Freezing Point Depression Research Articles

Factors contributing to ice nucleation and sequential freezing of leaves in wheat

Main conclusionAnatomical, metabolic and microbial factors were identified that contribute to sequential freezing in wheat leaves and likely contribute to supercooling in the youngest leaves and potentially meristematic regions.Infrared thermography (IR) has been used to observe wheat leaves freezing independently and in an age-related sequence with older leaves freezing first. To determine mechanisms that might explain this sequence of freezing several analytical approaches were used: (1) The size of xylem vessels, in proximity to where freezing initiated, was measured to see if capillary freezing point depression explained sequential freezing. The sequence of freezing in the four youngest leaves was correlated, with the largest vessels freezing first. (2) Carbohydrate and amino acids were analyzed to determine if solute concentrations as well as interactions with membranes explained the freezing sequence. Sucrose was highly correlated to the freezing sequence for all leaves suggesting a prominent role for this sugar as compared to other simple sugars and fructans. Among individual free amino acids proline and serine were correlated to the freezing sequence, with younger leaves having the highest concentrations. (3) Microflora within and on leaf surfaces were determined to measure potential freezing initiation. Levels of bacteria and fungi were correlated to the freezing sequence for all leaves, and species or genera associated with high ice nucleation activity were absent in younger leaves. Moisture content and transcript expression of ice binding proteins were also measured. As expected, our results show that no single mechanism explains the freezing sequence observed via infrared analyses. While these multiple mechanisms are operative at different levels according to the leaf age, they seem to converge when it comes to the protection of vital meristematic tissues. This provides potential phenotypic characters that could be used by breeders to develop more winter-hardy genotypes.

Surface thermodynamics at the nanoscale.

Fluid interfaces with nanoscale radii of curvature are generating great interest, both for their applications and as tools to probe our fundamental understanding. One important question is what is the smallest radius of curvature at which the three main thermodynamic combined equilibrium equations are valid: the Kelvin equation for the effect of curvature on vapor pressure, the Gibbs-Thomson equation for the curvature-induced freezing point depression, and the Ostwald-Freundlich equation for the curvature-induced increase in solubility. The objective of this Perspective is to provide conceptual, molecular modeling, and experimental support for the validity of these thermodynamic combined equilibrium equations down to the smallest interfacial radii of curvature. Important concepts underpinning thermodynamics, including ensemble averaging and Gibbs's treatment of bulk phase heterogeneities in the region of an interface, give reason to believe that these equations might be valid to smaller scales than was previously thought. There is significant molecular modeling and experimental support for all three of the Kelvin equation, the Gibbs-Thomson equation, and the Ostwald-Freundlich equation for interfacial radii of curvature from 1 to 4nm. There is even evidence of sub-nanometer quantitative accuracy for the Kelvin equation and the Gibbs-Thomson equation.

Evaluation of Milk Yield and Milk Composition of Honamlı Goats

The aim of this study was to determine the milk yield and milk composition (total solids, fat, protein and lactose), freezing point depressionand somatic cell counts of Honamlı goat during second lactationin Turkey. The animal material of the study consisted of a total of 30 goat. Total milk yield was detected by using Fleischmann’s method. Milk composition was analyzed by Bentley 150, and somatic cells were counted by Bentley Somacount FC. One-way ANOVA was used to determine the effect of lactation stages on milk yield and milk composition. In the study, mean lactation period and lactation milk yield of Honamlı goat were detected as 202.4 days, and 92.6 kg, respectively. The percentages of fat, protein, lactose, total solid, freezing point depression, and somatic cell counts /mL of milk were 2.4%, 4.2%, 5.1%, 12.7%, -0.57 °C, 82.8 and 2.9%, 4.2%, 4.7%, 12.7%, -0.59 °C, 483 on the 60th and 120thlactation day respectively. Total solids, fat, and protein values significantly increased especially towards the end of lactation (P <0.05). Lactose value decreased slowly from the beginning to the end of lactation. The somatic cell counts increased in milk particularly at the end of lactation (P < 0.05). The freezing point depression remained stable throughout lactation. It was thought that results of study were important representing the second lactation milk production of Honamlı goats that is one of the native goat breeds of Turkey.

Temperature Based Process Characterization of Pharmaceutical Freeze-Thaw Operations.

