In a surprising move, Russian President Dmitry Medvedev has signed a decree banning the delivery of the S-300 air defense system and a host of other major arms to Iran, apparently in response to the new UN sanctions. Since the S-300 system doesn't even make it to the UN list of conventional arms and would be entirely justified, the move is clearly a sign that the deal made between Washington and Moscow for more investment into Russia had a catch. More investment, fewer supplies to Iran.
Also included in the ban was entry to and transit through Russia for a Iranians connected with Iran's nuclear program while simultaneously banning Russians or Russian firms from rendering financial services if the services relate to Iran's nuclear activity.
The move by Moscow is a big deal. It signals that Russia's foreign policy may be returning to a more pragmatic view of the world based on self-interest. Ultimately, it is not in Russian's interest to have a strong Islamic state to the south that is very capable of causing trouble in Russian dominated regions of its neighbors or even its internal trouble spots of Chechnya and Ingusetia. It is in its national interest to attract Western investment of every type. In that scenario, Iran is dispensable.
The UN sanction regime still won't work in and of themselves - but losing allies like Russia at a time when Iran cannot be certain that the US may be changing its tactics regarding military intervention, may be the beginning of a change in Iran's tactics overall.