Linker-Induced Structural Diversity and Photophysical Property of MOFs for Selective and Sensitive Detection of Nitroaromatics

The linker [1,1′:3′,1″-terphenyl]-4,4′,4″,6′-tetracarboxylic acid (<b>H</b>_<b>4</b><b>L</b>) was used to construct two three-dimensional (3D) metal–organic frameworks (MOFs), namely, {[Cd₂(L)­(L₁)­(DMF)­(H₂O)]­(2DMF)­(3H₂O)}_<i>n</i> (<b>1</b>) and {[Cd₄(L)₂(L₂)₃(H₂O)₂]­(8DMF)­(8H₂O)}_<i>n</i> (<b>2</b>) (DMF = <i>N</i>,<i>N</i>′-dimethylformamide) in the presence of colinkers 4,4′-bipyridine (<b>L</b>_<b>1</b>) and 2-amino-4,4′-bipyridine (<b>L</b>_<b>2</b>), respectively, under solvothermal condition. A small change in the colinker leads to significant differences in the overall structure of the MOFs. Topological analysis reveals that the framework <b>1</b> exhibits 6,4-connected forbidden sub-configuration (FSC) topology, while the framework <b>2</b> exhibits twofold interpenetrated and (3,4,4)-connected new network topology with Schläfli point symbol {4.6²}­{4.6⁴.8}­{4².6².8²}. The crystallographic investigation reveals the framework <b>2</b> having single helix structure, which is further coiled through noncovalent interaction, afforded a double-helix structure similar to DNA. These double helices are further connected through the colinker <b>L</b>_<b>2</b> to form an overall 3D structure. Besides framework <b>2</b> exhibits remarkable fluorescence intensity compared to <b>1</b>. Framework <b>2</b> displayed a strong emission at 457 nm when a sample of <b>2</b> was dispersed in ethanol and excited at 334 nm. This emission is selectively and completely quenched in the presence of 2,4,6-trinitrophenol (TNP) allowing its detection in the presence of other nitroaromatic compounds. The quenching constant for TNP was found to be 3.89 × 10⁴ M^–1, which is 26 times higher than that of TNT demonstrating greater and selective quenching ability. The emission is restored to its original value when the sample after collected by filtration is dispersed in fresh ethanol for 1 d. Interestingly, when solid <b>2</b> is exposed to different nitroaromatic compounds, its emission is quenched selectively in the presence of nitrobenzene. In this case, the emission is restored upon heating the sample to 150 °C for 2 h

Linker-Induced Structural Diversity and Photophysical Property of MOFs for Selective and Sensitive Detection of Nitroaromatics

The linker [1,1′:3′,1″-terphenyl]-4,4′,4″,6′-tetracarboxylic acid (<b>H</b>_<b>4</b><b>L</b>) was used to construct two three-dimensional (3D) metal–organic frameworks (MOFs), namely, {[Cd₂(L)­(L₁)­(DMF)­(H₂O)]­(2DMF)­(3H₂O)}_<i>n</i> (<b>1</b>) and {[Cd₄(L)₂(L₂)₃(H₂O)₂]­(8DMF)­(8H₂O)}_<i>n</i> (<b>2</b>) (DMF = <i>N</i>,<i>N</i>′-dimethylformamide) in the presence of colinkers 4,4′-bipyridine (<b>L</b>_<b>1</b>) and 2-amino-4,4′-bipyridine (<b>L</b>_<b>2</b>), respectively, under solvothermal condition. A small change in the colinker leads to significant differences in the overall structure of the MOFs. Topological analysis reveals that the framework <b>1</b> exhibits 6,4-connected forbidden sub-configuration (FSC) topology, while the framework <b>2</b> exhibits twofold interpenetrated and (3,4,4)-connected new network topology with Schläfli point symbol {4.6²}­{4.6⁴.8}­{4².6².8²}. The crystallographic investigation reveals the framework <b>2</b> having single helix structure, which is further coiled through noncovalent interaction, afforded a double-helix structure similar to DNA. These double helices are further connected through the colinker <b>L</b>_<b>2</b> to form an overall 3D structure. Besides framework <b>2</b> exhibits remarkable fluorescence intensity compared to <b>1</b>. Framework <b>2</b> displayed a strong emission at 457 nm when a sample of <b>2</b> was dispersed in ethanol and excited at 334 nm. This emission is selectively and completely quenched in the presence of 2,4,6-trinitrophenol (TNP) allowing its detection in the presence of other nitroaromatic compounds. The quenching constant for TNP was found to be 3.89 × 10⁴ M^–1, which is 26 times higher than that of TNT demonstrating greater and selective quenching ability. The emission is restored to its original value when the sample after collected by filtration is dispersed in fresh ethanol for 1 d. Interestingly, when solid <b>2</b> is exposed to different nitroaromatic compounds, its emission is quenched selectively in the presence of nitrobenzene. In this case, the emission is restored upon heating the sample to 150 °C for 2 h

Amino acid alignment of Ntl with human and <i>A.aeolicus</i> SLC6 transporters.