In biopharmaceutical production processes, freeze-thaw operations are used to ensure product integrity during long hold times, but they also introduce additional stresses such as freeze concentration gradients that might lead to a loss of protein activity. Process characterization of freeze-thaw operations at different scales should be conducted with attention to freezing time and boundary effects to ensure the product stability throughout the process and process development. Currently, process characterization often relies on one or very few temperature probes that detect freezing times based on raw temperature, which is largely influenced by freezing-point depression in case of concentrated solutions. A method to detect freezing based on the second derivative of temperature measurements from Fiber-Bragg-Grating sensors is presented to overcome this issue. The applicability of the method is demonstrated by process characterization of a novel small-scale freeze-thaw device with minimized boundary effects using freezing times of purified water and concentrated formulations. Freezing times varied from 35 to 81 min for temperatures between −60 and −20°C and impacted freeze concentration profiles. Furthermore, freezing time estimations based on the Plank equation revealed model limitations due to start-up temperature gradients, that can be corrected by an empirically extended Plank model. As a hypothesis, we conclude that freezing temperature, from a freeze concentration view, is less important in containers with small characteristic freezing distances such as freeze bags. Using a 2D-resolved temperature profile, a shift of the last point to freeze position from top to bottom of a container was observed when freezing above −30°C.

Effect of Water Content on Thermodynamic Properties of Compressed Hydrogen.

Force field-based molecular simulations were used to calculate thermal expansivities, heat capacities, and Joule–Thomson coefficients of binary (standard) hydrogen–water mixtures for temperatures between 366.15 and 423.15 K and pressures between 50 and 1000 bar. The mole fraction of water in saturated hydrogen–water mixtures in the gas phase ranges from 0.004 to 0.138. The same properties were calculated for pure hydrogen at 323.15 K and pressures between 100 and 1000 bar. Simulations were performed using the TIP3P and a modified TIP4P force field for water and the Marx, Vrabec, Cracknell, Buch, and Hirschfelder force fields for hydrogen. The vapor–liquid equilibria of hydrogen–water mixtures were calculated along the melting line of ice Ih, corresponding to temperatures between 264.21 and 272.4 K, using the TIP3P force field for water and the Marx force field for hydrogen. In this temperature range, the solubilities and the chemical potentials of hydrogen and water were obtained. Based on the computed solubility data of hydrogen in water, the freezing-point depression of water was computed ranging from 264.21 to 272.4 K. The modified TIP4P and Marx force fields were used to improve the solubility calculations of hydrogen–water mixtures reported in our previous study [RahbariA.;J. Chem. Eng. Data2019, 64, 4103−4115] for temperatures between 323 and 423 K and pressures ranging from 100 to 1000 bar. The chemical potentials of ice Ih were calculated as a function of pressure between 100 and 1000 bar, along the melting line for temperatures between 264.21 and 272.4 K, using the IAPWS equation of state for ice Ih. We show that at low pressures, the presence of water has a large effect on the thermodynamic properties of compressed hydrogen. Our conclusions may have consequences for the energetics of a hydrogen refueling station using electrochemical hydrogen compressors.

Urine metabolomics analysis based on ultra performance liquid chromatography-high resolution mass spectrometry combined with osmolality calibration sample concentration variability

尿液是代谢组学研究中主要关注的体液样本之一。尿液样本中的代谢物浓度受饮食、疾病等因素影响变异较大,这极大阻碍了高质量组学数据的获取和可靠生物标志物的鉴定。研究为克服尿液样本的浓度变异性,在原始数据采集前,根据样本渗透压的大小,针对性地调整进样量或者稀释样本,从而确保代谢组学分析样本的渗透压与进样量的乘积相当,再经超高效液相色谱-高分辨质谱技术(UPLC-HRMS)分析,采用总离子丰度或总有用峰面积(MSTUS)对数据集进行归一化处理。研究利用临床样本及其梯度稀释的溶液,对该方法与现有研究普遍使用的方法进行了比较,随后通过先天性肾积水患者及健康志愿者的尿液样本做了进一步的方法学验证。数据集经校正后,峰面积RSD<30%的提取峰数量增加,主成分分析结果较校正前有更高的组内聚集和组间分群效应,正交偏最小二乘判别分析的统计模型更不易过拟合。与肌酐比较,渗透压值与质谱信号间呈现了更好的线性关系。以上结果表明,数据采集前通过样本渗透压进行校正,能有效消除因样本本身代谢物浓度变化引起的组内差异,提高方法的重复性和统计模型的可靠度。以渗透压为基准的校正策略,比肌酐校正法适用范围更广,结果也更准确。研究可对后续各类来源的尿液代谢组学研究提供数据归一化的指导和参考。

Discovery of Hyperactive Antifreeze Protein from Phylogenetically Distant Beetles Questions Its Evolutionary Origin.

