In the panic after Silicon Valley Bank collapsed in early March, some small and medium-size businesses yanked their money from regional banks and deposited it with the biggest ones, seeking the security of their gigantic balance sheets and the government’s implicit backstop of lenders deemed too big to fail, the New York Times reported. Regulators, bank executives and industry representatives have been trying desperately to persuade those depositors to stop. Treasury Secretary Janet L. Yellen yesterday expressed confidence in the nation’s banks and suggested that the government would step in to protect smaller banks if needed. Shares of many regional banks rallied after her remarks. Last week, Tim Mayopoulos, the new chief executive of Silicon Valley Bank, implored clients to leave their deposits with the bank or transfer them back. And some lawmakers in Washington are seeking to raise the limit for federal deposit insurance above $250,000 so that businesses don’t fret about losing their uninsured funds if their bank fails. But fear persists. More than 90 clients of Kruze Consulting, an accounting firm that specializes in start-ups, have changed banks in the last few weeks — and half went to JPMorgan Chase, said Scott Orn, the firm’s chief operating officer.