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Head of Institute: Prof. Oren Froy

Administrative manager: Ms. Yael Fruchter

Office Address:
Institute of Biochemistry, Food Science and Nutrition,
Robert H. Smith Faculty of Agriculture, Food and Environment,
The Hebrew University of Jerusalem, 
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Email Address: yaelf@savion.huji.ac.il

Publications

2019
Bissoyi, A. ; Reicher, N. ; Chasnitsky, M. ; Arad, S. ; Koop, T. ; Rudich, Y. ; Braslavsky, I. Ice Nucleation Properties of Ice-binding Proteins from Snow Fleas. Biomolecules 2019, 9.Abstract
Ice-binding proteins (IBPs) are found in many organisms, such as fish and hexapods, plants, and bacteria that need to cope with low temperatures. Ice nucleation and thermal hysteresis are two attributes of IBPs. While ice nucleation is promoted by large proteins, known as ice nucleating proteins, the smaller IBPs, referred to as antifreeze proteins (AFPs), inhibit the growth of ice crystals by up to several degrees below the melting point, resulting in a thermal hysteresis (TH) gap between melting and ice growth. Recently, we showed that the nucleation capacity of two types of IBPs corresponds to their size, in agreement with classical nucleation theory. Here, we expand this finding to additional IBPs that we isolated from snow fleas (the arthropod Collembola), collected in northern Israel. Chemical analyses using circular dichroism and Fourier-transform infrared spectroscopy data suggest that these IBPs have a similar structure to a previously reported snow flea antifreeze protein. Further experiments reveal that the ice-shell purified proteins have hyperactive antifreeze properties, as determined by nanoliter osmometry, and also exhibit low ice-nucleation activity in accordance with their size.
Wang, S. ; Duan, Y. ; Yan, Y. ; Adar, C. ; Braslavsky, I. ; Chen, B. ; Huang, T. ; Qiu, S. ; Li, X. ; Inglis, B. M. ; et al. Improvement of sperm cryo-survival of cynomolgus macaque (Macaca fascicularis) by commercial egg-yolk–free freezing medium with type III antifreeze protein. Animal Reproduction Science 2019, 210, 106177. Publisher's VersionAbstract
When nonhuman primate sperm undergoes cryopreservation in an egg yolk medium there is an increased risk that the egg yolk might adversely affect the sperm due to containing of avian pathogens. Although commercial egg-yolk-free medium for human sperm cryopreservation has been used for macaque sperm, the cryo-survival remains less than optimal. The present study, therefore, was conducted to determine the optimal concentration of antifreeze protein (AFP) III supplemented in a commercial egg-yolk-free medium for cynomolgus macaque (Macaca fascicularis) sperm cryo-survival. The function of frozen-thawed sperm was evaluated by post-thaw sperm motility, acrosome integrity, and mitochondrial function. Results indicate that the sperm motilities were greater when 0.1, 1, and 10 μg/ml of AFP III were supplemented into the sperm freezing medium (P < 0.05). In addition, the mitochondrial membrane potential was greater in the sperm cryopreserved with the medium that was supplemented with 0.1 μg/ml of AFP III (P < 0.05). The addition of AFP III at any of the concentrations, however, did not have any cryoprotection effect on the sperm acrosome, and the greatest concentrations of AFP III at 100 and 200 μg/ml had detrimental effects on acrosomal integrity (P < 0.05). Results of the present study indicated the methods used are effective for the cryopreservation of cynomolgus monkey sperm while reducing associated health risks due to avian pathogens being present in egg yolk-based extenders.
