THESIS
2020
xi, 76 pages : illustrations (chiefly color) ; 30 cm
Abstract
DNA stretching mechanics in Tris buffer and PBS buffer was briefly studied and compared.
When the buffer was changed from tris buffer to PBS buffer that has a much higher ionic
strength, the transition force didn’t change evidenly, however, the persistence length increased,
and the elastic modulus decreased.
In Chapter 2, optical tweezers were applied to study mechanical properties of a
nonapeptide PAQGQQGQQ from high-molecular weight glutenin subunit Cx1 and a design
variant GGPQQQAQQ. The study showed that the persistence length of wild-type was
increased from 1.1 nm to 4.9 nm in the presence of wheat protein disulfide isomerases, while
that of design variant maintained at 0.4 nm. The wheat protein disulfide isomerases rendered
the wild-type more rigid and less flexble, while...[
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DNA stretching mechanics in Tris buffer and PBS buffer was briefly studied and compared.
When the buffer was changed from tris buffer to PBS buffer that has a much higher ionic
strength, the transition force didn’t change evidenly, however, the persistence length increased,
and the elastic modulus decreased.
In Chapter 2, optical tweezers were applied to study mechanical properties of a
nonapeptide PAQGQQGQQ from high-molecular weight glutenin subunit Cx1 and a design
variant GGPQQQAQQ. The study showed that the persistence length of wild-type was
increased from 1.1 nm to 4.9 nm in the presence of wheat protein disulfide isomerases, while
that of design variant maintained at 0.4 nm. The wheat protein disulfide isomerases rendered
the wild-type more rigid and less flexble, while the design variant is always a simply
unstructured random coil, indicating the design variant has a much lower risk of suffering from
damage, thus it may be used to improve the bread-making quality. The change of persistence
length indicates the wheat protein disulfide isomerases could selectively recognize the amino
acid sequence and assists protein folding as a molecular chaperone independent of the
isomerase activity given there were no cysteines within the protein except for the two at the
termini designed for forming tethers with DNA handles.
A useful method was provided in the last chapter that helps determining optimal length of
DNA handles used for optical tweezers based single-molecule force spectroscopy study.
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