Not able to assign a string value to the string type attributes of a PR ITEM Type

string sattr1 = "PR-10005"

string sattr3 = "finalchange"

 Item pr1 = MyInnovator.newItem("PR", "add");

                        bRes = pr1.isError();

                        pr1.setProperty("item_number", sattr1);

                        pr1.setProperty("title", sattr3); /// Without this line of code , the PR gets created...

                        pr1.apply();

Please suggest what is wrong in the method of setting the property attribute.

Even if I use pr1.setPropertyAttribute("String","title",sattr3); it does not work