Hi Conrad, storing biological samples at RT can be a problem because airborne bugs can grow in you samples and destroy them.

I have seen mold in high and low pH buffers, let alone biologics.

Personally I always put 0.01% NaN3 in all my buffers and samples that I keep at RT.

The best way to store biological samples is at -80oC because most hydrolases are not active at that temp.

Thanks Steingrimur (Steingrimur Stefansson). Did you mean -8 or -80 oC? Can you clarify it? Thanks.

For both powder recieved in a bottle from the company as well as a solution prepared for bio-sensing, right? When using Biotin or Streptavidin and Linkers, are there any specific safety regulations that we must implement before preparing the sample? I have been continuously educating myself here. Thanks.

Biomarkers like organic molecules, peptides and proteins will be hydrolysed, loose side groups, being broken down by microorganism or proteases, lose glycan chains etc.

Freezing is in general the most easy way of saving them for future analysing the sample or for serving as ones own standard. If literature is not available for the particular substances you are interested in (Google XX + stability / preanalytical / storage / etc) then you have to try for yourselve.

First test whether the freezing / thawing cycle has any effect on the sample. Freeze/ thaw once or twice and compare the outcome with the same fresh sample. Once you have demonstrated that freeze / thawing has no undesired effcts you can store at - 80C and -20 for e.g. 2 weeks, one months, two months.

Probably you will notice that -80 C is preferable, but that the change at -20 for several weeks or months is also within the method error.

In some cases you will need to add a stabilizer to your sample, or use NaN3.

An example of a stability study http://clinchem.aaccjnls.org/content/55/8/1584

Dear Jos Wielders:

Thank you for your insightful response. I still have a question, however.

Are you suggesting that we go well below the freezing temperature to store bio-markers? That means storing at zero degree or slightly below it is not sufficient, right?

I will go through the Google search info & literature link you have recommended for.

Many thanks for your input, and it greatly helps.

- Conrad

Dear Conrad,

In my experience and also based om contacts with all kind of researchers involved in specialized clinical chemistry or protein research, no one stores slightly below zero. Mostly it is -20C for short term or -80 for long term or important standards / calibrators.

Jos

Thank you Jos Wielders again. What about these below:

Biotin: B4639; Streptavidin from Streptomyces: S0677; Avidin from egg white - A 9276 etc.

Somewhere in the manual, I read 2-8 0C as the storing temperature. These numbers are over the freezing temperature. Are these samples different from the bio-markers we are talking about? Am I missing some thing here? Thank you for the link to "Letter to Editor" -- I have just downloaded and going through it now.

- Conrad

Some reading to do ..

https://rockland-inc.com/uploadedFiles/Support/Streptavidin%20-%20S000-01.pdf

https://prozyme.com/pages/streptavidin-stability

https://www.sigmaaldrich.com/content/dam/sigma-aldrich/docs/Sigma/Product_Information_Sheet/a9275pis.pdf

simply google the substance and 'stability'

Hi Conrad, avidin is a rock solid protein with respect to denaturants. You have to go out of your way to denature it.

The only problem with storing proteins long term (months) at +2-8 C is that bugs can grow in it and use the protein as a food source. Including anti-microbial agents is a great prophylactic. 0.01% sodium azide (NaN3) will kill (forged in fire reference).

All other proteins that are going to be stored for months should ideally be aliquoted and kept at -80 C because even trace amounts of proteinases can destroy samples kept at +4 C for extended periods. I learned this the hard way.

At this temperature (-80 C) most hydrolases are inactive because there is no free water available.

Thanks Steingrimur Stefansson and Jos Wielders for your valuable inputs.

Scientific freezers seem to cost quite high, up to $2000 or even more per device. For now, applying through your suggestions, I have arranged a Freezer that can hold temperature in between -18 to -20 degrees Celsius .

With this arrangement available, I should be able to store the bio-samples at least for several months at this temperature. Thanks again.

You don't need "scientific freezers". A simple chest freezer does the same thing at 1/4 of the cost.