The biological activity of the immobilized enzyme is crucial for the performance of different nan... more The biological activity of the immobilized enzyme is crucial for the performance of different nanoparticle mediated enzymatic assays, where enzymatic conversion can be used for label-free analyte detection. In this article we have addressed two significant aspects of enzyme-nanoparticle interactions. First, we have developed copper sulfide (CuS) nanoparticles with an average diameter of 25 nm as a potential enzyme-interface using trypsin protease as a model enzyme. CuS nanoparticles showed high trypsin immobilization capacity of about 14.0 mg m(-2) with the significant retention of native enzymatic activity (75-98%) at room temperature, even beyond the calculated tightly packed monolayer coverage (which is around 4.1 mg m(-2)). Second, we report a quantitative correlation between the structure-functional relationship and the density of immobilized trypsin on a nanoparticle surface. The in situ conformation of immobilized trypsin could be efficiently analyzed by fluorescence, circular dichroism and FT-IR spectroscopic measurements because of the small size of the nanoparticles. Trypsin molecules appear to retain their close-native tertiary and secondary structural features (with a small loss of 1-2% of helical content) in the entire surface density range (2.0-14.0 mg m(-2)) on the CuS nanoparticles. However, interestingly, at a low surface coverage (2.0 mg m(-2)), immobilized trypsin retains almost 98% of its native enzymatic activity, leading to a highly functional bio-nanocomposite. However, at higher surface coverages, the enzyme activity decreases to 77%, indicating the influence of steric crowding. Furthermore, the high functionality of the immobilized trypsin at low surface density on CuS nanoparticle was also confirmed by determining the kinetic parameters of enzymatic activity.
ABSTRACT We have demonstrated an efficacious approach for tuning the selective adsorption of hen ... more ABSTRACT We have demonstrated an efficacious approach for tuning the selective adsorption of hen egg white lysozyme (HEWL) and bovine serum albumin (BSA) on the same carboxylate modified surface at different pH values. A basic alumina surface has been modified with trimesic acid to generate a carboxylated surface, and it has been used for the first time in differential protein interaction studies. We have found that very simple surface chemistry can be utilized for the controlled and selective adsorption of both proteins as a function of pH, which leads to the preferential binding of lysozyme over BSA at physiological pH 7.4. Significantly, we achieve a high retention of the enzymatic activity of the adsorbed lysozyme (98% of that of the native enzyme) at lower surface coverage, which also persists in different harsh conditions. In-depth conformational analysis revealed that selectively adsorbed lysozyme was partially unfolded but mostly retained its secondary structural content. In addition, we have also proposed an explanation of the possible interaction behaviour of the carboxylated surface with BSA and lysozyme molecules with the help of surface potential analysis, which provides an in-depth understanding of differential protein interaction.
ABSTRACT Morphosynthesis and stabilization of pure framboidal vaterite microspheres using a salic... more ABSTRACT Morphosynthesis and stabilization of pure framboidal vaterite microspheres using a salicylic acid–aniline dye as an additive has been reported in this paper. Formation and stabilization of vaterite crystals could be regulated by changing the dye concentration. Calcite rhombohedra were predominant species when no additive was added. As the concentration of dye was increased vaterite was more pronounced in the solution leading to the formation of pure framboidal vaterite (98% at 10 mM dye concentration). The size of these microspheres varied from 0.5 to 4.0 μm. Various instrumental analysis has been incorporated to study the dynamics of phase transformation throughout the process. Detailed analysis of TEM images reveals that vaterite microspheres were in turn aggregates of small vaterite nanospheres. The vaterite microspheres were stable up to a week in solution. The dissolution of the vaterite crystals to calcite was arrested by the presence of the dye at the nucleation process. The stability of the vaterite may be attributed to the strong electrostatic interaction of the Ca ions present on the surface of the crystal with the –COOH group of the dye. This finding opens up a new domain of organic additives to explore.
