Chemical approaches toward the bioinorganic chemistry of molybdenum and tungsten enzymes had been either biomimetic (structural modeling) or bioinspired (functional modeling). Among the dithiolene ...type of ligands, bdt (1,2-benzene dithiolate) and related aromatic molecules as model ene–dithiolene ligands were used to react with pre-designed molybdenum complexes in organic solvents. Whereas in the alternative approach mnt (maleonitrile dithiolate) is used to mimic the ligand backbone of the central atom in the active sites of these enzymes using molybdate or tungstate as the metal source in water. Structural–functional models are known for some selected enzymes, namely, sulfite oxidase, aldehyde ferredoxin oxidoreductase, tungsten formate dehydrogenase, acetylene hydratase, polysulfide reductase and dissimilatory nitrate reductase. The protocols and methodologies adopted to achieve these model systems compared with various other model systems described in this review give testimony to chemist's ability, through chemical manipulations, to achieve the model systems which may potentially serve as structural–functional mimics of natural enzyme systems.
A probe based on 2-(2′-hydroxyphenyl) benzothiazole (HBT) has been synthesized and used for the ratiometric detection of hydrazine. The probe is designed in such a way that the excited state ...intramolecular proton transfer (ESIPT) of the HBT moiety gets blocked. The chemodosimetric approach of hydrazine to the probe results in the recovery of the ESIPT by removal of a free HBT moiety through subsequent substitution, cyclization, and elimination processes. The probe is successfully demonstrated to enable the detection of hydrazine in live cells.
Three cyclic zinc(II) bis‐porphyrins (CB) with highly flexible linkers are employed as artificial molecular containers that efficiently encapsulate/coordinate various aromatic aldehydes within their ...cavities. Interestingly, the arrangements of guests and their reactivity inside the molecular clefts are significantly influenced by the cavity size of the cyclic containers. In the presence of polycyclic aromatic aldehydes, such as 3‐formylperylene, as a guest, the cyclic bis‐porphyrin host with a smaller cavity (CB1) forms a 1:1 sandwich complex. Upon slightly increasing the spacer length and thereby the cavity size, the cyclic host (CB2) encapsulates two molecules of 3‐formylperylene that are also stacked together due to strong π–π interactions between them and CH–π interactions with the porphyrin rings. However, in the cyclic host (CB3) with an even larger cavity, two metal centers of the bis‐porphyrin axially coordinate two molecules of 3‐formylperylene within its cavity. Different arrangements of guest inside the cyclic bis‐porphyrin hosts are investigated by using UV/Vis, ESI‐MS, and 1H NMR spectroscopy, along with X‐ray structure determination of the host–guest complexes. Moreover, strong binding of guests within the cyclic bis‐porphyrin hosts support the robust nature of the host–guest assemblies in solution. Such preferential binding of the bis‐porphyrinic cavity towards aromatic aldehydes through encapsulation/coordination has been employed successfully to catalyze the Knoevenagel condensation of a series of polycyclic aldehydes with active methylene compounds (such as Meldrum's acid and 1, 3‐dimethylbarbituric acid) under ambient conditions. Interestingly, the yields of the condensed products significantly increase upon increasing spacer lengths of the cyclic bis‐porphyrins because more substrates can then be encapsulated within the cavity. Such controllable cavity size of the cyclic containers has profound implications for constructing highly functional and modular enzyme mimics.
Accommodating substrates: Three cyclic zinc(II) bis‐porphyrins (CB) with flexible linkers are employed as artificial molecular containers. Interestingly, the arrangement of guests and reactivity inside the containers are significantly influenced by the cavity size (see figure).
