Publication Date: 2022
Environmental Research (0013-9351)204
Diverse glutathione-S-transferases (GSTs) are produced by insect pests including Helicoverpa armigera (HaGSTs) for detoxification of insecticides or xenobiotic compounds that they encounter. In an earlier study, the HaGST-8 gene was isolated from H. armigera larvae exposed to pesticide mixtures and the recombinant protein was expressed in the yeast Pichia pastoris. In this investigation, HaGST-8 was successfully immobilized on glutaraldehyde-activated APTES functionalized silica nanoparticles to obtain SiAPT-HaGST-8 nano-conjugates. Although enzyme activity associated with these conjugates was comparable to that of free HaGST-8, the specific activity of the former was found to be 1.25 times higher than the latter. In comparison with the free enzyme (that demonstrated a pH optimum of 9.0), for the nano-conjugates, the pH range was extended between pH 8.0 to 9.0. The optimum temperature for activity of both forms of the enzyme was found to be 30 °C. Stability of the enzyme was improved from 20 d for free HaGST-8 to 30 d for SiAPT-HaGST-8 nano-conjugates. Some loss in GST activity was detected after every reuse cycle of nano-conjugates and in all, 63% reduction was observed after three cycles. When 3 kinds of pesticides (namely, chlorpyrifos, dichlorvos and cypermethrin) were reacted with SiAPT-HaGST-8, more than 80% reduction in levels were observed. On the basis of the results obtained, the use of such silica nanoparticle-based systems for stable enzyme conjugation followed by effective removal of pesticides from aqueous media is envisaged. © 2021 Elsevier Inc.
Publication Date: 2021
Plant Gene (23524073)26
Plant defensins (γ-thionins) are antimicrobial peptides (AMPs) constituting the host defense system. They are known to interact with the cell membranes to exhibit antifungal and antibacterial activity. Though defensin genes are inducible under biotic and abiotic stress, their involvement in insect herbivore defense is not well studied. In this work we studied the phylogeny, structural diversity, biochemical and functional properties of defensins from Capsicum annuum L with particular emphasis on their interaction with insect and fungal pathogens. Phylogenetic analysis of defensin peptides from Solanaceae, Pinaceae, Fabaceae, Asteraceae, Brassicaceae and similar peptides from invertebrates divided them into ten groups and Capsicum peptides were represented in most of them. Three thionin (CanThio-1, −2, −3) and two defensin (CanDef-20, −21) genes isolated from the flowers of Capsicum annuum were cloned and recombinant proteins were expressed. The mature peptide amino acid sequences of CanThio and CanDef were 54–75 aa with 21.82 to 73.81% similarity. They contained the conserved features of defensin peptides like the gamma core region and the presence of eight cysteine residues. Predicted structural alignment indicated that CanThio and CanDef had structural diversity and structurally unaligned loop regions. The recombinant CanThio and CanDef inhibited 5% - 65% Aspergillus oryzae amylase activity at 20 μM and ~ 20% of Helicoverpa armigera gut amylase activity at 50 μM peptide concentrations. CanThio-2 displayed bovine trypsin inhibition (~14%) while all the CanThio and CanDef inhibited ~20% of H. armigera gut proteinase activity at 20 μM. H. armigera larvae fed on an artificial diet incorporated with recombinant CanThio-2 and CanDef-20 (125 μg/ml) exhibited a 15% reduction in larval mass and 13% reduction in pupal mass. The CanThio and CanDef peptides also exhibited antifungal properties against pathogenic fungus Fusarium oxysporum at 5 μg/ml, where CanThio-2 and CanDef-20 showed the strongest activity, which may be attributed to the positively charged amino acids in the γ-core region. We conclude that despite having relatively similar conserved three-dimensional structures CanThio and CanDef display functional variability, which can be utilized for enhancing insect and fungal resistance in plants. © 2021 Elsevier B.V.
