Kumaran G. Sreejalekshmi

ADSORPTION OF PB(II) AND PB(II)-CITRIC ACID ON SAWDUST ACTIVATED CARBON: KINETIC AND EQUILIBRIUM ISOTHERM STUDIES

The removal of Pb(II) and Pb(II)-citric acid (Pb(II)-CA) from aqueous solutions by sawdust activated carbon (SDAC) was investigated. The higher adsorptive removal of Pb(II) from aqueous solutions containing Pb(II)-CA than Pb(II) only was observed due to the presence of CA in the former system. The mechanism of adsorption process was studied by conducting pH as well as kinetic studies. Batch adsorption experiments were conducted to study the effect of adsorbent dose, initial concentration and temperature for the removal of Pb(II) from Pb(II) only and Pb(II)-CA aqueous systems. The adsorption was maximum for the initial pH in the range of 6.5-8.0 and 2.0-5.0 for Pb(II) and Pb(II)-CA, respectively. The solution pH, zero point charge (pH(zpc)) and species distribution of Pb(II) and Pb(II)-CA were found to play an important role in the adsorption of Pb(II) and Pb(II)-CA onto SDAC from water and wastewaters. SDAC exhibited very high adsorption potential for Pb(II) ions in presence of CA than when Pb(II) ions alone were present. The kinetic and equilibrium adsorption data were well modeled using pseudo-first-order kinetics and Langmuir isotherm model, respectively.

Nickel(II) adsorption onto biomass based activated carbon obtained from sugarcane bagasse pith

Bioavailability of Nickel in the form of hydrated Nickel(II) attributes to its toxicological effects and hence its removal from aqueous solution is of great concern. Adsorption is used as an efficient technique for the removal of Nickel(II), hereafter Ni(II), from water and wastewaters. Activated carbon obtained from sugarcane bagasse pith (SBP-AC), a waste biomass collected from juice shops in Sarkara Devi Temple, Chirayinkeezhu, Trivandrum, India during annual festival, is used as adsorbent in the study. The process of adsorption is highly dependent on solution pH, and maximum removal occurs in the pH range of 4.0-8.0. Moreover, the amount of Ni(II) adsorbed onto SBP-AC increased with the time increase and reached equilibrium at 4h. Adsorption kinetic and equilibrium data were analyzed for determining the best fit kinetic and isotherm models. The overall study reveals the potential value of steam pyrolysed SBP-AC as a possible commercial adsorbent in wastewater treatment strategies.

Biomimeticity in tissue engineering scaffolds through synthetic peptide modifications-altering chemistry for enhanced biological response.

Biomimetic and bioactive biomaterials are desirable as tissue engineering scaffolds by virtue of their capability to mimic natural environments of the extracellular matrix. Biomimeticity has been achieved by the incorporation of synthetic short peptide sequences into suitable materials either by surface modification or by bulk incorporation. Research in this area has identified several novel synthetic peptide segments, some of them with cell-specific interactions, which may serve as potential candidates for use in explicit tissue applications. This review focuses on the developments and prospective directions of incorporating short synthetic peptide sequences onto scaffolds for tissue engineering, with emphasis on the chemistry of peptide immobilization and subsequent cell responses toward modified scaffolds. The article provides a decision-tree-type flow chart indicating the most probable cellular events on a given peptide-modified scaffold along with the consolidated list of synthetic peptide sequences, supports as well as cell types used in various tissue engineering studies, and aims to serve as a quick reference guide to peptide chemists and material scientists interested in the field.

4-Amino-5-benzoyl-2-(4-methoxyphenylamino)thiazole (DAT1): a cytotoxic agent towards cancer cells and a probe for tubulin-microtubule system

1 Microtubule binding drugs are of special interest as they have important roles in the modulation of cellular functions and many of them act as anticancer agents. 4‐Amino‐5‐benzoyl‐2‐(4‐methoxyphenylamino)thiazole (DAT1) was identified as one of the active compounds from a series of diaminoketothiazoles in a cell‐based screening assay to discover cytotoxic compounds. 2 DAT1 shows cytotoxicity with GI50 values ranging from 0.05 to 1 μM in different malignant cell lines with an average value of 0.35 μM. It blocks mitosis in the prometaphase and metaphase stages. In HeLa cells, DAT1 blocks the spindle function by disturbing spindle microtubule and chromosome organization. 3 The drug also inhibits assembly of brain microtubules and binds tubulin specifically at a single site with induction of fluorescence. The dissociation constant of DAT1 binding to tubulin was determined as 2.9±1 μM at 24°C. The binding site of DAT1 on tubulin overlaps with that of the conventional colchicine‐binding site. 4 DAT1 can thus be considered as a lead compound of a new class of small molecules and this study can be used as a step to develop potent antimitotic agents for the control of cytoskeletal functions and cell proliferation. It would also be an interesting probe for the structure–function studies of tubulin–microtubule system.

Evaluation of adsorption properties of sulphurised activated carbon for the effective and economically viable removal of Zn(II) from aqueous solutions.