Croote, D. ; Braslavsky, I. ; Quake, S. R. Addressing Complex Matrix Interference Improves Multiplex Food Allergen Detection by Targeted LC–MS/MS. Analytical ChemistryAnalytical Chemistry 2019. Publisher's VersionAbstract
The frequent use of precautionary food allergen labeling (PAL) such as “may contain” frustrates allergic individuals who rely on such labeling to determine whether a food is safe to consume. One technique to study whether foods contain allergens is targeted liquid chromatography-tandem mass spectrometry (LC–MS/MS) employing scheduled multiple reaction monitoring (MRM). However, the applicability of a single MRM method to many commercial foods is unknown as complex and heterogeneous interferences derived from the unique composition of each food matrix can hinder quantification of trace amounts of allergen contamination. We developed a freely available, open source software package MAtrix-Dependent Interference Correction (MADIC) to identify interference and applied it with a method targeting 14 allergens. Among 84 unique food products, we found patterns of allergen contamination such as wheat in grains, milk in chocolate-containing products, and soy in breads and corn flours. We also found additional instances of contamination in products with and without PAL as well as highly variable soy content in foods containing only soybean oil and/or soy lecithin. These results demonstrate the feasibility of applying LC–MS/MS to a variety of food products with sensitive detection of multiple allergens in spite of variable matrix interference.The frequent use of precautionary food allergen labeling (PAL) such as “may contain” frustrates allergic individuals who rely on such labeling to determine whether a food is safe to consume. One technique to study whether foods contain allergens is targeted liquid chromatography-tandem mass spectrometry (LC–MS/MS) employing scheduled multiple reaction monitoring (MRM). However, the applicability of a single MRM method to many commercial foods is unknown as complex and heterogeneous interferences derived from the unique composition of each food matrix can hinder quantification of trace amounts of allergen contamination. We developed a freely available, open source software package MAtrix-Dependent Interference Correction (MADIC) to identify interference and applied it with a method targeting 14 allergens. Among 84 unique food products, we found patterns of allergen contamination such as wheat in grains, milk in chocolate-containing products, and soy in breads and corn flours. We also found additional instances of contamination in products with and without PAL as well as highly variable soy content in foods containing only soybean oil and/or soy lecithin. These results demonstrate the feasibility of applying LC–MS/MS to a variety of food products with sensitive detection of multiple allergens in spite of variable matrix interference.
Chasnitsky, M. ; Braslavsky, I. Ice-binding proteins and the applicability and limitations of the kinetic pinning model. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 2019, 377, 20180391. Publisher's Version
Guy Preis, S. ; Chayet, H. ; Katz, A. ; Yashunsky, V. ; Kaner, A. ; Ullman, S. ; Braslavsky, I. Labyrinth ice pattern formation induced by near-infrared irradiation. Science Advances 2019, 5 eaav1598. Publisher's VersionAbstract
Patterns are broad phenomena that relate to biology, chemistry, and physics. The dendritic growth of crystals is the most well-known ice pattern formation process. Tyndall figures are water-melting patterns that occur when ice absorbs light and becomes superheated. Here, we report a previously undescribed ice and water pattern formation process induced by near-infrared irradiation that heats one phase more than the other in a two-phase system. The pattern formed during the irradiation of ice crystals tens of micrometers thick in solution near equilibrium. Dynamic holes and a microchannel labyrinth then formed in specific regions and were characterized by a typical distance between melted points. We concluded that the differential absorption of water and ice was the driving force for the pattern formation. Heating ice by laser absorption might be useful in applications such as the cryopreservation of biological samples.
