Archive for the ‘Bio-Rad Tutorial’ Category
Are you getting the most from your western blot data? Does Imaging technique matter? Film or Imager? In this video, we describe a methodology to obtain reliable quantitative data from chemiluminescent western blots using standardization procedures coupled with the updated reagents and detection methods. For the best resolution, watch the video in full screen at HD resolution.
Recorded from a live webinar.
Statistics is probably one of the most important tools you will use in your research career. Stats have the ability to turn your seemingly beautiful data into a pile of useless junk, or to convert questionable data into an award winning publication.
Like many molecular biologists, I am statistically challenged. I’ve tried and tried again to learn the meaning behind important terms such a “p-value,” “ANOVA test” and “correlation coefficient” all to no avail. I am a stats flunkie. When I asked my supervisor about my learning disability he told me that I am a molecular biologist and that really there is not hope.
The best we can shoot for is p<0.05 and call it significant.
For many years, I was resigned to the fact that I’d never understand stats and that’s why the position of in-house statistician existed. To help, (if not to make fun of), people like me. Fortunately, there is new hope. Bio-Rad Laboratories has now produced a series of video tutorials geared towards helping those who have less fortunate statistical skills.
In the video below, Bio-Rad experts explain how to calculate a coefficient of variation. I found the video to be pretty clear and it has somewhat clarified this murky term for me. What about you?
Power supplies that are used for electrophoresis hold one parameter constant (either voltage, current, or power). The PowerPac™ HC and PowerPac Universal power supplies also have an automatic crossover capability that allows the power supply to switch over to a variable parameter if a set output limit is reached. This helps prevent damage to the transfer cell.
During transfer, if the resistance in the system decreases as a result of Joule heating, the consequences are different and depend on which parameter is held constant.
Transfers Under Constant Voltage
If the voltage is held constant throughout a transfer, the current in most transfer systems increases as the resistance drops due to heating (the exception is most semi-dry systems, where current actually drops as a result of buffer depletion). Therefore, the overall power increases during transfer, and more heating occurs. Despite the increased risk of heating, a constant voltage ensures that field strength remains constant, providing the most efficient transfer possible for tank blotting methods. Use of the cooling elements available with the various tank blotting systems should prevent problems with heating.
Transfers Under Constant Current
If the current is held constant during a run, a decrease in resistance results in a decrease in voltage and power over time. Though heating is minimized, proteins are transferred more slowly due to decreased field strength.
Transfers Under Constant Power
If the power is held constant during a transfer, changes in resistance result in increases in current, but to a lesser degree than when voltage is held constant. Constant power is an alternative to constant current for regulating heat production during transfer.