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Article Excerpt
Chair: Mudlagiri Goli, MS Valley State University
Vice-chair: Douglas Masterson, University of Southern Mississippi
THURSDAY MORNING
Hunter Henry Ballroom A
8:00 Divisional Business Meeting
8:30 THE SITE-DIRECTED MUTAGENESIS OF NEURAL CADHERIN BETWEEN DOMAIN 1 AND DOMAIN 2
Chinela Udemgba*, Nagamani Vunnam, Susan D. Pedigo, University of Mississippi, University, MS 38677
Neural cadherins are members of the cadherin family known for its calcium ion dependent cell adhesion. Classical cadherins contain 5 ectodomains, which are sevenstranded, beta-sheet gobular domains. Domain 1 and 2 were altered by mutating 6 different amino acids (D1C, W2A, R25C, E89A, D134A and D136N). The goal of this work is to discover the role of Ca3 and the linkages between the two domains through the mutations D134A and D136N. The mutant proteins were then over-expressed and purified for later testing. To confirm the mutation, the DNA will be sequenced and the molecular weight of the mutant proteins determined.
8:45 PREPERATION OF HOMOCHIRALLY SIMILAR TYROSINE AND SERINE ANALOGS FROM A COMMON INTERMEDIATE
Dale Rosado* and Douglas S. Masterson, University of Southern Mississippi, Hattiesburg, MS 39406
Recently, there has been much research in the area of unnatural ([alpha],[beta],[gamma], and [delta]) amino acids. It has been shown that incorporation of such unnatural amino acids into protease specific sites in small peptides (such as peptide hormones) increases the in vivo half-life of the peptide. This behavior could make such peptides powerful site specific drug delivery systems to cells, such as cancerous cells (i.e. pancreatic cancer cell lines), which produce and use relatively large quantities of peptide hormones composed of natural ([alpha]a) amino acids. Currently, synthetic routes to synthesize the unnatural analogs of the & aplha;-methyl amino acids easily, inexpensively, and with sufficient enantiomeric yields does not exist. The goal of this project is to develop a method to synthesize all homologues of the unnatural tyrosine and serine analogs via common synthetic intermediates. Furthermore, the synthetic path chosen allows for synthesis of both enantiomers of each in sufficient chemical and enantiomeric yields. This synthetic path uses derivitized prochiral malonate diesters on which a desymmetrization enzyme (i.e. Esterases) can be used to hydrolyze one of the ester substituents to a carboxylic acid. This produces a chiral propanoic acid derivative with an enantiomeric excess of either the (R) or (S) enantiomer. The acid substituent can then be derivatized via a combination of several well-known synthetic paths (Curtius, Wolff, Witting), to give one series of homochirally similar unnatural serine or tyrosine analogs. The current progress into the synthesis of both enantiomers of the & aplha;, [[beta].sup.2.2], and [[beta].sup.3.3] homochirally similar tyrosine and serine analogs will be presented.
9:00 A NOVEL METHOD TO SYNTHESIZE UNNATURAL CYSTEIN ANALOGS
Kinkini Roy and Douglas S. Masterson*, University of Southern Mississippi, Hattiesburg, MS 39406
The aim of this project is to synthesize a wide variety of unnatural cystein analogs (alpha, beta, gamma and carbon analogues of cysteine) from a common synthetic intermediate. This should allow for the construction of amino acids in optically pure form and for the parallel preparation of both enantiomers. The general approach will be as follows: 1) preparation of the prochiral intermediates of malonic acid by using tert-Butylchloromethylsulfide 2) Using esterase to perform a desymmetrization of the prochiral intermediates 3) Analysis of the resulting chiral half ester intermediates 4)Formation of different amino acids from that half ester by using different common organic synthetic pathway. We already prepared both enantiomers of alpha-Methyl Cysteine, both enantiomers of beta-2,2- Methyl Cysteine, both enantiomers of beta-3,3- Methyl Cysteine. Once the synthesis has been achieved in a large scale we shall use them to prepare unnatural Somatostatin analogs with potential biological or enhanced biological activity.
9:15 GRUBBS-TYPE METATHESIS CATALYSTS WITH FUNCTIONALIZED CARBENES FOR APPLICATIONS IN AQUEOUS MEDIA
Adam Roberts* and Hans Schanz, University of Southern Mississippi, Hattiesburg, MS 39406
Over the past four decades, metathesis has evolved to become a highly valuable and versatile tool in organic and polymer synthesis. Since the early 1990s ruthenium-based Grubbs-type metathesis catalysts, such as first generation Grubbs' Catalyst 1 have immensely broadened the application spectrum of this reaction due to their high tolerance towards functional groups as well as moisture and molecular oxygen compared to homogeneous molybdenum-based systems.
