Changes in the Secondary Structure of Bovine Casein by Fourier Transform Infrared Spectroscopy: Effects of Calcium and Temperature
| Autor: | Thomas F. Kumosinski, Harold M. Farrell, Joseph J. Unruh, Diane M. Curley |
|---|---|
| Rok vydání: | 1998 |
| Předmět: |
Aqueous solution
Chemistry Sodium Static Electricity Temperature Analytical chemistry Caseins Infrared spectroscopy Micelle Protein Structure Secondary Crystallography Casein Spectroscopy Fourier Transform Infrared Potassium Genetics Side chain Animals Calcium Cattle Female Animal Science and Zoology Fourier transform infrared spectroscopy Bond energy Protein secondary structure Food Science |
| Zdroj: | Journal of Dairy Science. 81:3154-3162 |
| ISSN: | 0022-0302 |
| DOI: | 10.3168/jds.s0022-0302(98)75881-3 |
| Popis: | Bovine casein submicelles and reformed micelles, produced by addition of Ca 2+ , were examined by Fourier transform infrared spectroscopy at 15 and 37°C in aqueous salt solutions of K + and Na + . Previous measurements of caseins, made in D 2 O and in the solid form, can now be made in a more realistic environment of H 2 O. When analyzed in detail, data obtained by Fourier transform infrared spectroscopy have the potential to show subtle changes in secondary structural elements that are associated with changes in protein environment. Electrostatic binding of Ca 2+ to casein resulted in a redistribution of the components of the infrared spectra. Addition of Ca 2+ in salt solutions of K + and Na + led to apparent decreases in large loop or helical structures at 37°C with concomitant increases in the percentage of structures having greater bond energy, such as turns and extended helical structures. At 15°C, Na + and K + have differential effects on the Ca 2+ -casein complexes. All of these observations are in accordance with the important role of serine phosphate side chains as sites for Ca 2+ binding in caseins and the swelling of the casein structure upon incorporation into reformed micelles at 37°C. This new open, hydrated structure is buttressed by a change in backbone as evidenced by a shift in absorbance to higher wave numbers (greater bond energies) as colloidal micelles are reformed. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|