Eickhoff, L. ; Dreischmeier, K. ; Zipori, A. ; Sirotinskaya, V. ; Adar, C. ; Reicher, N. ; Braslavsky, I. ; Rudich, Y. ; Koop, T. Contrasting Behavior of Antifreeze Proteins: Ice Growth Inhibitors and Ice Nucleation Promoters. The Journal of Physical Chemistry Letters 2019, 10, 966 - 972. Publisher's VersionAbstract
Several types of natural molecules interact specifically with ice crystals. Small antifreeze proteins (AFPs) adsorb to particular facets of ice crystals, thus inhibiting their growth, whereas larger ice-nucleating proteins (INPs) can trigger the formation of new ice crystals at temperatures much higher than the homogeneous ice nucleation temperature of pure water. It has been proposed that both types of proteins interact similarly with ice and that, in principle, they may be able to exhibit both functions. Here we investigated two naturally occurring antifreeze proteins, one from fish, type-III AFP, and one from beetles, TmAFP. We show that in addition to ice growth inhibition, both can also trigger ice nucleation above the homogeneous freezing temperature, providing unambiguous experimental proof for their contrasting behavior. Our analysis suggests that the predominant difference between AFPs and INPs is their molecular size, which is a very good predictor of their ice nucleation temperature.Several types of natural molecules interact specifically with ice crystals. Small antifreeze proteins (AFPs) adsorb to particular facets of ice crystals, thus inhibiting their growth, whereas larger ice-nucleating proteins (INPs) can trigger the formation of new ice crystals at temperatures much higher than the homogeneous ice nucleation temperature of pure water. It has been proposed that both types of proteins interact similarly with ice and that, in principle, they may be able to exhibit both functions. Here we investigated two naturally occurring antifreeze proteins, one from fish, type-III AFP, and one from beetles, TmAFP. We show that in addition to ice growth inhibition, both can also trigger ice nucleation above the homogeneous freezing temperature, providing unambiguous experimental proof for their contrasting behavior. Our analysis suggests that the predominant difference between AFPs and INPs is their molecular size, which is a very good predictor of their ice nucleation temperature.
Kaleda, A. ; Haleva, L. ; Sarusi, G. ; Pinsky, T. ; Mangiagalli, M. ; Bar Dolev, M. ; Lotti, M. ; Nardini, M. ; Braslavsky, I. Saturn-Shaped Ice Burst Pattern and Fast Basal Binding of an Ice-Binding Protein from an Antarctic Bacterial Consortium. Langmuir 2019, 35, 7337 - 7346. Publisher's VersionAbstract
Ice-binding proteins (IBPs) bind to ice crystals and control their growth, enabling host organisms to adapt to subzero temperatures. By binding to ice, IBPs can affect the shape and recrystallization of ice crystals. The shapes of ice crystals produced by IBPs vary and are partially due to which ice planes the IBPs are bound to. Previously, we have described a bacterial IBP found in the metagenome of the symbionts of Euplotes focardii (EfcIBP). EfcIBP shows remarkable ice recrystallization inhibition activity. As recrystallization inhibition of IBPs and other materials are important to the cryopreservation of cells and tissues, we speculate that the EfcIBP can play a future role as an ice recrystallization inhibitor in cryopreservation applications. Here we show that EfcIBP results in a Saturn-shaped ice burst pattern, which may be due to the unique ice-plane affinity of the protein that we elucidated using the fluorescent-based ice-plane affinity analysis. EfcIBP binds to ice at a speed similar to that of other moderate IBPs (5 ± 2 mM–1 s–1); however, it is unique in that it binds to the basal and previously unobserved pyramidal near-basal planes, while other moderate IBPs typically bind to the prism and pyramidal planes and not basal or near-basal planes. These insights into EfcIBP allow a better understanding of the recrystallization inhibition for this unique protein.Ice-binding proteins (IBPs) bind to ice crystals and control their growth, enabling host organisms to adapt to subzero temperatures. By binding to ice, IBPs can affect the shape and recrystallization of ice crystals. The shapes of ice crystals produced by IBPs vary and are partially due to which ice planes the IBPs are bound to. Previously, we have described a bacterial IBP found in the metagenome of the symbionts of Euplotes focardii (EfcIBP). EfcIBP shows remarkable ice recrystallization inhibition activity. As recrystallization inhibition of IBPs and other materials are important to the cryopreservation of cells and tissues, we speculate that the EfcIBP can play a future role as an ice recrystallization inhibitor in cryopreservation applications. Here we show that EfcIBP results in a Saturn-shaped ice burst pattern, which may be due to the unique ice-plane affinity of the protein that we elucidated using the fluorescent-based ice-plane affinity analysis. EfcIBP binds to ice at a speed similar to that of other moderate IBPs (5 ± 2 mM–1 s–1); however, it is unique in that it binds to the basal and previously unobserved pyramidal near-basal planes, while other moderate IBPs typically bind to the prism and pyramidal planes and not basal or near-basal planes. These insights into EfcIBP allow a better understanding of the recrystallization inhibition for this unique protein.
