Transitions of saturated monoacid triglycerides: Modeling conformational change at glycerol during α→β′→β transformation |
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Authors: | J W Hagemann J A Rothfus |
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Affiliation: | (1) Biopolymer Research, National Center for Agricultural Utilization Research, U.S. Department of Agriculture, Agricultural Research Service, 61604 Peoria, Illinois |
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Abstract: | The glycerol region geometry of modeled saturated monoacid triglycerides was altered by bond rotations and minor angle distortions
to convert theoretical α-forms into bent β′- and β-forms. Direct α to β conversion involves lateral disruption of fatty chain
packing to generate side-chain character typical of the β-form. Such disruption, which could contribute to fat bloom, allows
additional molecular movement and shifts in molecular mechanics energy (MME) that may approximate thermal changes observed
by differential scanning calorimetry during α to β transformations. Energy calculations at 100 points throughout each transformation
identified plausible conversion routes. A two-stage conversion, α to either of two stereospecific β′-forms bent at glycerol
followed by subsequent conversion to β, showed less chain movement and more favorable MME than direct α to β conversion. The
preferred path, based on energy profiles of each conversion, involves a β′-D form and rotation of carbonyl to α-carbon bonds
in chain #2 and a side chain (chain #3). |
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Keywords: | Computer modeling molecular mechanics energy phase transitions polymorphism triglycerides |
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