Creating Anti-icing Surfaces via the Direct Immobilization of Antifreeze Proteins on Aluminum.
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ABSTRACT:
SUBMITTER: Gwak Y
PROVIDER: S-EPMC4495550 | biostudies-other | 2015
REPOSITORIES: biostudies-other
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Project description:This study reports the potential of a unique functional composite for anti-icing applications. To date, various ionic salt formulations have been applied to prevent ice accumulation on surfaces. However, salt can be removed by external factors and large amounts must be used to attain anti-icing properties. Incorporating hydrophilic salts into hydrophobic mediums and controlled release of specific agents can provide effective solution to reduce ice accumulation on surfaces. Here, we developed functional polymer composites with salt pockets of altered ionic salts consisting of potassium formate (KCOOH), sodium chloride (NaCl), or magnesium chloride (MgCl2). We dissolved ionic salts in hydrophilic gel domains and dispersed in a hydrophobic styrene-butadiene-styrene polymer matrix. Na+ and Cl- ions delayed ice formation by 42.6 min at -2 °C compared to that for unmodified surfaces. Functional composites prepared with the NaCl ionic salt exhibited better anti-icing behavior at -2 °C because of their high concentration compared to that of the composites prepared with KCOOH and MgCl2 ionic salts. We also characterized the release of ionic salts from composite-modified hydrophobic medium separately up to 118 days. Furthermore, we monitored freezing of water on composite-incorporated or composite-coated hydrophobic surfaces in a camera-integrated cold chamber with a uniform temperature (-2 °C). The results demonstrated significant increases in the delay of freezing on composite-incorporated or composite-coated surfaces compared to that on controls. We observed altered effects of each ionic salt on the mechanical, morphological, and functional properties of the composite-incorporated or composite-coated hydrophobic surfaces. Our results suggested that the efficiency of a polymer composite to promote anti-icing behavior on a surface is directly related to the type and concentration of the particular ionic salt incorporation into the composite. This approach is promising and demonstrates significant potential of the ionic salt embedded within polymer composite-modified hydrophobic surfaces to attain delayed icing function.
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Project description:Protein chips are powerful tools as analytical and diagnostic devices for detection of biomolecular interactions, where the proteins are covalently or noncovalently attached to biosensing surfaces to capture and detect target molecules or biomarkers. Thus, fabrication of biosensing surfaces for regio- and chemoselective immobilization of biomolecules is a crucial step for better biosensor performance. In our previous studies, a regio- and chemoselective immobilization strategy was demonstrated on glass surfaces. This strategy is now used to regioselectively attach proteins to self-assembled monolayers (SAMs) on gold surfaces. Recombinant green fluorescent protein (GFP), glutathione S-transferase (GST), and antibody-binding protein G, bearing a C-terminal CVIA motif, were prepared and a farnesyl analogue with an ?-alkyne moiety was attached to the sulfhydryl moiety in the cysteine side chain by protein farnesyltransferase. The proteins, modified with the bioorthogonal alkyne functional group, were covalently and regioselectively immobilized on thiol or dithiocarbamate (DTC) SAMs on a gold surface by a Huigsen [3 + 2] cycloaddition reaction with minimal nonspecific binding. A concentration-dependent increase of fluorescence intensity was observed in wells treated with GFP on both thiol- and DTC-SAMs. The highly ordered, densely packed layer allowed for a high loading of immobilized protein, with a concomitant increase in substrate binding capacity. The DTC-SAMs were substantially more resistant to displacement of the immobilized proteins from the gold surface by ?-mercaptoethanol than alkane-thiol SAMs.
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Project description:The antifreeze protein (AFP) activity is explained using two models. The first model is using ice binding and the second is using antiice structuralization of water molecules. The description of AFP function using anti-ice structuralization of water molecules is less explored. Therefore, it is of interest to explain AFP function using this model. Protein folding is often described using models where hydrophobic residues move away from water getting buried and hydrophilic residues are exposed to the surface. Thus, the 3D Gauss function stretched on the protein molecule describes the hydrophobicity distribution in a protein molecule. Small antifreeze proteins (less than 150 residues) are often represented by structures with hydrophobic core. Large antifreeze proteins (above 200 residues) contain solenoid (modular repeats). The hydrophobic field of solenoid show different distribution with linear propagation of the bands of different hydrophobicity level having high and low hydrophobicity that is propagated parallel to the long axis of solenoid. This specific ordering of hydrophobicity implies water molecules ordering different from ice. We illustrate this phenomenon using two antifreeze proteins to describe the hypothesis.
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Project description:Antifreeze Proteins (AFPs) inhibit the growth of an ice crystal by binding to it. The detailed binding mechanism is, however, still not fully understood. We investigated three AFPs using Molecular Dynamics simulations in combination with Grid Inhomogeneous Solvation Theory, exploring their hydration thermodynamics. The observed enthalpic and entropic differences between the ice-binding sites and the inactive surface reveal key properties essential for proteins in order to bind ice: While entropic contributions are similar for all sites, the enthalpic gain for all ice-binding sites is lower than for the rest of the protein surface. In contrast to most of the recently published studies, our analyses show that enthalpic interactions are as important as an ice-like pre-ordering. Based on these observations, we propose a new, thermodynamically more refined mechanism of the ice recognition process showing that the appropriate balance between entropy and enthalpy facilitates ice-binding of proteins. Especially, high enthalpic interactions between the protein surface and water can hinder the ice-binding activity.
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Project description:Antifreeze proteins (AFPs) can bind to ice nuclei thereby inhibiting their growth and their hydration shell is believed to play a fundamental role. Here, we use molecular dynamics simulations to characterize the hydration shell of four moderately-active and four hyperactive AFPs. The local water density around the ice-binding-surface (IBS) is found to be lower than that around the non-ice-binding surface (NIBS) and this difference correlates with the higher hydrophobicity of the former. While the water-density increase (with respect to bulk) around the IBS is similar between moderately-active and hyperactive AFPs, it differs around the NIBS, being higher for the hyperactive AFPs. We hypothesize that while the lower water density at the IBS can pave the way to protein binding to ice nuclei, irrespective of the antifreeze activity, the higher density at the NIBS of the hyperactive AFPs contribute to their enhanced ability in inhibiting ice growth around the bound AFPs.
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Project description:The hydrophobicity and anti-icing performance of the surfaces of some artificial hydrophobic coatings degraded after several icing and de-icing cycles. In this paper, the frost formation on the surfaces of butterfly wings from ten different species was observed, and the contact angles were measured after 0 to 6 frosting/defrosting cycles. The results show that no obvious changes in contact angle for the butterfly wing specimens were not obvious during the frosting/defrosting process. Further, the conclusion was inferred that the topography of the butterfly wing surface forms a special space structure which has a larger space inside that can accommodate more frozen droplets; this behavior prevents destruction of the structure. The findings of this study may provide a basis and new concepts for the design of novel industrially important surfaces to inhibit frost/ice growth, such as durable anti-icing coatings, which may decrease or prevent the socio-economic loss.
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