Abstract
Photoremovable protecting groups (PPGs) when conjugated to biological effectors forming “caged compounds” are a powerful means to regulate the action of physiologically active messengers in vivo through 1-photon excitation (1PE) and 2-photon excitation (2PE). Understanding the photodeprotection mechanism is important for their physiological use. We compared the quantum efficiencies and product outcomes in different solvent and pH conditions for the photolysis reactions of (8-chloro-7-hydroxyquinolin-2-yl)methyl acetate (CHQ-OAc) and (8-bromo-7-hydroxyquinolin-2-yl)methyl acetate (BHQ-OAc), representatives of the quinoline class of phototriggers for biological use, and conducted nanosecond time-resolved spectroscopic studies using transient emission (ns-EM), transient absorption (ns-TA), transient resonance Raman (ns-TR2), and time-resolved resonance Raman (ns-TR3) spectroscopies. The results indicate differences in the photochemical mechanisms and product outcomes, and reveal that the triplet excited state is most likely on the pathway to the product and that dehalogenation competes with release of acetate from BHQ-OAc, but not CHQ-OAc. A high fluorescence quantum yield and a more efficient excited-state proton transfer (ESPT) in CHQ-OAc compared to BHQ-OAc explain the lower quantum efficiency of CHQ-OAc relative to BHQ-OAc.
Highlights
Photoremovable protecting groups (PPGs) have become powerful tools for probing biological systems through their conjugation to biological effectors, forming “caged compounds”.[1]
Synthesis: BHQ-OAc was synthesized from bromoquinoline 1[3b] by the route shown in Scheme 2, which is a modification of the route previously reported.[3a]. A methoxymethyl (MOM) ether was used as a protecting group instead of Scheme 2
Solvent effects on quantum efficiency: The quantum efficiencies (Qu) for the photolyses of BHQ-OAc and CHQOAc at 254 nm in each of the three solvents were determined by methods previously described (Table 1).[3b,9] Photolysis reactions were conducted at 254 nm, rather than near
Summary
Photoremovable protecting groups (PPGs) have become powerful tools for probing biological systems through their conjugation to biological effectors, forming “caged compounds”.[1]. We compared the UV/Vis absorption spectra of BHQ-OAc before and after irradiation under 266 nm wavelength laser pulses with different concentrations of PS in a neutral mixed aqueous solution (Figure 3).
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
