I optimized the ZnS nanotube and amino acid structure by DFT calculations(by DMOL3). i want to know how should i analyze that any bond formed between these 2 structures or not.

The most straightforward way to prove formation of chemical bonds is calculating Mayer bond order. If the value is evidently larger than zero, then chemical bond should have formed. Mayer bond order can be easily calculated via Multiwfn (//www.umsyar.com/multiwfn), example is given in Section 4.9.1 of Multiwfn manual. Multiwfn doesn't support Dmol3 because Multiwfn only supports Gauss type basis function, however you can use such as the freely available ORCA program to carry out a single point for the optimized geometry to yield .molden file, which could be used as input file of Multiwfn. More discussion about bond order can be found in my paper Phys. Chem. A, 117, 3100−3108 (2013), introduction of all kinds of bond orders supported by Multiwfn can be found in Section 3.11 of Multiwfn manual.

Other kinds of analyses, such as AIM analysis, ELF or LOL analysis, deformation map of electron density, are also quite useful for studying chemical bonding, all of them are fully supported by Multiwfn.

I have written a blog article devoted to discuss how to determine whether a chemical bond has formed, see //www.umsyar.com/414 or http://bbs.keinsci.com/thread-9840-1-1.html, it should be very useful for you, but it was written in Chinese (however you could use Google translator to try to understand article content)