Use uppercase as needed

Modifier Keys - GNU Emacs Manual
http://www.gnu.org/software/emacs/manual/html_node/emacs/Modifier-Keys.html#Modifier-Keys

> A \<Control>-modified alphabetical character is always considered case-insensitive: Emacs always treats C-A as C-a, C-B as C-b, and so forth. The reason for this is historical.
>
> For all other modifiers, you can make the modified alphabetical characters case-sensitive when you customize Emacs. For instance, you could make M-a and M-A run different commands.