Presentation on theme: "Trouble-shooting. (also a science). Things that didnt go as expected Gold color did not disappear over 2 hour time rocking at room temperature After reduction."— Presentation transcript:
Things that didnt 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?? Dark orange – somethings not right Gold – after two hours of rocking Clear – what it is supposed to look like!
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
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 werent enough phage) End result: reducing power is still in excess – this shouldnt be a problem
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 isnt something that would change how wed see the color change
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 isnt contributing to our problem
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)
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??
Gold color didnt disappear. Again. Now what? What about TBS? I mean, its a standard buffer, right? Apparently not...
Ionic Strength General Equation: or Biorad 1xTBS: pH = 7.50.020M TBS0.5M NaCl Rockland 1xTBS:pH = 7.50.1M TBS(HCl)0.15M NaCl Therefore, I Biorad TBS = 0.518 I Rockland 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