S-Cis Diene Conformation: A New Bathochromic Shift Strategy for Near-Infrared Fluorescence Switchable Dye and the Imaging Applications

Abstract

In this paper, we present a novel charge-free fluorescence-switchable near-infrared (IR) dye based on merocyanine for target specific imaging. In contrast to the typical bathochromic shift approach by extending πconjugation, the bathochromic shift of our merocyanine dye to the near-IR region is due to an unusual S-cis diene conformer. This is the first example where a fluorescent dye adopts the stable S-cis conformation. In addition to the novel bathochromic shift mechanism, the dye exhibits fluorescence-switchable properties in response to polarity and viscosity. By incorporating a protein-specific ligand to the dye, the probes (for SNAP-tag and hCAII proteins) exhibited dramatic fluorescence increase (up to 300-fold) upon binding with its target protein. The large fluorescence enhancement, near-IR absorption/ emission, and charge-free scaffold enabled no-wash and site-specific imaging of target proteins in living cells and in vivo with minimum background fluorescence. We believe that our unconventional approach for a near-IR dye with the S-cis diene conformation can lead to new strategies for the design of near-IR dyes.

Highly Efficient Multiple‐Labeling Probes for the Visualization of Enzyme Activities

“…Fluorescent dyes with absorption and emission at the range of near‐infrared zone are particularly useful for biomedical investigations due to the high tissue‐penetration ability and less interference by the intrinsic autofluorescence from living animals . Therefore, to further expand the application of our design, we replaced the fluorescent reporter with near‐infrared and switchable P‐Mero4 …”

“…[20] Therefore, tof urther expand the application of our design,w er eplaced the fluorescent reporter with near-infrared and switchable P-Mero4. [21] We performed in-gel fluorescence analysisa gain to evaluate these near-infrared imaging reagents. As depicted in Figure 4a, both ALP NIR-1 and multiple-functional ALP NIR-2 showede xcellent labeling ability to proteins,d elivering strong near-infrared fluorescenceo nA LP or BSA.…”

Produktive Modifikationen von Cyaninfarbstoff‐π‐Netzwerken

“…Chen, Tan und Mitarbeiter nutzten eine strategisch platzierte Phenylgruppe an Merocyanin 6 , um das Moleküle ausschließlich in die S‐cis ‐Konformation zu drücken. Die Autoren beobachteten, dass die Fluoreszenzhelligkeit von S‐cis ‐ 6 signifikant von der Viskosität abhängt und führten dies auf Mediumeffekte auf die freie Rotation der Bindung zwischen der Schlüsselphenylgruppe mit dem Tetramethinsystem zurück.…”

Rapid relaxation pathway of the excited state of linear merocyanines in solutions

“…Chen et al reported new near‐infrared merocyanine dyes with four‐methine linkers Mero4 and P‐Mero4 (structures as shown in Figure ). The linear merocyanines L‐Mero4 and P‐L‐Mero4, without the long carboxyl acid chain on the indole side, are displayed in Figure .…”