Can we spike with a different enzyme to a SYBR Green Master Mix?

Question

I followed the standard SYBR Green Protocol for doing a qPCR. For which I used

• 10 uL of 1X SYBR Green Master Mix
• Forward Primer and Reverse Primer (each at a final conc. = 8.5 uM)
• Template (unknown concentration from an aptamer selection)
• Made to 20 uL with water.

Performed the PCR amplification using

1. 95 C Initial denaturation
2. 95, 68, 72 - cycled 35 times.

But, one set of sample from my aptamer selection (probably high GC content) did not amplify at all. I checked on an agarose gel too.

Important Notes:

1. My primer conc. is intentionally high - I have always amplified with such concentrations and it works perfectly using Vent Polymerase.

2. My annealing temperature is also high at 68 C because my aptamer sequences tend to be GC Rich.

3. Using Vent polymerase my amplification is very strong

On reading notes from vendors, I found out that the polymerase in the mastermix to be some variant of Taq Polymerase[1][3] (varies from vendor to vendor) and also it is known to poorly amplify GC Rich Sequences[2].

1. https://www.thermofisher.com/order/catalog/product/4309155

2. https://www.thermofisher.com/order/catalog/product/N8080241

3. https://www.fishersci.co.uk/shop/products/powerup-sybr-green-master-mix/15366158

Hence, I wanted a suggestion from anyone working with aptamers, or if you have experience working with GC rich sequences on how I could amplify my sequences.

Much appreciated if I could have an answer before next week.

Thanks a lot for your help!!!