Novel Conjugated s-Tetrazine Derivatives Bearing a 4H-1,2,4-Triazole Scaffold: Synthesis and Luminescent Properties

A series of new symmetrical s-tetrazine derivatives, coupled via a 1,4-phenylene linkage with a 4H-1,2,4-triazole ring, were obtained. The combination of these two rings in an extensively coupled system has significant potential applications, mainly in optoelectronics. The methodology used turned out to be useful regardless of the type of five-membered ring or the nature of the individual substituents. All the products were identified by spectroscopic methods, and the target compounds were tested for luminescent properties. This study showed that all the synthesized highly-conjugated triazoles exhibited luminescence; in particular, one derivative, 3,6-bis(4-(5-(4-methoxyphenyl)-4-phenyl-4H-1,2,4-triazol-3-yl)phenyl)-1,2,4,5-tetrazine (13b), showed strong fluorescence emission and ahigh quantum yield close to 1.

A new replication medium enables a rapid identification of φx-174 virus by synchronous fluorescence of Tryptophan.

Development of rapid methods for identification of bacteriophages based on their intrinsic fluorescence is challenging. Pure bacteriophages may be detected based on the strong fluorescence of the amino acid Tryptophan that exist in their proteins. Nevertheless, Tryptophan is a molecule that also exist in high quantities in the bacterial hosts and their cultivation media. In this work, we show that simple separation of the bacteriophage φx-174 from its E.coli host (grown on standard cultivation medium) by filtration is not sufficient for its identification based on the intrinsic fluorescence of its Tryptophan content. This is mostly because of the tryptophan residues that derive from the cultivation medium. We fabricate a new cultivation medium that does not have any significant fluorescence overlap with Tryptophan. By utilization of this new cultivation medium, we can identify φx174 based on the spectral fingerprint of its intrinsic Tryptophan content by synchronous fluorescence measurements.

FLGS-03. Fluorescein sodium-guided biopsy or resection in patients with contrast enhancing brainstem lesion in MRI

BACKGROUND It is challenging to resect or just biopsy the lesions in the brainstem, due to the essential function of the surfaces and limited space. Neuro-navigation is not always reliable and stereotatic biopsy is infrequently inconclusive due to small or inadequate samples. We want to share our experiences in the application of fluorescein sodium in surgery on patients with brainstem lesion which is contrast enhancing in MRI. METHODS Between January 2017 and June 2021, 5 patients with brainstem lesion underwent fluorescein sodium-guided surgery in neurosurgery department of Sun Yat-sen University Cancer Center. After injection of low dose of sodium fluorescein (3 mg/kg), the lesions with strong fluorescence staining were identified as the target area for biopsy or resection. RESULTS 5 consecutive patients (aged 6–47 years) with brainstem lesions prospectively underwent fluorescein sodium-guided surgery. The lesions were located in pontine in 3 patients and in the medulla in 2 patients. Gross total resection was achieved in 2 patients, and partial resection in the other 3 patients. In all patients, a pathological diagnosis was obtained (4 gliomas and 1 metastasis from non-small cell lung carcinoma) without severe complications, including mild facial or abduct nerve palsy in 3 patients. And all the specimens with strong fluorescence staining sent for pathology were proved to be tumorous. CONCLUSION Fluorescein sodium-guided technique was helpful to locate the lesion in brainstem which was contrast-enhanced in MRI. It was effective and safe to figure out an ideal trajectory to avoid damage of the crucial structures and improve the diagnostic rate.

Effect of post-harvest temperature of tomato ‘Rinka 409’ on quality and autofluorescence during overripening

Japanese tomato cultivar ‘Rinka 409’ is suitable for harvesting at a fully ripe stage since it remains firm at the stage, resulting in longer shelf life. However, it is difficult to estimate the quality change because its color does not change after the fully ripe stage. For ‘Momotaro,’ we previously proposed a fluorescence-based indicator of overripening; however, its suitability for another cultivar, ‘Rinka 409’, and its relationship with temperature and quality were unclear. Therefore, in this study, we investigated the appropriateness of this fluorescence-based index for the above purposes. In 2021, 45 tomato seedlings planted in 2020 were harvested at the fully ripe stage and used for experiments. Weight loss and firmness were evaluated to determine the quality of the tomatoes. The post-harvest temperatures were set as 10, 17, and 25 °C. The results showed that the rate of weight loss increased linearly, whereas the firmness decreased exponentially. For non-destructive estimation of these properties, the excitation-emission matrix (EEM) was measured in the range of 250–460 nm and 280–750 nm for the excitation and emission, respectively. ‘Rinka 409’ showed a strong fluorescence emission at 400 nm/620 nm of the excitation/emission, respectively, regardless of days and temperature. The fluorescence intensity, as well as the firmness, decreased exponentially. Thus, a linear relationship was observed between them. The firmness of ‘Rinka 409’ can be estimated using a simpler linear regression model using this method than previous researches.

