| 1. |
- Ahmed, Naeem, et al.
(författare)
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A study to examine the ageing behaviour of cold plasma-treated agricultural seeds
- 2023
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Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 13
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Tidskriftsartikel (refereegranskat)abstract
- Cold plasma (low pressure) technology has been effectively used to boost the germination and growth of various crops in recent decades. The durability of these plasma-treated seeds is essential because of the need to store and distribute the seeds at different locations. However, these ageing effects are often not ascertained and reported because germination and related tests are carried out within a short time after the plasma-treatment. This research aims to fill that knowledge gap by subjecting three different types of seeds (and precursors): Bambara groundnuts (water), chilli (oxygen), and papaya (oxygen) to cold plasma-treatment. Common mechanisms found for these diverse seed types and treatment conditions were the physical and chemical changes induced by the physical etching and the cold plasma on the seeds and subsequent oxidation, which promoted germination and growth. The high glass transition temperature of the lignin-cellulose prevented any physical restructuring of the surfaces while maintaining the chemical changes to continue to promote the seeds germination and growth. These changes were monitored over 60 days of ageing using water contact angle (WCA), water uptake, electrical conductivity, field emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectroscopy (XPS). The vacuum effect was also investigated to separate its effect from cold plasma (low pressure). This finding offers a framework for determining how long agricultural seeds that have received plasma treatment can be used. Additionally, there is a need to transfer this research from the lab to the field. Once the impact of plasma treatment on seeds has been estimated, it will be simple to do so.
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| 2. |
- Ahmed, Naeem, et al.
(författare)
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Effects of Oxygen (O2) Plasma Treatment in Promoting the Germination and Growth of Chili
- 2022
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Ingår i: Plasma chemistry and plasma processing. - : Springer. - 0272-4324 .- 1572-8986. ; 42:1, s. 91-108
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Tidskriftsartikel (refereegranskat)abstract
- In general, seed germination is improved by low-pressure plasma treatment using precursors such as air, nitrogen, O2, and argon, etc. For the first time, low-pressure O2 plasma was used to treat chili seeds in this study. When compared to untreated and vacuum-treated seeds, O2 plasma treatment using the discharge power of 80 W for 60 s significantly improves chili seed germination and growth. The effect of vacuum on the germination and growth of chili seeds was also studied and shown to be negligible. The physical and chemical changes induced by O2 plasma treatment were investigated to understand the plasma treatment to germination improvement. Combinatory etching and chemical modification aided imbibition and increased germination percentage in this O2 plasma treatment on chili seeds. The success of this method has the potential to be scaled up to solve food security issues with seeds that would otherwise struggle to germinate.
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| 3. |
- Ahmed, Naeem, et al.
(författare)
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Germination and growth improvement of papaya utilizing oxygen (O2) plasma treatment
- 2022
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Ingår i: Journal of Physics D. - : Institute of Physics (IOP). - 0022-3727 .- 1361-6463. ; 55:25
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Tidskriftsartikel (refereegranskat)abstract
- In general, cold plasma treatment improves crop germination and growth. The purpose of this research is to examine the impact of low-pressure O2 plasma treatment on the germination and growth kinetics of papaya seeds. Seeds were treated for 40 s at a discharge power of 80 W using O2 as a monomer. Physical and chemical changes were studied to understand the mechanism of germination and growth improvement. Furthermore, changes in phytohormones and antioxidant activity that were beneficial to germination were also examined. O2 plasma treatment improved wettability, surface etching, and oxidation, and affected other molecular-level changes leading to a 16% germination improvement in papaya.
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| 4. |
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| 5. |
- Ahmed, Naeem, et al.
(författare)
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The Hydrophilization and Subsequent Hydrophobic Recovery Mechanism of Cold Plasma (CP) Treated Bambara Groundnuts
- 2022
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Ingår i: Materials Science Forum. - : Trans Tech Publications. - 0255-5476 .- 1662-9752. ; 1055, s. 161-169
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Tidskriftsartikel (refereegranskat)abstract
- Plasma hydrophilization and subsequent hydrophobic recovery in Bambara groundnuts are studied for the first time. Bambara groundnut seeds were treated with cold plasma (CP) for 10 seconds at 10 watts using water as a monomer. The contact angle, as well as physical and chemical changes, were used to determine the kinetics of hydrophobic recovery. The hydrophilic state of Bambara groundnut seeds had decreased after 60 days, but not to original hydrophobicity, and also the recovery rate is slower than those observed on synthetic polymer. However, this slower hydrophobic recovery makes CP treatment as an effective method for long-term seed storage.
