mathscript Note ：unexpected char: '@'

I was trying to use the mathscript to fit nonlinear curve with the function ‘lsqcurvefit’，and one error occured：unexpected char: '@'.

some code in the mathscript note is shown as following: out = lsqcurvefit(@TransferFunc,   [amplitudeGuess * frequencyGuess ^ 2, frequencyGuess], f, psd', [], [], fitOptions) ;

’TransferFunc‘ is the definition of the expression of the curve to be fitted.

Any help would very appreciated.