Fast and accurate detection of pathogens such as bacteria, their toxins and viruses at low concentrations is very important. The conventional techniques are time consuming where expensive equipment is required with a consumption of excess amount of blood from patients. Recently, immunosensors are used for the detection of pathogens because they are miniature, sensitive, biocompatible and require low power. According to the Centers for Disease Control and Prevention (CDCP), 76 million people become ill due to food poisoning and 5,000 of them die each year in United States. In addition, SEB causing food poisoning has listed as a bioterrorism agent by CDCP. Thus, accurate and selective detection in short time is very important for SEB detection. Candida albicans (C. albicans) is a yeast-like fungus and causes anxiety, insomnia, constipation, hiatal hernia, panic attacks, denture-induced stomatitis, angular cheilitis, gingivitis and prosthetic implant infections. In addition, it can cause death if the immune system of patient is under failure due to cancer, chemotherapy and AIDS. In this study, a new procedure was developed. A simple and highly selective homogeneous sandwich immunoassay was obtained for ultrasensitive detection of Staphylococcal Enterotoxin B (SEB) using Atomic Force Microscopy (AFM) and Surface Enhanced Raman Scattering (SERS) probe. In the developed procedure, thiolated antibodies were produced and SEB was immobilized on the biosensor surface using these antibodies. In addition, theory of SEB adsorption on a gold surface was studied and the reaction rate constant between SEB and its toxin was calculated. Moreover, C. albicans was detected using the developed procedure by a microscope. Thus, it is proved that, the developed procedure can be used for detection of different pathogens. Furthermore, nonspecific interaction between SEB antibody and BSA was determined in this study. Also, the developed procedure and a procedure found from literature were compared. In the procedure used in the literature (second procedure), self-assembled monolayer (SAM) was formed and antibodies were immobilized on SAM. After formation of sandwich structure, the roughness of gold surface and the minimum concentration of SEB detected were determined by AFM and SERS, respectively.

The conformation of paclitaxel in the bound state on the protein has been proposed to be the T-taxol conformation, and paclitaxel analogs constrained to the T-taxol conformation proved to be significantly more active than paclitaxel in both cytotoxicity and tubulin polymerization assays, thus validating the T-taxol conformation as the tubulin-binding conformation. In this work, eight compounds containing an aza-tricyclic moiety as a mimic of the baccatin core of paclitaxel have been designed and synthesized as water-soluble simplified paclitaxel analogs, among which 3.50-3.52 and 3.55 were conformationally constrained analogs designed to bind to the paclitaxel binding site of tubulin, based on their similarity to the T-taxol conformation. The open-chain analogs 3.41-3.43 and 3.57 and the bridged analogs 3.50-3.52 and 3.55 were evaluated for their antiproliferative activities against the A2780 cell lines. Analogs 3.50-3.52 and 3.55 which were designed to adopt the T-taxol conformation showed similar antiproliferative activities compared to their open-chain counterparts. They were all much less active than paclitaxel. In the second project, a series of paclitaxel analogs with various thio-containing linkers at C-2′ and C-7 positions were designed and synthesized in our lab. These analogs were attached to the surfaces of gold nanoparticles by CytImmune Sciences for the development of mutifunctional tumor-targeting agents. The native analogs and the gold bound analogs were evaluated for their antiproliferative activities against the A2780 cell line. All the compounds tested showed comparable or better activities than paclitaxel. Stability studies were performed for selected analogs in hydrolysis buffer, which showed that the analogs released paclitaxel in buffer over time. In the third project, the synthesis of a conformationally constrained paclitaxel analog which was designed to mimic the REDOR-taxol conformation was attempted. Two synthetic routes were tried and significant progress was made toward the synthesis of the conformationally constrained analog. However, both of the current synthetic routes failed to produce the key intermediate that would serve as the precursor for a ring-closing metathesis reaction to furnish the macrocyclic ring. / Ph. D.

The Turos laboratory has been working with N-thiolated β-lactams for years trying to understand the mode of action and structural features it needs to have biological activity. Over the years new data has shown promising inhibitory activity against various microbes. In this dissertation, a review of the vast amount of work carried out on N-thiolated β-lactams in Turos laboratory has been done and their novelty, in terms of structure and mechanism has been discussed. A complete outline of our work in the discovery and ongoing development of these compounds, starting from our initial, unexpected finding of antimicrobial activity for one of the lead compounds, to a more complete understanding of their chemical and biological mode of action and potential utility as antibacterial compounds, has been provided. Previous researches by graduate students in the Turos laboratory have shown that N-thiolated β-lactams targets Type II Fatty Acid Synthesis (FAS). In process of understanding this further, other FAS inhibiting antibiotics like Triclosan were compared to our lactams by adding excess of exogenous fatty acids. Results revealed vast differences in the MIC value of triclosan and N-thiolated β-lactams, giving an idea that there might be a different mode of action or a different target altogether. The third chapter discusses the study of attaching hydrophilic C3 side chains like amino acids and carbohydrates on N-thiolated β-lactams while studying the influence of microbiological activity. From the study it was found that the lengthening of the side chain halts the inhibitory activity regardless of whether the side chain contains unsaturation or branching. Results showed that polar groups were not well tolerated and the inhibitory activity goes down regardless of polarity. Finally, research on dual-action antibiotics was discussed. Antibiotics cause continuous bacterial resistance and in this aspect use of two drugs with different mode of action can call for reduction of the resistance. Herein, N-acyl ciprofloxacin and N-thiolated β-lactams were connected together via an ester linkage. Six new hybrid compounds have been synthesized successfully and tested against E. faecium, K. pneumoniae, A. baumannii, P. aeruginosa, and E. cloacae.