Publication Date: 2020
Proteins: Structure, Function and Bioinformatics (10970134)88(1)pp. 227-236
Thionins are small, cysteine-rich peptides that play an important role in plant defense, primarily through their interactions with membranes. Eight novel γ-thionin peptides (CanThio1-8) were isolated from the flower of Capsicum annuum. Sequence analysis revealed that the peptides cluster into three groups. A representative peptide from each group (CanThio1, 2, and 3) was used for experimental characterization. Interestingly, peptides were found to possess some cytotoxic activity against normal human embryonic kidney cell line but higher cytotoxicity against cancer cell line MCF-7. CanThio3 peptide was chosen as a representative peptide to study the molecular mechanism of action on membranes. Microsecond timescale atomistic simulations of CanThio3 were performed in the presence of a POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) lipid bilayer. Simulations revealed that CanThio3 interacts with the bilayer and causes lipid thinning in the vicinity. Nonpolar amino acids specific to the α-core region of CanThio3 along with nonpolar residues in the γ-core region are seen to interact with the lipid tails. The differences in the amino acid sequence of CanThio peptides in these regions explain the variability in cytotoxic activities. In summary, our results demonstrate the membrane-mediated activity of a novel series of γ-thionin peptides from C. annuum. © 2019 Wiley Periodicals, Inc.
Publication Date: 2019
SN Applied Sciences (25233971)1(4)
Nanoparticles have wide applications in various fields due to their small size. Titanium dioxide nanoparticles are bright with high refractive index (n = 2.4) which makes them suitable for industry dealing with toothpaste, pharmaceuticals, coatings, papers, inks, plastics, food products, cosmetics and textile. Three crystalline phases of titanium dioxide, are anatase (tetragonal), rutile (tetragonal), and brookite (orthorhombic) in which brookite has no commercial value. Due to their self cleaning and antifogging property, they are used in the preparation of cloths, windows, tiles and anti-fogging car mirrors. Titanium dioxide nanoparticles also serve as environment sanitizing agent. Sol–gel route, flame hydrolysis, co-precipitation, impregnation and chemical vapor deposition like techniques are used for the synthesis of TiO2 nanoparticles. Biosynthesis of titanium dioxide nanoparticles has gained wide interest among researchers due to its cost effective, eco-friendly and reproducible approach. The sol–gel route remediation of the titanium dioxide from the environment is an important step and it can be achieved by using physical processes like sedimentation and filtration. The biosynthesis of titanium dioxide nanoparticles can be used in comparison to chemical synthesis. The titanium dioxide nanoparticles have wide applications, viz., reducing toxicity of dyes and pharmaceutical drugs; waste water treatment; reproduction of silkworm; space applications; food industries; etc., and so have immense industrial importance. The applications of nanoparticles synthesized by biological approach will be advantageous for the industries; environment and agriculture. © 2019, Springer Nature Switzerland AG.
Publication Date: 2013
Journal of Applied Pharmaceutical Science (22313354)3(3)pp. 112-116
Present investigation was aimed to identify natural products of plant-origin as novel antibiotic resistance reversal agents. Aqueous and methanol extracts of Piper longum (fruits) were tested against multiple drug resistant (MDR) clinical isolates of Enterococcus faecalis, Staphylococcus aureus, Salmonella typhi, Shigella sonnei, as well as reference-plasmid-harboring strains of Escherichia coli (RP4) and Bacillus subtilis (pUB110). The crude methanol extract showed significant antibacterial activity with a minimal inhibitory concentration of 400 μg/mL against Bacillus subtilis (harboring pUB110 plasmid). Methanol extract could reverse the antibiotic resistance in clinical isolates of Shigella sonnei, with a curing efficiency of 42%. In comparison with methanol extract, aqueous extract showed antibiotic resistance reversal efficiency against wider range of clinical isolates. Aqueous extract showed strong antibiotic resistance reversal activities against R-plasmid harboring strains of clinical origin- Enterococcus faecalis, Staphylococcus aureus, Salmonella typhi with curing efficiencies of 64%, 50% and 32% respectively. This antibiotic resistance reversal may be attributed to the elimination of R-plasmids as the multiple antibiotic resistance genes are usually located on R-plasmids. Active biomolecules from P. longum may prove to be a source to develop MDR reversal agents of natural origin to contain the development and spread of plasmid borne multiple antibiotic resistance.
