Cyclization of alanyl-valine dipeptides in the solid state. The effects of molecular radiator and heat capacity.

Heating of linear dipeptides above a critical temperature initiates their cyclization even in the solid state. This method of obtaining cyclic dipeptides meets the requirements of "green chemistry", provides a high yield of the main product and releases only water as a by-product of the reaction, and does not require solvents. However, to date, the cyclization of only a small number of dipeptides in the solid state has been studied, and some correlations of the process were discovered.

Multi-functional imidazolium dendrimers based on thiacalix[4]arenes: self-assembly, catalysis and DNA binding.

For the first time, dendrimers based on thiacalix[4]arenes bearing imidazolium dendrons on one side and alkyl fragments on another side of the macrocyclic platform and symmetrical dendrimers with four dendrons on both sides were synthesized. Dendrons consist of gallic acid-based branches functionalized with imidazolium and triazolium groups. The physicochemical properties of the dendrimers such as micellar concentration (CMC), size, and solubilization capacity were measured.

Covalent Functionalization of Black Phosphorus Nanosheets with Dichlorocarbenes for Enhanced Electrocatalytic Hydrogen Evolution Reaction.

Two-dimensional black phosphorus (BP) has emerged as a perspective material for various micro- and opto-electronic, energy, catalytic, and biomedical applications. Chemical functionalization of black phosphorus nanosheets (BPNS) is an important pathway for the preparation of materials with improved ambient stability and enhanced physical properties. Currently, the covalent functionalization of BPNS with highly reactive intermediates, such as carbon-free radicals or nitrenes, has been widely implemented to modify the material's surface.

In-Situ Electrochemical Exfoliation and Methylation of Black Phosphorus into Functionalized Phosphorene Nanosheets.

Two-dimensional black phosphorus (BP) has attracted great attention as a perspective material for various applications. The chemical functionalization of BP is an important pathway for the preparation of materials with improved stability and enhanced intrinsic electronic properties. Currently, most of the methods for BP functionalization with organic substrates require either the use of low-stable precursors of highly reactive intermediates or the use of difficult-to-manufacture and flammable BP intercalates.

Supramolecular Structure and Mechanical Performance of κ-Carrageenan-Gelatin Gel.

In this work, by means of complex physicochemical methods the structural features of a composite κ-carrageenan-gelatin system were studied in comparison with initial protein gel. The correlation between the morphology of hydrogels and their mechanical properties was demonstrated through the example of changes in their rheological characteristics. The experiments carried out with PXRD, SAXS, AFM and rheology approaches gave new information on the structure and mechanical performance of κ-carrageenan-gelatin hydrogel.

Modulation of Molecular Structure and Mechanical Properties of κ-Carrageenan-Gelatin Hydrogel with Multi-Walled Carbon Nanotubes.

Hydrogels, three-dimensional hydrophilic water-insoluble polymer networks having mechanical properties inherent for solids, have attracted continuous research attention over a long time period. Here, we studied the structure and properties of hydrogel based on gelatin, κ-carrageenan and CNTs using the combination of SAXS, PXRD, AFM microscopy, SEM and rheology methods. We have shown that the integration of polysaccharide and protein in the composite hydrogel leads to suppression of their individual structural features and homogenization of two macromolecular components into a single structural formation.

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

Thermal treatment of short-chain oligopeptides is able to initiate the process of their self-assembly with the formation of organic nanostructures with unique properties. On the other hand, heating can lead to a chemical reaction with the formation of new substances with specific properties and ability to form structures with different morphology. Therefore, in order to have a desired process, researcher needs to find its temperature range.

Role of water in the formation of unusual organogels with cyclo(leucyl-leucyl).

The key role of water in the formation of cyclo(leucyl-leucyl) organogels was demonstrated. The conditions required for preparation of previously unknown gels with aliphatic hydrocarbons at room temperature were determined. Cyclo(leucyl-leucyl) self-assembles to form different structures depending on the medium used.

Thermally Induced Self-Assembly and Cyclization of l-Leucyl-l-Leucine in Solid State.

Thermal treatment of oligopeptides is one of the methods for synthesis of organic nanostructures. However, heating may lead not only to self-assembly of the initial molecules, but also to chemical reactions resulting in the formation of new unexpected nanostructures or change in the properties of the existing ones. In the present work, the reaction of cyclization of dipeptide l-leucyl-l-leucine in solid state under heating was studied.

Non-zeolitic properties of the dipeptide l-leucyl-l-leucine as a result of the specific nanostructure formation.

The non-zeolitic behavior of l-leucyl-l-leucine and its self-organization in solid state and from solutions with the formation of different nanostructures are reported. This dipeptide forms porous crystals, but does not exhibit molecular sieve effects typical of classical zeolites and biozeolites. The specific sorption properties of l-leucyl-l-leucine result from a change in its crystal packing from channel-type to layered-type, when binding strong proton acceptors or proton donors of molecular size greater than 18-20 cm mol.

A study of the formation of magnetically active solid dispersions of phenacetin using atomic and magnetic force microscopy.

A lot of pharmaceutical substances have a poor solubility that limits their absorption and distribution to the targeted sites to elicit the desired action without causing untoward effects on healthy cells or tissues. For such drugs, new modes of delivery have to be developed for efficient and effective delivery of the drug to the target site. Formation of magnetically active solid dispersion of such drugs could be a useful approach to addressing this problem because they combine targeted delivery and good solubility.

Interaction of L-alanyl-L-valine and L-valyl-L-alanine with organic vapors: thermal stability of clathrates, sorption capacity and the change in the morphology of dipeptide films.

The strong effect of the amino acid sequence in L-alanyl-L-valine and L-valyl-L-alanine on their sorption properties toward organic compounds and water, and the thermal stability of the inclusion compounds of these dipeptides have been found. Generally, L-valyl-L-alanine has a greater sorption capacity for the studied compounds, but the thermal stability of the L-alanyl-L-valine clathrates is higher. Unusual selectivity of L-valyl-L-alanine for vapors of few chloroalkanes was observed.

Interaction of L-leucyl-L-leucyl-L-leucine thin film with water and organic vapors: receptor properties and related morphology.

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.