The blade's molecular properties will have no effect on his adamantium bones.
I was under the impression that the Muramasa Blade (the one forged specifically for Wolverine, not the Black Blade) could cut basically anything. It apparently cut through one of Cyclops' eye beams once. However, it apparently can't cut through Armor's powered-by-her-ancestors-or-something armor, and its ability to cut through adamantium is suspect.
So can the Muramasa Blade cut through adamantium? Are there other things it can't cut through?