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James J.,CSIR - Central Leather Research Institute | James J.,Alphonsa College | Mandal A.B.,CSIR - Central Leather Research Institute
Colloids and Surfaces B: Biointerfaces | Year: 2011

The aggregation properties of Tyr-Phe dipeptide and Val-Tyr-Val tripeptide were studied in aqueous solution and in the presence of SDS and SDS-polymer environments using UV-visible, surface tension, fluorescence and circular dichroism (CD) techniques. Both the peptides formed micelles. The cmc values obtained for dipeptide and tripeptide are 2×10-5 and 4×10-5M, respectively in aqueous solution at 25°C. The presence of additives (SDS and polymer) hindered the micelle formation of peptides. The cmc values obtained by various methods are in good agreement with each other. Effect of peptides on the aggregation properties of SDS also was investigated. The cmc of SDS was decreased in presence of peptides and were reduced with increase in temperature. Using monophasic micellization concept, the association constant (KA) for the SDS-peptide mixed micellar systems was determined. Using biphasic model, the thermodynamic parameters viz; ΔG°m, ΔH°m and ΔS°m for SDS-water and SDS-peptide-water mixed micellar systems, the standard free energy for transfer of SDS from aqueous to peptide additive environments were estimated at various temperatures. These results suggest that the SDS is more stable in micellized form in the SDS-water-peptide ternary systems compared to the situation in the corresponding SDS-water binary systems. © 2011 Elsevier B.V.

James J.,CSIR - Central Leather Research Institute | James J.,Alphonsa College | Ramalechume C.,CSIR - Central Leather Research Institute | Ramalechume C.,Womens Christian College | Mandal A.B.,CSIR - Central Leather Research Institute
Colloids and Surfaces B: Biointerfaces | Year: 2011

Two-dimensional surface properties of PEO-PPO-PEO triblock copolymer film (Mol.Wt. 2800) in the absence and presence of Tyr-Phe dipeptide, Val-Tyr-Val tripeptide, sodium dodecylsulfate and stearic acid have been investigated for the first time at the air/water interface using Langmuir film balance technique. It is observed that the above polymer forms fairly stable film at the air/water interface. There are no significant changes observed in the surface pressure-area (π-. A) isotherms of polymer in the presence of SDS. However, more expanded film was formed in presence of SDS since the solubility of the polymer is more in SDS and the polymer network is disturbed in presence of SDS, which results in the increase in surface area of the polymer films. In the presence of dipeptide and tripeptide, the surface area of the polymer film decreased with a slight increase in the surface pressure indicating the binding of these peptides to polymer, which enhances the stability of the polymer film. Thermodynamic studies on the change in surface area (Δ. A) and excess free energy of mixing (ΔGmixE) associated with the formation of the mixed film suggest the occurrence of a thermodynamically unstable mixed film. The presence of SDS slightly decreases the formation of mixed film of stearic acid with triblock copolymer and peptides due to the solubilization of these compounds in SDS. However, the hydrophobicity of the polymer films increases in the presence of stearic acid, leading to the increase in surface pressure. The positive deviation of Δ. A and the positive ΔGmixE values show the non-ideality and incompatibility of thermodynamically unstable mixed films. The thermodynamic results suggest that the stability and compatibility of the polymer, peptides and their mixed films with stearic acid in the presence of SDS are decreased, which is in good agreement with the results obtained for other polymeric systems. © 2010 Elsevier B.V.

James J.,CSIR - Central Leather Research Institute | James J.,Alphonsa College | Mandal A.B.,CSIR - Central Leather Research Institute
Journal of Colloid and Interface Science | Year: 2011

The micelle formation of Tyr-Phe dipeptide and Val-Tyr-Val tripeptide has been studied for the first time. The aggregation numbers were determined for both the peptides in aqueous solution and in the presence of SDS and PEO-PPO-PEO triblock copolymer additive environments. The results obtained by steady state and time-resolved fluorescence spectroscopic techniques are in good agreement with each other. The higher value of aggregation number confirms the formation of mixed micelles. The fluorescence lifetime of tyrosine in various micellar and mixed micellar systems were also determined. The decreased lifetime values with the quencher suggested the dynamic nature of the quenching process. However, the possibility of static quenching cannot be ruled out. The accessibility of DPC quencher was found to be more in dipeptide than tripeptide. © 2011 Elsevier Inc.

Joseph P.V.,Kuriakose Elias College | Jacob C.,Alphonsa College
Asian Journal of Chemistry | Year: 2010

A short term, baseline study was undertaken to determine the occurrence of microbial pollution in the Pennar river. Four stations were selected for study on the basis of land use pattern. Bacteriological, fungal and algal examinations were made and the results obtained showed that 8 species of bacteria isolated were opportunistic pathogens and total coliform count ranged from 460-2400/100 mL, thus making the water unsafe to drink unless treated properly. Fecal pollution from non human and human source is one of the major factors that contribute to the degradation of water quality and that restrict its use. Four fungal species were identified which are also opportunistic pathogens. In the present study about 36 different genera comprising 61 species of algae were idetified. High pollution tolerant species like Scenedesmus. Coelastrum, Oscillatoria, Nitzchia paella, Ankistrodesmus, Anabaena, Synedra and Navicula were present in different sites of Pennar river especially in the site I which is highly populated. High socioanthropological activities, clogging of water body due to weeds and agricultural practices in the basins were identified as a contributory factors to the situation.

Mukherjee S.,Inter-University Center for Astronomy and Astrophysics | Das S.,Inter-University Center for Astronomy and Astrophysics | Joy M.,Alphonsa College | Souradeep T.,Inter-University Center for Astronomy and Astrophysics
Journal of Cosmology and Astroparticle Physics | Year: 2015

Cosmic Microwave Background (CMB) is an important probe for understanding the inflationary era of the Universe. We consider the Perturbed Power Law (PPL) model of inflation which is a soft deviation from Power Law (PL) inflationary model. This model captures the effect of higher order derivative of Hubble parameter during inflation, which in turn leads to a non-zero effective mass meff for the inflaton field. The higher order derivatives of Hubble parameter at leading order sources constant difference in the spectral index for scalar and tensor perturbation going beyond PL model of inflation. PPL model have two observable independent parameters, namely spectral index for tensor perturbation νt and change in spectral index for scalar perturbation νst to explain the observed features in the scalar and tensor power spectrum of perturbation. From the recent measurements of CMB power spectra by WMAP, Planck and BICEP-2 for temperature and polarization, we estimate the feasibility of PPL model with standard ΛCDM model. Although BICEP-2 claimed a detection of r=0.2, estimates of dust contamination provided by Planck have left open the possibility that only upper bound on r will be expected in a joint analysis. As a result we consider different upper bounds on the value of r and show that PPL model can explain a lower value of tensor to scalar ratio (r<0.1 or r<0.01) for a scalar spectral index of ns=0.96 by having a non-zero value of effective mass of the inflaton field m2 eff/H2. The analysis with WP + Planck likelihood shows a non-zero detection of m2 eff/H2 with 5.7 σ and 8.1 σ respectively for r<0.1 and r<0.01. Whereas, with BICEP-2 likelihood m2 eff/H2 = -0.0237 ± 0.0135 which is consistent with zero. © 2015 IOP Publishing Ltd and Sissa Medialab srl .

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