When i started my real time pcr experiment i was using applied biosystems power up sybr green qpcr master mix. i was getting my results with a proper melt curve of my target gene at 83.5 degree Celsius and housekeeping gene at 85 degree Celsius. but this reagent was limiting, so i had to shift to applied biosystems power sybr green, and after that my target gene did no show a melt curve. even for housekeeping gene the melt curve decreased to 83 degrees. in this entire experiment the only change was for sybr green reagent. i ran a control, where i freshly prepared rna, and set up real time experiment simultaneously with 2 sets of sybr green, i got the melt curve as well as band in agarose gel for power up sybr green, but not with the power sybr green.