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Trouble-shooting.

Trouble-shooting. (also a science). Things that didn’t go as expected. Gold color did not disappear over 2 hour time rocking at room temperature After reduction and silver step, purple color did not develop Are there nanowires? What happened??. Clear – what it is supposed to look like!.

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Trouble-shooting.

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  1. Trouble-shooting. (also a science)

  2. Things that didn’t go as expected • Gold color did not disappear over 2 hour time rocking at room temperature • After reduction and silver step, purple color did not develop • Are there nanowires? What happened?? Clear – what it is supposed to look like! Gold – after two hours of rocking Dark orange – something’s not right

  3. “Low hanging fruit” • Phage titered correctly? Concentrations calculated correctly? • T/R lab, John and Bridget went through all of your notebooks looking for these calculations • This is why you always right neatly and make sure to read directions! Only one group remarked on the color change that took place. • End result: even if there were slight calculation errors, all the phage added into the reaction mixture is in the correct order of magnitude

  4. Too much gold for the ascorbic acid? • Calculated the number of gold particles (based on molarity of gold solution) • Calculated the number of nucleation sites (based on concentration of phage and number of p8 proteins) • Phage reduces the gold that binds to the mutated p8 protein • Calculated amount of ascorbic acid able to reduce the extra free gold in solution (if there weren’t enough phage) • End result: reducing power is still in excess – this shouldn’t be a problem

  5. Problem of “cutting corners * 1000” • If we are an order of magnitude off in terms of phage and an order of magnitude off in terms of gold, does this make the experiment just fail? • End result: Maybe, but nothing so drastic. This “cutting corners * 1000” is more likely to have an effect on the nanoscale and create nanoparticles instead of nanowires…it isn’t something that would change how we’d see the color change

  6. Contamination? • Belcher Lab has had issues with E4 contamination in the past • Remember E4? • Normally perform a DNA sequencing analysis to check on this • How could this experiment be done? • End result: phage contamination would not change the goldclear or the purple color change, so this isn’t contributing to our problem

  7. pH? • What if the pH of both the water and TBS is off? • Nanopure water vs. DI water • End result: pH of both Belcher solutions and 20.109 solutions were similar (within 0.01)

  8. What about the other solutions? • Hmm, that gold looks sort of dark… • Absorbance on a spectrophotometer • Gold solution used T/R was significantly darker (error in solution-making?) • Bridget re-made gold solution for W/F lab • Is this it??

  9. Gold color didn’t disappear. Again. Now what? • What about TBS? I mean, it’s a standard buffer, right? • Apparently not. . .

  10. Ionic Strength or General Equation: Biorad 1xTBS: pH = 7.5 0.020M TBS 0.5M NaCl Rockland 1xTBS: pH = 7.5 0.1M TBS(HCl) 0.15M NaCl Therefore, IBiorad TBS = 0.518 IRockland TBS = 0.241 • Qualitatively increased ionic strength results in: • Increased ionic charge shielding • Decreased ionic mobility (and diffusivity) • These factors should: • Decrease the ability of gold ions to penetrate CTAB bilayer • A high [NaCl] might lead to Na+ binding at p8

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