Journal of Environmental Chemical Engineering, 2013
ABSTRACT The ability of the Malachite nanoparticles (NPs) for differential adsorption of dye with... more ABSTRACT The ability of the Malachite nanoparticles (NPs) for differential adsorption of dye with differential functionality was explored. Fluorescein (with COOH and OH), Rhodamine B (with COOH) and Rhodamine 6G each having same xanthene moiety but differing in their functionality was taken for the study. Fluorescein was adsorbed more followed by other two dyes at pH ∼ 7. Electrostatic interaction was sought to play a major role in the adsorption process. Batch studies were conducted to evaluate the effects of regulating parameters viz. contact time, temperature, adsorbent dosage, and solution pH. Experimental results showed that a steady state was achieved at ∼6 h after which the adsorption seemed constant for all the three dyes. Temperature range of 10-40 C was taken for the study and the adsorption was found to increase with the temperature. The concentration of dye was varied from 10 to 500 mg L -1 and the maximum adsorption was obtained for Flu with qe value ∼29.54 mg g-1 followed by RB qe value ∼20.74 mg g-1. R6G was least adsorbed with qe value ∼6.4 mg g-1. The experimental data found to follow the Langmuir isotherm preferentially and followed second order kinetics. Furthermore effective desorption was carried out using 50% ethanol. Flu was desorbed to ∼99.5% whereas complete extraction of RB and R6G were obtained. The multi-cycle efficiency was also investigated. Overall, the work substantiates the possible use of Malachite NPs as an effective adsorbent for removal of dye from aqueous solution.
The iron oxide nanoparticles, having an average size of 20−40 nm with a surface area of 70 m 2 g ... more The iron oxide nanoparticles, having an average size of 20−40 nm with a surface area of 70 m 2 g −1 , have been synthesized and used for selective adsorption of various dyes (selectively containing hydroxyl groups) from aqueous solution. The nanoparticles are ferromagnetic ...
Malachite nanoparticles of 100-150 nm have been efficiently and for the first time used as an ads... more Malachite nanoparticles of 100-150 nm have been efficiently and for the first time used as an adsorbent for the removal of toxic arsenate and chromate. We report a high adsorption capacity for chromate and arsenate on malachite nanoparticle from both individual and mixed solution in pH ∼4-5. However, the adsorption efficiency decreases with the increase of solution pH. Batch studies revealed that initial pH, temperature, malachite nanoparticles dose and initial concentration of chromate and arsenate were important parameters for the adsorption process. Thermodynamic analysis showed that adsorption of chromate and arsenate on malachite nanoparticles is endothermic and spontaneous. The adsorption of these anions has also been investigated quantitatively with the help of adsorption kinetics, isotherm, and selectivity coefficient (K) analysis. The adsorption data for both chromate and arsenate were fitted well in Langmuir isotherm and preferentially followed the second order kinetics. The binding affinity of chromate is found to be slightly higher than arsenate in a competitive adsorption process which leads to the comparatively higher adsorption of chromate on malachite nanoparticles surface.
The biological activity of the immobilized enzyme is crucial for the performance of different nan... more The biological activity of the immobilized enzyme is crucial for the performance of different nanoparticle mediated enzymatic assays, where enzymatic conversion can be used for label-free analyte detection. In this article we have addressed two significant aspects of enzyme-nanoparticle interactions. First, we have developed copper sulfide (CuS) nanoparticles with an average diameter of 25 nm as a potential enzyme-interface using trypsin protease as a model enzyme. CuS nanoparticles showed high trypsin immobilization capacity of about 14.0 mg m(-2) with the significant retention of native enzymatic activity (75-98%) at room temperature, even beyond the calculated tightly packed monolayer coverage (which is around 4.1 mg m(-2)). Second, we report a quantitative correlation between the structure-functional relationship and the density of immobilized trypsin on a nanoparticle surface. The in situ conformation of immobilized trypsin could be efficiently analyzed by fluorescence, circular dichroism and FT-IR spectroscopic measurements because of the small size of the nanoparticles. Trypsin molecules appear to retain their close-native tertiary and secondary structural features (with a small loss of 1-2% of helical content) in the entire surface density range (2.0-14.0 mg m(-2)) on the CuS nanoparticles. However, interestingly, at a low surface coverage (2.0 mg m(-2)), immobilized trypsin retains almost 98% of its native enzymatic activity, leading to a highly functional bio-nanocomposite. However, at higher surface coverages, the enzyme activity decreases to 77%, indicating the influence of steric crowding. Furthermore, the high functionality of the immobilized trypsin at low surface density on CuS nanoparticle was also confirmed by determining the kinetic parameters of enzymatic activity.
ABSTRACT We have demonstrated an efficacious approach for tuning the selective adsorption of hen ... more ABSTRACT We have demonstrated an efficacious approach for tuning the selective adsorption of hen egg white lysozyme (HEWL) and bovine serum albumin (BSA) on the same carboxylate modified surface at different pH values. A basic alumina surface has been modified with trimesic acid to generate a carboxylated surface, and it has been used for the first time in differential protein interaction studies. We have found that very simple surface chemistry can be utilized for the controlled and selective adsorption of both proteins as a function of pH, which leads to the preferential binding of lysozyme over BSA at physiological pH 7.4. Significantly, we achieve a high retention of the enzymatic activity of the adsorbed lysozyme (98% of that of the native enzyme) at lower surface coverage, which also persists in different harsh conditions. In-depth conformational analysis revealed that selectively adsorbed lysozyme was partially unfolded but mostly retained its secondary structural content. In addition, we have also proposed an explanation of the possible interaction behaviour of the carboxylated surface with BSA and lysozyme molecules with the help of surface potential analysis, which provides an in-depth understanding of differential protein interaction.