Karlsson, J. O. ; M., ; Braslavsky, I. ; Elliott, J. A. W. Protein–Water–Ice Contact Angle. Langmuir 2019, 35, 7383 - 7387. Publisher's VersionAbstract
The protein–water–ice contact angle is a controlling parameter in diverse fields. Here we show that data from three different experiments, at three different length scales, with three different proteins, in three different laboratories yield a consistent value for the protein–water–ice contact angle (88.0 ± 1.3°) when analyzed using the Gibbs–Thomson equation. The measurements reinforce the validity of each other, and the fact that similar values are obtained across diverse length scales, experiments, and proteins yields insight into protein–water interactions and the applicability of thermodynamics at the nanoscale.The protein–water–ice contact angle is a controlling parameter in diverse fields. Here we show that data from three different experiments, at three different length scales, with three different proteins, in three different laboratories yield a consistent value for the protein–water–ice contact angle (88.0 ± 1.3°) when analyzed using the Gibbs–Thomson equation. The measurements reinforce the validity of each other, and the fact that similar values are obtained across diverse length scales, experiments, and proteins yields insight into protein–water interactions and the applicability of thermodynamics at the nanoscale.
Kam, D. ; Chasnitsky, M. ; Nowogrodski, C. ; Braslavsky, I. ; Abitbol, T. ; Magdassi, S. ; Shoseyov, O. Direct Cryo Writing of Aerogels via 3D Printing of Aligned Cellulose Nanocrystals Inspired by the Plant Cell Wall. Colloids and Interfaces 2019, 3. Publisher's VersionAbstract
Aerogel objects inspired by plant cell wall components and structures were fabricated using extrusion-based 3D printing at cryogenic temperatures. The printing process combines 3D printing with the alignment of rod-shaped nanoparticles through the freeze-casting of aqueous inks. We have named this method direct cryo writing (DCW) as it encompasses in a single processing step traditional directional freeze casting and the spatial fidelity of 3D printing. DCW is demonstrated with inks that are composed of an aqueous mixture of cellulose nanocrystals (CNCs) and xyloglucan (XG), which are the major building blocks of plant cell walls. Rapid fixation of the inks is achieved through tailored rheological properties and controlled directional freezing. Morphological evaluation revealed the role of ice crystal growth in the alignment of CNCs and XG. The structure of the aerogels changed from organized and tubular to disordered and flakey pores with an increase in XG content. The internal structure of the printed objects mimics the structure of various wood species and can therefore be used to create wood-like structures via additive manufacturing technologies using only renewable wood-based materials.
2018
Adar, C. ; Sirotinskaya, V. ; Bar Dolev, M. ; Friehmann, T. ; Braslavsky, I. Falling water ice affinity purification of ice-binding proteins. Scientific Reports 2018, 8 11046. Publisher's VersionAbstract
Ice-binding proteins (IBPs) permit their hosts to thrive in the presence of ice. The ability of IBPs to control ice growth makes them potential additives in industries ranging from food storage and cryopreservation to anti-icing systems. For IBPs to be used in commercial applications, however, methods are needed to produce sufficient quantities of high-quality proteins. Here, we describe a new method for IBP purification, termed falling water ice affinity purification (FWIP). The method is based on the affinity of IBPs for ice and does not require molecular tags. A crude IBP solution is allowed to flow over a chilled vertical surface of a commercial ice machine. The temperature of the surface is lowered gradually until ice crystals are produced, to which the IBPs bind but other solutes do not. We found that a maximum of 35 mg of IBP was incorporated in 1 kg of ice. Two rounds of FWIP resulted in >95% purity. An ice machine that produces 60 kg of ice per day can be used to purify one gram of IBP per day. In combination with efficient concentration of the protein solution by tangential flow filtration the FWIP method is suitable for the purification of grams of IBPs for research purposes and applications.