Beetle hyperactive antifreeze protein (AFP) has a unique ability to maintain a supercooling state of its body fluids, however, less is known about its origination. Here, we found that a popular stag beetle Dorcus hopei binodulosus (Dhb) synthesizes at least 6 isoforms of hyperactive AFP (DhbAFP). Cold-acclimated Dhb larvae tolerated −5 °C chilled storage for 24 h and fully recovered after warming, suggesting that DhbAFP facilitates overwintering of this beetle. A DhbAFP isoform (~10 kDa) appeared to consist of 6−8 tandem repeats of a 12-residue consensus sequence (TCTxSxNCxxAx), which exhibited 3 °C of high freezing point depression and the ability of binding to an entire surface of a single ice crystal. Significantly, these properties as well as DNA sequences including the untranslated region, signal peptide region, and an AFP-encoding region of Dhb are highly similar to those identified for a known hyperactive AFP (TmAFP) from the beetle Tenebrio molitor (Tm). Progenitor of Dhb and Tm was branched off approximately 300 million years ago, so no known evolution mechanism hardly explains the retainment of the DNA sequence for such a lo­ng divergence period. Existence of unrevealed gene transfer mechanism will be hypothesized between these two phylogenetically distant beetles to acquire this type of hyperactive AFP.

Chemical products for crop protection against freezing stress: A review

AbstractFrost is an important abiotic stress for plants and crops because of the economic losses that are incurred. Plants have two mechanisms for freezing protection: freezing avoidance and freezing tolerance. The former prevents extrinsic and/or intrinsic ice nucleation, while the latter provides plants with tools to survive apoplastic ice formation, by several coordinated physiological and biochemical features such as the increase in cryoprotectants (metabolites and proteins) which in general maintain cell membrane and cells macromolecules stability, cause a freezing point depression or decrease the cell osmolarity preventing the severe cell dehydration caused by apoplastic freezing. Many products against freezing have been developed, and there are at least 20 products on the international market. Ten products mainly avoid ice formation by forming semi‐permeable or permeable membranes that inhibit extrinsic ice nucleation over leaves, three products work for favouring tolerating ice formation in plants, and two use both mechanisms of action. Some kind of lipids, such as phospholipids and α‐tocopherol, effectively maintain the stability and integrity of cell membranes, while some osmolytes (mainly polyols) decrease the freezing point of water, both inside and outside the cell, but also can interact with the polar moieties of phospholipids stabilizing membranes. Despite this, more information on products for crop protection against freezing is required in order to determine their effectiveness. New formulations that protect crops against freezing must include ingredients that employ both mechanisms. The use of lipids is likely to continue while new alternatives that reduce ice formation are evaluated, among which antifreeze and cryoprotective proteins may offer attractive alternatives.

Modelling ice growth and inclusion behaviour of sucrose and proteins during progressive freeze concentration

This study focused on modelling ice growth and solute inclusion behaviour during progressive freeze concentration of sucrose, soy protein, and whey protein. Experiments were conducted in a small stirred tank set-up and ice growth was modelled using mass and heat balances. Solute inclusion was estimated using an intrinsic distribution coefficient. For sucrose solutions, the intrinsic distribution coefficient is proposed dependent on the initial and critical concentrations, where the last is related to the fast increase in viscosity and decrease in diffusivity when the solution approaches glass transition. Predictions were found in agreement with experimental data, except when dendritic ice growth was observed. Solutions of whey and soy proteins behaved differently due to their large difference in solubility. These proteins also showed different inclusion behaviour compared to sucrose, due to lower freezing point depression and lower concentrations far away from glass transition.

Controlling the hardness of ice cream, gelato and similar frozen desserts

Controlling the hardness of ice cream, gelato and similar frozen desserts

Water and salt migration mechanisms of saturated chloride clay during freeze-thaw in an open system

