Kinetic and spectroscopic responses of pH-sensitive nanoparticles: influence of the silica matrix.

Intracellular pH sensing with fluorescent nanoparticles is an emerging topic as pH plays several roles in physiology and pathologic processes. Here, nanoparticle-sized pH sensors (diameter far below 50 nm) for fluorescence imaging have been described. Consequently, a fluorescent derivative of pH-sensitive hydroxypyrene with p = 6.

A high-affinity fluorescence probe for copper(II) ions and its application in fluorescence lifetime correlation spectroscopy.

Copper is one of the most important transition metals in many organisms where it catalyzes a manifold of different processes. As a result of copper's redox activity, organisms have to avoid unbound ions, and a dysfunctional copper homeostasis may lead to multifarious pathological processes in cells with very severe ramifications for the affected organisms. In many neurodegenerative diseases, however, the exact role of copper ions is still not completely clarified.

Monomolecular pyrenol-derivatives as multi-emissive probes for orthogonal reactivities.

Photoacids on the basis of pyrenol have been extensively studied in the past 60 years. As their photophysical properties strongly depend on the substituents at the aromatic scaffold, we introduced two reactive moieties with different electronic coefficients thus creating multi-wavelength fluorescent probes. One probe is capable of monitoring two orthogonal transformations by four fluorescence colors, distinguishable even by the naked human eye.

Two-color emissive probes for click reactions.

Cu(I)-catalyzed azide-alkyne cyclization (CuAAC) is the paradigmatic click reaction of continuous interest. Especially fluorogenic and FRET probes have become indispensable tools for life sciences. Here, we present a fluorescent alkyne for monitoring CuAAC, which undergoes a bathochromic shift upon reaction.

Highly photostable "super"-photoacids for ultrasensitive fluorescence spectroscopy.

The photoacid 8-hydroxypyren-1,3,6-trisulfonic acid (HPTS, pyranine) is a widely used model compound for the examination of excited state proton transfer (ESPT). We synthesized five "super"-photoacids with varying hydrophilicity and acidity on the basis of HPTS. By chemical modification of the three sulfonic acid substituents, the photoacidity is enhanced by up to more than five logarithmic units from pK*≈ 1.

Solvatochromism of pyranine-derived photoacids.

Photoacidity is frequently found in aromatic alcohols where the equilibrium dissociation constant increases by some orders of magnitude upon electronic excitation. In this study we investigated the solvatochromism of a family of recently synthesized super-photoacids and their methylated counterparts based on pyrene. The chemical similarity of these molecules on the one hand and their differing photoacidity with pKa* values between -0.

Solvent-dependent steady-state fluorescence spectroscopy for searching ESPT-dyes: solvatochromism of HPTS revisited.

We reinvestigated the solvatochromism of 8-hydroxypyrene-1,3,6-trisulfonate (pyranine) in conjunction with that of 8-methoxypyrene-1,3,6-trisulfonate and of 1-hydroxypyrene (pyrenol) by use of 25 different solvents. Conclusions for the prediction of ESPT behaviour of synthetic dyes were drawn by comparison with the solvatochromism of p-hydroxystyryl Bodipy dyes. Solvents were chosen according to their Kamlet-Taft parameters alpha and beta for elucidating the acidicity of the dyes and the basicity of their conjugated bases in the ground and excited state.

Efficient photoconversion distorts the fluorescence lifetime of GFP in confocal microscopy: a model kinetic study on mutant Thr203Val.

Phototransformations of autofluorescent proteins are applied in high-resolution microscopy and in studying cellular transport, but they are detrimental when accidentally occurring in blinking or photobleaching (BL). Here, we investigate the kinetics of phototransformations of a photoactivatable green fluorescent protein (GFP) in confocal microscopy. Photoconversion (PC) is achieved by excitation of the barely present anionic chromophore state R(eq) (-) in the GFP mutant Thr203Val.