Despite a second straight day of light economic data, investors today took their cues to lock in their gains and pushed the broad-based S&P 500 (SNPINDEX:^GSPC) decisively lower.

The big issue that continues to haunt the market on a daily basis is the mounting standoff between Russia and Ukraine. Some estimates show that a conflict in this region could drastically reduce Russia's GDP growth, which would negatively affect the rest of the industrialized nations around the world, including the United States. Russia is a vital member of the BRIC nations that the U.S. is relying on to help grow its own exports, and mounting tensions between the Washington and Moscow could harm global growth if those exports are impacted.

Data to keep your eyes on for later this week includes weekly initial jobless claims and retail sales on Thursday, as well as the Bureau of Labor Statistics' Producer Price Index and the University of Michigan consumer sentiment index on Friday. Although the weather has been brutal across much of the nation, the expectation from economists is that the data should be dramatically better from last month.

For today, though, investors were more than content to take money off the table, sending the S&P 500 lower by 9.54 points (-0.51%) to close at 1,867.63. Despite the drop, the S&P still sits less than 1% from a new all-time high.

Leading all stocks to the upside today was flavor ingredients developer Senomyx (NASDAQ: SNMX), which soared 17.2% after the Food and Drug Administration found its Sweetmyx flavor ingredient to be generally recognized as safe. Senomyx has geared Sweetmyx to be used in beverages where sugar content has been reduced, but which still keeps the beverage sweet-tasting. Senomyx's partner PepsiCo (NASDAQ:PEP) will now be able to pursue the commercialization of Sweetmyx, which could result in new low-calorie beverages for the carbonated and still beverage giant. For Senomyx, it could represent the start of a valuable revenue stream, while for PepsiCo it might help jump-start its stagnant U.S. growth.

Clinical-stage biopharmaceutical company Northwest Biotherapeutics (OTC:NWBO) soared for a second straight day, this time up 16.9%, following yesterday's positive news that its lead drug, DCVax-L had been granted a hospital exemption in Germany for use in all types of glioma brain cancers. This five-year term approval gives Northwest an opportunity to generate revenue from DCVax-L and also allows it a chance to highlight the product in a number of glioma brain cancers that are outside the realm of its current U.S. trial. While I still agree wholeheartedly that this is good news, the magnitude of the rise just doesn't make a lot of sense, and I would suggest investors wait for the U.S. phase 3 data before attempting to chase this stock any higher.

Finally, casino, resort, and gaming products operator Boyd Gaming (NYSE:BYD) vaulted higher by 16.5% after hedge fund Elliott Management disclosed in a regulatory filing that it had obtained 4.99% of Boyd's outstanding shares and had additional exposure of 2.05% through derivatives. The filing notes Elliott Management's intention to talk with Boyd's management team about possible strategic alternatives which have the potential to unlock shareholder value. On the other side of the coin, though, research firm Janney Capital commented that Boyd Gaming shares appear a bit pricey. I happen to agree with Janney here given that Boyd is valued at 33 times forward earnings and the best casino growth can be found right now outside the United States.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.