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Curriculum Testing – Viability of Using Dry Ice to Alter pH

Ran some basic tests to get an idea of how well (or poorly) the use of dry ice and universal indicator would be for this lesson.

Instant Ocean mix (per mfg’s recs): 0.036g/mL

Universal Indicator (per mfg’s recs): 15μL/mL

Played around a bit with different solution volumes, different dry ice amounts, and different Universal Indicator amounts.

Indicator Vol (mL) Solution Solution Vol (mL) Dry Ice (g) Time to Color Change (m) Notes
3 Tap H2O 200 1.5 <0.5
3 Tap H2O 200 0.5 >5 Doesn’t trigger full color change and not much bubbling (not very exciting)
5 Tap H2O 1000 12 <1
3 Instant Ocean 200 1.5 <0.5 Begins at higher pH than just tap water. Full color change is slower than just tap water, but still too quick for timing.
2 1M Na2CO3 200 5 >5 No color change and dry ice fully sublimated.
2 1M Tris Base 200 5 >5 No color change and dry ice fully sublimated.
2 Tap H2O + 20 drops 1M NaOH 200 5 2.75 ~Same color as Na2CO3 and Tris Base solutions to begin. Dry ice gone after ~5m and final pH color is ~6.0.

 

Summary

  • Universal Indicator amount doesn’t have an effect. It’s solely needed for ease-of-viewing color changes. Use whatever volume is desired to facilitate easy observations of color changes.
  • Larger solution volumes should be used in order to slow the rate of pH change, so that it’s easier to see differences in rates of change between different solutions.
  • 1M solutions of Na2CO3 and Tris Base have too much buffering capacity and will not exhibit a decrease in pH (i.e. color change) from simply using dry ice. May want to try out different dilutions.
  • Use of water + NaOH to match starting color of Na2CO3 and/or Tris Base is a good way to illustrate differences in buffering capacity to students.
  • Overall, dry ice will work as a tool to demonstrate effect(s) of CO2 on pH of solutions!

Some pictures (to add some zest to this entry):

 

 

 

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Cart Repair

 

We’ve had a disabled cart sitting in lab for months that has locked up wheels and all of the bolts attaching the wheels to the cart are so rusted, the bolts and nuts cannot be separated by normal means (believe me, I’ve tried numerous methods over the last few months to no avail). Since we’re planning a significant lab cleanup next week, having this cart repaired will be good, so that it’s not sitting upside down in the lab any more AND fixing it will provide us with a second cart for cleanup day!

In any case, I ended up having to drill out the rusted bolts/nuts on three of the four wheels. After that, I put on the new wheel hardware and it’s good as new!

Some before and after pics below.

 

 

 

 

 

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PCR – RLOv Clones

Colony PCRs were performed on each of the transformations from 20151015 (RLOv_ DNA_helicase, RLOv_head_to_tail, RLOv_membrane_gene_1, RLOv_membrane_gene_2, RLOv_tail_to_fiber) to confirm successful ligations in plasmid pCR2.1 using the M13F/R vector primers.

Colonies were picked form the transformation plates with pipette tips, re-streaked on a secondary, gridded, numbered LBAmp100+x-gal plate and then used to inoculate the respective PCR reactions.

Six white colonies (positive clones) and a single blue colony (negative clone) were selected from each transformation.

Master mix calcs are here (Google Sheet): 20151019 – Colony PCRs RLOv

Restreaked plates were incubated @ 37C O/N and then stored @ 4C (Parafilmed).

30μL of each reaction was run on a 1% agarose 1x Low TAE gel, stained w/EtBr.

Results:

 

All the PCRs look good. All white colonies selected contain a PCR product of appropriate size (i.e. larger than the blue colonies; negative [-C] control). Will select clones #1 from each to grow up for plasmid prep.

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Abalone Sampling – Post-esophagus & Digestive Gland

Helped Ava sample 162 red abalone (Haliotis rufescens).

Accession numbers 15:11-1 through 15:11-162

  • Animals were weighed.
  • Took one post-esophagus sample and one digestive gland sample for histology, placed in histology cassette; three animals per cassette.
  • Took one post-esophagus sample in 95% ethanol for qPCR
  • Shells were labeled and retained for post-sampling weighing/measurements.

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Abalone Sampling – Post-esophagus & Digestive Gland

Helped Ava sample 74 red abalone (Haliotis rufescens).

Accession numbers 15:10-1 through 15:10-74

  • Animals were weighed.

  • Took one post-esophagus sample and one digestive gland sample for histology, placed in histology cassette; three animals per cassette.

  • Took one post-esophagus sample in 95% ethanol for qPCR

  • Shells were labeled and retained for post-sampling weighing/measurements.

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