The thermal denaturation of proteins has been extensively studied using several methods including differential scanning calorimetry (DSC). A custom-built optical system was used to study thermal effects on protein as an alternative method to DSC measurements. It was used to investigate the thermal stability of bovine serum albumin (BSA) with a focus on comparisons with published DSC data.
In the first study, the effect of protein concentration on the thermal denaturation (Td) of BSA was determined and validated using published DSC data for bovine serum albumin (BSA). The optical rotation (OR) and transmitted light (TL) signals indicating protein conformational changes and gel formation, respectively, were collected during the heating of BSA solutions at ~6��C/min from room temperature to ~85��C. The experiments were performed on 1, 2.5 and 5% (w/v) BSA in 0.01 M phosphate buffer at pH 7 and ionic strength (IS) 0.08. BSA���s Td values obtained from this investigation were consistent with published values and had low experimental variability (CV<2.5%). In agreement with some but not all published data, increasing BSA concentration did not affect its thermal stability. Protein gel formation, however, increased with protein concentration.
In the second study, changes in the OR and TL signal of BSA in 0.01 M phosphate buffer at pH 6.1, 7 and 7.9 with IS maintained at 0.04, 0.08 and 0.16 were recorded during the heating of BSA solutions at ~6��C/min from room temperature to ~85��C. BSA showed a maximum and minimum thermostability at pH 7 and 7.9, respectively, consistent with published values determined by DSC. BSA formed opaque gel at pH 6.1 approaching the BSA���s pI values. Increasing IS level did not have a significant effect on BSA���s Td value but promoted gel formation.
In the third study, the optical method was applied to investigate the heat stability of BSA as affected by low concentrations of sucrose, trehalose or sorbitol. BSA solutions (2.5% w/v) in the presence of 0 5% sucrose, trehalose and sorbitol were heated at ~6��C/min from ambient temperature to ~85��C. In contrast with published work on the thermal stability of BSA in the presence of higher sugar concentrations, this study showed that increasing sugar concentration did not enhance the thermal stability of this protein. Also, the ability to promote protein stability among sucrose, trehalose and sorbitol were not significantly different.
The significance of these studies is that they demonstrate that the custom-built optical methods here developed can be used to study heat-induced protein denaturation and the effect of environmental conditions. Future studies will examine other proteins such as ��-lactoglobulin or ��-lacactalbumin. A further advantage of optical systems is their ability to conduct real-time measurements which could be used for food processing control. / Graduation date: 2007
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/4100 |
| Date | 14 March 2007 |
| Creators | Kongraksawech, Teepakorn |
| Contributors | Torres, J. Antonio, Anderson, Sonia R. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis |
| Format | 558327 bytes, application/pdf |
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