Question

Which amino acids are commonly found in beta sheets and why?

Answer 1

are the R groups in contact with water, or are they hidden from water?

Answer 2

With water

Answer 3

so they wont be non-polar amino acids. what are some polar or charged (at physiological pH) amino acids?

Answer 4

I do not know

Answer 5

Val and Ile are common to be found in β sheets because there are non-polar.
I think without water.