setting viewmodel's object property

[Ahmet]

I have two separate js files. one contains a kendo observable object. when I set viewmodel's object property from another js file, the object is set but object's properties are still undefined.

<script type="text/javascript">
    var previewModel = kendo.observable({
        question: {}
    });
    kendo.bind($("#preview-question"), previewModel);
</script>
<div id="preview-question">
    <div data-bind="text: question.QuestionText"></div>
</div>

another-js-file.js
previewModel.set("question", ko.toJSON(self.question()));

this code sets the question object but its properties still undefined.

[Ahmet]

solved the problem 
in the setting part it should be set to an object not json string.