Yellen's comments rattle markets

Comments by Federal Reserve Chair Janet Yellen about stock valuations rattled biotech and social media investors which pushed the Nasdaq into negative territory to close at 4,416, down 24 points. The Dow edged up 5 points to finish the session at 17,060.

On the upside

FBR Capital Markets began coverage of Plug Power (Nasdaq: PLUG) with an outperform rating due to the company's potential growth in the alternative fuel industry.

JPMorgan Chase (NYSE: JPM) posted lower earnings that beat expectations while offering a positive update on CEO Jamie Dimon's fight against throat cancer.

GoPro (Nasdaq: GPRO) bucked the trend among momentum stocks on a positive report by analysts about its market size.

Shares of Rockwood Holdings (NYSE: ROC) surged after the producer of lithium batteries agreed to be acquired by Albermarle Corp. (NYSE: ALB) for $6.2 billion in cash and stock.

On the downside

Reynold American (NYSE: RAI) announced a $25 billion deal to buy Lorillard Inc. (NYSE: LO) to create the 2nd largest tobacco company in the United States. Reynolds plans to keep Lorillard's flagship Newport brand while selling off the e-cigarette Blu brand.

Investors sold off on momentum stocks like Tesla Motors (Nasdaq: TSLA), Netflix (Nasdaq: NFLX) and Yelp (Nasdaq: YELP).

In the broad market, declining issues outpaced advancers by a margin of nearly 2 to 1 on the NYSE and by more than 5 to 2 on Nasdaq. The broader S&P 500 slipped 3 points to close at 1,973. Bitcoin lost $9 to $617.