Stretching a polymer film induces a conformational change (from the twisted to planar state) in the embedded porphyrin dimer, as evidenced by steady-state and time-resolved emission spectra.

The fluorescence of BODIPY and click-BODIPY dyes was found to substantially increase in the presence of bovine serum albumin (BSA). BSA acted as a solubilizer for dye aggregates, in addition to being a conventional binding scaffold for the click-BODIPY dyes, indicating that disaggregation of fluorophores should be considered when evaluating dye–protein interactions.

Photophysical behaviour of a novel trimeric BODIPY rotor with a high extinction coefficient is reported. Steady state and time resolved fluorescence measurements established that the trimer could be used as a viscometer for molecular solvents, membrane-like environments and several cancer cell lines.

1,1-Dichloroethane induces a monomer–aggregate equilibrium of common BODIPY dyes in organic solvents at low μM dye concentrations, thus providing an opportunity to study monomeric, aggregate-free forms of BODIPY dyes.

The nature of the anion of imidazolium-based ionic liquids was found to control the aggregate–monomer equilibrium of amphotericin B. This is in contrast to aqueous solutions of inorganic salts and imidazolium-based ionic liquids, which were previously found to favor the disaggregation of amphotericin B. The results further establish the designer solvent ability of ionic liquids, specifically as it relates to their ability to influence intermolecular interactions.

A symmetrical BODIPY–BODIPY dyad with a diyne linker was prepared in two steps; the lifetime decay of this rotor appeared to correlate with the viscosity of the media, thus making this dyad a suitable small molecule viscometer for molecular solvents. The potential of using the rotor to probe the viscosity of ionic liquids was also investigated.

The conformational bias of tetracycline was investigated in a series of room-temperature 1-alkyl-3-methyl-imidazolium ionic liquids. Spectroscopic techniques such as circular dichroism, absorbance and fluorescence suggested that the switch between the extended and twisted conformation of tetracycline might be controlled by the aggregation state of the ionic liquids, which could be easily assessed by the resonance light scattering of homologous sets of ionic liquids with a common anion.

Structure of the cationic and anionic counterparts of ionic liquids has a significant impact on the conformational bias of the porphyrin rotor; an apparent correlation between the conformation and the viscosity of ionic liquids was noted, albeit it was found to be distinct and more complex from that found in molecular solvents.

Dye-binding assays that are used to evaluate anti-aggregation ability of small molecule inhibitors towards amyloids are known to be prone to false-positive effects due to spectral overlaps between the dye and the inhibitor. Aza-BODIPY dye, which has both excitation and emission maxima above 600 nm, exhibits a significant increase in its fluorescence intensity in the presence of soluble oligomers of Aβ1–42. These results indicate that aza-BODIPY could serve as a near-IR probe for detecting conformational changes of Aβ1–42 soluble oligomers in vitro, and it should eliminate false-positive effects that are associated with currently utilized thioflavin T-based dyes. In addition, a facile synthesis of aza-BODIPY has been developed, which might further expand the applications of this dye.

Dye-binding assays, such as those utilizing Congo red and thioflavin T, are among the most widely used tools to probe the aggregation of amyloidogenic biomolecules and for the evaluation of small molecule inhibitors of amyloid aggregation and fibrillization. A number of recent reports have indicated that these dye-binding assays could be prone to false positive effects when assessing inhibitors’ potential toward Aβ peptides, species involved in Alzheimer’s disease. Specifically, this review focuses on the application of thioflavin T for determining the efficiency of small molecule inhibitors of Aβ aggregation and addresses potential reasons that might be associated with the false positive effects in an effort to increase reliability of dye-binding assays.Keywords: Alzheimer’s disease; amyloid peptide; dye-binding assay; fluorescence; small molecule inhibitor; thioflavin T

Circular dichroism and steady-state fluorescence of tetracycline (1) were investigated in a series of 1-butyl-3-methylimidazolium room-temperature ionic liquids. The identity of the anion of the ionic liquids was found to modulate the conformation as well as the emission intensity of tetracycline over a wide range.

