Rambus (RMBS) is a big mover today. Shares are up $1 to $8.32 after the chipmaker signed a licensing agreement with Broadcom (BRCM). Meanwhile, 7,730 calls and 1,680 puts traded on RMBS so far today. Jan 9 calls, which are now 8.2 percent OTM and expiring in four weeks, are the most actives. 2,670 traded. Jan 7.5 and Feb 9s are seeing interest as well. Heightened activity and the big move in the underlying has helped send implied volatility in options on the stock up 16.5 percent to 53.

*Scanning all single-stocks subject to 2500 contracts minimum call or put volume

Chelsea Therapeutics (CHTP) adds 3 cents to $5.25 and options volume on the biotech is running 3X the daily average, being led by a 1610-lot of Mar 4 puts for $1.05 on ISE. It’s an opening buyer, according to data from the exchange. 2,944 traded total. Open interest is already 3,050 and the largest position in the name. Mar 4 puts, if bought for $1.05, have a downside breakeven at the expiration at $2.95 per share, which represents a 43.8 percent nosedive over the next 84 days. The stock saw volatile action during the first few months of 2011, but haven’t done much of late. Shares are at the same levels today as they were in June. Implied vols are steady around 56 and today’s put buyers are perhaps hedging their bets ahead of an expected Feb 2012 FDA meeting related to Chelsea’s NORTHERA drug for Parkinsons patients.

*Scanning all single-stocks subject to 2500 contracts minimum call or put volume

Mosaic (MOS) adds 44 cents to $52.06 and options on the stock are actively traded today. 17,000 calls and 4,175 puts so far. The expiring Weekly 52.5 calls, which are 44 cents out-of-the-money and coming off the board today, are the most actives. 3,560 traded against 351 in open interest. The market is 9 to 13 cents. Jan 52.5, Jan 57.5 and next weeks (12/30) 55 calls are the next most actives. Implied volatility is up 6.5 percent to 41.5, as upside call buyers seem to be dominating the flow in the stock during the first two hours of Friday’s session.