Renewed worries over the Fed's rate plans and another selloff in crude teamed up to beat down Wall Street in a sour start to the week. Oil ended at its lowest level in a month on doubts OPEC members can agree upon a production freeze when they meet in mid-April. Brocade (BRCD) slid after agreeing to buy Ruckus Wireless (RKUS) for $1.2 billion, a deal which grows the company's wireless portfolio in the services industry. Meanwhile, Ruckus shares surged. The offers represents a roughly 44 percent premium to the company's Friday close. Twitter (TWTR) - Get Report climbed after MasterCard (MA) - Get Report said it is interested in partnering with the social network. An exec from the company said she could see a mutually beneficial relationship, pointing to Twitter's Buy Now button as a possible platform for cooperation. TheStreet's Keris Lahiff reports from Wall Street.