In the present research work we evaluate the in vivo distribution of gold nanoparticles (AuNPs) at different time durations after intravenous administration in mice. AuNPs with size of about 20 nm and concentration of 1 mM were synthesized by gamma irradiation method using 0.5% alginate as a stabilizer. AuNPs were characterized by UV-Vis spectrum and transmission electron microscope (TEM) image. The as-synthesized AuNPs solution was centrifuged to concentrate to 2 mg AuNPs/1 ml solution. Intravenous administration of AuNPs in mice was done at the tail with 1 mg AuNPs (0.5 ml). After 1, 3, 6 and 12 h of injection, blood was collected, mice were sacrificed and various tissues/organs were removed. The blood haematology and serum clinical chemistry indexes of mice intravenously injected with AuNPs were not significantly different compared to those of the control ones. In addition, gold content in the samples was quantitatively determined by k 0 -neutron activation analysis (k 0 -NAA) at nuclear research reactor, Da Lat Vietnam. Results showed that after 1 h of administration, AuNPs were mainly accumulated in blood (41.56%), in liver (51.60.%), in lung (6.16%) and in kidney (0.53%). After that the content of AuNPs in blood was decreased to nearly normal at 6 h while the content of AuNPs in liver, lung and kidney was accumulatively increased. After 6 h of administration AuNPs were mainly accumulated in organs like liver (76.33%), lung (11.86%) and kidney (2.23%). Thus, the obtained results are practically useful for using AuNPs as x-ray contrast agent, especially for blood and liver.

The β-glucan extracted from the yeast cell wall was irradiated by gamma rays from a Co-60 source at doses from 100 to 300kGy in swelling condition of 10% (w/v) for degradation. The water soluble content of irradiated sample increased from 25.89 to 66.71% by the increasing of doses from 100 to 300kGy. While the molecular weight of water soluble β-glucan was found to be decreased from 48.13 (at 100kGy) to 10.77 kDa (at 300kGy). The UV-spectra of resultant water soluble β-glucan were appeared a new peak at 265nm with the intensity increased by the increase of the dose. The IR spectra of irradiated β-glucan samples were also recognized by an increase of peak intensity at1731cm-1 assigned to C=O linkages and a decrease of peak intensity at 1156cm-1 assigned to C-O-C glycosidic linkages by the increasing of dose. In addition, the oligoβ-glucan with Mw about 18 kDa obtained at 250kGy-irradiated sample strongly promoted the growth of mustard green and lettuce. The oligoβ-glucan prepared by radiation techniques showed as a high effective plant growth promoter. This product is potentially promising for application in high-technological agriculture for production of clean vegetables and agro-products.

The mixtures β-glucan extracted from the yeast cell wall were irradiated under gamma rays from a Co-60 source at doses of 100, 200 and 300 kGy in order to prepare water-soluble β-glucan. Yields of the water soluble β-glucan produced are 25.9, 49.1, 66.71%, and their molecular weights (Mw) are 30.5, 24.9 and 10.8 kDa, respectively. There are no any new peak in the IR spectra of the irradiated β-glucan samples, but the intensity ratio between the peaks at wavenumber of 1156 cm-1 (assigned to C-O-C bond) and of 1040 cm-1 (assigned to C-C bond) in glycosidic linkages was reduced with irradiation dose. These results revealed that gamma irradiation did not cause any change in the β-glucan structure except the scissions of glycosidic linkages. In this study, immuno stimulation of the irradiated b-glucan was also investigated for the Swiss mice. After 28 days supplying with the irradiated b-glucan, not only cellular indexes (white blood cell, neutrophils and lymphocytes counts), but also humoral  immunity indexes (IgA and IgM) of the mice significantly increased and the highest effects was obtained for the mice supplied with the oligoβ-glucan prepared by gamma irradiation at 200 kGy. Thus, the water soluble oligoβ-glucan with Mw ~ 24.9 kDa prepared by gamma radiation much stimulated the natural immune system (non-specific immunity) in mice including both the cellular and humoral immunities. Particularly, the irradiated b-glucan is a very promising product for preparation of functional foods aiming at cancer prevention.

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Theoretical models have been developed to understand kinetics of ribosomes and F 1 -ATPase which are important enzymes responsible for protein synthesis and ATP production in cells respectively. One important aspects of protein synthesis is accuracytranslation speed relation and how it is related to overall cell growth. For F 1 -ATPase , it is important to understand how F 1 -ATPase hydrolyzes ATP molecules based on which the mechanism of ATP synthesis is deduced due to the assumption that synthesis is just the reverse of hydrolysis.A novel pseudo-GTPase activated state, which was discovered recently, may play a role in selection of cognate during initial selection phase of protein synthesis. By assuming the state to exist after codon recognition and prior GTPase activation, kinetic analysis shows that rates between codon recognition and pseudo-GTPase activation are comparable for cognates (7 s −1 ) and near cognates (3 s −1 ). However, cognate in pseudo-GTPase activated state can proceed at significantly faster rate (138 s −1 ) to GTPase activated compared to near cognate (0.3 s −1 ). The effective rate from codon recognition to GTPase activated is slowed down, thus requiring less intrinsic selectivity between two states for selection while maintain good accuracy and fast speed.The effect of free [M g 2+ ] on translation kinetics and accuracy has been investigated based on a coarse-grained model of detailed translation scheme. Ribosomes can be broady categorized into three states: free, initial selection and proofreading. Increasing [M g 2+ ] will accelerate association speed between ternary complexes (both cognates and near cognates) and free ribosomes, resulting in decrease in accuracy. Increasing [M g 2+ ] from 1 mM to 3 mM results in faster translation speed due to increasing association speed of cognates with sufficient free ribosomes. Despite the drop in accuracy, it is still sufficient for selection and with faster speed, ribosomes seem to operate in "effizienter" regime. Further increase of [M g 2+ ] to 7 mM leads to plummet of translation speed. This is attributed to more sluggish ribosomes occupied with near cognates, causing less ribosomes for cognates. The regime is termed "competition" highlighting the effect of near cognates on translation. The translation model is incorporated into a growth model in an attempt to study the effect of accuracy on cellular proteome and growth during exponential phase. The proteome consists of free amino acids, metabolic proteins and ribosomes. The assumption i It may not be rare but interesting enough to have two main supervisors during PhD. I would like to thank my current supervisor Dr. Dong Zhili and former supervisor Dr. Su Haibin for this four year journey. Dr. Zhili has shown kind support after my supervisor Dr. Haibin left Singapore for Hong Kong. Despite his departure, Dr. Haibin still helps me with projects by giving me an opportunity to stay in Hong Kong for 5 months funded by his research grant and Matching-Fund scheme for International Visiting Internship...