Qualification: 
Ph.D
sobhavn@am.amrita.edu

Dr. Sobha V. Nair currently serves as Associate Professor at the School of Biotechnology. Ph. D. in Chemistry(Polymer Technology), MG University in 2006. Dr. Nair joins us from PES-IT, Bangalore.

Awards and Scholarships

  • Research Fellow, Polymer Interface & Adhesion Laboratory, POSTECH, S. Korea (Aug 2003)
  • DST-DAAD Fellow, Institut fuer Verbundwerkstoffe GmbH, Technical University of Kaiserslautern, Germany (Mar 2002)
  • Young Scientist Award, Indian Science Congress 2003, Bangalore, India
  • Best Presentation Award, TATHVA 2003, National Conference held at National Institute of Technology, Calicut
  • CSIR Senior Research Fellowship
  • Qualified Graduate Aptitude Test in Engineering(GATE)

Teaching

Research Interests

  • Bioconjugate Chemistry: Protein Chemistry, Chemical Conjugates and their applications
  • Molecular Recognition
  • Polymer Blends: Reactive compatibilization, Morphology, Mechanical, Dynamic mechanical, Thermal and Rheological properties

Publications

Publication Type: Journal Article

Year of Publication Title

2020

Drishya G., Dr. Jyotsna Nambiar, Sanu K. Shaji, Muralidharan Vanuopadath, A., A., Abishek, K., Ashna, A., Ayesha Sherif, Catherine Joseph, Divya P., Damu Sunilkumar, Chinchu Bose, Dr. Sobha V. Nair, S. Sudarslal, Dr. Geetha Kumar, S., L., and Dr. Bipin G. Nair, “RECK and TIMP-2 mediate inhibition of MMP-2 and MMP-9 by Annona muricata”, Journal of Biosciences, vol. 45, no. 1, p. 89, 2020.[Abstract]


Up-regulation of MMP-2 and MMP-9 plays a significant role in promoting cancer progression by degrading the components of the extracellular matrix, thereby enhancing the migration of tumor cells. Although the anti-proliferative and apoptotic effect of Annona muricata is well established, its effect on MMP-2 and MMP-9, a major target in several types of cancers, has not been studied. Powdered samples of various parts of A. muricata like fruit, stem, seed, and twig extracted using aqueous methanol showed significant dose-dependent inhibition of MMP-2 and MMP-9 in a highly metastatic fibrosarcoma cell line, HT1080. Additionally, these extracts also up-regulated the expression of several endogenous inhibitors of MMP-2 and MMP-9 like REversion-inducing Cysteine-rich protein with Kazal motifs (RECK) and Tissue Inhibitor of Metalloproteinase-2 (TIMP-2). Furthermore, primary cells developed from tumor tissues obtained from patients not exposed to chemotherapy, also exhibited similar results. Remarkably, the inhibition of MMP-2 and MMP-9 observed was tumor specific, with the A. muricata fruit extract showing only 2% inhibition in cells obtained from normal tissues, when compared to 60% inhibition observed in cells obtained from tumor samples. The present study elucidates a novel mechanism by which A. muricata extracts selectively exhibit their anti-cancer activity in tumor cells by down-regulating MMP-2 and MMP-9 that are important biomarkers in cancer.

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2018

K. R. Raghi, Sherin, D. R., Saumya, M. J., Arun, P. S., Dr. Sobha V. Nair, and Manojkumar, T. K., “Computational study of molecular electrostatic potential, docking and dynamics simulations of gallic acid derivatives as ABL inhibitors.”, Comput Biol Chem, vol. 74, pp. 239-246, 2018.[Abstract]