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| 6. |
- Barai, Manas, et al.
(författare)
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Interfacial and Aggregation Behavior of Dicarboxylic Amino Acid-Based Surfactants in Combination with a Cationic Surfactant
- 2019
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 35:47, s. 15306-15314
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Tidskriftsartikel (refereegranskat)abstract
- The interfacial and micellization behavior of three dicarboxylic amino acid-based anionic surfactants, abbreviated as AAS (N-dodecyl derivative of -aminomalonate, -aspartate, and -glutamate) in combination with hexadecyltrimethylammonium bromide (HTAB) were investigated by surface tension, conductance, UV–vis absorption/emission spectroscopy, dynamic light scattering (DLS), and viscosity studies. Critical micelle concentration (CMC) values of the surfactant mixtures are significantly lower than the predicted values, indicating associative interaction between the components. Surface excess, limiting molecular area, surface pressure at the CMC, and Gibbs free energy indicate spontaneity of the micellization processes compared to the pure components. CMC values were also determined from the sigmoidal variation in the plot of micellar polarity and pyrene UV–vis absorption/emission intensities with surfactant concentration. The aggregation number, determined by static fluorescence quenching method, increases with decreasing mole fraction of the AAS (αAAS), where the micelles are mainly dominated by the HTAB molecules. The size of the micelle increases with decreasing αAAS, leading to the formation of larger and complex aggregates, as also supported by the viscosity studies. Micelles comprising 20–40 mol % AAS are highly viscous, in consonance with their sizes. Some of the mixed surfactant systems show unusual viscosity (shear thickening and increased viscosity with increasing temperature). Such mixed surfactant systems are considered to have potential in gel-based drug delivery and nanoparticle synthesis.
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| 7. |
- Barai, Manas, et al.
(författare)
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Micro-structural investigations on oppositely charged mixed surfactant gels with potential dermal applications
- 2021
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Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- Dicarboxylic amino acid-based surfactants (N-dodecyl derivatives of -aminomalonate, -aspartate, and -glutamate) in combination with hexadecyltrimethylammonium bromide (HTAB) form a variety of aggregates. Composition and concentration-dependent mixtures exhibit liquid crystal, gel, precipitate, and clear isotropic phases. Liquid crystalline patterns, formed by surfactant mixtures, were identified by polarizing optical microscopy. FE-SEM studies reveal the existence of surface morphologies of different mixed aggregates. Phase transition and associated weight loss were found to depend on the composition where thermotropic behaviours were revealed through combined differential scanning calorimetry and thermogravimetric studies. Systems comprising more than 60 mol% HTAB demonstrate shear-thinning behaviour. Gels cause insignificant toxicity to human peripheral lymphocytes and irritation to bare mouse skin; they do not display the symptoms of cutaneous irritation, neutrophilic invasion, and inflammation (erythema, edema, and skin thinning) as evidenced by cumulative irritancy index score. Gels also exhibit substantial antibacterial effects on Staphylococcus aureus, a potent causative agent of skin and soft tissue infections, suggesting its possible application as a vehicle for topical dermatological drug delivery.
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| 8. |
- Barai, Manas, et al.
(författare)
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Physicochemical Studies on Amino Acid Based Metallosurfactants in Combination with Phospholipid
- 2024
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Ingår i: Chemistry - An Asian Journal. - : John Wiley & Sons. - 1861-4728 .- 1861-471X.
