Interaction of l‐leucyl‐l‐leucyl‐l‐leucine thin film with water and organic vapors: receptor properties and related morphology

Abstract

The ability of highly ordered tripeptide structures to keep or change their morphology in contact with organic vapors was studied. A thin film of tripeptide L-leucyl-L-leucyl-L-leucine (LLL) was prepared having microcrystals and nanocrystals on its surface, which are stable upon vacuum drying but become objects of selective morphology change after a contact with vapors of organic solvents. Fine separate LLL crystals and their agglomerates of submicron and larger dimensions were observed by atomic force microscopy and scanning electron microscopy. After saturation with guest vapors, these crystals can remain intact or change their morphology with the increase in size or complete destruction depending on the guest molecular structure. The crystals completely lose their shape after the binding of pyridine vapors. The other studied guests produce much smaller transformations or have no effect on crystal morphology despite being sorbed by solid LLL, which was shown using quartz crystal microbalance sensor. The observed size-exclusion effect for guest sorption by LLL was found to be broken by the same guests that can change the initial crystal shape. This helps to explain the morphology changes of LLL crystals after the guest sorption and release.

Thermal analysis of clathrates of tripeptide LLL with organic compounds and water

“…The TG/DSC/MS experiment gives a clathrate composition S that is lower than the stoichiometry calculated from QCM data [31] for methanol, ethanol, and acetonitrile. This difference is due to partial decomposition of the clathrate before the start of the analysis when the sample was stored in a flow of argon for 20 min at 298 K. The compositions of the more stable clathrates of LLL are in agreement within experimental error of the stoichiometry obtained from QCM data (for water and benzene) [31], and with X-ray data (for pyridine) [35].…”

“…Thermal analysis of clathrates of tripeptide LLL 1813 could be due to changes in the packing of the tripeptides during the guest desorption process. Indirectly, this is supported by the ability of pyridine vapors to destroy the LLL crystals without dissolution [31].…”

“…The ''soft nature'' of the interactions in the oligopeptide phase also provides increased reversibility of binding and allows the release of gas just by reducing of pressure [29,30]. This aspect of oligopeptide nanomaterials is also the reason for the changes in the surface morphology of a dipeptide film [31][32][33] or the formation of new nanostructures [34] when they interact with any vapors from either water or organic compounds.…”

“…LLL has previously been shown to effectively bind organic compounds and water [31,35,36], as well as undergo changes in the morphology of a thin film as induced by the binding of an organic vapor [31].…”

Thermally induced cyclization of L‐isoleucyl‐L‐alanine in solid state: Effect of dipeptide structure on reaction temperature and self‐assembly

“…For AFM experiments, dipeptide films with diameter of 3 to 5 mm were prepared from hexafluoro‐2‐propanol or methanol solution on the surfaces of highly oriented pyrolytic graphite (HOPG) plates (1 × 1 cm). For this, 2 to 5 μL of solution on the substrate was dried as described early . HOPG was freshly cleaved before use.…”