title: Binding of λ-carrageenan (a food additive) to almond cystatin: An insight involving spectroscopic and thermodynamic approach.
abstract: Carrageenan is a high molecular weight linear sulphated polysaccharide, primarily used in food industry as gelling, thickening, and stabilizing agent. Almond milk prepared from almonds is low in fat, but high in antioxidants, energy, proteins, lipids and fibre. Purified almond cystatin was incubated with increasing concentrations of carrageenan at 25°C for different time interval and significant loss in inhibitory activity was observed. Interaction between carrageenan and cystatin resulted in complex formation as depicted by the decrease in fluorescence intensity with increase in the concentration of carrageenan. Stern-volmer analysis of fluorescence quenching data showed binding constant to be 1.84±0.20×104M-1and number of binding sites close to unity. These results were further confirmed by supporting results obtained in UV-vis spectroscopy. FTIR analysis shows significant shift in the peak intensity and this change clearly depict change in the structure of cystatin from that of α helix to β-sheet. CD spectra further confirmed the structural transition of the cystatin from α helix to β-sheet structure on interaction with increased concentrations of carrageenan. The contributing thermodynamic parameters were determined by ITC. The negative ΔH° and positive TΔS° values suggest involvement of electrostatic forces and hydrophobic interaction in the formation of the λ-carrageenan-cystatin complex.
authors.affiliation: Department of Biochemistry, Faculty of Life Sciences, Aligarh Muslim University, Aligarh 202002, U.P., India.
authors.forename: Azad Alam
authors.initials: AA
authors.lastname: Siddiqui
authors.affiliation: Department of Biochemistry, Faculty of Life Sciences, Aligarh Muslim University, Aligarh 202002, U.P., India.
authors.forename: Anna
authors.initials: A
authors.lastname: Feroz
authors.affiliation: Department of Biochemistry, Faculty of Life Sciences, Aligarh Muslim University, Aligarh 202002, U.P., India.
authors.forename: Peerzada Shariq Shaheen
authors.initials: PS
authors.lastname: Khaki
authors.affiliation: Department of Biochemistry, Faculty of Life Sciences, Aligarh Muslim University, Aligarh 202002, U.P., India. Electronic address: bilqees.alig@gmail.com.
authors.forename: Bilqees
authors.initials: B
authors.lastname: Bano
mesh_terms: D000975:Antioxidants / Q000737:chemistry; D001665:Binding Sites; D002351:Carrageenan / Q000138:chemical synthesis / Q000737:chemistry*; D002942:Circular Dichroism; D015891:Cystatins / Q000138:chemical synthesis / Q000737:chemistry*; D005503:Food Additives / Q000138:chemical synthesis / Q000737:chemistry*; D000068181:Prunus dulcis / Q000737:chemistry; D013050:Spectrometry, Fluorescence; D013816:Thermodynamics
chemical_list: D000975:Antioxidants; D015891:Cystatins; D005503:Food Additives; D002351:Carrageenan
keywords: Almond milk; ITC; Phytocystatin; Spectroscopy; λ-Carrageenan