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Tidskriftsartikel (refereegranskat)abstract
- Dicarboxylate metallosurfactants (AASM), synthesized by mixing N-dodecyl aminomalonate, -aspartate and -glutamate with CaCl2, MnCl2 and CdCl2, were characterized by XRD, FTIR, and NMR spectroscopy. Layered structures, formed by metallosurfactants, were evidenced from differential scanning calorimetry and thermogravimetric analyses. Solvent-spread monolayer of AASM in combination with soyphosphatidylcholine (SPC) and cholesterol (CHOL) were studied using Langmuir surface balance. With increasing mole fraction of AASM mean molecular area increased and passed through maxima at ~60 mol% of AASMs, indicating molecular packing reorganization. Systems with 20 and 60 mol% AASM exhibited positive deviations from ideal behavior signifying repulsive interaction between the AASM and SPC, while synergistic interactions were established from the negative deviation at other combinations. Dynamic surface elasticity increased with increasing surface pressure signifying formation of rigid monolayer. Transition of monolayer from gaseous to liquid expanded to liquid condensed state was established by Brewster angle microscopic studies. Stability of the hybrid vesicles, formed by AASM+SPC+CHOL, was established by monitoring their size, zeta potential and polydispersity index values over 100 days. Size and spherical morphology of hybrid vesicles were confirmed by transmission electron microscopic studies. Biocompatibility of the hybrid vesicles were established by cytotoxicity studies revealing their possible applications in drug delivery and imaging.
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| 9. |
- Barai, Manas, et al.
(författare)
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Theoretical Approaches on the Synergistic Interaction between Double‐Headed Anionic Amino Acid‐Based Surfactants and Hexadecyltrimethylammonium Bromide
- 2020
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Ingår i: Journal of Surfactants and Detergents (JSD). - : John Wiley & Sons. - 1097-3958 .- 1558-9293. ; 23:5, s. 891-902
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Tidskriftsartikel (refereegranskat)abstract
- Theoretical investigations on the micellization of mixtures of (i) amino acid-based anionic surfactants [AAS: N-dodecyl derivatives of aminomalonate, -aspartate, and -glutamate] and (ii) hexadecyltrimethylammonium bromide (HTAB), were carried out at different mole ratios. Variation in the theoretical values of critical micelle concentration (CMC), mole fraction of surfactants in the micellar phase (X), at the interface (X-sigma), interaction parameters at the bulk/interface (beta(R)/beta(sigma)), ideality/nonideality of the mixing processes, and activity coefficients (f) were evaluated using Rubingh, Rosen, Motomora, and Sarmoria-Puvvada-Blankschtein models. CMC values significantly deviate from the theroretically calculated values, indicating associative interaction. With increasing mole fraction of AAS (alpha(AAS)), the magnitude of the (beta(R)/beta(sigma)) values gradually decreased, considered to attributable to hydrophobic interactions. With increasing alpha(AAS), the micellar mole fraction of HTAB (X-2) decreased insignificantly and X-2 values were higher than those compared to AAS for all combinations, due to the dominance of HTAB in micelles. Micellar mole fraction at the ideal state of AAS (X1ideal) differed from micellar mole fraction of AAS (X-1), indicating nonideality in the mixed micellization process. Gibbs free energy of micellization ( increment G(m)) values are more negative than the free energy of micellization for ideal mixing ( increment Gmideal), indicating the micellization process is spontaneous. With increasing alpha(AAS), the enthalpy of micellization (Delta H-m) and entropy of micellization (Delta S-m) values gradually increased, which indicates micellization is exothermic. The different physicochemical parameters of the mixed micelles are correlated with the variation in the spacer length between the two carboxylate groups of AAS.
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| 10. |
- Dey, Subhamoy, et al.
(författare)
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Biosynthesis of Lantibiotics
- 2023. - 1
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Ingår i: Lantibiotics as Alternative Therapeutics. - : Academic Press. - 9780323991421 - 9780323991414 ; , s. 43-63
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Bokkapitel (refereegranskat)abstract
- In the last few decades, the prevalence of multidrug resistance and importunate virulence in bacteria emerged as one of the serious concerns in health-care system. Lantibiotics, the well-conserved antimicrobial peptides predominantly rich in atypical sulfur-containing amino acids, lanthionine (Lan), and 3-methyl-lanthionine (MeLan), synthesized ribosomally from bacterial cells and modified posttranslationally, have drawn considerable interest in the therapeutic management of infectious diseases because of their effectiveness against multidrug-resistant bacteria. So far studied, the other reasons remain their potency, broad-spectrum nature, and negligible cytotoxicity. The biosynthesis of the lantibiotics involves two major steps, the modification of precursor peptides and their proteolytic activation. The gene cluster constituting the biosynthetic machinery codes essentially for the prepeptide and modification enzymes besides the proteases, ATP-binding cassette transporters, immunity factors, and regulatory proteins required as accessory factors. Herein, in this chapter a comprehensive discussion has been made on the biosynthesis of lantibiotics, which may be noteworthy in biomedical science for technology advancement.
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