Chronic myeloid leukemia (CML), a hematological malignancy arises due to the spontaneous fusion of the BCR and ABL gene, resulting in a constitutively active tyrosine kinase (BCR-ABL). Pharmacological activity of Gallic acid and 1,3,4-Oxadiazole as potential inhibitors of ABL kinase has already been reported. Objective of this study is to evaluate the ABL kinase inhibitory activity of derivatives of Gallic acid fused with 1,3,4-Oxadiazole moieties. Attempts have been made to identify the key structural features responsible for drug likeness of the Gallic acid and the 1,3,4-Oxadiazole ring using molecular electrostatic potential maps (MESP). To investigate the inhibitory activity of Gallic acid derivatives towards the ABL receptor, we have applied molecular docking and molecular dynamics (MD) simulation approaches. A comparative study was performed using Bosutinib as the standard which is an approved CML drug acting on the same receptor. Furthermore, the novel compounds designed and reported here in were evaluated for ADME properties and the results indicate that they show acceptable pharmacokinetic properties. Accordingly these compounds are predicted to be drug like with low toxicity potential.

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2006

S. Jose, Dr. Sobha V. Nair, Thomas, S., and Karger-Kocsis, J., “Effect of reactive compatibilisation on the phase morphology and tensile properties of PA12/PP blends”, Journal of Applied Polymer Science, vol. 99, pp. 2640-2660, 2006.[Abstract]


Abstract Both uncompatibilized and compatibilized blends based on polyamide 12 (PA12) and isotactic polypropylene (PP) were prepared in a Brabender Plastograph®. The compatibiliser used was maleic anhydride functionalized polypropylene (PP-g-MA). Phase morphology of the blends was inspected in scanning electron microscope (SEM) on cryogenically fractured etched surfaces of the specimens. PA12/PP blends possessed a nonuniform and unstable morphology owing to the incompatibility between their constituents. Addition of compatibiliser improved the interfacial characteristics of the blends by retarding the rate of coalescence. So, the phase morphology became more fine, uniform, and stable. Tensile properties of both uncompatibilized and compatibilized blends were measured as a function of blend composition and compatibiliser concentration. Uncompatibilized blends displayed inferior mechanical properties to compatibilized ones; especially for those containing 40–60 wt % of PP. Reactive compatibilisation of blends was found to be efficient and improved the tensile strength of the blends considerably. Addition of PP-g-MA improved the interfacial adhesion, decreased the interfacial tension, and thereby, enhanced the tensile strength by 85%. Finally, various models were adopted to describe the tensile strength of the blends. The experimental data exhibited a reasonably good fit with Nielsen's first power law model. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006

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2005

K. Cho, Yang, J., Yoon, S., Hwang, M., and Dr. Sobha V. Nair, “Toughening of polycarbonate: Effect of particle size and rubber phase contents of the core‐shell impact modifier”, Journal of Applied Polymer Science, vol. 95, pp. 748-755, 2005.[Abstract]


The toughening behavior of polycarbonate modified with core-shell type particles was investigated. The alloys were found to exhibit maximum impact strength upon addition of a modifier with a poly(butyl acrylate) rubbery core of 0.25 μm diameter. The incorporation of particles with diameter greater than 0.25 μm resulted in decreased impact strength. The influence of rubber phase contents on toughness was also studied. It was observed that the alloys exhibited maximum impact strength upon addition of 4 wt % rubber phase. Further increase in the rubber phase content resulted in reduced impact strength. Fractography of the samples showed that, below 4 wt % rubber phase content, the fracture occurs mainly by internal crazing and, from 4 wt % onward, only by shear deformation. When the effect of dual particle size distribution was analyzed, it was found that there was only a moderate increase in toughness compared with alloys containing monosized particles.

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2003

R. C. Kumar, Dr. Sobha V. Nair, George, K. E., Oommen, Z., and Thomas, S., “Blends of nylon/acrylonitrile butadiene rubber: Effects of blend ratio, dynamic vulcanization and reactive compatibilization on rheology and extrudate morphology”, Polymer Engineering & Science, vol. 43, pp. 1555-1565, 2003.[Abstract]


Abstract The melt flow behavior of thermoplastic elastomers from nylon and nitrile rubber (NBR) was studied as a function of blend ratio, dynamic crosslinking, compatibilization and temperature. The morphology of the extrudates, i.e., the size, shape and distribution of the domains, was analyzed. Uncompatibilized and compatibilized blends showed pseudoplastic behavior. The viscosity of the blends showed positive deviation from a linear rule of mixtures. Compatibilization using chlorinated polyethylene (CPE) increased the melt viscosity of the blends. The addition of the compatibilizer decreased the domain size of the dispersed phase, followed by an increase after a critical concentration of the compatibilizer, where the interface was saturated. The influence of dynamic vulcanization on the rheological behavior was also studied. The extrudate morphology depended on blend ratio, compatibilization and shear rate.