Metabolism of food protein by gut microbes produce trimethylamine which on oxidation by hepatic flavin-containing monooxygenases is transformed to trimethylamine-
N
-oxide (TMAO). TMAO has recently ...been implicated as a biomarker for atherosclerosis. TMAO, as (CH
3
)
3
N
+
–O
−
), is ionic and so a hydrophilic molecule that is freely available in blood plasma. For the effective interaction with lipid-soluble molecules, TMAO should be phase transferred to the lipid site. We show that the free TMAO is effectively bonded to zinc protoporphyrin IX dimethyl ester ZnPPDME to yield TMAOZnPPDME using phase transfer reaction. The zinc protoporphyrin IX, ZnPP, in general, available in blood may form TMAOZnPP complex. The nature of such interaction between TMAO and ZnPP has been structurally shown using a model complex, TMAOZnTPP (TPP = tetraphenylporphyrin). These complexes readily move from the polar plasma to the non-polar (lipid) site to act as the oxo-transfer agent to oxidize cholesterol causing atherosclerosis. Chromatographic and circular dichroism (CD) studies show that either TMAO or ZnPP alone cannot oxidize cholesterol.
Graphic abstract
Free TMAO bonded with zinc-protoporphyrin IX, ZnPP, in blood plasma as TMAOZnPP is transported to the lipid site and this is the reacting species to oxidize cholesterol causing atherosclerosis.
Real‐time X‐ray or magnetic resonance imaging are known methods used for biomedical diagnosis. By the oral administration of barium meal, X‐ray imaging can be extended for use in soft tissue imaging. ...The oral ingestion of a fluorescent probe is a new approach to imaging a living species. Here, water‐soluble carbon nano‐onions are introduced as a nontoxic, fluorescent reagent enabling Drosophila melanogaster (fruit flies) to be imaged alive. It is demonstrated that these water‐soluble carbon nano‐onions, synthesized from wood waste, colorfully image all the development phases of Drosophila melanogaster from its egg to adulthood. Oral ingestion of up to 4 ppm of soluble carbon nano‐onions allows the optical fluorescence microscopy imaging of all the stages of the fruit fly life cycle without showing any toxic effects. The fluorescent Drosophila melanogaster excretes this fluorescing material upon the withdrawal of carbon nano‐onions from its food.
Ingestion of noninvasive, nontoxic, water‐soluble carbon nano‐onions causes Drosophila melanogester to fluoresce. The carbon nano‐onion allows Drosophila to be imaged in multiple colors in all the different stages of its life cycle.
A colorimetric and fluorescence turn-off probe 10-(4-azido phenyl)-5,5-difluoro-5h-dipyrrolo1,2-c:1’,2’-f1,3,2 diazaborinin-4-ium-5-uide,
1
, for selective detection of H
2
S is reported. The probe ...displayed a robust decrease in fluorescence intensity with high sensitivity, specificity and least toxicity to detect exogenous H
2
S and also in live normal human oral fibroblast cells loaded with probe
1
. The detection limit of probe
1
being 0.17 µm for H
2
S.
Graphic abstract
A colorimetric and fluorescence turn-off BODIPY probe
1
, for selective detection of exogenous H
2
S in live normal human oral fibroblast cells loaded with probe
1
and poisonous H
2
S gas formed under biodegradation in sewage waters and water tanks and corroded pipe lines. The detection limit of probe
1
being 0.17 μM
Water-soluble carbon nano-onions (wsCNOs) isolated from wood wool-a wood-based pyrolysis waste product of wood, can enhance the overall growth rate of gram (Cicer arietinum) plants. Treatment of ...plants with upto 30 μg mL(-1) of wsCNOs for an initial 10 day period in laboratory conditions led to an increase in the overall growth of the plant biomass. In order to examine the growth stimulating effects of wsCNOs under natural conditions, 10 day-old plants treated with and without wsCNOs were transplanted into soil of standard carbon and nitrogen composition. We observed an enhanced growth rate of the wsCNOs pre-treated plants in soil, which finally led to an increased productivity of plants in terms of a larger number of grams. On analyzing the carbon, hydrogen, and nitrogen (CHN) content for the shoot and fruit sections of the plants treated with and without wsCNOs, only a minor difference in the composition was noticed. However, a slight increase in the percentage of carbon and hydrogen in shoots reflects the synthesis of more organic biomass in the case of treated plants. This work shows that wsCNOs are non-toxic to plant cells and can act as efficient growth stimulants which can be used as benign growth promoters.