<p>Amino acid sequence alignment of <i>Drosophila melanogaster</i> Ntl (Ntl; NP_609135.1) with A.aeolicus Leu T_Aa (Leu; NP_214423), human homologues for Serotonin (5HT;P31645), Glycine (Gly, I57956), GABA (GABA; P30531), Dopamine (DOPA; Q01959) using Clustal W alignment [<a href="http://www.ebi.ac.uk/Tools/clustalw2/index.html" target="_blank">http://www.ebi.ac.uk/Tools/clustalw2/index.html</a>]. Strictly conserved residues are highlighted in red; α coils and β sheets are depicted as blocks and arrows respectively. Open and filled green circles represent putative cationic gates at extra and intra cellular surfaces (EL and IL) respectively. Open and filled blue triangles indicate sites that interact with sodium ions in the <i>LeuA</i> structure. Tyrosine in TM3 is a critical residue present in Ntl, which is indispensable for substrate binding and transport. Adapted from Yamashita <i>et al</i>, 2005.</p

<i>Ntl</i> expression is testis specific and limited to the germline.

<p>A) From the left: <i>Ntl</i> RT-PCR products from wt whole males, wt male heads, wt male testis, 129A whole male; <i>Ntl</i> RT-PCR products from wt whole females, wt female heads and wt female ovaries. The last lane is a negative control without RNA. B) <i>Ntl</i> RT-PCR products from <i>Ntl/Ntl</i> mutant males carrying a pTMR-<i>Ntl</i> cDNA construct (Lane 1; <i>yw; Ntl^129A/Ntl^129A; pTMR-Ntl1/TM3,Sb</i>) and a genomic pCaSpeR4 construct (Lane 2; <i>yw; Ntl^129A/Ntl^129A</i>; pCaSpeR 4- Ntl1/<i>TM3,Sb</i>). Lane 3: <i>Ntl</i> RT-PCR product from testes of male offspring of <i>tud/tud</i> females, which lack germ cells.</p

Deletion analysis of <i>Ntl</i> alleles.

<p>Numbers correspond to coordinates of Ntl genomic sequence.</p><p>+/− Refer to presence or absence of the band respectively.</p>a<p>Non specific bands.</p

Primers.

<p>Primers.</p

<i>Ntl</i> mutant sperm are immotile and are not transferred into seminal vesicles.

<p>Panels A, B, E, and F: Phase contrast images of testes from <i>Ntl⁺</i> (A, E) and <i>Ntl^-</i> (B, F) males. The major phenotypic feature of the mutants is the accumulation of coiled cysts at the base of the testis (asterisks), and the empty/shrunken state of the seminal vesicle (arrows). Panels, C, D, G, and H: <i>don juan-</i>GFP fluorescence images corresponding to phase images immediately above them, showing the disposition of elongated cysts and mature sperm in the testis and seminal vesicle. Note the complete absence of fluorescence from the seminal vesicle of <i>Ntl/Ntl</i> mutants (arrows) compared to the accumulated fluorescence in wild type seminal vesicles (arrowheads), and accumulation of coiled cysts in the base of the mutant testes (asterisks). In panels A and C, the letter M demotes dense masses of mature motile sperm which is not seen in the mutants. Left hand panels: wild type (<i>Ntl/+</i>); right hand panels: <i>Ntl</i>^129A/<i>Ntl</i>^129A mutants. Bars, 20 µm.</p

Porous Polyurea Network Showing Aggregation Induced White Light Emission, Applications as Biosensor and Scaffold for Drug Delivery

We have designed a urea functionalized novel nanoporous material, POP-PU, which showsaggregation induced white light emission in the presence of suitable polar solvents. This nanomaterial has been explored as a pseudowhite light emitter where the polymeric luminogen moiety can interact with the suitable polar solvent, leading to charge transfer. Thus, solvent assisted rotational freezing of nonrigid polymeric nanoparticles gives radiative emission and the whole solution emits white light with color temperature of 8533 K. This nanoporous material also holds the pockets (donor–donor–acceptor array) for specific biomolecular interaction. Among three pyrimidine based nucleotide bases, only cytosine can amplify the PL emission intensity of POP-PU and the other two bases cannot, suggesting its future potential as a biosensor. Further, this urea functionalized porous organic nanomaterial can be utilized as an efficient drug-delivery vehicle for liver cancer diagnostics and therapy based on the specific biomolecular interaction at its surface

Analysis of apoptosis and cell cycle arrest in U937 cells by flow cytometry.

<p>Cells were treated with 150 μg/ml of pLLD and binding of Annexin-V/FITC to phosphatidyl serine was measured by flow cytometry to determine the percentages of apoptotic cells in time dependent manner (A). Study of cell cycle arrest in U937 cells was carried out by propidium iodide staining. Percentage of G0/G1 cell population increases after treatment of 150 μg/ml of pLLD in time dependent manner (B). The data are represented as mean ± SEM from triplicate independent experiments (*P>0.05; ** P>0.01).</p

ROS generation in U937 cells upon treatment with pLLD (150 μg/ml).

<p>Flow cytometric analysis of ROS by DCFDA showed the degrees of scavenging effect in time dependent manner (A). Evaluation of mitochondrial membrane potential using JC-1 showed time dependent changes (B). Assessment of activation of caspases 9 and 3 with inhibitors and of DNA fragmentation by pLLD was done in a time dependent analysis by ELISA (C, D, E and F, respectively). Expression of pro- and anti-apoptotic molecules was assessed by western blot (G). Analysis of cytochrome C activation upon pLLD treatment was performed by confocal microscopy (H). The data are reported as the mean ± SEM of triplicate experiments (*P>0.05; ** P>0.01; *** P>0.001).</p