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2003

R. Stephen, Raju, K. V. S. N., Dr. Sobha V. Nair, Varghese, S., Oommen, Z., and Thomas, S., “Mechanical and viscoelastic behavior of natural rubber and carboxylated styrene-butadiene rubber latex blends”, Journal of Applied Polymer Science, vol. 88, pp. 2639-2648, 2003.[Abstract]


Abstract The morphology, mechanical and viscoelastic behavior of latex blends of unvulcanized natural rubber (NR) with carboxylated styrene-butadiene rubber (XSBR) were investigated, with special reference to the effect of the blend ratio, temperature, and frequency. Mechanical properties like tensile strength, modulus, and elongation at break were also studied. As the XSBR content increased, the tensile strength increased up to a 50:50 NR/XSBR ratio and then decreased as a result of the self-curing nature of XSBR. The dynamic mechanical properties of these latex blends were analyzed for loss tangent, storage modulus, and loss modulus. The entire blend yielded two glass-transition temperatures, which corresponded to the transitions of individual components, indicating that the system was immiscible. To determine the change in modulus with time, a master curve of 50:50 NR/XSBR blends was plotted. Time–temperature superposition and Cole–Cole analysis were done to understand the phase behavior of the latex blends. The experimental and theoretical values of storage modulus of blends were compared using the Kerner and Halpin–Tsai models. With the help of optical micrographs, attempts were made to correlate the morphology and viscoelastic behavior of these blends. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2639–2648, 2003

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2002

Dr. Sobha V. Nair, Oommen, Z., and Sabu Thomas, “Melt elasticity and flow activation energy of nylon 6/polystyrene blends”, Materials Letters, vol. 57, pp. 475 - 480, 2002.[Abstract]


Nylon 6 (PA 6) is blended with polystyrene (PS), so as to reduce the moisture absorption and hence to impart dimensional stability to the polymer. The melt elastic properties of the blends including die swell, principal normal stress difference and recoverable shear strain have been analysed. The temperature sensitivity of the flow behaviour of the blends is studied using Arrhenius plots.

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2002

Dr. Sobha V. Nair, Oommen, Z., and Thomas, S., “Phase morphology development and melt rheological behavior in nylon 6/polystyrene blends”, Journal of Applied Polymer Science, vol. 86, pp. 3537-3555, 2002.[Abstract]


Abstract Phase morphology development in immiscible blends of polystyrene (PS)/nylon 6 was investigated. The blends were prepared by melt blending in a twin-screw extruder. The influence of the blend ratio, rotation speed of the rotors, and time of mixing on the phase morphology of the blends was carefully analyzed. The morphology of the samples was examined under a scanning electron microscope (SEM) and the SEM micrographs were quantitatively analyzed for domain-size measurements. From the morphology studies, it is evident that the minor component, whether PS or nylon, forms the dispersed phase, whereas the major component forms the continuous phase. The 50/50 PS/nylon blend exhibits cocontinuous morphology. The continuity of the dispersed phase was estimated quantitatively based on the preferential solvent-extraction technique, which suggested that both phases are almost continuous at a 50/50 blend composition. The effect of the rotor speed on the blend morphology was investigated. It was observed that the most significant breakdown occurred at an increasing rotor speed from 9 to 20 rpm and, thereafter, the domain size remained almost the same even when the rotor speed was increased. The studies on the influence of the mixing time on the blend morphology indicated that the major breakdown of the dispersed phase occurred at the early stages of mixing. The melt rheological behavior of the blend system was studied using a capillary rheometer. The effect of the blend ratio and the shear stress on the melt viscosity of the system was investigated. Melt viscosity decreased with increase in the shear stress, indicating pseudoplastic behavior. With increase of the weight fraction of PS, the melt viscosity of the system decreased. The negative deviation of the measured viscosity from the additivity rule indicated the immiscibility of the blends. The domain size versus the viscosity ratio showed a minimum value when the viscosities of the two phases were matched, in agreement with Wu's prediction. The morphology of the extrudates was analyzed by SEM. From these observations, it was noted that as the shear rate increased the particle size decreased considerably. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3537–3555, 2002

