Bîrla Liliana, Bertorelle Franck, Rodrigues Fernanda, Badré Sophie, Pansu Robert, Fery-Forgues Suzanne
Laboratoire des Interactions Moléculaires Réactivité Chimique et Photochimique, UMR CNRS 5623, Université Paul Sabatier, 31062 Toulouse Cedex 9, France.
Langmuir. 2006 Jul 4;22(14):6256-65. doi: 10.1021/la0532510.
The reprecipitation method, which is a solvent-exchange process, was used to prepare free-standing microcrystals from an organic fluorescent dye, 4-n-octylamino-7-nitrobenz-2-oxa-1,3-diazole. Calf thymus DNA was introduced as an additive into the reprecipitation medium, strongly accelerating the process. The reprecipitation kinetics was monitored by UV/vis absorption spectroscopy, and the analysis of the rate constants allowed the role played by the additive to be clarified. DNA was also found to affect the shape and size of the dye microcrystals obtained. In particular, its presence induced the formation of a new type of microcrystal that displays original two-color fluorescence. The emission properties were first analyzed on the suspensions, using a traditional fluorimeter, and then on individual microcrystals by means of a space- and time-correlated photon-counting photomutiplier installed on a microscope. The study on single microcrystals suggests that the dual coloration observed originates from the reabsorption of the blue component of the emitted light, whereas the remaining red component propagates through the microcrystal body and is scattered by the edges. However, the color of the other types of microcrystals can be explained only by specific arrangements of molecules at the surface of the crystal.
再沉淀法是一种溶剂交换过程，用于从有机荧光染料4-正辛基氨基-7-硝基苯并-2-恶唑-1,3-二唑制备独立的微晶。将小牛胸腺DNA作为添加剂引入再沉淀介质中，极大地加速了这一过程。通过紫外/可见吸收光谱监测再沉淀动力学，对速率常数的分析有助于阐明添加剂所起的作用。还发现DNA会影响所得染料微晶的形状和尺寸。特别是，它的存在诱导形成了一种新型微晶，该微晶呈现出原始的双色荧光。首先使用传统荧光计对悬浮液的发射特性进行分析，然后通过安装在显微镜上的空间和时间相关光子计数光电倍增管对单个微晶进行分析。对单个微晶的研究表明，观察到的双色现象源于发射光蓝色成分的再吸收，而其余红色成分则穿过微晶体并被边缘散射。然而，其他类型微晶的颜色只能通过晶体表面分子的特定排列来解释。
