An Insight into the Ice Nucleation Process via Design of Crystalline Ice Nucleators of Variable Size

Abstract

Monolayers of the long-chain alcohols on water promote nucleation of ice. In order to determine the minimum size of crystalline alcohol monolayer domains that induce ice nucleation, we reduced their size in two distinct ways. One approach encompassed embedding the pure hydrocarbon alcohol, C n H2 n +1OH (n = 20, 31), into a matrix of an immiscible monolayer of perfluoro alcohol C10F21C2H4OH, which is inert as an ice nucleator. The second set of experiments involved the introduction of random defects into the monolayer crystalline domains of C29H59OH through the use of the fully miscible guest alcohol molecule, C31H63OH, as additive. By these methods we estimated that ∼450 water molecules are necessary to form a stable ice cluster at the onset of induced ice nucleation at a temperature just below 0 °C.

An energy-based mapping method for identifying the in-plane orientations of polypeptides and other macromolecules at crystalline interfaces

“…As demonstrated in this report, the POINTER-determined orientations for each benchmark system are in agreement with experimental and theoretical data. 2,4,5,10,17,[21][22][23][24][25][26] Moreover, we find that the simple forcefield allows correct identification of the lowest energy polypeptide chain or monolayer alignment, and, a reasonably correct positioning of the macromolecular surface with regard to the interfacial surface.…”

“…56,57 As shown in Table I, results obtained by POINTER are in agreement ͑within Ϯ 0.5°͒ with published benchmark findings. 2,4,5,10,17,[21][22][23][24][25][26] Note that the original CHASM algorithm computes lattice coincidences between 2D macromolecule lattices and 2D surface lattice coordinates; there is no chemical information ͑i.e., specific atoms, energy parameters, etc.͒ to guide the search. As a result, the CHASM algorithm generates geometrically equivalent global minima for all macromolecule-lattice pairings ͑Table I͒.…”

“…macromolecule interacts with a perfect surface, i.e., devoid of any fissures, pits, growth steps, or other irregularities. This assumption is also predicated upon the necessity to compare our simulation data with previous modeling studies conducted using the same simplifying assumptions, 2,4,5,10,17,[21][22][23][24][25][26] and, the absence of experimental data with which to recreate these defects at atomic level resolution in all of the crystalline solids under consideration.…”

“…To benchmark the POINTER algorithm, we performed simulations on eight different macromolecules which exhibit preferred orientations with defined interfaces of a crystalline solid ͑Table I͒: ͑i͒ Ice antifreeze 2,5,17 or nucleation 4 polypeptides which adsorb onto specific Miller planes of hexagonal ice (I h ), as observed via polypeptide-ice etching experiments 2,5,17 or deduced from modeling studies; 4 ͑ii͒ polypeptides which adsorb onto inorganic solid interfaces, as determined from x-ray diffraction studies [21][22][23] or from combined mineral inhibition-modeling studies; 10 and ͑iii͒ a C31 alcohol monolayer, which stereospecifically nucleates hexagonal ice ͕͑001͖ plane͒, as evidenced from x-ray diffraction measurements of monolayerice nucleation systems. [24][25][26] The alcohol monolayer-ice system represents an important benchmark for exploring different multipole energy potentials ͑e.g., dipole-dipole, dipole-charge, charge-charge͒ and their effect on identifying the lowest energy orientation. As demonstrated in this report, the POINTER-determined orientations for each benchmark system are in agreement with experimental and theoretical data.…”

Crystalline architectures at the air-liquid interface: From nucleation to engineering

“…Certain amphiphiles spontaneously form multilayers on liquid formamide [lo]. A variety of other molecules were found to form crystalline multilayers on water, such as bolaform amphiphiles containing hydrogen-bonding groups at both ends of the chain [11,12], pure long-chain alkanes [13] and heterocyclic aromatics [14]. Their packing arrangements could be determined to almost atomic resolution by means of GIXD.…”