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Effects of physicochemical factors on the secondary structure of β-lactoglobulin

Published online by Cambridge University Press:  01 June 2009

Joyce I. Boye ,
Ashraf A. Ismail  and
Inteaz Alli
Joyce I. Boye
Affiliation:
Department of Food Science and Agricultural Chemistry, Macdonald Campus of McGill University, 21 111 Lakeshore Road, Ste-Anne-de-Bellevue, Montréal, Québec, Canada H9X 3V9
Ashraf A. Ismail
Affiliation:
Department of Food Science and Agricultural Chemistry, Macdonald Campus of McGill University, 21 111 Lakeshore Road, Ste-Anne-de-Bellevue, Montréal, Québec, Canada H9X 3V9
Inteaz Alli
Affiliation:
Department of Food Science and Agricultural Chemistry, Macdonald Campus of McGill University, 21 111 Lakeshore Road, Ste-Anne-de-Bellevue, Montréal, Québec, Canada H9X 3V9
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Summary

Fourier transform infrared spectroscopy and differential scanning calorimetry were used as complementary techniques to study changes in the secondary structure of β-lactoglobulin under various physicochemical conditions. The effects of pH (3–9), NaCl (0–2 M), and lactose, glucose and sucrose (100–500 g/l) in the temperature range 25–100 °C on the conformation sensitive amide I band in the i.r. spectrum of β-lactoglobulin in D2O solution were examined. The 1692 cm−1 band in the amide I band profile had not been definitively assigned in previous studies of the i.r. spectrum of β-lactoglobulin. The decrease in this band at ambient temperature with time or upon mild heating was attributed to slow H-D exchange, indicating that it was due to a structure buried deep within the protein. The disappearance of the 1692 cm−1 band on heating was accompanied by the appearance of two bands at 1684 and 1629 cm–1, assigned to β-sheets. The 1692 cm−1 band was therefore attributed to a β-type structure. β-Lactoglobulin showed maximum thermal stability at pH 3 and was easily denatured at pH 9. On denaturation, the protein unfolded into more extensive random coil structures at pH 9 than at pH 3. After 10 h at pH 9 (25 °C), β-lactoglobulin was partly denatured. Heating to 60–80 °C generally resulted in the loss of secondary structure. At all pH values studied, two new bands at 1618 and 1684 cm−1, characteristic of intermolecular β-sheet structure and associated with aggregation, were observed after the initial denaturation. Differential scanning calorimetry studies indicated that the thermal stability of β-lactoglobulin was enhanced in the presence of sugars. The Fourier transform i.r. results obtained provide evidence that sugars promoted the unfolding of β-lactoglobulin via multiple transition pathways leading to a transition state resisting aggregation.

Type
Original Articles
Information
Journal of Dairy Research , Volume 63 , Issue 1 , February 1996 , pp. 97 - 109
Copyright
Copyright © Proprietors of Journal of Dairy Research 1996

