Synthesis of Carbazole-Thiazole Dyes via One-Pot Tricomponent Reaction: Exploring Photophysical Properties, Tyrosinase Inhibition, and Molecular Docking

Carbazole is an aromatic heterocyclic organic compound consisting of two fused benzene rings and a pyrrole ring and is a very valuable building structure for the design of many compounds for use in various fields of chemistry and medicine. This study presents three new carbazole-based thiazole derivatives that differ in the presence of a different halogen atom: chlorine, bromine, and fluorine. Experimental studies and quantum-chemical simulations show the effect of changing a halogen atom on the physicochemical, biological, and linear and nonlinear optical properties. We have also found that carbazoles C-Cl, C-Br, and C-F exhibit high tyrosinase inhibitory activity, with IC50 values in the range of 68-105 µM with mixed mechanism of action. Finally, molecular docking to the active site of Concanavalin A (ConA) and bioavailability for all compounds were evaluated.

Interaction of bifunctional peptide-carbazole complexes with DNA and antimicrobial activity

Two peptide-carbazole conjugates, CTAT and CNLS, were designed and synthesized using carbazole Schiff base to modify the cell membrane penetrating peptide TAT (47-57) and the nuclear localization peptide NLS at the N terminus. The interaction with ctDNA was investigated by multispectral and agarose gel electrophoresis. And the effects of CNLS and CTAT on the G-quadruplex structure were explored by circular dichroism titration experiments. The results show that both CTAT and CNLS interact with ctDNA in a minor groove binding manner. Both conjugates bind more tightly to DNA than the individual substances CIBA, TAT and NLS. In addition, CTAT and CNLS are capable of unfolding parallel G-quadruplex structures and are potential G-quadruplex unfolding agents. Finally, broth microdilution was performed to test the antimicrobial activity of the peptides. The results showed that CTAT and CNLS had a 4-fold increase in antimicrobial activity compared with the parent peptides TAT and NLS. They could exert antimicrobial activity by disrupting the integrity of cell membrane bilayer and binding to DNA, and could be used as novel antimicrobial peptides for the development of novel antimicrobial antibiotics.

Carbazole appended trans-dicationic pyridinium porphyrin finds supremacy in DNA binding/photocleavage over a non-carbazolyl analogue

A carbazolyl appended trans-pyridyl porphyrin (1) was synthesized and its dicationic form 2 was obtained by methylation of the pyridyl group. Copper and zinc complexes of porphyrin 2 (Cu(II), 3; Zn(II), 4) were isolated and characterized by various modern spectroscopic techniques. The DNA binding properties of 2, 3, and 4 have been explored against calf thymus-DNA (CT-DNA). DNA binding was quantized using the intrinsic binding constant (K_b) that was calculated by UV-visible absorption spectroscopy, and the value K_b = 1.6 × 10⁶ M^-1 for compound 2 reveals a better interaction of 2 towards CT-DNA than those of 3 (3.1 × 10⁵ M^-1) and 4 (3.4 × 10⁵ M^-1), which follows the order 2 > 4 > 3. The fluorescence quenching efficiency and ethidium bromide quenching assay also indicated a good binding affinity of all the compounds towards CT-DNA. Furthermore, the spectroscopic data suggest that the possible mode of interaction is intercalation. The docking studies were in accordance with the experimental results. Notably, DNA cleavage studies reveal that 2 shows better damage than 3 and 4 which is in accordance with the binding affinity order 2 > 4 > 3. The observed quantum yield (2: 0.65, 3: 0.33, and 4: 0.97) and no change in DNA cleavage in the presence of NaN₃ reveal the involvement of singlet oxygen. The singlet excited state lifetimes were in the range of 6.3-1.2 ns. Furthermore, these porphyrins can be investigated as interesting photosensitizers in photodynamic therapy and photochemotherapy.

Platinum Complexes as Inhibitors of DNA Repair Protein Ku70 and Topoisomerase IIα in Cancer Cells

Ku70 protein and topoisomerase IIα (Topo IIα) are promising targets of anticancer drugs, which play critical roles in DNA repair and replication processes. Three platinum(II) complexes, [PtCl(NH3)2(9-(pyridin-2-ylmethyl)-9H-carbazole)]NO3 (OPPC), [PtCl(NH3)2(9-(pyridin-3-ylmethyl)-9H-carbazole)]NO3 (MPPC),...