Braslavsky, I. ; Stavans, J. Application of Algebraic Topology to Homologous Recombination of DNA. iScience 2018, 4 64 - 67. Publisher's VersionAbstract
SummaryBrouwer's fixed point theorem, a fundamental theorem in algebraic topology proved more than a hundred years ago, states that given any continuous map from a closed, simply connected set into itself, there is a point that is mapped unto itself. Here we point out the connection between a one-dimensional application of Brouwer's fixed point theorem and a mechanism proposed to explain how extension of single-stranded DNA substrates by recombinases of the RecA superfamily facilitates significantly the search for homologous sequences on long chromosomes.
Bahari, L. ; Bein, A. ; Yashunsky, V. ; Braslavsky, I. Directional freezing for the cryopreservation of adherent mammalian cells on a substrate. PLOS ONE 2018, 13, e0192265 -. Publisher's VersionAbstract
Successfully cryopreserving cells adhered to a substrate would facilitate the growth of a vital confluent cell culture after thawing while dramatically shortening the post-thaw culturing time. Herein we propose a controlled slow cooling method combining initial directional freezing followed by gradual cooling down to -80°C for robust preservation of cell monolayers adherent to a substrate. Using computer controlled cryostages we examined the effect of cooling rates and dimethylsulfoxide (DMSO) concentration on cell survival and established an optimal cryopreservation protocol. Experimental results show the highest post-thawing viability for directional ice growth at a speed of 30 μm/sec (equivalent to freezing rate of 3.8°C/min), followed by gradual cooling of the sample with decreasing rate of 0.5°C/min. Efficient cryopreservation of three widely used epithelial cell lines: IEC-18, HeLa, and Caco-2, provides proof-of-concept support for this new freezing protocol applied to adherent cells. This method is highly reproducible, significantly increases the post-thaw cell viability and can be readily applied for cryopreservation of cellular cultures in microfluidic devices.
Mangiagalli, M. ; Sarusi, G. ; Kaleda, A. ; Bar Dolev, M. ; Nardone, V. ; Vena, V. F. ; Braslavsky, I. ; Lotti, M. ; Nardini, M. Structure of a bacterial ice binding protein with two faces of interaction with ice. The FEBS Journal 2018, 285, 1653 - 1666. Publisher's VersionAbstract
Ice-binding proteins (IBPs) contribute to the survival of many living beings at subzero temperature by controlling the formation and growth of ice crystals. This work investigates the structural basis of the ice-binding properties of EfcIBP, obtained from Antarctic bacteria. EfcIBP is endowed with a unique combination of thermal hysteresis and ice recrystallization inhibition activity. The three-dimensional structure, solved at 0.84 Å resolution, shows that EfcIBP belongs to the IBP-1 fold family, and is organized in a right-handed ?-solenoid with a triangular cross-section that forms three protein surfaces, named A, B, and C faces. However, EfcIBP diverges from other IBP-1 fold proteins in relevant structural features including the lack of a ?capping? region on top of the ?-solenoid, and in the sequence and organization of the regions exposed to ice that, in EfcIBP, reveal the presence of threonine-rich ice-binding motifs. Docking experiments and site-directed mutagenesis pinpoint that EfcIBP binds ice crystals not only via its B face, as common to other IBPs, but also via ice-binding sites on the C face. Database Coordinates and structure factors have been deposited in the Protein Data Bank under accession number 6EIO.
