Liu Mengran, Chen Chih-Yuan, Mandal Amit Kumar, Chandrashaker Vanampally, Evans-Storms Rosemary B, Pitner J Bruce, Bocian David F, Holten Dewey, Lindsey Jonathan S
Department of Chemistry, North Carolina State University, Raleigh, NC 27695-8204.
Department of Chemistry, Washington University, St. Louis, MO 63130-4889.
New J Chem. 2016;40(9):7721-7740. doi: 10.1039/C6NJ01154C. Epub 2016 Jul 21.
Chromophores that absorb and emit in the red spectral region (600-700 nm), are water soluble, and bear a bioconjugatable tether are relatively rare yet would fulfill many applications in photochemistry and photomedicine. Here, three molecular designs have been developed wherein stable synthetic chlorins - analogues of chlorophylls - have been tailored with PEG groups for use in aqueous solution. The designs differ with regard to order of the installation (pre/post-formation of the chlorin macrocycle) and position of the PEG groups. Six PEGylated synthetic chlorins (three free bases, three zinc chelates) have been prepared, of which four are equipped with a bioconjugatable (carboxylic acid) tether. The most effective design for aqueous solubilization entails facial encumbrance where PEG groups project above and below the plane of the hydrophobic disk-like chlorin macrocycle. The chlorins possess strong absorption at ~400 nm (B band) and in the red region (Q band); regardless of wavelength of excitation, emission occurs in the red region. Excitation in the ~400 nm region thus provides an effective Stokes shift of >200 nm. The four bioconjugatable water-soluble chlorins exhibit Q absorption/emission in water at 613/614, 636/638, 698/700 and 706/710 nm. The spectral properties are essentially unchanged in DMF and water for the facially encumbered chlorins, which also exhibit narrow Q absorption and emission bands (full-width-at-half maximum of each <25 nm). The water-solubility was assessed by absorption spectroscopy over the concentration range ~0.4 μM - 0.4 mM. One chlorin was conjugated to a mouse polyclonal IgG antibody for use in flow cytometry with compensation beads for proof-of-principle. The conjugate displayed a sharp signal when excited by a violet laser (405 nm) with emission in the 620-660 nm range. Taken together, the designs described herein augur well for development of a set of spectrally distinct chlorins with relatively sharp bands in the red region.
在红色光谱区域（600 - 700纳米）吸收和发射光、水溶性且带有可生物共轭连接基团的发色团相对较少，但在光化学和光医学中能满足许多应用需求。在此，已开发出三种分子设计，其中稳定的合成二氢卟吩（叶绿素的类似物）已用聚乙二醇（PEG）基团进行修饰，以便在水溶液中使用。这些设计在安装顺序（二氢卟吩大环形成之前/之后）和PEG基团的位置方面有所不同。已制备出六种聚乙二醇化的合成二氢卟吩（三种游离碱，三种锌螯合物），其中四种配备了可生物共轭的（羧酸）连接基团。实现水溶的最有效设计涉及表面阻碍，即PEG基团在疏水性盘状二氢卟吩大环平面的上方和下方突出。这些二氢卟吩在约400纳米（B带）和红色区域（Q带）具有强烈吸收；无论激发波长如何，发射都发生在红色区域。因此，在约400纳米区域的激发提供了大于200纳米的有效斯托克斯位移。四种可生物共轭的水溶性二氢卟吩在水中的Q吸收/发射波长分别为613/614、636/638、698/700和706/710纳米。对于表面受阻的二氢卟吩，其光谱特性在二甲基甲酰胺（DMF）和水中基本不变，它们还表现出狭窄的Q吸收和发射带（半高宽均<25纳米）。通过吸收光谱在约0.4微摩尔 - 0.4毫摩尔的浓度范围内评估了水溶性。将一种二氢卟吩与小鼠多克隆IgG抗体偶联，用于带有补偿微珠的流式细胞术以验证原理。当用紫光激光（405纳米）激发时，该偶联物在620 - 660纳米范围内发射出尖锐信号。综上所述，本文所述的设计对于开发一组在红色区域具有相对尖锐谱带的光谱不同的二氢卟吩具有良好的预示作用。