The true potential of aqueous metathesis, i.e. its scope and limitations, has yet to be explored. The concept, while proven to be feasible for certain ruthenium (Ru)-based Grubbs-type catalysts, we find that water-soluble examples of such catalysts with an excellent performance profile remain elusive. Our research targets the synthesis of novel Ru-based metathesis catalysts which bear functionalized carbene moieties 2-5 which should enhance catalyst solubility in aqueous solvents for application in Ring Opening Metathesis Polymerization (ROMP) of water-soluble norbornene derivatives (Figure 1). Therefore, we will exchange the initial carbene of highly active metathesis catalysts using functional olefins. ROMP will retain the function carbene as a tethered group, thus the catalyst will not change its solubility profile. Due to the favorable ratio of the rate of initiation vs. propagation, first generation catalysts are favored to provide materials with narrow molecular weight distributions under "living" conditions. We will present recent results on the catalyst syntheses and initial polymerization experiments.
9:30 REVERSIBILE INHIBITION/ACTIVATION OF GRUBBS' CATALYST
Steven J. P'Pool*, Nancy J. Berger, and Hans Schanz, University of Southern Mississippi, Hattiesburg, MS 39406
Over the last four decades olefin metathesis has increasingly become an important synthetic tool in organic and polymer chemistry. Grubbs' first and second-generation catalysts are the most common catalysts used for these transformations. 1 Various ligand modifications have been designed to accommodate special applications, such as temporary catalyst inhibition for ROMP of DCPD2. Little research has been invested in catalyst systems, which can reversibly be activated and inhibited. Our project investigates the influence of electron-rich N-donor ligands on the catalytic activity of Grubbs' catalyst. We have found that addition donor ligands such as 1-methylimidazole or 4-dimethylaminopyridine (DMAP) are capable of completely inhibiting the metathesis reaction, such as RCM and ROMP, when at least two equivalents are used to completely produce a six-coordinate species of low activity. Upon acid addition, the initial Grubbs' Catalyst is restored and the metathesis reaction proceeds according to the additive-free catalyst. We will present new synthetic and kinetic data on reversible catalyst inhibition/activation of Grubbs' catalyst.
9:45 SYNTHESIS OF UNNATURAL ISOLEUCINE ANALOGS FROM A COMMON INTERMEDIATES
Sandipan Dawn* and Douglas S. Masterson, University of Southern Mississippi, Hattiesburg, MS 39046
he aim of this project is to synthesize a wide variety of unnatural isoleucine analogs ([alpha], [beta] and [gamma]) from a common synthetic intermediate. This should allow for the construction of amino acids in optically pure form. The general approach will be as follows: 1) preparation of the diastereotopic intermediates of malonic acid 2) Using esterase to perform a desymmetrization of the intermediates 3) Analysis of the resulting half ester intermediates 4)Formation of different amino acids: [alpha](Curtius),[beta](Wolff,Curtius),[gamma](Wittig, Curtius) from that half ester. Once the synthesis has been achieved we can use that to prepare unnatural peptides with potential biological or enhanced biological activity. These unnatural amino acids can be used to replace their natural counterparts in some hormones (eg Neurotensin) to increase their half-life inside a biological system. New Synthetic Approaches to Water-Soluble Ruthenium-Based Second Generation Olefin Metathesis Catalysts
10:00 Break
10:15 NEW SYNTHETIC APPROACHES TO WATER-SOLUBLE RUTHENIUM-BASED SECOND GENERATION OLEFIN METATHESIS CATALYSTS
Hans Schanz (1*), Nancy J. Berger (2), and Steven J. P'Pool (1), (1) University of Southern Mississippi, Hattiesburg, MS 39406 and (2) Lycoming College, Williamsport, PA 17701
Despite environmental and commercial benefits, metathesis in aqueous media has not been vigorously pursued over the last decade apart from conceptual studies. Various factors have contributed to the slow development in this area: 1) Dissatisfactory Cost/Benefit Ratio: Water-soluble phosphines are expensive and cumbersome to synthesize. Commercially available phosphine ligand Cy2P(CH2)2NMe3+Cl- is near ten times the cost of PCy3. Thus, competitive water-soluble olefin metathesis catalysts need to be: A) Highly active designs based on less expensive water-soluble NHC-ligands, B) Recyclable to improve the cost/benefit ratio. 2) Hydrolysis of Catalysts Bearing Water-Soluble NHC-ligands: Protic solvents often cause slow hydrolysis of the metal-NHC bond. This observation was made for various catalysts. Steric protection of this bond is needed. 3) Problematic Catalyst Synthesis: The NHC ligand/phosphine exchange reaction at first generation catalysts, to date the method of choice for the synthesis of second generation catalysts, requires solvents of low polarity. This renders almost all ionic NHC-ligand designs unfeasible as they display low solubility and thus very slow conversion rates. We have recently synthesized a ruthenium carbene complex which is a reversibly water-soluble, pH-responsive catalyst which has potential for improved catalyst separation and recycling. Only a handful of water-soluble designs have been reported thus far, none of which is pH-responsive. the neutrally charged catalyst is soluble in organic media, highly active and bears an NHC ligand with two dimethylamino groups. Upon acid addition, the catalyst should be suitable for reactions in aqueous media. We will present results on the synthesis, thermal stability and catalytic activity of both, neutral and double-protonated catalysts. We propose, such catalysts can be effective in aqueous and organic media, can perform co-polymerizations of largely different monomers, and can be recycled upon pH change.