Carbon nano onion (CNO) from dried grass has been synthesized by carbonization in the size range, 20 to 100 nm. This shows catalytic property to transform aerial oxygen under visible light to ...generate reactive oxygen species (ROS). A concept has been presented herein to show that this CNO even under room light generates hydrogen peroxide which inhibits WSN influenza virus (H1N1). The advantage of introducing CNO, synthesized from a cheap source to cater to the global need, is to sterilize infected hospitals indoor and outdoor, aircraft carriers, air conditioner vents due to its sustained conversion of air to ROS. Thus, CNO use could prevent frequent evacuation as used by conventional sanitisers to sterilize infected places from other RNA virus and hospital pathogens under COVID-19 pandemic.
Graphical abstract
Carbon nano onion (CNO) under aerial oxygen on exposure with visible light generates ROS which is capable to rupture the lipid envelope of SARS-CoV-2 followed by disintegrating its RNA.
Understanding the nature of interactions of targeted drug‐delivery vehicles, such as functionalized carbon nanotubes (f‐CNTs) and their composites, with a cell or its organelles or DNA, where water ...is a major constituent, requires molecular‐level understanding of f‐CNTs with analogous chemical systems. The nature of interaction has not yet been explored within the scope of formation of giant aggregates by self‐assembly processes. Crystals of platinum(II) dithiolene Pt(mnt)2PPh42 (1) and gadolinium(III) dithiolene Gd(mnt)3PPh43 (2) (mnt=maleonitrile dithiolate) form nanospheres (diameter 88 nm) and nanoflowers (400–600 nm) in acetonitrile/water and DMF/water solvent mixtures, respectively. The formation of nanospheres or nanoflowers is proposed to be a water‐induced phenomenon. These nanospheres and nanoflowers interact with f‐CNTs by forming either spherical supramolecular assemblies (3, diameter up to 45. 5 μm) in the case of platinum(II) dithiolene or composite flowers (4) with CNT buckling for gadolinium(III) dithiolene. Both nanostructures, (3) and (4), show emission upon excitation at a range of wavelengths (λex=385–560 nm). The fluorescence emissions of the composite materials 3 and 4 are proposed to be due to separation of energy states of the nanospheres of 1 or the nanoflowers of 2 by the energy states of the f‐CNTs, leading to the possibility of new electronic transitions.
Bioimaging model: Gadolinium(III) and platinum(II) dithiolenes display water‐induced formation of nanoflowers and nanospheres, which further form carbon nanotube (CNT)‐based composite flowers and spheres. These CNT‐based composite materials display a high‐intensity photoluminescence in the visible region that is reminiscent of cellular bioimaging.
The science on the anthropogenic airborne aerosols impacting the World Heritage marble monument, the Taj Mahal, at Agra, has been studied in the light of modern physico-chemical approaches. The study ...is an effort to understand unrecognized airborne species which were found on the surface of the Taj Mahal monument. These species have been analyzed in the light of current analytical methods to impart characterization features and their possible impacts on the surface of the marble. Chemical constituents of these substrates, which were incorporated over the top surface of the monument, have been identified. Interestingly, the carbon particulates which were found on the micro level, popularly called “particulate matters”, have now been identified in the nano domain entity, which is chemically more reactive, and have been found on the surface of the monument. Because of their high chemical activity, these nano carbons have a newer chemistry in the presence of air and sunlight, generating several reactive oxygen species (ROS). These ROS are capable of responding to complicated chemical reactions on the surface of the marble in association with deposited cyanophyceae and other deposits of plant origin, causing rapid degradation. This study provides the nature of the onslaught of such monuments exposed under the prevalent smoggy environmental scenario.
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