[sinbo]

So I was looking at the malate shuttle that brings the NADH into the mitochondrial matrix from the glyolysis that occours in the cytosol.
So, it can not transport OAA over the membrane, but it can transport Malate over the membrane.

When we look at the different structures of these compounds we find that they only differ in one alcohol / carbonyl respectively.
It got me curious.. how have we been able to determine that this shuttle transporter can take malate but not OAA over the membrane?

Does anyone have the original papers on this?
Like.. how the hell could this transporter be so specific that it can transport the alcohol substrate yet not the carbonyl form of the same substrate...
I am actually somewhat amazed by this..

[Borek]

No idea how they did it, but in general that's what radiochemistry is for. You use reagents marked with radionuclides and trace them.

[Babcock_Hall]

https://pubmed.ncbi.nlm.nih.gov
I do not know the answer.  I suggest trying a PubMed search, possibly using "review" as a filter, to keep the number of references from becoming unmanageable.