Take a look

http://www.bio-rad.com/featured/en/agarose.html

Of course we have different agaroses for different tests.

@Rodolfo Matias Ortiz Flores

Did you use the same PCR product for both gels?

There is no such difference in those two agarose, as it happened to you, one give band and other does not. MB is generally used molecular biology grade agarose and LE is used for the high mobility and clean separation of bands. The reason might be something else, unless you check the same PCR product on both agarose simultaneously, to prove if it was because of agarose.

Hello Rodolfo,

different kinds of agarose will influence the quality of separation of your fragment.

But they will not be responsible for the presence or absence of your fragment.

Hi Rodolfo,

Try to use around 1-1.5% gel to see your 400 bp product. Also run ladder to see the quality of the running gel. And of course, if your PCR is positive then quality or grades of agarose gel does not matter alot.

Thank you very much for all the answers. I tried many of your suggestions and others.

I had PCR products and I ran two different gels at the same time, under the same conditions.

The problem it could be the SybrGreen. I dont know, because my Sybr still worked.

I try with a new Sybr and, in both gels, i see the PCR products (beautyfull).

Anyway, I learnd about the MB and LE agarose.

Again, thank to all you.

Best!

Rodolfo Matias Ortiz Flores Agarose LE (low EEO) typically has enhanced electrophoretic mobility and as a result, also yields improved resolution and reduced distortion caused by counterflow which could stem from the presence of a high degree of sulfate-rich (-) icons. So depending on how strong the band was in MB, this could have played a role.