A fluorescence-based assay for transcription using a novel fluorescent GTP analogue

A coumarin embedded highly sensitive nitric oxide fluorescent sensor: kinetic assay and bio-imaging applications

Fluorescence spectroscopy is a significant bio-analytical technique for specific detection of nitric oxide (NO) and for broadcasting the in vitro and in vivo biological activities of this gasotransmitter. Herein, a benzo-coumarin embedded smart molecular probe (BCM) is employed for NO sensing through detailed fluorescence studies in purely aqueous medium. All the spectroscopic analysis and literature reports clearly validate the mechanistic insight of this sensing strategy i.e., the initial formation of 1,2,3,4-oxatriazole on treatment of the probe with NO which finally converted to its carboxylic acid derivative. This oxatriazole formation results in a drastic enhancement in fluoroscence intensity due to the photoinduced electron transfer (PET) effect. The kinetic investigation unveils the second and first-order dependency on [NO] and [BCM] respectively. The very low detection limit (16 nM), high fluorescence enhancement (123 fold) in aqueous medium and good formation constant (K_f = (4.33 ± 0.48) × 10⁴ M^-1) along with pH invariability, non-cytotoxicity, biocompatibility and cell permeability make this probe a very effective one for tracking NO intracellularly.

Photophysical investigation of 3-substituted 4-alkyl and/or 7-acetoxy coumarin derivatives--a study of the effect of substituents on fluorescence

In the present work an array of novel substituted 2H-chromen-2-one (coumarin) derivatives has been subjected to photophysical analysis. Though the influence of the electron-donating groups such as amino, substituted amino, hydroxyl, alkoxy groups, etc. at position 7 of the coumarin ring system has been extensively studied, the luminescent properties of the coumarin moieties with an acetoxy substituent have not been explored. Herein it is attempted to study the variation of fluorescence behavior of substituted coumarin derivatives with change of nature and position of the substituents on the 2H-chromen-2-one skeleton. Effect of a methyl substituent at position 4 which imposes abnormal photophysical behavior to the chromenone unit has also been briefly described.

Synthesis of adenosine derivatives as transcription initiators and preparation of 5' fluorescein- and biotin-labeled RNA through one-step in vitro transcription

Expanding our previous finding of an adenosine-initiated transcription system, we now demonstrate that either the 5' site or the N6 site of adenosine nucleotides can be modified extensively without abolishing their ability to initiate transcription under the T7 phi2.5 promoter. Two series of amino derivatives of adenosine nucleotides were synthesized. Fluorescein and biotin groups were coupled to AMP derivatives through linkers of different sizes and hydrophobicities. Both fluorescein- and biotin-conjugated (at either the 5' or N6 site) adenosine nucleotides can act as efficient transcription initiators, producing fluorescein- and biotin-labeled RNA at the specific 5' end by a one-step transcription procedure, eliminating posttranscriptional modification. Furthermore, N6-modified adenosine derivative-initiated transcription synthesizes 5' end modified RNA with a free phosphate group, providing the possibility for further derivatization. The current finding makes easily available a variety of site-specifically functionalized RNA, which may be used in nucleic acid detection, RNA structural and functional investigation, and generation and isolation of novel functional RNA.

Efficient incorporation of CoA, NAD and FAD into RNA by in vitro transcription

Protein enzymes frequently recruit small molecule coenzymes to perform a variety of biochemical reactions. While the catalytic activities of RNA have been expanding rapidly, a similar strategy for RNA to utilize coenzymes and to increase its functional capabilities has yet to be demonstrated. A general in vitro transcription procedure has been developed to efficiently prepare RNA with coenzymes CoA, NAD and FAD covalently attached to the 5' end. These adenosine-containing coenzymes initiate transcription under the T7 class II promoter by T7 RNA polymerase. In addition to the three coenzymes, other adenosine-containing molecules may be incorporated into the first nucleotide position of RNA as well. This method provides easy access to CoA-, NAD- and FAD-RNA, which may find broad applications in generating coenzyme- utilizing ribozymes. In addition, both oxidized FAD and reduced NADH are highly fluorescent. NADH-RNA and FAD-RNA can therefore be used as probes for DNA/RNA detection and for structural investigation of RNA function by fluorescence spectroscopy.