The thiol bond can be broken under reducing conditions, for example at intracellular environment.  Reducing agents such as DTT, glutathione or mercaptoethano can also break thiol bond. 

Thank you Miss Moraima. Can I please ask if you came across any specific reference or any literature available.

Kind Regards,

Rakesh 

I am not sure but it appears that Moraima is discussing the reduction of disulfide bonds, not gold-thiol bonds. Please see the link for papers discussing the exchange of gold-thiol bonds. For the gold-thiol bond, a strength of about 50 kJ/mol - 100 kJ/mol can be found. This is in the order of weak covalent bonds.

http://pubs.acs.org/doi/abs/10.1021/la00054a029

http://www.nature.com/nchem/journal/v4/n6/full/nchem.1352.html?WT.mc_id=TWT_NatureChemistry

http://www.nature.com/ncomms/2014/140707/ncomms5348/abs/ncomms5348.html

Thank you Dr. Sanjay, Dr. Joao, and Dr. Robert for your expert suggestions. Thank you

You can electrochemically desorb thiols from a gold surface. I do not know if your thiol-Au bond is in a surface that can be used as an electrode. In that case this method is suitable.

Using this method you can actually even quantifiy the amount of thiol attached to your Au. You can see a description in the attached publication.

Article Desorption of Spontaneously Adsorbed and Electrochemically R...

sorry for the naive questio. What is the nature of the S-Au(I)-S cluster?

Is Au ionized in Au+? If Au as oxidation number I how can form two bonds. Maybe one is a covalent bond and the second is a coordination bond but finally it results in a hybrid coordination/ covalents bond delocalized between the two sulfur centers?

Thiol-Stabilized Gold Nanoparticles: New Ways To Displace Thiol Layers Using Yttrium or Lanthanide Chlorides, check this paper

Hi Sanjay Sankaranarayanan

Greetings: I also look forward receiving reference on breakage of thiol-Au bond by sonication. Thanks Ailsa McMilan and Dr. Sanjay Sankaranarayanan.