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Chemical modification of cereal starch mutants differing in amylose content劉惠君, Liu, Huijun. January 1999 (has links)
published_or_final_version / Botany / Doctoral / Doctor of Philosophy
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Chemical modifications of proteins from soymilk residue (Okara)陳穎敏, Chan, Wing-man. January 1998 (has links)
published_or_final_version / Botany / Master / Master of Philosophy
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Structure/function relationships in Jack bean α-mannosidaseBurrows, Heidi January 1999 (has links)
No description available.
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Solution spinning and characterization of poly(vinyl alcohol)/soybean protein polyblend fibersZhang, Xiefei January 2001 (has links)
No description available.
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Amyloid Fibrils in BionanomaterialsRao, Shiva Priya January 2008 (has links)
Amyloid fibrils are a type of protein nanofibres that form when a normally soluble protein aggregates in a regular fashion via self-association. Their organised and repetitive β-sheet structure is thought to be a generic property of all proteins, depending on the environmental conditions. The nanometre size and high stability of these protein nanofibres are attractive features to exploit in bionanomaterials.
This thesis aimed to manipulate insulin amyloid fibrils, as a model protein nanofibre system, through investigating the effect of chemical modification on insulin fibril formation in heterogeneous mixtures. Using acetylation, reduction carboxymethylation, reduction pyridylethylation, trypsin digestion and chymotrypsin digestion, it was shown that nanofibres can form in heterogeneous mixtures of modified insulin at variable rates to produce fibrils of distinct morphologies. Distinctively well defined, long, unbranched nanofibres were observed in the crude reduced carboxymethylated insulin mixture after incubation at 60°C (pH 7.4), which formed at a faster rate than native insulin. The crude reduced pyridylethylated insulin revealed the formation of “wavy” fibrils when exposed to 60°C and pH 1.6, compared to the straight native insulin amyloid fibrils. Although, the trypsin digestion inhibited nanofibre formation at 60°C and pH 1.6, chymotrypsin digestion of insulin produced a mixture of long and short nanofibres under the same conditons. Thus chemical modification provides a simple means of manipulating protein nanofibre assembly for use in bionanotechnology.
Protein nanofibres were incorporated into a model polymer polyvinylalcohol (PVOH) film in order to assess the impact on material properties. A systematic study involving both insulin and a crude source of crystallin proteins derived from bovine eye lens was undertaken. A protein nanofibre-PVOH nanocomposite was successfully fabricated by a procedure of solution mixing and casting. Dynamic mechanical analysis showed that the addition of insulin fibrils did not change the stiffness of the PVOH. However, an increase in the stiffness of the PVOH-crude bovine eye lens composites was found. Both insulin and bovine eye lens nanofibres reduced the damping properties of the polymer, which suggested a reduction in molecular mobility/slipping.
The results revealed that protein nanofibre formation can be controlled through the modification of the protein and that nanofibres may alter polymer properties in a protein specific manner. Employing these findings in the development of novel bionanomaterials that use the protein nanofibres as a form of natural scaffolding offers a fruitful avenue of future research.
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Chemical modification, mutagenesis and characterisation of the glycerol dehydrogenase from Bacillus stearothermophilusPaine, Lisa Jane January 1992 (has links)
No description available.
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The chemical reactivity of thermo mechanical pulp (TMP) fibres : a detailed kinetic study of the reaction between fibre and isolated fractions of hollcellulose and cellulose with succinic anhydrideElias, Robert M. January 1994 (has links)
No description available.
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Characterization of the nuclease of Vibrio vulnificusWu, Hui-Chi 22 June 2001 (has links)
The periplasmic nuclease of Vibrio vulnificus, Vvn, has been purified to homogeneity by a one step purification procedure using chromatography on a SP Sepharose column. The purified enzyme showed different mobilities on reducing and non-reducing SDS-PAGE, suggesting that disulfide bonds are involved in the maintenance of a stable tertiary conformation of the protein. Vvn randomly cleaved single and double stranded DNA and RNA, and possessed endonucleolytic activity. The enzyme exhibited an optimal activity between pH 8.0 and pH 10.0, and the optimal temperatures for the DNase and RNase activity were 40 oC ¡V 60 oC and 40 oC ¡V 50 oC, respectively. The enzymatic activity was inhibited by EDTA and EGTA, indicating that Vvn was a metalloenzyme. The DNase and RNase activity of Vvn had different requirements for divalent cations. Chemical modification studies on Vvn revealed the involvement of lysine, arginine, tryptophan and carboxylate residues in the catalytic activity of the enzyme. The extents of inactivation of the DNase and RNase activity of Vvn by modification of the carboxylate group with EDC were different. Substrate DNA and RNA protected the DNase and RNase activity of Vvn from inactivation by PLP, PGO, NBS and EDC which modified lysine, arginine, tryptophan and the carboxylate group. Mg2+ could not protect the DNase and RNase activity of Vvn against the inactivation by PLP and PGO. Whereas Mg2+ protection was observed in NBS- and EDC-mediated inactivation of the DNase but not the RNase activity of Vvn . From these results, it is postulate that there may be two distinct but overlapping active sites, for the DNase and RNase activity, respectively.
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Surface Modification and Characterization of Cellulose Nanocrystal for Biomedical ApplicationsAkhlaghi, Seyedeh Parinaz 06 September 2014 (has links)
There is an ever-increasing desire to develop novel materials that could control the
release of active compounds and increase their stability. Replacing petroleum-based synthetic polymers with sustainable materials has many advantages, such as reducing the
dependence on fossil fuels, and diminishing environmental pollution. Recently, cellulose
nanocrystal (CNC) obtained by acid hydrolysis of cellulose fibres has gained a lot of interest.
