how to get rid of curly brackets writing minimization output to file

I have the following code

SetDirectory["C:\test"]; fname = FileNameJoin[{%, "results.dat"}]; str = OpenWrite[fname, FormatType -> StandardForm]  D1 = 0.4; D2start = 0.26; D2fin = 0.5; Ntot = 12; D2step = (D2fin - D2start)/Ntot;  For[i = 0, i <= Ntot, i++,   D2 = D2start + i*D2step ;   With[{minsol = NMinimize[fnew[D1, D2, x], x]},   fmin = First@minsol;   xn = Values@ Last@ minsol;];   Write[str, D2, " ", xn]; ]   Close[str]; 

i.e I minimize the function fnew wrt x and write the value of x in the file results.dat. The problem is that the output is

0.26 {0.711259} 0.28 {0.744881} 0.3 {0.776204} 0.32 {0.805418} etc. 

How do I get rid of these annoying curly brackets?