Hi Oksana!

There are several method of estimation of SOD, CAT, GSH, MDA, LOOH, SH-groups of proteins , you may apply. Even kits are also available for their assessment.

So far serum storage is concerned, generally less stable samples like RNA, Bacteria or its strains are stored best at -80. However −20 °C is best for serum, DNA and protein.

−20 °C storage for as long as 90 d is acceptable for common analytes.

Thank You, and when this serum is stored for 2-3 years, it is not possible to use it?

Hi, Oksana, GSH at -20°C is relatively stable, but I am not sure about enzyme activity. At -70 (80)°C it seems to be OK.

Many company produced now kits, but you can do it without kits both total activity and with separation for different isoform (what is important for correct data interpretation).

My best wishes!.

Dear Oksana,

Sometimes very long freezing even at very low minus temperature depletes enzyme activity of some enzymes if stored for a long time. If you want so store your serum sample in my experience, samples should not be freeze more than 2 years at -80 °C .

Freezing the protein initially in liquid nitrogen before -80 °C storage may be beneficial. The rapid freezing prevents formation of larger crystals and most of the ice is amorphous which reduces shearing forces during freezing.

Best wishes,

Manju

So, if it has been stored for 3 years, without put into liquid nitrogen before -80 °C storage it is not good to use it for determining the values of the oxidative stress?

Ho, Oksana, I am not sure that after 3 years storage all enzyme activities remain initial level. However, only MDA can shown you, indirect, oxidative stress level. Enzyme activity as well as GSH level, give only information about activity, but not about level of stress. The best marker of stress level is ROS accumulation, what can be determined from living tissue.

My best wishes.

I understand, and what about levels of LOOH, 4-HNE, SH-groups of proteins - can they be informative for the determining the level of oxidative stress?

May be You know - will it be informative to measure fragmented DNA in serum too?

Thank You in advance

Hi, Oksana, DNA fragmentation suggest about aopotosis, what may be a results of long oxidative stress. But cant serve as a direct marker of stress at the moment of fixation/freesing.

My best wishes

DNA fragmentation is measuring in tissues, but can it be measured in blood?

Thank You!

Please refer to the attached PDF where you will find methods for practically everything. Although we did assays for animal tissues, a method is method and should work for any biological sample.