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DRT

Member Since 19 Feb 2009
Offline Last Active Yesterday, 11:43 AM

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Posts I've Made

In Topic: Protein folding in different species

Yesterday, 11:42 AM

2xzwei, on 17 May 2013 - 06:36 AM, said:

Hi!

I've overexpressed a protein in both bacteria and human cells (293T). This protein is immunomodulatory and can inhibit TNFalpha secretion of immune cells. So I designed a wildtype and also mutated form that should be expressed by both species.

Now I have this curious findings:
The WT protein from both bacteria and 293T is working well in-vitro (positve effect).
The MUT protein from 293T cells has no effect at all (that's alright as it should serve as negative control).

BUT: The MUT protein from bacteria is also able to abrogate TNFalpha secretion (which should not be the case!).

I've confirmed the sequences of the vectors that have been used for transformation and they were okay. Also the isolated plasmid from bacteria carries the mutation and is fine.
Furthermore the MUT protein from 293T is recognized by ELISA, but NOT the MUT protein from bacteria (although they should be the same). So I'm wondering whether the folding of the MUT protein is different in human 293T and bacterial cells?! Or what explanation would you give for this fact?

I'd be grateful for some advice...
Regards Posted Image

addition of functional groups?

In Topic: Method of calculating p value for Pearson's correlation coefficient

30 April 2013 - 01:01 PM

Curtis, on 29 April 2013 - 09:35 PM, said:

DRT, on 29 April 2013 - 03:37 PM, said:

The formula you have given looks like it should be t=r/Sqrt((1-r^2)/(N—2)) the t statistic for testing if the correlation coefficient is significant, it can then be converted to a p value using the T.DIST function in Excel.

I checked TDIST. don't know how to fill those gaps.

I found this link with the instructions for getting the obtaining a p value from the correlation coefficient.
http://www.ehow.com/...excel-2007.html

You may also like to install the ‘data analysis’ add-in for excel (under File-Options-Add-Ins) but make sure you come to grips with the different sorts of t-tests first Posted Image

In Topic: Method of calculating p value for Pearson's correlation coefficient

29 April 2013 - 03:37 PM

In Topic: spline curve

16 April 2013 - 12:01 PM

Putting aside that you should not be doing it (the error may be huge).
A spline curve is not the best formula to extrapolate with. It is used as a way of smoothing disjointed curves/data. Better instead to try one of the binding equations, I’m not sure what graphpad calls them, maybe Hill-equation? These at least will asymptote to your blank levels.

In Topic: a simple question to statistics

20 March 2013 - 11:24 AM

Inmost sun, on 15 May 2012 - 02:22 AM, said:

Let´s say I have 3 groups of independent data sets (n=3), each group of sample size N=5;
for each group I can determine mean (X1,X2,X3) and standard deviation (SD1,SD2,SD3);

my question is: How to correctly determine the standard error of means (SEM) of the mean of the 3 means (X1-X3)? I think I have to take the SD of each group into account, but by which method? Posted Image

My interpretation of this is that you are after the intergroup variation in which case you calculate the standard deviation of just the three means (remembering to use sample stdev, n-1=2). You would then use the pooled standard deviation as the within-group variation.

red_monkey, on 15 July 2012 - 09:03 AM, said:

So...3 samples/animals, 3 repeats each. If I want to summarise the whole lot, do I take the mean and SEM of the mean for each animal or the mean and SEM of all 9 repeats...or some other method?

Whereas this is asking for the global standard deviation; grouping all 9 repeats.

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