Conde Nast pulled the plug Monday on Portfolio, its $100 million experiment in business journalism.The glossy monthly bowed amid great fanfare in 2007 under the editorial direction of longtime Wall Street Journal vet Joanne Lipman. Its proposition was to deliver business insight with the same mix of expert writing, investigative zeal and luxe design that had propelled sister publications Vanity Fair and Vogue over the years. Hollywood coverage was a fairly prominent part of the mix — not surprising given that Lipman had spearheaded the Journal’s push into lifestyle and entertainment coverage in recent years. Portfolio ran features about financier Ryan Kavanaugh and the battle over the rights to Superman and sought to brand itself in Gotham with events featuring prominent media figures. Fate intervened in the end, however, when the credit crunch of early 2008 gave way to the Bear Stearns collapse and then the full-blown crisis on Wall Street that proved difficult for a monthly to cover. The environment for magazines, as with newspapers, darkened considerably, with privately held Conde shuttering Domino and reducing Men’s Vogue to an occasional title. Last fall, Portfolio cut about 20% of its staff and went from publishing 12 times a year to just 10. Ad pages in the first quarter plummeted 61%, and the circulation when the end came was 415,000.