Spontaneous Gelation of a Novel Histamine H4 Receptor Antagonist in Aqueous Solution

Abstract

We hypothesize that this spontaneous gelation is due to the so-called "spring" effect, a high energy salt form that transiently increases aqueous solubility above its equilibrium limit. Upon equilibration, this supersaturated system undergoes aggregation that avoids crystallization and produces a hydrogel.

The Plot Thickens: Gelation by Phenylalanine in Water and Dimethyl Sulfoxide

“…In water, the gelation is dependent on ionic strength of the solution and its pH, as described by Thakur and co-workers (Table S2.1 and Figure S2). As highlighted by Popov and co-workers on a different compound, pH and ionic strength of the water utilized in the gelation of the zwitterionic compound, like Phe, can result in changing behavior . We noted that the gels were rheologically weaker upon changing the pH away from its pI value and addition of salt (NaCl) (Table S2.1).…”

“…4 As highlighted by Popov and coworkers on a different compound, pH and ionic strength of the water utilised in the gelation of the zwitterionic compound, like Phe, can result in changing behaviour. 43 We noted that the gels were rheologically weaker upon changing the pH away from its pI value and addition of salt (NaCl) (Table S2.1). The gels became metastable upon addition of NaCl (> 100 mg per 5 ml), preferring the formation of the crystalline anhydrous Form 1.…”

A theoretical study of molecular conformations and gelation ability of N,N′-dipyridyl urea compounds in ethanol solution: DFT calculations and MD simulations

“…Hydrogen-bond interactions have been the focus of much attention in supramolecular chemistry. [1][2][3][4][5][6][7][8][9][10][11] Urea-based compounds, especially those with aryl substituents, are significantly strong hydrogen-bond donors and acceptors, which is conducive for self-association processes. [12][13][14][15][16][17][18] Recently, a series of pyridyl-urea-based compounds, such as N,N9-bis(4-pyridyl) urea (1), N,N9-bis(3-pyridyl) urea (2) and N,N9-bis(2-pyridyl) urea (3) have been designed and synthesized, 18 in which two additional pyridyl rings are incorporated into the urea group to reinforce the non-covalent interactions, as displayed in Scheme 1.…”