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2000

Dr. Sobha V. Nair, Stephen, R., Oommen, Z., and Sabu Thomas, “Phase Morphology Development in nylon/PS blends”, nternational Plastics Engineering and Technology, vol. 4, no. 1, 2000.

2000

Dr. Sobha V. Nair, Sreekala, M. S., Unnikrishnan, G., Johnson, T., Sabu Thomas, and Groeninckx, G., “The role of crosslinking and crystallisation on the transport characteristics of ethylene–propylene rubber membranes”, Journal of Membrane Science, vol. 177, pp. 1 - 7, 2000.[Abstract]


The transport characteristics of ethylene–propylene rubber (EPR) membranes have been examined using four aromatic hydrocarbons as probe molecules. The EPR was crosslinked by different percentage of dicumyl peroxide (DCP). Solvent uptake by EPR membranes has been found to increase with increase in the crosslinker dosage, unlike many other rubbers, up to a threshold level which is followed by a decrease at higher crosslinker content. This has been explained in terms of the differences in the degrees of crystallinity and crosslinking. The mechanism of transport has been found to deviate from the regular Fickian trend observed with conventional rubbers. The influence of penetrant size and temperature on the transport process has also been examined. A sorption–desorption–resorption–redesorption technique has been utilised to examine the structural changes during the transport process.

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Publication Type: Patent

Year of Publication Title

2019

Dr. Sobha V. Nair, Nair, P. Chandran R., Nair, B., and Ajayan, K., “Detergent Compatible Assay for Protein Estimation”, U.S. Patent 16/366865 2019.[Abstract]


The invention discloses a detergent-compatible protein assay method, composition and kit based on bio-conjugation reaction between protein and Meldrum's acid activated furfural. The method includes adding MAF in dimethyl sulfoxide (DMSO) to a protein sample solution. The amine functionalities present on the amino acid residues reacts with the MAF instantaneously at room temperature to yield deep purple colored solutions of the corresponding conjugated proteins. The reagent composition added to protein may be in the range of 90-450 mM. The intensities of purple colored solutions were proportional to the protein concentration captured by spectrophotometric measurements. The assay is sensitive in the range of 0.125-15 mg/mL, is compatible with commonly used detergents and reducing agents in protein solutions and may be employed for estimation of protein samples in the presence of detergents and reducing agents.

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Publication Type: Conference Paper

Year of Publication Title

2013

Dr. Sobha V. Nair, Krishnan, R., B, A. Merlin K., and Chandran, R. P., “Novel chemically modified chitosans: Synthesis and applications”, in Amrita Bioquest, 2013.

Patents Filed

  • United States Patent Application No. US 2019/0219591 A1
  • Indian Patent Application No. 201841012852

Conferences (Invited Talks/Proceedings)

  • 2019: Sobha V. Nair and R. Prakash Chandran, Bioconjugate Chemistry of Activated Furfurals:Applications, International Conference on Photochemistry and Sustainable Energy(ICPSE 2019), Alappuzha, October 2019 (Invited Talk)
  • 2017: Krishnaraj K.U., Sobha Vijayan Nair, R.Prakash Chandran, Solvolytic reactions of α-Oxoketene Dithioacetals: A green chemistry approach to β-Oxo thiolcarboxylates, International Conference on Tropical Plants and Molecular Design, TKM College of Arts and Science, Kollam, Feb 2017 (Poster)
  • 2013: Sobha V. Nair, Krishnan, R., B, A. Merlin K., and R.Prakash Chandran , Novel chemically modified chitosans: Synthesis and applications, Amrita Bioquest, 2013 (Poster)