10.1021/acsmedchemlett.9b00569.s001 Azzurra Stefanucci Azzurra Stefanucci Marilisa Pia Dimmito Marilisa Pia Dimmito Gabriela Molnar Gabriela Molnar John M. Streicher John M. Streicher Ettore Novellino Ettore Novellino Gokhan Zengin Gokhan Zengin Adriano Mollica Adriano Mollica Developing Cyclic Opioid Analogues: Fluorescently Labeled Bioconjugates of Biphalin American Chemical Society 2020 bioconjugate characterization δ- opioid receptor probe binding agent vivo DOR motif analogue nm novel opioid peptides fluorescently dansyl-maleimide application affinity compound 1 D fluorescence emission spectrum synthesis Cyclic Opioid Analogues Biphalin importance control drug release potency imaging 1 D cyclic biphalin derivatives Fluorescently Labeled Bioconjugates toxicity 2020-01-10 14:43:02 Journal contribution https://acs.figshare.com/articles/journal_contribution/Developing_Cyclic_Opioid_Analogues_Fluorescently_Labeled_Bioconjugates_of_Biphalin/11568738 The development of bioconjugates is of pivotal importance in medicinal chemistry due to their potential applications as therapeutic agents to improve the targeting of specific diseases, decrease toxicity, or control drug release. In this work we achieved the synthesis and characterization of three novel opioid peptides fluorescently labeled, analogues of cyclic biphalin derivatives, namely <b>1D</b>, <b>1C</b>, and <b>2C</b>. Among them, compound <b>1D</b>, containing a dansyl-maleimide motif, exhibited an excellent binding affinity and functional potency for the δ-opioid receptor (DOR). <b>1D</b> also demonstrated a strong fluorescence emission spectrum ranging from 300 to 700 nm. These features could be highly desirable for medical and biological applications needed for targeting the DOR, including <i>in vivo</i> imaging, and as a lead for the design of fluorescent probes.