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References

REFERENCES

Arntfield, S. D., Ismond, M. A. H. & Murray, E. D. 1990 Thermal analysis of food proteins in relation to processing effects. In Thermal Analysis of Foods, pp. 51–91 (Eds Harvalkar, V. R. and Ma, C. -Y.). New York: Elsevier Applied ScienceGoogle Scholar
Bell, K. & McKenzie, H. A. 1967 The isolation and properties of bovine β-Lactoglobulin C. Biochimica el Biophysica Acta 147 109–122Google Scholar
Byler, D. M. & Earrell, H. M. 1989 Infrared spectroscopic evidence for calcium ion interaction with carboxylate groups of casein. Journal of Dairy Science 72 1719–1723Google Scholar
Casal, H. L., Köhler, U. & Mantsch, H. H. 1988 Structural and conformational changes of β-Lactoglobulin B: an infrared spectroscopic study of the effect of pH and temperature. Biochimica el Biophysica Acta 957 11–20CrossRefGoogle ScholarPubMed
Damodaran, S. 1994 Structure–function relationship of food proteins. In Protein Functionality in Food Systems, pp. 1–38 (Eds Hettiarachchy, N. S. and Ziegler, G. R.). New York: Marcel DekkerGoogle Scholar
De Wit, J. N. 1989 Functional properties of whey proteins. In Developments in Dairy Chemistry—4. Functional Milk Proteins, pp. 285–321 (Ed. Fox, P. F.). London: Elsevier Applied ScienceGoogle Scholar
De Wit, J. X. & Klarenbeek, G. 1981 A differential scanning calorimetric study of the thermal behaviour of bovine β-laetoglobulin at temperatures up to 160°C. Journal of Dairy Research 48 293–302Google Scholar
Dufour, E. & Haertlé, T. 1990 Alcohol-induced changes of β-lactoglobulin-retinol-binding stoiehiometry. Protein Engineering 4 185–190Google Scholar
Hamblng, S. G., McAlpine, A. S. & Sawyer, L. 1992 β-Laetoglobulin. In Advanced Dairy Chemistry—J. Proteins, pp. 141–190 (Ed. Fox, P. F.). London: Elsevier Applied ScienceGoogle Scholar
Harwalkar, V. R. & Ma, C. -Y. 1988 Effects of medium composition, preheating and chemical modification upon thermal behavior of oat globulin and β-laetoglobulin. In Food Proteins, pp. 210–231 (Eds Kinsella, J. E. and Soucie, W. G.). Champaign, IL: American Oil Chemists' SocietyGoogle Scholar
Ismail, A. A., Mantsch, H. H. & Wong, P. T. T. 1992 Aggregation of chymotrypsinogen: portrait by infrared spectroscopy. Biochimica et Biophysica Acta 1121 183–188CrossRefGoogle ScholarPubMed
Kauppinen, J. K., Moffatt, D. J., Mantsch, H. H. & Cameron, D. G. 1981 Fourier transforms in the computation of self-deeonvoluted and first-order derivative spectra of overlapped band contours. Analytical Chemistry 53 1454–1457Google Scholar
Krlmm, S. & Bandekar, J. 1986 Vibrational spectroscopy and conformation of peptides, polypeptides, and proteins. Advances in Protein Chemistry 38 181–364Google Scholar
Lee, J. C. & Timasheff, S. N. 1981 The stabilization of proteins by sucrose. Journal of Biological Chemistry 256 7193–7201Google Scholar
McKenzie, H. A. 1971 β-Lactoglobulins. In Milk Proteins: Chemistry and Molecular Biology, vol. 2, pp. 257–330 (Ed. McKenzie, H. A.). New York: Academic PressCrossRefGoogle Scholar
Matsuura, J. E. & Manning, M. C. 1994 Heat-induced gel formation of β-lactoglobulin: a study on the secondary and tertiary structure as followed by circular dichroism spectroscopy. Journal of Agricultural and Food Chemistry 42 1650–1656CrossRefGoogle Scholar
Privalov, P. L. 1982 Stability of proteins. Proteins which do not present a single cooperative system. Advances in Protein Chemistry 35 1–104CrossRefGoogle ScholarPubMed
Su, Y. -Y. T. & Jlrgensons, B. 1977 Further studies on detergent-induced conformational transitions in proteins. Circular dichroism of ovalbumin, bacterial α-amylase, papain, and β-lactoglobulin at various pH values. Archives of Biochemistry and Biophysics 181 137–146Google Scholar
Susi, H. & Byler, D. M. 1983 Protein structure by Fourier transform infrared spectroscopy: second derivative spectra. Biochemical and Biophysical Research Communications 115 391–397Google Scholar
Susi, H. & Byler, D. M. 1986 Resolution-enhanced Fourier transform infrared spectroscopy of enzymes. Methods in Enzymology 130 290–311Google Scholar
Susi, H. & Byler, D. M. 1988 Fourier transform infrared spectroscopy in protein conformation studies. In Methods for Protein Analysis, pp. 235–255 (Eds Cherry, J. P. and Barford, R. A.). Champaign, IL: American Oil Chemists' SocietyGoogle Scholar
Timasheff, S. N., Townend, R. & Mescanti, L. 1966 The optical rotatory dispersion of the β-laetoglobulins. Journal of Biological Chemistry 241 1863–1870CrossRefGoogle Scholar