos, Burgos, Spain.
J Phys Chem B. 2009 Feb 5;113(5):1294-1302. doi: 10.1021/jp806353y.
The interaction between three poly(9,9-bis(6-N,N,N-trimethylammonium)hexyl)fluorene phenylene) bromide (HTMA-PFP) samples of different molecular weights (Mn=14.5, 30.1 and 61.3 kg/mol) and both dsDNA and ssDNA secondary structures has been studied using UV-visible absorption and fluorescence spectroscopies (including steady-state, time-resolved, and anisotropy measurements for the latter), viscosity, and electrical conductivity in 4% (v/v) DMSO-water mixtures. At low nucleic acid concentrations, formation of a 1:1 complex in terms of HTMA-PFP repeat units and DNA bases occurs. This interaction results in quenching of polymer emission. For higher molar ratios of DNA to HTMA-PFP, corresponding to charge neutralization, a second process is observed that is attributed to aggregate formation. From the changes in the absorption spectra, the polymer aggregation constant and the aggregate absorption spectra were calculated by applying an iterative method. Polymer aggregation dramatically quenches HTMA-PFP fluorescence in the region of the electroneutrality point. Under these conditions, the ratio of the emission intensity at 412 nm (maximum) to that at 434 nm (I412/I434) reaches a minimum, the electrical conductivity decreases, and the viscosity of the solution remains constant, showing that the DNA concentration can be determined through various HTMA-PFP physicochemical properties. With respect to the photophysical parameters (emission quantum yield, shape and shift of emission spectra), no significant differences were observed between dsDNA and ssDNA or with conjugated polymer or DNA molecular weight. The two short-lived components in the fluorescence decays are attributed to the presence of aggregates. Aggregates are also suggested to be responsible for the decrease in the fluorescence anisotropy through interchain exciton migration.
利用紫外可见吸收光谱和荧光光谱（包括后者的稳态、时间分辨和各向异性测量）、粘度以及在4%（v/v）二甲基亚砜-水混合物中的电导率，研究了三种不同分子量（Mn = 14.5、30.1和61.3 kg/mol）的聚（9,9-双（6-N,N,N-三甲基铵）己基）芴亚苯基）溴化物（HTMA-PFP）样品与双链DNA和单链DNA二级结构之间的相互作用。在低核酸浓度下，就HTMA-PFP重复单元和DNA碱基而言，会形成1:1的复合物。这种相互作用导致聚合物发射猝灭。对于DNA与HTMA-PFP的摩尔比更高（对应电荷中和）的情况，观察到第二个过程，这归因于聚集体的形成。通过应用迭代方法，从吸收光谱的变化计算出聚合物聚集常数和聚集体吸收光谱。在电中性点区域，聚合物聚集显著猝灭HTMA-PFP荧光。在这些条件下，412 nm（最大值）处的发射强度与434 nm处的发射强度之比（I412/I434）达到最小值，电导率降低，溶液粘度保持不变，表明可以通过各种HTMA-PFP物理化学性质来测定DNA浓度。关于光物理参数（发射量子产率、发射光谱的形状和位移），在双链DNA和单链DNA之间或与共轭聚合物或DNA分子量之间未观察到显著差异。荧光衰减中的两个短寿命成分归因于聚集体的存在。聚集体也被认为是通过链间激子迁移导致荧光各向异性降低的原因。
