Who revealed biochemical nature of the transforming principle?

Explanation

Oswald, Avery, Colin MecLeod and Maclyn McCarty revealed biochemical nature of the transforming principle.
They reported Griffith's experiment in an in vitro system in order to determine biochemical nature of transformaing principle.
They reported that DNA from the heat-killed S-type bacteria caused the transformation of non-virulent R-type bacteria into virulent S-type bacteria. They also discovered that proteases and RNase did not affect transformation while DNase inhibited the process. They concluded that DNA is the hereditary material.