Water and salt migration mechanisms are of great significance for understanding the frost heave and thaw settlement of saline soils during freeze-thaw (F-T). In this study, unidirectional open-system F-T tests were conducted on saturated clay specimens with various chloride salt contents to investigate water and salt migration mechanisms. Relevant parameters, including temperature, unfrozen water content, bulk electrical conductivity, matric suction, and water intake volume, were measured continuously during testing. Besides, the water molecule mobility was obtained by the Nuclear Magnetic Resonance relaxometry tests to help understand the water and salt migration mechanisms. The test results indicated that the freezing front development was highly dependent on salt content. The matric suction gradient was found to be the driving force of water-salt migration, which was larger in specimens with lower salt content and led to more water intake. The migration of water and salt was asynchronous due to their different driving mechanisms during F-T. Specifically, salt migration was affected by both convection and diffusion, while water migration was primarily driven by convection. This phenomenon was also confirmed by the different patterns in water and salt redistributions after F-T. Meanwhile, pore water in the frozen specimens with different salinity and the same unfrozen water content was found to have the same water molecule mobility. Both the matric suction and water molecule mobility were dependent on unfrozen water content but independent on salt content. However, the salt content has a significant effect on the soil freezing point depression, which further affects the matric suction and water molecule mobility.

Crystal waters on the nine polyproline type II helical bundle springtail antifreeze protein from Granisotoma rainieri match the ice lattice.

A springtail (Collembola) identified as Granisotomarainieri was collected from snow in Hokkaido, Japan, in late winter when nighttime temperatures were below zero. Extracts of these arthropods showed antifreeze activity by shaping ice crystals and stopping their growth. The glycine-rich proteins responsible for this freezing point depression were isolated by ice-affinity purification and had principal masses of ~6.9 and 9.6kDa. We identified a transcript for a 9.6-kDa component and produced it as a His-tagged recombinant protein for structural analysis. Its crystal structure was solved to a resolution of 1.21Å and revealed a polyproline type II helical bundle, similar to the six-helix Hypogastruraharveyi AFP, but with nine helices organized into two layers held together by an extensive network of hydrogen bonds. One of the layers is flat, regular, and hydrophobic and likely serves as the ice-binding side. Although this surface makes close protein-protein contacts with its symmetry mate in the crystal, it has bound chains of waters present that resemble those on the basal and primary prism planes of ice. Molecular dynamic simulations indicate most of these crystal waters would preferentially occupy these sites if exposed to bulk solvent in the absence of the symmetry mate. These prepositioned waters lend further support to the ice-binding mechanism in which AFPs organize ice-like waters on one surface to adsorb to ice. DATABASES: Structural data are available in the Protein Data Bank under the accession number 7JJV. Transcript data are available in GenBank under accession numbers MT780727, MT780728, MT780729, MT780730, MT780731 and MT985982.

MD Simulation of Solvated DAFP-1-Ice Surface Binding using Umbrella Sampling

The ability of antifreeze proteins (AFPs) to depress a freezing point without affecting the equilibrium melting point remains a mystery. This disparity between freezing and melting point is also known as thermal hysteresis. Previous Molecular Dynamic (MD) studies have found that the glycoprotein AFP variants bind to ice predominantly through hydrophobic resides but there are other classes of AFP without sugar structural components. DAFP-1 is an AFP found in a Dendroides canadensis species of beetle, consisting of 83 amino acid residues bound together in a helical shape by disulfide bridges, and lacking a sugar component. Using biased molecular dynamics, we are simulating DAFP-1 at ice/water interfaces and characterizing the free energy profile. This is done by rotating the protein using a biasing potential and then working backwards to the unbiased free energy using umbrella sampling. By characterizing the side chain interactions with both the water and the ice we hope to illustrate the binding interactions contributing to the freezing point depression for AFPs without sugar components. We can then use the free energy profile improve the overall understanding of AFP to thermal hysteresis.

Ice recrystallization inhibition activity varies with ice-binding protein type and does not correlate with thermal hysteresis

Ice-binding proteins (IBPs) inhibit the growth of ice through surface adsorption. In some freeze-resistant fishes and insects, circulating IBPs serve as antifreeze proteins to stop ice growth by lowering the freezing point. Plants are less able to avoid freezing and some use IBPs to minimize the damage caused in the frozen state by ice recrystallization, which is the growth of large ice grains at the expense of small ones. Here we have accurately and reproducibly measured the ice recrystallization inhibition (IRI) activity of over a dozen naturally occurring IBPs from fishes, insects, plants, and microorganisms using a modified ‘splat’ method on serial dilutions of IBPs whose concentrations were determined by amino acid analysis. The endpoint of IRI, which was scored as the lowest protein concentration at which no recrystallization was observed, varied for the different IBPs over two orders of magnitude from 1000 nM to 5 nM. Moreover, there was no apparent correlation between their IRI levels and reported antifreeze activities. IBPs from insects and fishes had similar IRI activity, even though the insect IBPs are typically 10x more active in freezing point depression. Plant IBPs had weak antifreeze activity but were more effective at IRI. Bacterial IBPs involved in ice adhesion showed both strong freezing point depression and IRI. Two trends did emerge, including that basal plane binding IBPs correlated with stronger IRI activity and larger IBPs had higher IRI activity.