An insight into DNA binding properties of newly designed cationic δ,δ'‑diazacarbazoles: Spectroscopy, AFM imaging and living cells staining studies

Two cationic δ,δ'‑diazacarbazoles, 1‑Methyl‑5H‑pyrrolo[3,2‑b:4,5‑b']dipyridinium iodide (MPDPI) and 1,5‑Dimethyl‑5H‑pyrrolo[3,2‑b:4,5‑b']dipyridinium iodide (DPDPI), were devised and synthesized. Through characterizations of the interactions between DNA and the two δ,δ'‑diazacarbazoles by various spectroscopy means, the strong interactions between the two compounds and double-strand DNA have been observed and the interaction types and mechanisms were explored. UV-Vis and fluorescent data have shown the big changes of DNA in the presence of either of the two compounds, demonstrating that both of the δ,δ'‑diazacarbazoles can bind to DNA tightly, and high ionic strength decreased the intercalative interactions. The UV-Vis and fluorescence of dsDNA in the presence of DPDPI showed more profound changes than those in the presence of MPDPI, due to CH₃ (in the structure of DPDPI) taking place of H (in the structure of MPDPI) at the position of 5‑NH. And the circular dichroism (CD) spectra of CT-DNA and atomic force microscopy (AFM) results indicated more compacted conformation of DNA in the presence of DPDPI than MPDPI, implying that DPDPI has a more significant effect on DNA conformations than MPDPI. Most interestingly, fluorescence enhancement of cationic δ,δ'‑diazacarbazoles occurred in the presence of DNA. With ionic strength increasing, the intercalative interactions between δ,δ'‑diazacarbazoles and DNA were weakened, but δ,δ'‑diazacarbazoles-DNA complexes showed enhanced fluorescence, which indicated that there are other interactions present at high ionic strength. Furthermore, laser confocal fluorescence microscopy results proved that DPDPI was membrane-permeable and stained living cells.

Synthesis and fluorescence properties of 3,6-diaminocarbazole-modified pyrrolidinyl peptide nucleic acid

Diaminocarbazole-labeled acpcPNA as a self-reporting probe for determination of DNA sequences.

Bis((1,4-dimethyl-9H-carbazol-3-yl)methyl)amine-mediated anticancer effect triggered by sequence-specific cleavage of DNA leading to programmed cell death in the human U87 cell line

Bis((1,4-dimethyl-9H-carbazol-3-yl)methyl)amine (DMCM) has been designed as a novel anti-cancer agent which is believed to have a sequence-specific groove binding interaction with DNA, leading to anticancer effects.

Investigation of the binding modes between AIE-active molecules and dsDNA by single molecule force spectroscopy

AIE (aggregation-induced emission)-active molecules hold promise for the labeling of biomolecules as well as living cells. The study of the binding modes of such molecules to biomolecules, such as nucleic acids and proteins, will shed light on a deeper understanding of the mechanisms of molecular interactions and eventually facilitate the design/preparation of new AIE-active bioprobes. Herein, we studied the binding modes of double-stranded DNA (dsDNA) with two types of synthetic AIE-active molecules, namely, tetraphenylethene-derived dicationic compounds (cis-TPEDPy and trans-TPEDPy) and anthracene-derived dicationic compounds (DSAI and DSABr-C6) using single molecule force spectroscopy (SMFS) and circular dichroism (CD) spectroscopy. The experimental data indicate that DSAI can strongly intercalate into DNA base pairs, while DSABr-C6 is unable to intercalate into DNA due to the steric hindrance of the alkyl side chains. Cis-TPEDPy and trans-TPEDPy can also intercalate into DNA base pairs, but the binding shows strong ionic strength dependence. Multiple binding modes of TPEDPy with dsDNA have been discussed. In addition, the electrostatic interaction enhanced intercalation of cis-TPEDPy with dsDNA has also been revealed.

Synthesis and DNA binding profile of N-mono- and N,N'-disubstituted indolo[3,2-b]carbazoles

A series of N-monosubstituted and N,N'-disubstituted derivatives of the indolo[3,2-b]carbazole chromophore have been prepared, and their binding affinity for duplex DNA has been evaluated by ultraviolet and fluorescence spectroscopies. It has been found that indolo[3,2-b]carbazoles bearing basic N-alkyl substituents are intercalators that bind DNA with affinities in the micromolar and submicromolar range and a preference for associating with sequences of mixed composition and purine-pyrimidine steps.

Characterizations of cationic γ-carbolines binding with double-stranded DNA by spectroscopic methods and AFM imaging

Two cationic γ-carbolines, 2-methyl-5H-pyrido[4,3-b]indolium iodide (MPII) and 2,5-dimethyl-5H-pyrido[4,3-b]indolium iodide (DPII), were synthesized, and the DNA-binding properties of the cationic γ-carbolines were elucidated. Through a series of experiments, we proved that the two cationic γ-carbolines could strongly interact with DNA by intercalative binding. However, DPII, with a methyl group substituting H atom of 5-NH, has shown a stronger intercalative interaction with DNA compared to MPII. The dissociation of H from the 5-NH of MPII resulted in better water solubility and less binding affinity to DNA. Atomic force microscopy (AFM) images of pBR322 showed that both MPII and DPII strongly interacted with DNA and induced conformational changes in DNA. Moreover, the CT-DNA circular dichroism (CD) spectra changes and the statistics of the node numbers of pBR322 in AFM images indicated that MPII had more profound effects on DNA conformations compared to DPII. Furthermore, our studies have shown that the interactions between cationic γ-carbolines and DNA were sensitive to ionic strength. Increased ionic strength in the buffer caused the DNA helix to shrink, and the base stacking would be more compact, which resulted in minimal intercalation of cationic γ-carbolines into DNA.