Investigating rhodamine B‐labeled peptoids: Scopes and limitations of its applications

Abstract

The fluorophore rhodamine B is often used in biological assays. It is inexpensive, robust under a variety of reaction conditions, can be covalently linked to bioactive molecules, and has suitable spectral properties in terms of absorption and fluorescence wavelength. Nonetheless, there are some drawbacks: it can readily form a spirolactam compound, which is nonfluorescent, and therefore may not be the dye of choice for all fluorescence microscopy applications. Herein this spirolactam formation was observed by purifying such a labeled peptoid with high performance liquid chromatography (HPLC) and monitored in detail by making a series of analytical HPLC runs over time. Additionally, a small library of eight peptoids with rhodamine B as label was synthesized. Analysis of the absorption properties of these molecules demonstrated that the problem of fluorescence loss can be overcome by coupling secondary amines with rhodamine B.

Hepatocyte-targeted fluorescent nanoparticles based on a polyaspartamide for potential theranostic applications

“…It was found that the maximum wavelength was shift from 554 nm to 561 nm starting from RhB to PHEA-RhB, and ε resulted to be 117,000 M À1 cm À1 for RhB (in accordance with data reported in the literature) and 53,200 M À1 cm À1 for PHEA-RhB [25]. However, although this latter is halved than that of RhB, this value is still high to confer fluorescence properties to PHEA-RhB derivatives.…”

“…Being well known from the literature that the conjugation of RhB to molecules or polymers could cause the shift of the maxima wavelength, the reduction of molar extinction coefficient (ε) of the obtained derivative or the total fluorescence disappearance [25], either maximum wavelength or ε values of PHEA-RhB were determined and compared to that of RhB aqueous solutions by recording UVevis spectra. It was found that the maximum wavelength was shift from 554 nm to 561 nm starting from RhB to PHEA-RhB, and ε resulted to be 117,000 M À1 cm À1 for RhB (in accordance with data reported in the literature) and 53,200 M À1 cm À1 for PHEA-RhB [25].…”

Polyaspartamide–Polylactide Graft Copolymers with Tunable Properties for the Realization of Fluorescent Nanoparticles for Imaging

“…However, although this latter is halved than that of free RhB, this value is still high to allow that fluorescence properties of RhB are maintained after conjugation with PHEA. Contrasting behavior has been reported in literature for other RhB derivatives such as RhB‐labeled peptoids, where conjugation caused a dramatic reduction of fluorescence …”

A facile method for monitoring solid-phase peptide synthesis and for N-terminal modification of peptides: synthesis of short peptides for imaging specific cells

“…Synthesis of peptides labelled with rhodamine, dansyl, and FITC moieties have been reported in the literature. [18][19][20] In principle, any N-terminal peptide labelling reaction can be used for monitoring the stepwise synthesis of peptides. Recently, Lenk et al, have reported the synthesis and reactivity of 1-oxo-1H-phenalene-2,3-dicarbonitrile (2) with amines and thiols.…”