Please answer a question about the following article about Greece:

Greeks have a long tradition of valuing and investing in paideia (education). Paideia was one of the highest societal values in the Greek and Hellenistic world while the first European institution described as a university was founded in 5th century Constantinople and operated in various incarnations until the city's fall to the Ottomans in 1453. The University of Constantinople was Christian Europe's first secular institution of higher learning since no theological subjects were taught, and considering the original meaning of the world university as a corporation of students, the world’s first university as well.

When was Constantinople taken over by the Ottoman?
1453