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Cancer is a group of diseases caused by aberrant continuously proliferating cells capable of metastasis. Despite significant advances in preventive, diagnostic and treatment measures, cancer is one of the major causes of death in the United States, second only to heart diseases. Main treatment approaches are surgery, radiotherapy, chemotherapy, and the recently expanding immunotherapeutic approaches. The main challenge in treating cancer is the ability of cancer cells to mutate and develop resistance to drug treatments therefore lowering the efficacy of chemotherapy in preventing metastatic tumors. Cancer vaccines are a treatment modality that employs the potential of the immune system to recognize and eliminate tumor cells by unmasking tumor cell antigens and generating an effective anti-tumor immune response with an immune memory capable of preventing metastases formation. This dissertation describes and evaluates an innovative cell-particle hybrid cancer vaccine construct involving irradiated tumor cell surface-engineered with polymeric particles using streptavidin-biotin cross-linking. The tumor cells were biotinylated indirectly using biotin-linked antibodies targeting a surface integrin and the particles were loaded with an immune adjuvant and coated with streptavidin. The tumor cells served as the source of tumor antigens and the anchored particles served to confine loaded immune adjuvant to the tumor cells. The vaccine construct was designed to co-deliver tumor antigens and the immune adjuvant to the same antigen presenting cell, a criteria that has been suggested recently to be important for optimal cancer vaccine potency. The first report on this cell-particle construct was published in my master’s thesis defended in May 2013. In that report, the feasibility of assembling the cell-particle hybrid was demonstrated. However, loading of the immune adjuvant, CpG ODN (cytosine phosphate guanine oligonucleotide), into streptavidin-coated particles was not optimal. In the current studies, this problem was addressed and the cancer vaccine potential of the cell-particle construct was assessed. We first evaluated a new TLR4 (toll like receptor 4) agonist, PET lipid A (pentaeryhtritol lipid A), for its potential use in cancer vaccines with the intention to incorporate it in the cell-particle hybrid. PET lipid A is a fully synthetic lipid A analog that has been demonstrated to have immunostimulatory properties. We evaluated the potential use of PET lipid A in cancer vaccine applications and the effect of particulate formulations on its adjuvant properties. Results showed improved in vitro immunostimulatory properties for particle based formulations. Upon testing the immunostimulatory properties of PET lipid A in vivo, moderate enhancement in antigen specific cytotoxic T cells stimulation was observed when PET lipid A was delivered in particles, which then translated into a corresponding trend toward increased survival in a prophylactic tumor study. PET lipid A was concluded to be a weak potential cancer vaccine adjuvant and was not chosen as the immune adjuvant to use in the cell-particle hybrid assembly. Instead, CpG ODN (TLR9 agonist) was chosen due to its strong record of efficacy as a cancer vaccine adjuvant. The second part of this research project aimed at addressing the challenges we encountered previously in achieving acceptable CpG ODN loading of the final streptavidin-coated PLGA (Polylactic-co-glycolic acid) particles. The approach taken was to modify the method used earlier to make the particles in order to circumvent CpG ODN loss. In the modified method the number of steps required to make streptavidin-coated CpG ODN-loaded PLGA particles was reduced and the fabrication media was altered to allow simultaneous particle fabrication and activation of surface carboxyl groups. The modified method resulted in 5-fold higher loading in the final streptavidin-coated particles compared to the original method. Subsequent to establishing the feasibility of constructing the cell-particle hybrid and characterizing the assembled hybrid in vitro, the in vivo cancer vaccine potential of the designed construct was examined. Two independent murine tumor models were chosen for this purpose, namely prostate cancer and melanoma. The proposed cell-particle hybrid vaccine construct had significant therapeutic outcomes in the prostate cancer tumor model where mice vaccinated with cell-particle hybrids were the only group to show significant improvement in survival compared to untreated controls whereas no other vaccine formulation had such an effect. Unfortunately, no prophylactic benefit was observed from any of the vaccine formulations used in the melanoma tumor model involving irradiated GM-CSF (granulocyte macrophage colony stimulating factor)-secreting B16.F10 cells. In vitro examination of the immunostimulatory properties of all cell lines used in these studies revealed that transfected and parent B16.F10 cells (representing murine melanoma) were possibly immunoinhibitory whereas RM11 (representing murine prostate cancer) cells lacked such immunosuppressive effect in vitro. Our objective was to design and evaluate a new cancer vaccine construct that improved the immunostimulatory properties of irradiated tumor cell based vaccines. The approach taken was to surface engineer tumor cells with immune adjuvant loaded polymeric particles. We reported a simple method for fabricating streptavidin-coated PLGA particles and a versatile method of tumor cell surface engineering. We found that the efficacy of tumor cell-based vaccines can be inconsistent across tumor models and the in vitro immunosuppressive effect of tumor cells might be a contributing factor.