ABSTRACT Morphosynthesis and stabilization of pure framboidal vaterite microspheres using a salic... more ABSTRACT Morphosynthesis and stabilization of pure framboidal vaterite microspheres using a salicylic acid–aniline dye as an additive has been reported in this paper. Formation and stabilization of vaterite crystals could be regulated by changing the dye concentration. Calcite rhombohedra were predominant species when no additive was added. As the concentration of dye was increased vaterite was more pronounced in the solution leading to the formation of pure framboidal vaterite (98% at 10 mM dye concentration). The size of these microspheres varied from 0.5 to 4.0 μm. Various instrumental analysis has been incorporated to study the dynamics of phase transformation throughout the process. Detailed analysis of TEM images reveals that vaterite microspheres were in turn aggregates of small vaterite nanospheres. The vaterite microspheres were stable up to a week in solution. The dissolution of the vaterite crystals to calcite was arrested by the presence of the dye at the nucleation process. The stability of the vaterite may be attributed to the strong electrostatic interaction of the Ca ions present on the surface of the crystal with the –COOH group of the dye. This finding opens up a new domain of organic additives to explore.
Journal of Environmental Chemical Engineering, 2013
ABSTRACT The ability of the Malachite nanoparticles (NPs) for differential adsorption of dye with... more ABSTRACT The ability of the Malachite nanoparticles (NPs) for differential adsorption of dye with differential functionality was explored. Fluorescein (with COOH and OH), Rhodamine B (with COOH) and Rhodamine 6G each having same xanthene moiety but differing in their functionality was taken for the study. Fluorescein was adsorbed more followed by other two dyes at pH ∼ 7. Electrostatic interaction was sought to play a major role in the adsorption process. Batch studies were conducted to evaluate the effects of regulating parameters viz. contact time, temperature, adsorbent dosage, and solution pH. Experimental results showed that a steady state was achieved at ∼6 h after which the adsorption seemed constant for all the three dyes. Temperature range of 10-40 C was taken for the study and the adsorption was found to increase with the temperature. The concentration of dye was varied from 10 to 500 mg L -1 and the maximum adsorption was obtained for Flu with qe value ∼29.54 mg g-1 followed by RB qe value ∼20.74 mg g-1. R6G was least adsorbed with qe value ∼6.4 mg g-1. The experimental data found to follow the Langmuir isotherm preferentially and followed second order kinetics. Furthermore effective desorption was carried out using 50% ethanol. Flu was desorbed to ∼99.5% whereas complete extraction of RB and R6G were obtained. The multi-cycle efficiency was also investigated. Overall, the work substantiates the possible use of Malachite NPs as an effective adsorbent for removal of dye from aqueous solution.
The iron oxide nanoparticles, having an average size of 20−40 nm with a surface area of 70 m 2 g ... more The iron oxide nanoparticles, having an average size of 20−40 nm with a surface area of 70 m 2 g −1 , have been synthesized and used for selective adsorption of various dyes (selectively containing hydroxyl groups) from aqueous solution. The nanoparticles are ferromagnetic ...
Malachite nanoparticles of 100-150 nm have been efficiently and for the first time used as an ads... more Malachite nanoparticles of 100-150 nm have been efficiently and for the first time used as an adsorbent for the removal of toxic arsenate and chromate. We report a high adsorption capacity for chromate and arsenate on malachite nanoparticle from both individual and mixed solution in pH ∼4-5. However, the adsorption efficiency decreases with the increase of solution pH. Batch studies revealed that initial pH, temperature, malachite nanoparticles dose and initial concentration of chromate and arsenate were important parameters for the adsorption process. Thermodynamic analysis showed that adsorption of chromate and arsenate on malachite nanoparticles is endothermic and spontaneous. The adsorption of these anions has also been investigated quantitatively with the help of adsorption kinetics, isotherm, and selectivity coefficient (K) analysis. The adsorption data for both chromate and arsenate were fitted well in Langmuir isotherm and preferentially followed the second order kinetics. The binding affinity of chromate is found to be slightly higher than arsenate in a competitive adsorption process which leads to the comparatively higher adsorption of chromate on malachite nanoparticles surface.
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Papers by Jiban Saikia