EnergySolutions, Meritor, Rubicon, SemGroup: U.S. Equity Movers

Shares of the following companies had unusual moves in U.S. trading. Stock symbols are in parentheses, and prices are as of 4 p.m. in New York.

Carmax Inc. (KMX US) slumped 7.2 percent, the most since Dec. 10, to $32.10. The largest U.S. seller of used cars said gross margin for the fourth-quarter fell to 14.2 percent from 14.5 percent in the year-ago period.

EnergySolutions (ES US) dropped 13 percent, the most since February 2010, to $5.96. The provider of technical services to the nuclear industry reported fourth-quarter earnings that missed analysts’ estimates and said financial statement for previous quarters shouldn’t be relied upon because of a revision in accounting on its Zion Station transaction.

Horizon Lines Inc. (HRZ US) slid 33 percent to 85 cents, the lowest price since its initial public offering in September 2005. The owner of U.S.-flagged container vessels may file for bankruptcy as soon as April, according to three people familiar with the matter.

Luna Innovations Inc. (LUNA US) rose 37 percent, the most since January 2010, to $2.47. Intuitive Surgical Inc. (ISRG US) extended its development agreement with the maker of sensors used in medical devices.

Mako Surgical Corp. (MAKO US) advanced 13 percent to $24.12, the highest price since its initial public offering in February 2008. Hospital Management Associate Inc. (HMA US) expanded its relationship with Mako Surgical, agreeing to 11 more sites that use the company’s orthopedic surgery device.

Meritor Inc. (MTOR US) fell 15 percent, the most since May 2009, to $16.97. The maker of parts for cars and trucks reduced its second-quarter earnings forecast and said it’s closing its European trailer axle business on July 31.

Pharmasset Inc. (VRUS US) surged 10 percent to $78.71, the highest price since its April 2007 initial public offering. The drugmaker’s treatment for hepatitis C was effective in 98 percent of patients in a 121-person clinical trial, researchers said at the European Association for the Study of the Liver conference in Berlin.

Rubicon Minerals Corp. (RBY US) rose 16 percent, the most since Nov. 29, to $5.20. The mining company revised its estimate of minerals at its Phoenix Gold Project.

SemGroup Corp. (SEMG US) slumped 13 percent, the most since March 2010, to $28.16. The energy transport company said 2011 adjusted earnings before interest, taxes, depreciation and amortization will range between $120 million and $140 million, less than Ebitda of $152.8 million in 2010.

Tesla Motors Inc. (TSLA US) rallied 17 percent, the most since Nov. 10, to $27.75. The U.S. electric carmaker was raised to “overweight” from “equal-weight” by Morgan Stanley’s Adam Jonas, who said the company will benefit from a shift away from internal-combustion engines.

United Community Bank Inc. (UCBI US) climbed 16 percent to $2.33, the highest price since Dec. 23. The regional bank, which has branches in Georgia and North Carolina, raised $380 million by selling shares and convertible preferred stock and received board approval to accelerate the sale of $142 million in foreclosed properties.

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