The high mechanical strength, large and negatively charged surface area, and the
presence of several hydroxyl groups that allow for modification with different functionalities
make CNC an excellent candidate for various applications in the biomedical field. This
thesis explores (i) the surface modification and characterization of modified CNC and (ii)
the biomedical applications of these novel sustainable nanomaterials.
In the first part, amine functionalized CNC was prepared. Ammonium hydroxide was
reacted with epichlorohydrin (EPH) to produce 2-hydroxy-3-chloro propylamine (HCPA),
which was then grafted to CNC using an etherification reaction. A series of reactions were
carried out to determine the optimal conditions. The final product (CNC-NH2(T)) was
dialyzed for one week. Further purification via centrifugation yielded the sediment (CNC-NH2(P)) and supernatant (POLY-NH2). The presence of amine groups was confirmed by
FT-IR and the amine content was determined by potentiometric titration and elemental
analysis. A high amine content of 2.2 and 0.6 mmol amine/g was achieved for CNC-NH2(T) and CNC-NH2(P), respectively. Zeta potential measurements confirmed the charge
reversal of amine CNC from negative to positive when the pH was decreased from 10
to 3. TEM images showed similar structural properties of the nanocrystals along with
some minor aggregation. This simple, yet effective synthesis method can be used for
further conjugation as required for various biomedical applications. Moreover, the surface
of CNC was modified with chitosan oligosaccharide (CSos). First, the primary alcohol
groups of CNC were selectively oxidized to carboxyl groups using the catalyst, 2,2,6,6-
tetramethylpiperidine-1-oxyl radical (TEMPO), and were then reacted with the amino
groups of CSos via the carbodiimide reaction using N-hydroxysuccinimide (NHS) and
1-Ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC). The appearance of C=O peak
in FT-IR spectrum of oxidized CNC (CNC-OX), accompanied by calculations based on
potentiometric titration revealed that CNC was successfully oxidized with a degree of
oxidation of 0.28. The grafting of CSos on oxidized CNC was confirmed by the following
observations: (i) the reduction of the C=O peak in FT-IR of CNC-CSos and the appearance
of new amide peaks; (ii) the significant reduction of the carbonyl peak at 175 ppm in the
13C NMR spectrum for CNC-CSos; (iii) a higher decomposition temperature in TGA of
CNC-CSos; (iv) a positive zeta potential of CNC-CSos at acidic pH; and (v) a degree of substitution of 0.26, which is close to the DO (0.28), indicating that 90% of COOH
groups on CNC-OX were involved in the formation of amide bonds with CSos. TEM and
AFM studies also revealed a completely diff erent morphology for CNC-CSos.
In the second part, the potential of exploiting CNCs as delivery carriers for two cationic
model drugs, procaine hydrochloride (PrHy) and imipramine hydrochloride (IMI), were
investigated. IMI displayed a higher binding to CNC derivatives compared to PrHy.
Isothermal titration calorimetry (ITC), transmittance and zeta potential measurements
were used to elucidate the complexation between model drugs and CNC samples. It was
observed that the more dominant exothermic peak observed in the ITC isotherms leading
to the formation of larger particle-drug complexes could explain the increased binding
of IMI to CNC samples. Drug selective membranes were prepared for each model drug
that displayed adequate stability and rapid responses. Different in vitro release profiles
at varying pH conditions were observed due to the pH responsive properties of the systems. Both drugs were released rapidly from CNC samples due to the ion-exchange e ffect, and CNC-CSos displayed a more sustained release profile. Furthermore, the antioxidant properties of CNC samples and the potential of CNC-CSos as a carrier for the delivery of vitamin C was investigated. CNC-CSos/vitamin C complexes (CNCS/VC) were formed between CNC-CSos and vitamin C via ionic complexation using sodium tripolyphosphate (TPP). The complexation was confirmed via DSC and UV-Vis absorbance measurements.
TEM images showed complexes with a size of approximately 1 micron. The encapsulation
efficiency of vitamin C was higher (91%) at pH 5 compared to pH 3 (72%). The in
vitro release of vitamin C from CNCS/VC complexes exhibited a sustained release of up
to 3 weeks, with the released vitamin C displaying higher stability compared to a control
vitamin C solution. Antioxidant activity and kinetics of various CNC samples were studied
using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. CNC-CSos possessed a higher
scavenging activity and faster antioxidant activity compared to its precursors, CNC-OX
and CSos, and their physical mixture. Therefore, by loading vitamin C into CNC-CSos
particles, a dynamic antioxidant system was produced. Vitamin C can be released over a
prolonged time period displaying enhanced and sustained antioxidant properties since the
carrier CNC-CSos also possesses antioxidant properties.
As a result of this doctoral study, knowledge on the surface modification of CNC with
amine groups and CSos have been advanced. The in vitro drug release and antioxidant
studies suggest that systems comprising of CNC could be further explored as potential
carriers in biomedical applications.
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Ultrastructural Effects of Chemical Modification on Olfactory ReceptorsThompson, Rebecca M. (Rebecca Mae) 08 1900 (has links)
The ultrastructural effects of chemical modification on olfactory receptors were investigated with scanning electron microscopy, transmission electron microscopy and fluorescent microscopy. Mason and Morton (1984) hypothesized that a two-step chemical treatment would covalently modify receptor proteins. Their two-step protocol was modified in an attempt to label olfactory receptor proteins and the ultra structural effects of the original two-step protocol were examined.
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