Novel biocatalysts are highly demanded in the white biotechnology. Hence, the development of highly stable and enantioselective biocatalysts with novel functionalities is an ongoing research topic. Here, an osmium ligating single-site ArM was created based on the biotinstreptavidin technology for the dihydroxylation of olefins. For the creation of the artificial catalytic metal center in the streptavidin (SAV) cavity, efficient osmium tetroxide (OsO4) chelating biotin-ligands were created. The unspecific metal binding of the host scaffold was diminished through genetical and chemical modification of the host protein. The created single-site OsO4 chelating ArM was successfully applied in the asymmetric cyclopropanation, revealing a stable and tunable catalytic hybrid system for application. The structural analysis of protein-ligand complexes is essential for the advanced rational design and engineering of artificial metalloenzymes. In previous studies, a SAV-dirhodium ArM was created and successfully applied in the asymmetric cyclopropanation reaction. To improve the selectivity of the SAV-dirhodium complex, the structural location of the organometallic complex in the SAV cavity was targeted and small-angle x-ray scattering (SAXS) was used to obtain the structural information. The SAXS analysis revealed valuable information of the molecular state of the complexes; hence, the method proved to be useful for the structural analysis of protein-ligand interactions. The discovery of novel enzymes from nature is still the major source for improved biocatalysts. One of the most important enzymes used in the molecular biology are DNA polymerases in PCR reactions. The halothermophilic brine-pool 3 polymerase (BR3 Pol) from the Atlantis II Red Sea brine pool showed optimal activities at 55 °C and salt concentrations up to 0.5 M NaCl, and was stable at temperatures above 95 °C. The comparison with the hyperthermophilic KOD polymerase revealed the haloadaptation of BR3 Pol due to an increased negative electrostatic surface charge and an overall higher structural flexibility. Engineered chimeric KOD polymerases with swapped single BR3 Pol domains revealed increased salt tolerance in the PCR, showing increased structural flexibility and a local negative surface charge. The understanding of the BR3 Pol haloadaptation might enable the development of a DNA polymerase tailored for specific PCR reactions with increased salt concentrations.

The aim of the work was the selective isolation of bacterial DNA with help of magnetic carriers covered by streptavidine (PGMA-NH2-STV, MPG® Streptavidin). Conditions of functionalisation of carriers using two biotinylated probes were optimized: the amount of carrier, the amount of probe, binding of biotinyled probe to streptavidine. Purified DNA Lactobacillus was used for hybridization. DNA binding to the probe (DNA/DNA hybridization) and nospecific adsorption of DNA to the carrier were tested. Target DNA eluted from the carrier was identified using PCR with primers R16-1 and LbLMA1-rev and with primers P_eub and F_eub. The amount of probe bound to the carrier was estimated using UV spectrophotometry. It was estimated that biotinyled probe can be used for functionalisation in concentration 5 pmol/µl added to the carrier in the ration carrier : probe 1:1. It was shown that nonspecific DNA adsorption to the MPG® Streptavidin is significantly lower than to the carrier PGMA-NH2-STV.Using DNA/DNA hybridization and the MPG® Streptavidin, DNA from pure culture Lactobacillus was isolated. Procedure was applicated for DNA isolation from milk products.

No description available.

The Streptomyces avidinii protein streptavidin binds the small molecule biotin (vitamin H / B₇) with extraordinary stability, resulting in the streptavidin-biotin interaction being one of the strongest non-covalent interactions known in nature (K_d ~ 10^-14 M). The stable and rapid biotin-binding, together with high resistance to heat, pH and proteolysis, has given streptavidin huge utility, both in vivo and in vitro. Accordingly, streptavidin has become a widely used tool in many different biotechnological applications. Streptavidin has also been the subject of extensive research efforts to glean insights into this paradigm for a high-affinity interaction, with over 200 mutants of the protein reported to date. Despite the high stability of the streptavidin-biotin interaction, it can and does fail under certain experimental conditions. For example, streptavidin-biotin dissociation is accelerated by an increased temperature or lower pH (conditions often encountered in cellular imaging experiments), and by mechanical stress, such as the shear force arising from fluid flow (encountered when streptavidin is used as a molecular anchor in biosensor chips and arrays). This study details efforts made at increasing further the utility of streptavidin, by increasing the stability of biotin and biotin-conjugate binding. A rational site-directed mutagenesis approach was used to create 27 mutants, with eight of these mutants possessing higher-stability biotin-binding. The most stable biotin-binding mutant was named traptavidin and was extensively characterised. Kinetic characterisation revealed traptavidin had a decreased dissociation rate from biotin and biotin-conjugates when compared to wildtype streptavidin, at both neutral pH and pH 5. Atomic force microscopy and molecular motor displacement assays revealed the traptavidin-biotin interaction possessed higher mechanical stability than the streptavidin-biotin interaction. Cellular imaging experiments revealed the non-specific cell binding properties of streptavidin were unchanged in traptavidin. X-ray crystallography was also used to generate structures of both apo- and biotinbound traptavidin at 1.5 Å resolution. The structures were analysed in detail and compared to the published structures of streptavidin, revealing the characteristics of traptavidin arose from the mutations stabilising a flexible loop over the biotin-binding pocket, as well as reducing the conformational change on biotin-binding to traptavidin. Traptavidin has the potential to replace streptavidin in many of its diverse applications, as well as providing an insight into the nature of ultra-stable noncovalent interactions.

