Arsenal have confirmed the signing of Brazil full-back Andre Santos and German defender Per Mertesacker.
Santos, 28, joins the Gunners from Turkish champions Fenerbahce, and will add some much-needed experience to an Arsenal backline which shipped eight goals in their humiliating defeat at Manchester United on Saturday.
Manager Arsene Wenger told the club's official website, www.arsenal.com: "Santos is a quality player, with the ability to both defend well and get forward and help with attacks."
He added: "He has experience in the Champions League and for Brazil and has proven he can deliver at the highest level. We welcome Santos to the club and look forward to him having a big impact for us."
The Brazilian full-back, who did not feature in the 2010 World Cup squad, is understood to have joined the Gunners in a £6.2million deal and becomes the latest Brazilian to head to Arsenal, following the likes of Denilson, Sylvinho, Edu and Gilberto Silva.
"It was one of my dreams to play for a major European football club and I have accomplished this. I am very happy to be part of this team," he said.
"All the Brazilians who came to this club spoke wonders about it and I am delighted to be part of the Arsenal family."
Confirmation of the arrival of Mertesacker, meanwhile, is expected shortly after the German centre-back completed a medical and agreed personal terms on an £8million move from Werder Bremen.
Wenger has been busy in the final days of the transfer window, having brought in South Korea captain Park Chu-Young from Monaco.
The Arsenal manager is also expected to add at least one more new signing ahead of the deadline. With Scott Dann's imminent move to Blackburn, reports have suggested Christopher Samba could be set for a transfer to Arsenal, who appear to have cooled interest in Bolton's England centre-half Gary Cahill.