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Fathima N.N.,CSIR - Central Leather Research Institute | Dhathathreyan A.,CSIR - Central Leather Research Institute | Ramasami T.,New Mehrauli Road
Journal of Chemical Sciences | Year: 2010

The effect of additives like curcumin and surfactants on the self-assembly of collagen from a simple 2-dimensional system of Langmuir films of the protein at air/solution interface has been attempted in this study using quartz crystal microbalance (QCM) and dynamic surface tensiometer. Though pure curcumin is not surface active, a synergistic effect of collagen with curcumin seems to lead to enhanced surface activity in the protein. In general, the presence of additives, increases the surface activity of collagen even for the lowest concentration and the largest change in surface activity is seen for collagen with sodium dodecyl sulfate (SDS). The results suggest interplay between the unexposed hydrophobic groups, and the opening out and solvation of the more charged or polar groups at the surface leading to aggregation followed by self-assembly. Modulation of aggregation at interface in collagen due to these additives may be an approach that could be explored for possible applications in bio-materials and for delivery of protein-drug complexes. © Indian Academy of Sciences.

Katyal N.,University of Delhi | Chitkara N.,University of Delhi | Roy A.,New Mehrauli Road | Kapoor A.,University of Delhi
Journal of Optics (India) | Year: 2012

This theoretical study is about generation of two higher order diffraction beams by considering off-Bragg diffraction in an optically active, absorptive photorefractive crystal of 23 symmetry in diffusion regime. This study has been done via two-wave mixing in transmission geometry in Bismuth Titanium Oxide (BTO) crystal. Effect of input beam polarization state and off-Bragg parameter has been studied on the output beam intensities. It has been observed that the off-Bragg parameter should be optimized to a low value for coupling significant energy to the higher order beams. It has also been observed that by varying input polarization angle of pump beam, the properties of output higher order beams such as amplitude, polarization can be modified. This feature can be utilized in optical beam splitter and optical interconnects etc. © Optical Society of India 2012.

Katyal N.,University of Delhi | Natasha,University of Delhi | Roy A.,New Mehrauli Road | Kapoor A.,University of Delhi
Optik | Year: 2013

Generation of two higher-order diffraction beams in two-wave mixing in transmission geometry have been analyzed theoretically in photorefractive cubic crystal of 23 symmetry, BSO (Bismuth Silicon Oxide) and considering its optical activity as one of the important parameter. Results are shown graphically by solving coupled wave equations using fourth-order Runge-Kutta method. The effect of polarization state of pump beam, optical activity, off-Bragg parameter, coupling coefficients, absorption and thickness of crystal has been analyzed on the beam intensities and their respective polarizations. It has been observed that as the value of the off-Bragg parameter reduces the transfer of energy to the higher-order beams increases. It has been also observed that by selecting proper input beam polarization and crystal thickness, diffracted beam intensity and its polarization could be controlled considerably. It has also been seen that by controlling input pump beam polarization, particular higher-order beam can be selectively amplified. © 2011 Elsevier GmbH. All rights reserved.

Katyal N.,University of Delhi | Natasha,University of Delhi | Roy A.,New Mehrauli Road | Kapoor A.,University of Delhi
Optik | Year: 2011

Two-wave mixing (TWM) in transmission geometry of photorefractive (PR) crystals of 23 symmetry such as BSO, BGO is investigated by solving a set of coupled wave equations and taking their optical activity as one of the effective parameter. Coupled wave equations are solved numerically by fourth order Runge-kutta method and results are presented in graphical form. The effects of various parameters such as crystal thickness, optical activity, coupling coefficient, absorption, and input polarization angle of pump beam has been studied on the input beam polarization components. It has been observed that by varying the behaviour of pump beam polarization, signal beam can be modified. This can be used in various applications such as spatial light modulation and optical information processing, etc. © 2010 Published by Elsevier GmbH.

Singam E.R.A.,CSIR - Central Leather Research Institute | Balamurugan K.,CSIR - Central Leather Research Institute | Gopalakrishnan R.,CSIR - Central Leather Research Institute | Subramanian S.R.,CSIR - Central Leather Research Institute | And 2 more authors.
Biopolymers | Year: 2012

A systematic molecular dynamics (MD) simulation has been carried out on collagen-like peptides with different combinations of interruptions in the Gly-X AA-Y AA repeats. Although experimental studies have been carried out to elucidate the structural consequences of homotrimeric collagen-like peptides, this is the first report on the structural effect on the heterotrimeric models with G4G and G1G breaks present simultaneously in the constituent chains with difference in one residue chain staggering. The results reveal that the axial registry of the interrupted region changes significantly from that of conventional triple helical peptide without interruption. Further, results from MD simulations show the formation of a kink in the interrupted region of the triple-helical peptides. The conformational analysis reveals that the interruption in the Gly-X AA-Y AA pattern in these peptides induces β-strand conformation in triple helical peptides. The conventional hydrogen bonds in the interrupted triad are affected and new nonconventional H-bonds are formed in the triple helical structure, and as a result interrupted region becomes locally fragile. MM-PBSA calculations on the different systems clearly suggest that the binding affinity varies marginally due to one residue staggering. However, it is found from the structural parameters that hydrogen-bonding pattern differs significantly due to the difference in the staggering of chains. Copyright © 2012 Wiley Periodicals, Inc.

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