Hmmmm!! the protein concentrations are on the X-axis and OD on the Yaxis. Always dependent variables on the Y-axis. Jay
________________________________________ From: [email protected] [[email protected]] On Behalf Of WS [[email protected]] Sent: Monday, March 21, 2011 8:19 AM To: [email protected] Subject: Re: Can anyone please tell about slope function Dear Sudheer, the slope is the "m" in your equation. In real life, colorimetric protein measurement standard curves sometimes get a bit far from linear, so in times of computerized curve fits by eg excel, sigma{plot, stat} or openoffice.org, you might be better off with a 2nd order fit (y=ax2 + bx + c); simply plot the OD readings on the x- axis and the protein standard concentrations on the y-axis, then you'll get directly the formula to calculate actual concentrations from the OD values when performing a regression analysis. By having a look at the R value you may compare various regression methods (like linear vs 2nd order) and determine which one fits the situation better. BTW, the linear approximation is just an approximation which fits most needs and is easily done when you have just a ruler and a sheet of paper (when one wouldn't want to apply for mainframe computing time just for a protein determination :). The chemistry that converts protein into color is not really linear in respect of dose/response. Have fun! Wo _______________________________________________ Methods mailing list [email protected] http://www.bio.net/biomail/listinfo/methods This email message may contain legally privileged and/or confidential information. If you are not the intended recipient(s), or the employee or agent responsible for the delivery of this message to the intended recipient(s), you are hereby notified that any disclosure, copying, distribution, or use of this email message is prohibited. If you have received this message in error, please notify the sender immediately by e-mail and delete this email message from your computer. Thank you. _______________________________________________ Methods mailing list [email protected] http://www.bio.net/biomail/listinfo/methods
