Smart Behavior of Leucyl-Leucine Dipeptide: Recognition of Organic Guests and Tunable Thermal Stability

Abstract

New properties of leucyl-leucine dipeptide crystals were discovered. They can remember vapors of methanol and n-propanol and distinguish these compounds from ethanol after their inclusion and release. The memory of the dipeptide appears to have specific thermal effects on the curves of differential scanning calorimetry in the temperature range after the evolution of methanol and n-propanol from the clathrates. The number of thermal effects depends on the guest in the clathrate. The memory of leucyl-leucine to methanol vapors depends on the way of clathrate is prepared and can be erased. It was found that the onset temperature of dipeptide cyclization in the solid state can be changed by binding and removal of vapors of water and organic compounds. The explanation for this effect is discussed. The special behavior of leucyl-leucine was explained and the possibility to control the polymorphic state of the dipeptide using organic vapors was shown.