Mountain View, Calif.--Chemdex Corp. announced Monday that it has agreed to form a joint venture with Tenet Healthcare Corp., Santa Barbara, Calif., to create a new electronic-commerce company serving the health care industry. Chemdex, which creates vertical industry portals, brings to the deal its scalable e-commerce platform. Tenet brings its BuyPower group purchasing organization, which buys more than $3 billion annually in medical supplies for its members. Separately, Chemdex announced Monday that it has agreed to acquire SpecialtyMD.com in a stock deal valued at $115 million. SpecialtyMD.com's search software enables the delivery of unbiased information about medical products and procedures via the Web.