The Dansyl-Edman method for peptide sequencing

Lessons in Organic Fluorescent Probe Discovery

Fluorescent probes have gained profound use in biotechnology, drug discovery, medical diagnostics, molecular and cell biology. The development of methods for the translation of fluorophores into fluorescent probes continues to be a robust field for medicinal chemists and chemical biologists, alike. Access to new experimental designs has enabled molecular diversification and led to the identification of new approaches to probe discovery. This review provides a synopsis of the recent lessons in modern fluorescent probe discovery.

Making Nitronaphthalene Fluoresce

Nitroaromatic compounds are inherently nonfluorescent, and the subpicosecond lifetimes of the singlet excited states of many small nitrated polycyclic aromatic hydrocarbons, such as nitronaphthalenes, render them unfeasible for photosensitizers and photo-oxidants, despite their immensely beneficial reduction potentials. This article reports up to a 7000-fold increase in the singlet-excited-state lifetime of 1-nitronaphthalene upon attaching an amine or an N-amide to the ring lacking the nitro group. Varying the charge-transfer (CT) character of the excited states and the medium polarity balances the decay rates along the radiative and the two nonradiative pathways and can make these nitronaphthalene derivatives fluoresce. The strong electron-donating amine suppresses intersystem crossing (ISC) but accommodates CT pathways of nonradiate deactivation. Conversely, the N-amide does not induce a pronounced CT character but slows down ISC enough to achieve relatively long lifetimes of the singlet excited state. These paradigms are key for the pursuit of electron-deficient (n-type) organic conjugates with promising optical characteristics.

Dansyl-Labelled Ag@SiO2 Core-Shell Nanostructures-Synthesis, Characterization, and Metal-Enhanced Fluorescence

The present work describes synthesis, characterization, and use of a new dansyl-labelled Ag@SiO2 nanocomposite as an element of a new plasmonic platform to enhance the fluorescence intensity. Keeping in mind that typical surface plasmon resonance (SPR) characteristics of silver nanoparticles coincide well enough with the absorption of dansyl molecules, we used them to build the core of the nanocomposite. Moreover, we utilized 10 nm amino-functionalized silica shell as a separator between silver nanoparticles and the dansyl dye to prevent the dye-to-metal energy transfer. The dansyl group was incorporated into Ag@SiO2 core-shell nanostructures by the reaction of aminopropyltrimethoxysilane with dansyl chloride and we characterized the new dansyl-labelled Ag@SiO2 nanocomposite using transmission electron microscopy (TEM) and Fourier-transform infrared spectroscopy (FTIR). Additionally, water wettability measurements (WWM) were carried out to assess the hydrophobicity and hydrophilicity of the studied surface. We found that the nanocomposite deposited on a semitransparent silver mirror strongly increased the fluorescence intensity of dansyl dye (about 87-fold) compared with the control sample on the glass, proving that the system is a perfect candidate for a sensitive plasmonic platform.