Electrical and Computer Systems Engineering Postgraduate Student Research Forum 2001

1. Experimental measurements of dielectric and conduction properties of amino acids Author’s Name: Elena Pirogova Supervisor: A/Prof. I. Cosic Associate supervisor: Mr. B. Lithgow INTRODUCTION Proteins are macromolecules involved in various biological processes at the cellular level. They consist of the sequentially linked amino acids. Proteins can only express its biological function when they achieve a certain active 3-D structure. Both protein's function and 3-D structure are primarily determined by the amino acid sequence within the protein molecule. The Resonant Recognition Model is a physico-mathematical model interpreted protein sequence using methods of signal analysis. The RRM is based on the representation of the amino acid sequence as a numerical series by assigning to each amino acid a physical parameter value relevant to the protein's biological activity. In our previous studies the electron-ion interaction potential (EIIP) was used for this purpose. The assignment of a particular number for each amino acid is a crucial step in all RRM calculations. Therefore, in this study we have investigated the dielectric and conduction properties of single amino acid solutions for the use in the RRM. Dielectric spectroscopy method, so called bridge method, has been employed in this study for direct measurements of dielectric and conduction properties of amino acid solutions. Obtained values of capacity and conductivity of analysed samples are reported here. Figure 1. The RRM procedure. TECHNIQUE Experimental dielectric bridge methods have been employed in some form for low molecular mass materials and polymers, but never been used on amino acids, for more than forty years and to then, describe in more detail the use of frequency response analyzers and time domain reflectometry, which are relatively new techniques. Although there are a number of different bridge configurations, the basic principle of operation is the same and involves the balancing of the impedances of the two opposite arm pairs of the bridge. One of these arms contains the sample, which may be modeled as a resistor Rs in parallel with a capacitor Cs. The experimental measurements of capacity (Cp) and conductivity (G) of our samples have been undertaken at the Department of Physics and Materials Engineering using Dr. George Simon’s Software Win DETA V3.71 and HP4284 RLC Bridge (20 - 10MHz). The liquid cell used in these measurements consist of the glass container and the sensor attached. The description of the sensor is presented in Fig. 2. SAMPLE PREPARATION We have prepared aqueous solutions of 0.5M concentration for each analysed single amino acid (obtained in the form of powder). Most of them were prepared at room temperature using the magnetic stirrer. RESULTS Results obtained are shown in Table 1. Figure 2. Sensor. Figure 3. The change of capacity values in a frequency range (red line), the change of permittivity (dielectric constant) values in a frequency range (green line). Electrical and Computer Systems Engineering Postgraduate Student Research Forum 2001