The prospective application of sulphurised activated carbon (SAC) as an ecofriendly and cost-effective adsorbent for Zinc(II) removal from aqueous phase is evaluated, with an emphasis on kinetic and isotherm aspects. SAC was prepared from sugarcane bagasse pith obtained from local juice shops in Sree Bhadrakali Devi Temple located at Ooruttukala, Neyyattinkara, Trivandrum, India during annual festive seasons. Activated carbon modified with sulphur containing ligands was opted as the adsorbent to leverage on the affinity of Zn(II) for sulphur. We report batch-adsorption experiments for parameter optimisations aiming at maximum removal of Zn(II) from liquid-phase using SAC. Adsorption of Zn(II) onto SAC was maximum at pH 6.5. For initial concentrations of 25 and 100mgL(-1), maximum of 12.3mgg(-1) (98.2%) and 23.7mgg(-1) (94.8%) of Zn(II) was adsorbed onto SAC at pH 6.5. Kinetic and equilibrium data were best described by pseudo-second-order and Langmuir models, respectively. A maximum adsorption capacity of 147mgg(-1) was obtained for the adsorption of Zn(II) onto SAC from aqueous solutions. The reusability of the spent adsorbent was also determined.

Adsorptive removal of 2,4-dinitrophenol using active carbon: kinetic and equilibrium modeling at solid–liquid interface

AbstractAdsorption is found to be a feasible technique for the removal of even trace amounts 2,4-dinitrophenol (2,4-DNP) from aqueous phase using active carbon from rubber wood. Prior to adsorption studies, surface and physical properties of active carbon were determined using X-RD, FT-IR, and particle size analyzer. Batch adsorption experiments were carried out to optimize various conditions, such as solution pH, contact time, initial solute concentration, and adsorbent dose, for the effective removal of 2,4-DNP from aqueous phase. The favorable pH range for the adsorption process was found to be 2.0–5.0. The maximum adsorption of 99.9% (24.98 mg/g), 98.2% (49.10 mg/g) and 96.9% (96.89 mg/g) of 2,4-DNP onto active carbon was observed at pH 4.0 for different initial concentrations of 50, 100, and 200 mg/L, respectively. Kinetics and isotherm studies showed that the adsorptive removal process follows pseudo-second-order kinetics and Langmuir isotherm, respectively.

Expanding the donor–acceptor toolbox with a minimal 5-(thiophen-2-yl)-1,3-thiazole core: transition metal-free synthesis and molecular design for HOMO–LUMO energy modulations

Synthesis of a minimal 5-(thiophen-2-yl)-1,3-thiazole core through a transition metal-free, versatile [4+1] route is reported. DFT calculations on a prototype library of D–A–D–A tetrads established the exquisite HOMO–LUMO energy modulation by varying peripheral D/A groups. Our results indicate the vast scope of this novel core in molecular engineering of materials for optoelectronics.

Enriching biologically relevant chemical space around 2-aminothiazole template for anticancer drug development

Combinatorial library based on a biologically relevant core template, 2-aminothiazole, with immense scope of diversity multiplication was designed for anticancer therapeutics. The diversity elements were incorporated through azomethine linkage on C4 hydrazine terminus in 5-benzoyl-2-arylamino-1,3-thiazole using isopropyl, isobutyl, cyclohexyl, and benzyl fragments and enrichment of chemical space therein was evaluated. Molecular docking of an in-house 200-member virtual library in anticancer target proteins- estrogen receptor (3ERT), cyclin dependent kinase (3FDN), and Aurora kinase (3LAU), identified selective binding of the compounds as ATP competitive inhibitors of 3LAU. The synthetic access to the compounds was realized through a facile and economically viable [4 + 1] ring synthesis strategy employing commercially available reagents. The in vitro cytotoxicity of selected members against human cancer cell lines indicated the potential of the designed scaffold in anticancer drug discovery, where compounds 2b, 3b, and 4b were found to be active against MCF-7 and A549 cell lines in less than ten micro molar concentrations. Moreover the predicted physicochemical properties pointed to the drug appropriateness for most of these molecules, that they obey the rule of five (RO5). Thus we present 2-alkyl/arylamino-4-alkylidene/arylidenehydrazino-5-benzoyl-1,3-thiazoles as a prospective and expandable skeleton for diversity oriented synthesis and in the discovery of selective Aurora kinase inhibitors.

Fluorophores based on a minimal thienylthiazole core: towards multifunctional materials with solid state red emissions, solvatochromism and AIE behaviour

We introduce 5-(thiophen-2-yl)-1,3-thiazole [5-TPTZ] as a novel core for the design of luminescent organic materials. Donor–acceptor–donor–acceptor (D–A–D–A) tetrads based on [5-TPTZ] exhibited solid state red emission, positive solvatochromism, large Stokes shift, and aggregation induced emission (AIE) behaviour. The observed photophysical properties of these multifunctional materials were elucidated by crystal structure analysis, computational studies and molecular dynamics (MD) simulations.

Propeller-shaped molecules with a thiazole hub: structural landscape and hydrazone cap mediated tunable host behavior in 4-hydrazino-1,3-thiazoles

Propeller-shaped molecules with 2,4,5-trisubstituted-1,3-thiazole as the hub and tunable blades (B1–B3) were synthesized as trivariant scaffolds. B1–B3 were modulated by varying the hydrazone capping in B1, the isothiocyanate in B2 and the α-haloketone in B3 and the structural landscapes examined. Multicomponent molecular crystals formed nitrogen rich channels (NRCs) of varied shapes and dimensions which were largely steered by the substitution pattern in B1 and established by varying carbonyl components. Isopropylidene derivatives (IPHAT) stabilized single file water inside the NRC (~34 A2) between B1 and B2, benzylidene derivatives (BzHAT) formed a constricted NRC and accommodated solvates inside a hydrophobic cavity between B1 and B3 whereas a pincer-shaped NRC devoid of guest molecules was formed by cyclohexylidene derivatives (CyHAT). The hydrazone substituent-driven variation in solid state landscapes indicates a wide scope of expandability of these thiazole templates as supramolecular synthons for tunable hosts.