2017
Mangiagalli, M. ; Bar-Dolev, M. ; Tedesco, P. ; Natalello, A. ; Kaleda, A. ; Brocca, S. ; de Pascale, D. ; Pucciarelli, S. ; Miceli, C. ; Braslavsky, I. ; et al. Cryo-protective effect of an ice-binding protein derived from Antarctic bacteria. The FEBS Journal 2017, 284, 163-177. Publisher's VersionAbstract
Cold environments are populated by organisms able to contravene deleterious effects of low temperature by diverse adaptive strategies, including the production of ice binding proteins (IBPs) that inhibit the growth of ice crystals inside and outside cells. We describe the properties of such a protein (EfcIBP) identified in the metagenome of an Antarctic biological consortium composed of the ciliate Euplotes focardii and psychrophilic non-cultured bacteria. Recombinant EfcIBP can resist freezing without any conformational damage and is moderately heat stable, with a midpoint temperature of 66.4 °C. Tested for its effects on ice, EfcIBP shows an unusual combination of properties not reported in other bacterial IBPs. First, it is one of the best-performing IBPs described to date in the inhibition of ice recrystallization, with effective concentrations in the nanomolar range. Moreover, EfcIBP has thermal hysteresis activity (0.53 °C at 50 μm) and it can stop a crystal from growing when held at a constant temperature within the thermal hysteresis gap. EfcIBP protects purified proteins and bacterial cells from freezing damage when exposed to challenging temperatures. EfcIBP also possesses a potential N-terminal signal sequence for protein transport and a DUF3494 domain that is common to secreted IBPs. These features lead us to hypothesize that the protein is either anchored at the outer cell surface or concentrated around cells to provide survival advantage to the whole cell consortium.
Bar Dolev, M. ; Braslavsky, I. Ice-binding proteins—not only for ice growth control. Temperature 2017, 4 112-113. Publisher's Version
Guo, S. ; Stevens, C. A. ; Vance, T. D. R. ; Olijve, L. L. C. ; Graham, L. A. ; Campbell, R. L. ; Yazdi, S. R. ; Escobedo, C. ; Bar-Dolev, M. ; Yashunsky, V. ; et al. Structure of a 1.5-MDa adhesin that binds its Antarctic bacterium to diatoms and ice. Science Advances 2017, 3. Publisher's VersionAbstract
Bacterial adhesins are modular cell-surface proteins that mediate adherence to other cells, surfaces, and ligands. The Antarctic bacterium Marinomonas primoryensis uses a 1.5-MDa adhesin comprising over 130 domains to position it on ice at the top of the water column for better access to oxygen and nutrients. We have reconstructed this 0.6-μm-long adhesin using a “dissect and build” structural biology approach and have established complementary roles for its five distinct regions. Domains in region I (RI) tether the adhesin to the type I secretion machinery in the periplasm of the bacterium and pass it through the outer membrane. RII comprises  120 identical immunoglobulin-like β-sandwich domains that rigidify on binding Ca2+ to project the adhesion regions RIII and RIV into the medium. RIII contains ligand-binding domains that join diatoms and bacteria together in a mixed-species community on the underside of sea ice where incident light is maximal. RIV is the ice-binding domain, and the terminal RV domain contains several “repeats-in-toxin” motifs and a noncleavable signal sequence that target proteins for export via the type I secretion system. Similar structural architecture is present in the adhesins of many pathogenic bacteria and provides a guide to finding and blocking binding domains to weaken infectivity.
