Abstract: Sulfur is a constituent atom in two naturally occurring amino acids, namely, methionine and cysteine. It has been well established that in many proteins and enzymes the non-covalent interactions involving sulfur atom in these two amino acids play important role in lending them their intrinsic structures and also in enzymatic catalysis. These interactions have been interchangeably categorized as either as generic non-covalent interactions or specifically hydrogen bonding interactions. However, in many instances their structural properties do not necessarily confirm to those of the conventional hydrogen bonds. We have been investigating the spectroscopic and electronic structure properties of sulfur centered non-covalent contacts using a variety of laser spectroscopic techniques in gas phase and have been able to show that they satisfy all the criteria of hydrogen bonding interaction. We have also determined the dissociation energies of OH---S hydrogen bonded complexes using a combination of the ZEKE photoelectron spectroscopy and photo-fragmentation spectroscopy. In this talk I will present some of these results.