Energy transfer in collisions of peptide ions with surfaces

Time- and energy-resolved surface induced dissociation (SID) of a singly protonated octapeptide des-Arg1-bradykinin was used to study the effect of physical properties of the SID target on the efficiency of translational to vibrational energy transfer (T→V) in collisions of peptide ions with surfaces. Four SID targets of varying chemical composition and stiffness were examined in this work: self-assembled monolayers of 1-dodecane thiol (HSAM) and its fluorinated analog (CF3(CF2)9C2H4SH — FSAM) on gold, a 300 nm thick layer of lithium fluoride (LiF) on a polished titanium surface, and a 2 μm carbon vapor deposited diamond layer on a titanium surface. A RRKM-based modeling approach was utilized to extract internal energy distributions deposited into the precursor ion upon collisions with different surfaces. We found that the percent of T→V transfer increases in the order: HSAM (10.1%), LiF (12.0%), diamond (19.2%), FSAM (20.5%). Furthermore, the width of the energy deposition function (EDF) is affected by the properties of the SID target. Collisions of peptide ions with the HSAM surface results in deposition of relatively narrow internal energy distributions with the width of the EDF increasing in the order: HSAM