Hi Shatha,

It has taken a bit of a hunt as I haven't seen the paper for years, but the following paper 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC484200/

suggests that typical 10000x stock solutions of Sybr Green in DMSO are approximately 10mg / ml or a molarity of ~20mM.  

As a student 21 years ago, I helped to trial Sybr Green in the laboratory where I undertook my undergrad final year project as a direct comparison with the ubiquitous Ethidium Bromide - we had been given a free sample (for 5 gels).  Although we were advised that the preferred usage method was addition to the cooled agarose gel prior to casting, I found that SG could be mixed directly with DNA by preparing loading buffer containing diluted SG and did not have any obvious effects on the mobility of the DNA.  Ethidium in contrast caused terrible problems when mixed direct with DNA.  As an additional bonus, the sensitivity was great owing to zero background in the gel, and the 5 gel sample lasted me >6 months.  Sadly I cannot remember the dilution factor for this to work.  

Good luck.

Thanks Robin for your reply