2016
Lewis, J. K. ; Bischof, J. C. ; Braslavsky, I. ; Brockbank, K. G. M. ; Fahy, G. M. ; Fuller, B. J. ; Rabin, Y. ; Tocchio, A. ; Woods, E. J. ; Wowk, B. G. ; et al. The Grand Challenges of Organ Banking: Proceedings from the first global summit on complex tissue cryopreservation. 2016, 72, 169 - 182. Publisher's VersionAbstract
The first Organ Banking Summit was convened from Feb. 27 - March 1, 2015 in Palo Alto, CA, with events at Stanford University, NASA Research Park, and Lawrence Berkeley National Labs. Experts at the summit outlined the potential public health impact of organ banking, discussed the major remaining scientific challenges that need to be overcome in order to bank organs, and identified key opportunities to accelerate progress toward this goal. Many areas of public health could be revolutionized by the banking of organs and other complex tissues, including transplantation, oncofertility, tissue engineering, trauma medicine and emergency preparedness, basic biomedical research and drug discovery – and even space travel. Key remaining scientific sub-challenges were discussed including ice nucleation and growth, cryoprotectant and osmotic toxicities, chilling injury, thermo-mechanical stress, the need for rapid and uniform rewarming, and ischemia/reperfusion injury. A variety of opportunities to overcome these challenge areas were discussed, i.e. preconditioning for enhanced stress tolerance, nanoparticle rewarming, cyroprotectant screening strategies, and the use of cryoprotectant cocktails including ice binding agents.
Bar Dolev, M. ; Braslavsky, I. ; Davies, P. L. Ice-Binding Proteins and Their Function. Annual Review of BiochemistryAnnual Review of Biochemistry 2016, 85, 515 - 542. Publisher's VersionAbstract
Ice-binding proteins (IBPs) are a diverse class of proteins that assist organism survival in the presence of ice in cold climates. They have different origins in many organisms, including bacteria, fungi, algae, diatoms, plants, insects, and fish. This review covers the gamut of IBP structures and functions and the common features they use to bind ice. We discuss mechanisms by which IBPs adsorb to ice and interfere with its growth, evidence for their irreversible association with ice, and methods for enhancing the activity of IBPs. The applications of IBPs in the food industry, in cryopreservation, and in other technologies are vast, and we chart out some possibilities.Ice-binding proteins (IBPs) are a diverse class of proteins that assist organism survival in the presence of ice in cold climates. They have different origins in many organisms, including bacteria, fungi, algae, diatoms, plants, insects, and fish. This review covers the gamut of IBP structures and functions and the common features they use to bind ice. We discuss mechanisms by which IBPs adsorb to ice and interfere with its growth, evidence for their irreversible association with ice, and methods for enhancing the activity of IBPs. The applications of IBPs in the food industry, in cryopreservation, and in other technologies are vast, and we chart out some possibilities.
Bar Dolev, M. ; Bernheim, R. ; Guo, S. ; Davies, P. L. ; Braslavsky, I. Putting life on ice: bacteria that bind to frozen water. Journal of The Royal Society InterfaceJournal of The Royal Society Interface 2016, 13, 20160210. Publisher's Version
Haleva, L. ; Celik, Y. ; Bar-Dolev, M. ; Pertaya-Braun, N. ; Kaner, A. ; Davies, P.  L. ; Braslavsky, I. Microfluidic Cold-Finger Device for the Investigation of Ice-Binding Proteins. 2016, 111, 1143 - 1150. Publisher's VersionAbstract
Ice-binding proteins (IBPs) bind to ice crystals and control their structure, enlargement, and melting, thereby helping their host organisms to avoid injuries associated with ice growth. IBPs are useful in applications where ice growth control is necessary, such as cryopreservation, food storage, and anti-icing. The study of an IBP’s mechanism of action is limited by the technological difficulties of in situ observations of molecules at the dynamic interface between ice and water. We describe herein a new, to our knowledge, apparatus designed to generate a controlled temperature gradient in a microfluidic chip, called a microfluidic cold finger (MCF). This device allows growth of a stable ice crystal that can be easily manipulated with or without IBPs in solution. Using the MCF, we show that the fluorescence signal of IBPs conjugated to green fluorescent protein is reduced upon freezing and recovers at melting. This finding strengthens the evidence for irreversible binding of IBPs to their ligand, ice. We also used the MCF to demonstrate the basal-plane affinity of several IBPs, including a recently described IBP from Rhagium inquisitor. Use of the MCF device, along with a temperature-controlled setup, provides a relatively simple and robust technique that can be widely used for further analysis of materials at the ice/water interface.