COLUMN-Vladimir Putin's most effective weapon is gas - but not the poison kind

July 28 (Reuters) - At face value, Russia's $400 billion deal to supply natural gas to China National Petroleum Corporation, via the state-controlled energy behemoth Gazprom, sounds like a coup for Moscow. But according to recent analysis, the deal is strongly tilted in China's favor. Gazprom will be lucky to break even on the contract and may even lose substantial amounts of money.