LPS concentration determination - (May/02/2006 )
Is there any protocol available for determining the concentration of LPS?
absolutely
LAL (limulus amoebocyte lysate) assays work pretty well; there are several out there, and several variations on the assay
I use one from a company called Charles River; it is set up to be colorimetric so you can run many samples in an Elisa-type format, as long as you have a microplate reader at the correct wavelength. there are other versions...here is a link for you
you have to know your stuff is endotoxin-free when you're doing immunological assays 
LAL is very sensitive for detection of LPS, but one has to keep in mind that the LAL assay is very sensitive in the other meaning of the word - presence of detergents, urea, wrong pH etc. will influence strongly on the test and can yield false positve or (worse, but more often) false negative results. So you should always include an apropriate negative control when testing immunological properties of potentially LPS contaminated samples.
Mike
absolutely...controls are the name of the game. otherwise how could you ever trust your results? an experiment without controls is meaningless
Thanks for your kindly help.
LAL (limulus amoebocyte lysate) assays work pretty well; there are several out there, and several variations on the assay
I use one from a company called Charles River; it is set up to be colorimetric so you can run many samples in an Elisa-type format, as long as you have a microplate reader at the correct wavelength. there are other versions...here is a link for you
you have to know your stuff is endotoxin-free when you're doing immunological assays
Thanks for your kindly help.
Mike
Sorry to be pedantic but the LAL test measures Endotoxin not necessarily just LPS. I know that the two are often used interchangeably but many other molecules (other bacterial cell wall components for example but also others) will give a positive result in the LAL test and an Endotoxic response. If you are interested in the potential for your your sample to cause an inflammatory response then the LAL test is definitely the method of choice. If you really want to quantitate the lipopolysachharide molecule itself and not just the inflammatory potential of your sample, then more complicated means will probably be necessary.
excellent point, I stand corrected
you're right. shame on me being careless
what you said has been known really for a long time (and probably long forgotten again):Infect Immun. 1984 Aug;45(2):350-5.
Influence of fine structure of lipid A on Limulus amebocyte lysate clotting and toxic activities.
"..These results show that the LAL test is not a valid measure of all parameters of toxicity of a lipid A or lipid A-like compound and can yield false-positive results. However, these findings are not in conflict with the widespread use of the LAL assay for pyrogens in the pharmaceutical industry since a good correlation exists between LAL results and pyrogenicity when undegraded endotoxin is evaluated in parallel assays..."
Mike
Thank you for you guys' comments. I guess I'm responsible for the confusion made as I didn't put my question clearly. I really want to quantify the LPS extracted from bacterial culture using TCA (Trichloroacetic acid). Is there any good and esay method to quantify the LPS?