SierraCities.com

(BTOB)

was up 38.3% in midafternoon trading after announcing that it will be purchased by financial services giant

American Express

(AXP) - Get Report

. American Express said its

Travel Related Services

unit would pay $107.5 million, or 5.68 per share, for SierraCities, an equipment financing company. American Express said the deal would help expand its small business lending. American Express was down 0.4%.