MySearch DS-1 can be uninstalled via Google Chrome's Extensions tab. To find it in Windows or OS X, go to Chrome's Tools menu in the upper right corner of a Chrome window, and hover your mouse pointer over More tools:
When the More Tools submenu appears, click on Extensions:
Once you've arrived on the Extensions tab, find "MySearch DS-1" in the list of currently installed extensions. Click the trash can icon to the right, and the app will uninstall:
After removing the app, your default new tab in Chrome should revert to whatever it was previously. If not, or if you'd like to change it manually, please refer to this article.