10:30 SPECIFIC DELIVERY OF ANTI-SURVIVIN SIRNA TO KB CELLS BASED ON FOLATE RECEPTOR
Jun He*, University of Southern Mississippi, Hattiesburg, MS 39406
The recent discovery of RNAi has provided a powerful means of regulating gene expression. RNAi is not only revolutionizing the ways bioscientists perform basic science research such as studying gene function and mechanism, but also presents immense potentials for developing the next generation biomedicine with unmatched high potency and low side toxicity. The advancement of understanding of cellular functions at molecular levels has revealed differences in gene expression profiles between normal cells and cancerous cells. Such differences may become the basis for biomedical intervention of cancer genesis and progression. For example, folate receptor (FR) is not expressed in normal cells but high levels of FR expression are associated with certain cancers, which require a steady supply of folic acid for the biosynthesis of nucleic acids. Based on expertise in chemistry, RNA, and enzomolgy, we are exploiting FR as a cancer-specific delivery vehicle of anti-survivin siRNA. Survivin belongs to the family of inhibitors of apoptosis protein (IAP). Expression of survivin is essential for cancer proliferation. Down regulation of survivin can induce apoptosis of cancerous cells. Therefore, our experiments may lead to new cancer therapy based on RNAi.
10:45 DOWN REGULATION OF VEGF AND VEGFR BY RNAI THROUGH CANCER-SPECIFIC DELIVERY
Yilin Zhang*, Yanlin Guo, and Faqing Huang, University of Southern Mississippi, Hattiesburg, MS 39406
Angiogenesis is a process of initiation, growth, and development of new blood vessels from pre-existing ones. Angiogenesis is critical for cancer genesis and tumor growth. Numerous studies have established vascular endothelial growth factor (VEGF) as an essential factor for angiogenesis. Cells can obtain VEGF by either self VEGF expression or from extracellular environment. With the powerful RNAi technology, we are investigating siRNA's effect against both VEGF and VEGFR. Using the transfection agent Lipofectamine and quantitative real time PCR, we have demonstrated that our self-designed and prepared siRNAs are efficient inhibitors of VEGF and VEGFR expression. However, Lipofectamine-based siRNA is not cell specific and displays a certain degree of toxicity. Taking the advantage of high level folate receptor (FR) expression by certain cancer cells, we are developing cancer-specific delivery tools for siRNA application. By binding and stabilizing siRNA and using cancer-specific receptors, the new siRNA delivery agents will lead to significant improvement on siRNA delivery, paving the way for applications of RNAi in biomedicine.
11:00 THE EFFECT OF ROTATIONAL ACCELERATION ON DIFFUSION BETWEEN MISCIBLE FLUIDS
John A. Pojman (1*), Gloria Viner (1), and Renato Lombardo (2), (1) University of Southern Mississippi, MS, 39406 and (2) Universita di Palermo, Italy
We studied three types of miscible systems in a spinning drop tensiometer. The first system, isobutyric acid and water, exhibits an Upper Critical Solution Temperature at 26.5[degrees] C above which it is miscible in all proportions. The second, butanol and water, has a solubility limit. The third system, dodecyl acrylate and poly(dodecyl acrylate), is miscible in all proportions. We analyzed the effect of the rotational acceleration and show why the isobutyric acid system is more affected by writing the equation for the flux and including a term for the buoyancy. Finally, we explain why the first two systems retain very sharp concentration gradients even as one fluid dissolves into the other but the monomer-polymer system does not.
11:15 THE USE OF SQUARAINE DYES AS MOLECULAR SENSORS
Karl Wallace*, University of Southern Mississippi, Hattiesburg, MS 39406
Squaraine molecules are an unusual class of molecules that have some unique physical properties. Squaraine dyes are interesting materials to work with and have been used for many applications in materials science. For example, electrophotography, optical data storage, and non-linear optics, have all incorporated squaraine dyes. An interesting property of squaraine dyes is the sharp intense Q-band seen at wavelengths between 600-670 nm, with extinction coefficients ([epsilon]) [greater than or equal to] [10.sup.5] [cm.sup.-1] [M.sup.-1]. This intense absorption band is a very attractive property for sensor design, as it is close to the near infrared (NIR) region of the spectrum, which is desirable for integration with optical instrumentation. However, squaraine dyes have only recently been utilized as molecular sensors in the field host-guest recognition (an area of supramolecular chemistry). For example, in their use for the detection of trace elements, such as, iron and zinc. Iron and zinc are important in biological systems and in the environment. Many of us are...
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