User:Douglas M. Fox/Notebook/AU CHEM-571 F2011 Lab Support/2014/09/10: Difference between revisions
mNo edit summary |
(fix raw html notebook nav) |
||
(One intermediate revision by one other user not shown) | |||
Line 2: | Line 2: | ||
|- | |- | ||
|style="background-color: #EEE"|[[Image:owwnotebook_icon.png|128px]]<span style="font-size:22px;"> Project name</span> | |style="background-color: #EEE"|[[Image:owwnotebook_icon.png|128px]]<span style="font-size:22px;"> Project name</span> | ||
|style="background-color: #F2F2F2" align="center"| | |style="background-color: #F2F2F2" align="center"|[[File:Report.png|frameless|link={{#sub:{{FULLPAGENAME}}|0|-11}}]][[{{#sub:{{FULLPAGENAME}}|0|-11}}|Main project page]]<br />{{#if:{{#lnpreventry:{{FULLPAGENAME}}}}|[[File:Resultset_previous.png|frameless|link={{#lnpreventry:{{FULLPAGENAME}}}}]][[{{#lnpreventry:{{FULLPAGENAME}}}}{{!}}Previous entry]] }}{{#if:{{#lnnextentry:{{FULLPAGENAME}}}}|[[{{#lnnextentry:{{FULLPAGENAME}}}}{{!}}Next entry]][[File:Resultset_next.png|frameless|link={{#lnnextentry:{{FULLPAGENAME}}}}]]}} | ||
|- | |- | ||
| colspan="2"| | | colspan="2"| | ||
Line 39: | Line 39: | ||
<br> | <br> | ||
'''Coordination will be helpful here. Record one spectrum at a time and allow other groups to measure a spectrum in between.''' | '''Coordination will be helpful here. Record one spectrum at a time and allow other groups to measure a spectrum in between.''' | ||
=== Data Analysis === | === Data Analysis === |
Latest revision as of 00:16, 27 September 2017
Project name | Main project page Previous entry Next entry |
Today's Experiment - Bradford AssayObjectiveThe most direct method for measuring the protein concentration is the use of the Beer - Lambert Law, using published extinction coefficients (molar absorptivities) for the proteins at λ = 280 nm in a UV-VIS spectrum. For low concentrations of proteins, UV-VIS of just the protein is often not sensitive enough to accurately measure concentration. (The limit of detection is about 2 - 3 μM for most proteins.) During the semester, we will likely need to measure protein concentrations that are lower than this. In addition, molar masses and/or extinction coefficients of some proteins are not well quantified. One tool we have can use to measure protein concentrations on the μg/mL level is called the Bradford Assay. The Bradford Assay makes use of the Coomassie Blue dye, which binds to proteins. Upon binding to a protein, this dye undergoes a change in its absorption features. (No protein: peak at 460. Protein: peak at around 600). We will be making calibration curves (using the Bradford Assay) for the different proteins we'll be using throughout the semester. Since this method depends on the number of peptide bonds, concentrations are reported by mass and the method is fairly independent of the particular protein being measured. There are a few interferences, such as co-factors that absorb near λ = 600 nm (e.g. hemes) or basic pH buffers.
TasklistThe basic protocol can be found here (*Note: use section 2.3, page 5) or here.
Data AnalysisFirst, you will want to find the purity of your protein solution. Using the UV-VIS spectra of your stock solutions, calculate the concentrations of your solutions in both molarity (M or μM) and g/L. The extinction coefficient for BSA is 38,940 M-1cm-1 (λ = 279 nm) and for Lysozyme is 37,800 M-1cm-1 (λ = 280 nm). The purity of the lyophilized powder you used is [UV measured]/[mass measured].
ReferencesMany thanks go to Prof. Hartings, who wrote the original protocol for this class. |