Brown: Team Resistance/14 July 2008

14 July 2008

Update Meeting

We’re ready to start running resistance tests by lysing our pVJ4 cells and measuring the change

• Last week,
• We have a meeting with Professor Jerry Daniels later today and Dan Ludwig to fix our apparatus and hopefully today we can run tests with it today
• Submitted our part (SRRz) to the registry (not the DNA yet)
• We re-did the lysis test with pVJ4 taking OD readings in smaller time increments (results in Kate’s notebook) and found that lysis happens with pVJ4 in 2 hours
• Worked on the background/application of our project and the wiki page
• With Dan’s help, we will install the a CD amp chip into our circuit so that we can amplify a small voltage outputted into our solution (Professor Palmore said the 5V was too much to put across solution, so we will output 2-5mV and have it amplified to give us a resistance reading in the range we have been getting
• Compare resistance readings of our set-up with readings from a voltmeter to test accuracy of apparatus
• Lyse cells in minimal media instead of LB because the ion content of minimal media is controlled and known
• Suggestion that we simply use OD measurements as a reporter instead of resistance measurements (implement a small laser in a chip)

Meeting with Professor Jerry Daniels

We went to his classroom/office (BH)

Suggestions:

• Try using a potentiometer instead of constantly changing comparison resistors
• use standard copper wire in the breadboard for the circuit and only use gold/platinum for the part of the wire that enters solution
• make sure to specify our labview program between single-ended and differential (under properties)

bipolar +/- analog outputs 0→8 1→9 2→10 3→11 4→12

• Use Maex to test the efficiency of the circuit (program comes with Labview)
• Try inputting a signal in a sawtooth-wave instead of in a sinusoidal wave
• To relieve strain in the wires, braid them
• wire everything to only one ground

AI0: 68 AGND: 67

• Daniels used a braided potentiometer and channel 1 in Maex
• input:5V
• Used an oscilloscope to test circuit→seems to work
• there appears to be noise in the system

if it’s comes to be too much, use a capacitor (low pass filter) or a lower intensity to reduce noise

Labview program

• use single point read
• while loop
• toggle-switch with shading
• numerical indicator

Signal amplification

• needed in order to keep input voltage low in order to prevent redox chemistry
• keep amplifier as close to cell solution as possible to reduce noise
• need a power supply to power amplifer (1-15 volts)

Lent us: CD amp chip ($20) Blue box (power supply)

Back to lab after meeting

→ worked with Labview and Maex to fix apparatus

Dan came to the lab around 6pm to help me with the system

• Got voltage output to work with Maex
• Test reading resistance of a resistor with the circuit
• Voltage(input)<voltage(output) which makes sense because current goes through 2 resistors
• After it works with Maex, we switched to Labview

Diagrams of circuits on pg __ of my (Rima’s) notebook

Daniel Ludwig came to lab *helped me set up amplifier with power source

Diagrams of the AD524 (CD amp chip) and circuit set-up on power supply on page__ of my (Rima’s) notebook

Daniel drew simple diagram of our two resistors in series on page __ of my (Rima’s) notebook

Equations that set parameters of our system:

i=V/(R1+R2)

V1= iR1

V2= iR2

V(input)=V(R1/[R1+R2])

With R1 being the comparison resistor and R2 being the solution of cells (or whatever is being measured)

Our test: R1= 9.91kΩ R2= 477.7kΩ

V(input)= 1.02V

Saved as “test” under Team resistance documents

Initially, the circuit was wired under the consideration that it was under the property RSE (reference single ended) because the circuit was wired to a single ground.

However, Maex keeps switching to Differential, so Dan helped me re-wire the system according to the differential setting. To do this we wired each input with the respective input ground across from it (0→8, 1→9, 2→10, as described in meeting with Professor Daniels).

Labview program

• because the voltage out is amplified, program divides the voltage input by the same degree to give the correct resistance
• created dial so that when the amplification on the CD amp chip is switched, we can switch the amount that the voltage input is divided by

To potentially reduce noise (fluctuations)

• use low pass filter
• braid wires→ to avoid confusion, use different colored wires
• take the mean of several readings and then take the mean of means

Apparatus is now ready for testing

Made 2 pVJ4 cultures for dilutions tomorrow

Incubate 8:20pm