Following Google's $12.5 billion purchase of Motorola Mobility Inc., with one of the largest patent libraries in the industry, speculation is rife that Apple will respond in kind.

According to the brokerage firm Jefferies & Co, the deal will affect Apple's ability to pressure the Android ecosystem, making the iPhone maker opt for buying up more patents itself.

Who could Apple be eyeing? The brokerage firm sees the patents of Nokia, InterDigital and Research In Motion as the potential targets for Apple.

"MMI in our view had the broadest and deepest patent portfolio amongst the wireless players," Jefferies said in a note to clients, adding that the buy may prompt Apple, with a large cash pile, to make a purchase of its own.

According to the brokerage, Apple is a licensee of Nokia, which also pays significant royalties for cross-licensing. "Nokia likely has at least 50 essential 4G patents and likely over 100 essential 3G patents," it said.

On the other hand, for acquiring and developing its patent portfolio, RIM spent more than $5 billion, and as per Jefferies' calculations, the BlackBerry-maker has vital security related patents that Apple may covet. Based on the 63 percent premium that Google paid for Motorola Mobility, RIM could be valued at something over $20 billion, Reuters reported.

Thanks to its iPhone 4, which has been ruling the smartphone market for more than a year, Apple is dominant now. But once Motorola starts developing more advanced products with Google's support, Apple will have to put extra efforts to stay a step ahead.

On Tuesday, Apple's shares traded down $2.52 pre-market, after closing at $383.41 on Monday on the Nasdaq.