Microsoft ( MSFT) has shuffled a number of high-ranking executives and formed a new group to coordinate Internet search- and ad-related research. The moves illustrate Microsoft's increasing emphasis on catching up with Google ( GOOG), which leads the search business by a wide margin, and second-place Yahoo! ( YHOO). Satya Nadella, who leads the Microsoft Dynamics line of business software, will head the search and ad platform group. Having one person lead research-and-development efforts in search and advertising is a key object of the realignment, Microsoft said. Google has a bit more than 48% of the search market, Yahoo! about 26% and Microsoft roughly 12%, according to Nielsen/Net Ratings. Harry Shum will be chief scientist in the new group, and Tami Reller will become acting leader of Dynamics. Shares of Microsoft were recently off a dime to $28.24 after hours.