DST Global, the investment firm started by a Russian venture capitalist, Yuri Milner, has led an $80 million private investment in a Brazilian start-up called <a href="https://www.nytimes.com/2015/06/03/business/dealbook/nubank-raises-30-million-to-challenge-banking-in-brazil.html">Nubank</a>, the company is expected to announce this week. The new financing suggests that despite Brazil’s political and economic upheaval, the financial technology sector remains a bright spot.