Nitrate-containing 1-alkyl-3-methylimidazolium ionic liquids, [Cn-mim]NO3, where n = 4, 6, 8, 12, are synthesized in one step by reacting 1-methylimidazole with alkyl nitrates under various conditions without using AgNO3 and 1-alkyl-3-methylimidazolium halides.

Tetrafluoroborate-containing ionic liquids allow for a room temperature gelation of dimethylsulfoxide, which contains an organogelator at below the minimum gelation concentration. The gel formation has no effect on the mobility of ions, as the conductivity values of ionic liquid-DMSO gels are virtually identical to those of ionic liquid-DMSO solutions.

Formation of 5-iodo-triazoles in CuI-promoted cycloadditions between alkynes and azides is controlled by DMAP and low alkyne concentrations.Formation of 5-iodo-triazoles in CuI-promoted cycloadditions between alkynes and azides is controlled by DMAP and low alkyne concentrations.

Amphotericin B has recently been suggested as an efficient inhibitor of amyloid peptide fibril formation; however its interactions with more neurotoxic, soluble forms of amyloid peptides have not been reported to date. Circular dichroism spectroscopy allowed for distinguishing between the binding and inhibition of aggregation events: amphotericin B distinctly interacts with both unordered and ordered, β-structure-rich soluble oligomeric forms of Aβ1-42 peptide, yet amphotericin B has no measurable impact neither on the secondary structure nor on time-dependent aggregation profile of the amyloid peptide.Amphotericin B is a potential spectroscopic probe for a random coil and β-sheet conformations of soluble Aβ1-42 oligomers.

The beneficial effects of Ginkgo biloba extract in the “treatment” of dementia are attributed to its terpene trilactone (TTL) constituents. The interactions between TTLs and amyloid peptide are believed to be responsible in preventing the aggregation of peptide. These interactions have been investigated using infrared vibrational absorption (VA) and circular dichroism (VCD) spectra. Four TTLs, namely ginkgolide A (GA), ginkgolide B (GB), ginkgolide C (GC) and bilobalide (BB) and amyloid Aβ(25–35) peptide, as a model for the full length peptide, are used in this study. GA-monoether and GA-diether have also been synthesized and investigated to help understand the role of individual carbonyl groups in these interactions. The precipitation and solubility issues encountered with the mixture of ginkgolide + Aβ peptide for VA and VCD studies were overcome using binary ethanol–D2O solvent mixture. The experimental VA and VCD spectra of GA, GB, GC and BB, GA-monoether and GA-diether have been analyzed using the corresponding spectra predicted with density functional theory. The time-dependent experimental VA and VCD spectra of Aβ(25–35) peptide and the corresponding experimental spectra in the presence of TTLs indicated that the effect of the TTLs in modulating the aggregation of Aβ(25–35) peptide is relatively small. Such small effects might indicate the absence of a specific interaction between the TTLs and Aβ(25–35) peptide as a major force leading to the reduced aggregation of amyloid peptides. It is possible that the therapeutic effect of G. biloba extract does not originate from direct interactions between TTLs and the Aβ(25–35) peptide and is more complex.

Site-selective introduction of biotin and benzophenone probes onto ginkgolide scaffolds is described.

The fluorescence of BODIPY and click-BODIPY dyes was found to substantially increase in the presence of bovine serum albumin (BSA). BSA acted as a solubilizer for dye aggregates, in addition to being a conventional binding scaffold for the click-BODIPY dyes, indicating that disaggregation of fluorophores should be considered when evaluating dye–protein interactions.

Stretching a polymer film induces a conformational change (from the twisted to planar state) in the embedded porphyrin dimer, as evidenced by steady-state and time-resolved emission spectra.

Site-selective introduction of biotin and benzophenone probes onto ginkgolide scaffolds is described.

Photophysical behaviour of a novel trimeric BODIPY rotor with a high extinction coefficient is reported. Steady state and time resolved fluorescence measurements established that the trimer could be used as a viscometer for molecular solvents, membrane-like environments and several cancer cell lines.