Ice nucleation of an insect lipoprotein ice nucleator (LPIN) correlates with retardation of the hydrogen bond dynamics at the myo-inositol ring

Remarkably little is known about the mechanism of action of ice nucleation proteins (INPs), although their ability to trigger ice nucleation could be used in a broad variety of applications. We present CD measurements of an insect lipoprotein ice nucleator (LPIN) which show that the lipoproteins con...

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Bibliographic Details
Published in:Physical chemistry chemical physics : PCCP 2016-07, Vol.18 (28), p.19318-19323
Main Authors: Bäumer, Alexander, Duman, John G, Havenith, Martina
Format: Article
Language:English
Subjects:
Animals
Antifreeze Proteins - chemistry
Bacterial Outer Membrane Proteins
Dynamics
Hydrogen
Hydrogen Bonding
Hydrogen bonds
Inositol - chemistry
Insecta - chemistry
Insects
Lipoproteins
Lipoproteins - chemistry
Lipoproteins - metabolism
Networks
Nucleation
Order disorder
Sodium borates
Water
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Summary:Remarkably little is known about the mechanism of action of ice nucleation proteins (INPs), although their ability to trigger ice nucleation could be used in a broad variety of applications. We present CD measurements of an insect lipoprotein ice nucleator (LPIN) which show that the lipoproteins consist of a high amount of β-structures (35%). Terahertz absorption spectroscopy is used to probe the influence of the LPIN on the H-bond network dynamics. We observe a small, but significant THz excess, as an indication of an influence on the H-bond network dynamics. When adding the ice nucleation inhibitor sodium borate, this effect is considerably reduced, similar to that observed before for antifreeze glycoproteins (AFGPs). We propose that myo-inositol, the functional group of phosphatidylinositols, is crucial for the observed change of the H-bond network dynamics of hydration water. This hypothesis is confirmed by additional THz experiments which revealed that the influence of myo-inositol on the hydrogen bond network can be blocked by sodium borate, similar to the case of LPINs. Interestingly, we find a less significant effect when myo-inositol is replaced for chiro- and allo-inositol which underlines the importance of the exact positioning of the OH groups for the interaction with the H-bond network. We propose that a local ordering of water molecules is supporting ice nucleation activity for the LPIN in a similar way to that found for AFP activity in the case of hyperactive insect AFPs.
ISSN:1463-9076
1463-9084
DOI:10.1039/c6cp02399a