The first generation Phase I Dielectric Spectrometer (P1DS), with a frequency range of 1 mHz to 250 kHz, has been built and successfully operating since mid 2004.  It has proven that dielectric measurements can be achieved at room temperature with gelatin, myoglobin, and hemoglobin.  This work could not have been achieved without the corporate support of Ametek, National Instruments, Tektronix, Fluke, 3M, Mettler-Toledo, and Millipore Corporation.  Their gracious contributions, totaling over $70,000, have propelled the PDP to new and unexpected heights.

2006 Annual Objective and Budget

The primary objective for 2006 is to further develop the electronics, software, and sample cells to confirm our previous findings, as well as, progress the chemical techniques and sample preparation to amplify the dielectric signatures of the structural motifs of peptides and proteins.  It is intended to use off-the-shelf voltage sources, amplifiers, and detectors, coupled with in-house programming for real-time computational and instrumental control, to create the next generation of dielectric spectrometers, the Phase II through IV Dielectric Spectrometers (P2DS – P4DS).  The culmination of these three spectrometers will increase the frequency range from 1 Hz to 240 MHz with a marked increase in stability and reproducibility of the measured signal.  This year focus on the funding and creation of the P2DS.

Essentially, two pieces of hardware are required: a refrigerated/heated circulator to freeze or heat the samples, and a highly sensitive detector to measure the dielectric signals.  The temperature controller is the Julabo FP50-HE circulator which has a temperature range of –50 to 200°C and a stability of 0.01°C.  This controller will gently and precisely warm the protein samples to loosen the bonds between the -helices and allow them to move more freely.  Or, by decreasing the viscosity within the protein, the effective torque will increase on a particular -helix applied by the external electric field, thus increasing the probability of observing and resolving the various dielectric signals from each of the -helical dipoles within the protein.  These experiments have never been performed on proteins and are therefore highly publishable once the data and results are observed.

The measurements of the dielectric signals for these temperature-dependent experiments will be carried out with the Stanford Research SR850 Dual-Phase DSP Lock-In Amplifier.  This amplifier comes complete with a voltage source to excite the samples to the proper voltage and frequency and a highly sensitive lock-in detector to measure the dielectric signals.  The effective frequency range will be 1 mHz to 102 kHz, a frequency and phase resolution of 0.1 mHz and 0.001°, respectively, and a dynamic reserve of 120 dB.  This detector is the most sensitive and stable detector available on the market.

The above temperature controller and detector form the heart of the P2DS.  Both devices will be interfaced to a computer and controlled using National Instruments LabView.  A custom software application will be created to control the temperature, voltage, and frequency of the experiment while monitoring and collecting the data, thus forming a complete scientific instrument, as shown above.  A custom interface circuit will be implemented which will allow low-noise switching of the electrical signals to multiple sample cells and calibration circuits to ensure absolute measurements.  And finally, the instrument will be completed with the fabrication of an insulated circulating bath for the temperature-dependent studies and cylindrically-symmetric capacitive sample cells.

The proposed budget for the P2DS is

In summary, the primary objective for 2006 centers on integrating the off-the-shelf electronics, temperature control, and software for the P2DS, with the secondary objective centering on the sample cell design and calibration.

2007 Annual Objective and Budget

The objectives for 2007 are extensions of those of 2006.  This year, 2007, the primary objective centers on extending the instrumentation to observe fast transient phenomena while continuing the chemical techniques for peptide and protein sample preparation, sample cell design, and environmental control.  The P3DS will be developed using a few new components, but also amalgamating common components from the P2DS to save over $15,000.

Essentially, the P3DS will include the addition of the Stanford Research SR785 Dual-Channel Dual-Phase Dynamic Signal Analyzer to the P2DS temperature controller, circulating bath, computer, and application software.  A second interface and calibration circuit will be fabricated to include the SR785 analyzer and new sample cells will also be created, as shown below.

The SR785 dynamic signal analyzer also comes complete, as the P2DS SR850, above, with a voltage source to excite the samples, however, it is designed to measure extremely fast, or transient, changes of the dielectric responses.  Therefore, when the voltage is first applied to the samples, the SR785 will observe the fast “snap” that may occur to the protein, while the SR850 will observe the long-term changes-in-state as the voltage is continually applied to the protein.  Additionally, the SR785 analyzer will efficiently find frequency or temperature areas-of-interest in which more detailed and thorough studies will be performed with the SR850 amplifier.  The effective frequency range of the SR785 dynamic signal analyzer is DC to 102 kHz and a dynamic reserve of 90 dB.

The proposed budget for the P3DS is

In summary, the primary objective for 2007 centers on extending the capability and observable point-of-view by measuring fast transient behavior within the peptides and proteins.