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Fun with Serial Dilutions and Spectrophotometry

From spectrophotometers to serial dilutions, this week is all about concentration.

This week at PCC's Bioscience Technology program, we started working with the program’s spectrophotometers. I’ve had labs on spectrophotometry from two other classes. Those labs familiarized us with the concept of the light spectrum and wavelength. They both let us see how light exists at different wavelengths and intensities based on the light’s source as well as it's ability to transmit through an object versus the object's ability to absorb the light. This week we applied the lesson that we can measure the amount of light absorbed by different substances at different wavelengths, to see how we can measure the purity of DNA and protein. We also spent some time in excel making titration curves, which as one of my classmates pointed out, aren’t really curves at all. It made me think of classes that are graded on a curve and that made me wonder why it’s called a curve.

Also this week, we began our first attempts at serial dilutions. We also used the spectrophotometers to test the accuracy of our serial dilution’s concentration. Serial dilutions with water and food coloring are fairly easy; doing serial dilutions with BVS, not so much. Triturating 20 microliters of BVS and dH2O in a 0.5 ml microfuge tube without getting bubbles is no problem unless you actually are trying to get a homogenous mix. Since that’s the key to serial dilutions we spent an entire lab focused on doing exactly this. Using the way we all geeked out as my yardstick, I’m confident the entire class loved this lab.

My African Violet plate is faring along well. Hear that mold?! We’re continuing on with passages in cell culture and learning about freezing and thawing cells. On that note, this coming week has a Workplace Safety, Lab Math and Cell Culture tests. I anticipate I’ll do much better on these since I’m sequestered in the wilderness house/pet sitting for a client (although the clients do have cable).

Also, for cell culture I need to find a research paper that interests me on PubMed. I should be able to read and understand what is being done in methods and materials. Additionally, I need to be able to explain why or why not I would have used the same cells. I’m not sure where to start but wading through PubMed actually sounds like fun.


Also this week, we had our first meeting of the Bioscience Technology Club! We elected officers and got down to business on those sweatshirts. I'm hoping the sweatshirts will make our program more visible to PCC students. A lot of them don't even know what Bioscience Technology is about. 

And finally, I made a fantastically HUGE mistake this week in Cell Culture lab while passaging cells. After carefully removing the spent media, delicately washing them with PBS, then adding my Trypsin and letting it sit in the incubator a few minutes I immediately took my flask back to the hood and pipetted out my Trypsin and all of my cells along with it! Aghhhhhhh! That’s all it takes. Life lesson learned. Removing Trypsin is fine if you’ve centrifuged your cells into a pellet. However, if your protocol calls for adding 9 mls of media to your 1 ml of Trypsin and zero centrifugation, removing Trypsin is a bad idea. A really, really bad idea. I won’t be making that mistake again.

This is a picture of me NOT throwing cells away, but passaging and preparing to use a hemacytometer for a cell count using Trypan Blue. 


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