Polycationic Monomeric and Homodimeric Asymmetric Monomethine Cyanine Dyes with Hydroxypropyl Functionality—Strong Affinity Nucleic Acids Binders

New analogs of the commercial asymmetric monomethine cyanine dyes thiazole orange (TO) and thiazole orange homodimer (TOTO) with hydroxypropyl functionality were synthesized and their properties in the presence of different nucleic acids were studied. The novel compounds showed strong, micromolar and submicromolar affinities to all examined DNA ds-polynucleotides and poly rA–poly rU. The compounds studied showed selectivity towards GC-DNA base pairs over AT-DNA, which included both binding affinity and a strong fluorescence response. CD titrations showed aggregation along the polynucleotide with well-defined supramolecular chirality. The single dipyridinium-bridged dimer showed intercalation at low dye-DNA/RNA ratios. All new cyanine dyes showed potent micromolar antiproliferative activity against cancer cell lines, making them promising theranostic agents.

Berberrubine Phosphate: A Selective Fluorescent Probe for Quadruplex DNA

A phosphate-substituted, zwitterionic berberine derivative was synthesized and its binding properties with duplex DNA and G4-DNA were studied using photometric, fluorimetric and polarimetric titrations and thermal DNA denaturation experiments. The ligand binds with high affinity toward both DNA forms (Kb = 2–7 × 105 M−1) and induces a slight stabilization of G4-DNA toward thermally induced unfolding, mostly pronounced for the telomeric quadruplex 22AG. The ligand likely binds by aggregation and intercalation with ct DNA and by terminal stacking with G4-DNA. Thus, this compound represents one of the rare examples of phosphate-substituted DNA binders. In an aqueous solution, the title compound has a very weak fluorescence intensity (Φfl < 0.01) that increases significantly upon binding to G4-DNA (Φfl = 0.01). In contrast, the association with duplex DNA was not accompanied by such a strong fluorescence light-up effect (Φfl < 0.01). These different fluorimetric responses upon binding to particular DNA forms are proposed to be caused by the different binding modes and may be used for the selective fluorimetric detection of G4-DNA.

Occurrence of bioluminescent and nonbioluminescent species in the littoral earthworm genus Pontodrilus

Pontodrilus litoralis is a cosmopolitan littoral earthworm known to exhibit bioluminescence. Recently, a congeneric species, Pontodrilus longissimus, from Thailand was described. These species are sympatric, but their burrowing depths on Thai beaches are different. In this study, we examined the in vivo and in vitro bioluminescent properties of P. longissimus and P. litoralis. Mechanical stimulation induced in vivo luminescence in P. litoralis, as reported previously, but not in P. longissimus. In vitro cross-reaction tests between these species revealed the absence of luciferin and luciferase activities in P. longissimus. The coelomic fluid of P. litoralis had strong fluorescence that matched the spectral maximum of its bioluminescence, but the same result was not observed for P. longissimus. These results suggest that P. litoralis has luminescence abilities due to the creation of bioluminescent components (i.e., luciferin, luciferase, and light emitters). The presence of both luminous and nonluminous species in a single genus is likely widespread, but only a few examples have been confirmed. Our findings provide insight into the possible functions of bioluminescence in earthworms, such as avoiding predation by littoral earwigs.

π-Extended Ladder-Type Conjugated Polymers via BN-Annulation

Two kinds of ladder-type conjugated polymers were concisely synthesized by the formation of single-stranded conjugated polymers via Stille cross-couplings, followed by nitrogen-directed electrophilic borylations at electron-rich aromatic rings. The resulting BN-annulated polymers show good film-forming behaviors and high air and thermal stability. Their structurally shape-persistent rigid backbones render them with π-extended conjugation, allowing for efficient light harvesting in the low-energy regions, and emitting strong fluorescence with narrow emission widths.