Mountain View, Calif.--After failing to find a buyer for two struggling e-marketplaces, Ventro Corp. said it will close its Chemdex and Promedix e-markets. In October, Ventro said it was exiting the business of owning and operating e-marketplaces, focusing instead on providing services to other e-marketplaces. The company apparently searched for a buyer for the two pioneering marketplaces but, in an ominous sign for the entire sector, couldn't land a deal. Ventro will lay off 235 employees with the move and take restructuring charges of about $400 million in its year-end fiscal results. The two marketplaces, but particularly Chemdex, were veritable poster children for the e-market industry. Ventro still has four markets in its portfolio, but they are jointly owned with large brick-and-mortar players. The markets are MarketMile, Broadlane, Industria and Amphire.