<p>The human glucose transporter GLUT1 facilitates glucose to be accumulated on the other side of the cell membrane. The functional state of GLUT1 is uncertain due to diversity of the reports. In this thesis, the activity of red blood cell GLUT1 was extensively studied to further characterize this protein.</p><p>The human red blood cell membranes were stripped to become vesicles with low-ionic alkaline solution in the presence or absence of dithioerithritol. The supernatant of partially solubilized membrane vesicles provided approximately 65% of the vesicle proteins. GLUT1 purified from this supernatant showed a little high-affinity cytochalasin B binding activity. On the other hand, the vesicles stripped with dithioerythritol provided mostly monomeric GLUT1 and those without dithioerythritol provided monomeric and oligomeric GLUT1. MALDI-ToF-MS detected variant GLUT1 fragments between the two preparations. Residual endogenous phospholipids per GLUT1 also showed difference. However, the equilibrium exchange of glucose was retained for both GLUT1 preparations. Cytochalasin B-binding activity of GLUT1 in streptoavidin-biotin-immobilized red blood cells showed that both dissociation constant and binding sites per GLUT1 fell between those of wheat germ lectin-immobilized red blood cells with or without polylysine coating, which indicated the switching of two cytochalasin B-binding states of GLUT1. It is concluded that GLUT1 in red blood cells contains approximately two equal portions, monomeric with high-affinity cytochalasin B-binding activity and oligomeric without high-affinity cytochalasin B-binding activity. In the partial solubilization of the membrane vesicles, GLUT1 which does not have high-affinity cytochalasin B-binding activity is pooled. This might provide a resolution to select oligomerically and functionally different GLUT1 for crystallization.</p><p>In addition a modified micro-Bradford assay with CaPE precipitation was developed to achieve a routine quantitation method for membrane proteins and the effects of cholesterol and PEG(5000)-DSPE on reconstituted GLUT1 were preliminarily determined.</p>

The human glucose transporter GLUT1 facilitates glucose to be accumulated on the other side of the cell membrane. The functional state of GLUT1 is uncertain due to diversity of the reports. In this thesis, the activity of red blood cell GLUT1 was extensively studied to further characterize this protein. The human red blood cell membranes were stripped to become vesicles with low-ionic alkaline solution in the presence or absence of dithioerithritol. The supernatant of partially solubilized membrane vesicles provided approximately 65% of the vesicle proteins. GLUT1 purified from this supernatant showed a little high-affinity cytochalasin B binding activity. On the other hand, the vesicles stripped with dithioerythritol provided mostly monomeric GLUT1 and those without dithioerythritol provided monomeric and oligomeric GLUT1. MALDI-ToF-MS detected variant GLUT1 fragments between the two preparations. Residual endogenous phospholipids per GLUT1 also showed difference. However, the equilibrium exchange of glucose was retained for both GLUT1 preparations. Cytochalasin B-binding activity of GLUT1 in streptoavidin-biotin-immobilized red blood cells showed that both dissociation constant and binding sites per GLUT1 fell between those of wheat germ lectin-immobilized red blood cells with or without polylysine coating, which indicated the switching of two cytochalasin B-binding states of GLUT1. It is concluded that GLUT1 in red blood cells contains approximately two equal portions, monomeric with high-affinity cytochalasin B-binding activity and oligomeric without high-affinity cytochalasin B-binding activity. In the partial solubilization of the membrane vesicles, GLUT1 which does not have high-affinity cytochalasin B-binding activity is pooled. This might provide a resolution to select oligomerically and functionally different GLUT1 for crystallization. In addition a modified micro-Bradford assay with CaPE precipitation was developed to achieve a routine quantitation method for membrane proteins and the effects of cholesterol and PEG(5000)-DSPE on reconstituted GLUT1 were preliminarily determined.

This master thesis deals with nanotechnology, nanoparticles and nanostructured surfaces, electrochemical methods, especially voltammetry, cyclic voltammetry, electrochemical impedance spectroscopy and contact angle measurement. One part is focused on electrodes primarily nanostructured and modified by substancies with thiol bound. Tutorial for preparation of gold nanostructured electrods is introduced in practical section including SEM photos of electrode surface. Nanostructured and bare gold electrodes were modified by 11-mercaptoundecanoic acid, streptavidin, glycine and biotin and measured by cyclic voltammetry, electrochemical impedance spectroscopy and contact angle.