Monday, May 5, 2008

We've all been there

I have a student who has been working on a "research" project for me. The project is to extract a protein called concanavalin A from Jack beans. I use quotes because this isn't a novel area of research by a long shot. My goals for this project were to #1 develop a method of extraction that I could use in my Principles of Biochemistry course and #2 teach my student a variety of laboratory methods.

Concanavalin A (con A) is a lectin from the Jack Bean. A lectin is a protein that binds carbohydrates. In the case of con A, it binds with glucose and mannose but not galactose (or other carbohydrates). It does not have enzymatic activity, and its role in the plant is not clear (as is the case for most lectins).

My student has been working on this project all semester. Briefly, the Jack beans are soaked in pH 4-5 buffer and then blended in a blender. The supernate is removed after centrifugation. It is saturated with ammonium sulfate. The precipitate is collected and dialyzed against 1M NaCl. The protein solution is passed through a sephadex column and the Con A binds with the sephadex. It is displaced by glucose. The solvent used in the sephadex column is 1M NaCl (that's important to remember for this story).

Through trial and error and up the steep learning curve that is undergraduate research, my student eventually got enough sample to the sephadex column part. She loaded the sample onto the column . However, instead of running 1 M NaCl through the column, she used 1 M HCl instead. ugh! There is a big difference between a pH of 7 and a pH of 0. It wasn't good for the protein which, for the most part, appeared to cease to exist intact.

I should point out that she is NOT a bad student or a lab disaster waiting to happen. She is a very good student and one who absolutely knows the difference between NaCl and HCl. But these things happen. Unfortunately for her, that meant the end of her project.

We've all been there. If you've spent anytime in a lab, you've probably made a stupid mistake. I'm not talking about the frustration of dealing with things that don't work. I'm talking about the things that you ruined by a stupid mistake. It happens. The goal is to never repeat it.

5 comments:

Anonymous said...

I really feel for her, I am also an undergrad doing research. In my head multiplied 5 x 6 to 35, and put way to much MgSO4 in the fungi media I was making. I didn't notice the error till a couple steps later. There went a couple days work (in prepping other parts of the medium) and about 1200 dollars. It was most certainly a very bad day.
I am still working on the project and haven't made such a mistake since. My PI still trusts me, now maybe even more so.
I guess the moral is do what you can to learn from your mistakes so you don't repeat them. Also not hiding those mistakes from your PI is a big plus.

Chemgeek said...

Students will break things. Guaranteed. The important thing as a PI or lab teacher is to not break their spirit. There is a big difference between a student who screws around or does not listen to advice and the one who puts in an honest and conscientious effort and still breaks stuff. The latter is forgivable, the former is intolerable.

the indefatigable mjenks said...

If it will help her self-esteem at all...I have a master's degree and 5+ years of experience in the organic lab, and I crap in my flask about once a month.

More often, if I have to rely on others for starting material, but don't tell her that part.

Ψ*Ψ said...

Recently I left some crude product sitting around for about a week. (In my defense, I was really sick.) When I came back, I still had the stuff I intended to make...but also some other crap that was, most unfortunately, inseparable.
Sometimes it's the project, and sometimes it's the chemist. The nice thing about working in an analytical lab is that you ALWAYS assume it's the instrument's fault. (And usually it's not too hard to tell what went wrong.)

thx1138 said...

If this were my project, I would have purchased the ConA from Aldrich and stapled the receipt in my lab book.