Amine Polymerization is a New Observed Molecular Behavior in Co2 Capture

Understanding the solid-liquid phase boundaries for CO2 capture solvents are important for the prevention of solid formation doing process operation. Solid formation in e.g. absorber, and stripper may lead to costly shut-downs. The objectives of this study has been to determine the solid-liquid equilibrium (SLE) of 2-amino-2-methyl-1-propanol (AMP)-water and AMP-CO2-water and to create a deeper understanding of the interactions between AMP and water and AMP, CO2, and water. The aim is to generate a deeper understanding of the AMP-water and the AMP-CO2-water interactions in order to create better thermodynamic modelling of the CO2 capture process. The presented results is based on newly published data [1] for the aqueous AMP system and additional unpublished results for the AMP-CO2-water system. We have used experimental techniques such as powder x-ray diffraction (PXRD), freezing point depression, and solid phase boundary equilibrium determinations. We found a new crystal structure, AMP tetrahydrate (AMP·4H2O) and several eutectic points in the AMP-water system. We extended our work compared to the recent publication, saturating a 30 wt% aqueous AMP solution with CO2. We found a new crystal structure using powder x-ray diffraction (PXRD). The new structure is an AMPH-HCO3 hydrate.

Development in Tear Film Osmolarity Assessments: A Review.

The aim of this article is to review the development in the assessment of tear film with tear osmolarity techniques. Also, to find out the average score for tear osmolarity in normal and keratoconjunctivitis sicca (KCS) patients based on the published work. The use of tear osmolarity techniques has been started about 50 years ago. Over the last years a number of researchers have investigated the human tear osmolarity. The tear osmolarity assessment techniques have two procedures. The first procedure which is old, that involves the detection of freezing point depression and vapour pressure. The second one which is more advance and known as the electronic method, that involves the use of electrical impedance technique. All techniques used to assess tear osmolarity are good, accurate, reliable and provide comparable data. Based on the published work reviewed in this article, the average tear osmolarity for normal subjects is 303.2 ± 7.0 compared to 322.7 ± 15.9 in subjects with KCS.

Interfacial behavior of polar and nonpolar frozen/unfrozen liquids interacting with hydrophilic and hydrophobic nanosilicas alone and in blends

HypothesisVarious nanosilica characteristics depend on hydrophobization strongly affecting interfacial phenomena. Is it possible to prepare hydrophilic samples with hydrophobic silica (AM1) alone and in blends with hydrophilic one (A–300)? It can be done with addition of a small amount of water to the powders which then are mechanically treated. ExperimentsNanosilicas were characterized using adsorption, desorption, microscopic, spectroscopic, and quantum chemistry methods. 1H NMR spectroscopy and cryoporometry were applied to AM1 and AM1/A–300 blends wetted and mechanically treated. Wetted blends were studied with additions of n-decane and chloroform-d. FindingsThe powders wetted at h = 0.3–3.0 g of water per gram of dry solids have increased bulk density. Samples are in gel-like state at h = 4–5 g/g. Water interaction energy with nanoparticles nonmonotonically depends on h (maximal at h = 3 g/g). Upon mechanical treatment of wetted blends (h < 1.5 g/g), separated AM1 structures are absent. At greater h values, blend reorganization occurs to form AM1 aggregates covered by A–300 shells. Organics can displace water from mesovoids toward narrower pores inaccessible for larger molecules or into larger voids to reduce the contact area between immiscible liquids. Freezing point depression caused by confined space and dissolution effects is affected by the blend organization.

Aqueous eutectic lithium-ion electrolytes for wide-temperature operation

Enabling reliable operation of energy storage devices over a wide temperature range without safety failures is an urgent prerequisite for extending their applications. Conventional liquid electrolytes in energy storage devices fail to reach this goal due to their limitations in freezing/boiling temperatures and flammability (for organic electrolytes). Here, we demonstrate a new class of aqueous eutectic electrolyte (AEE) based on a colligative property of lithium bis(trifluoromethane sulfonyl)imide (LiTFSI)-water binary mixture. The AEE (5.2 m LiTFSI in water) maximizes effect of freezing-point depression (below −40°C) and shows good electrochemical stability with electrode materials. We identify that a key-underlying mechanism of AEE is coordination of water molecules with Li+ and TFSI-. To explore potential use of AEE, we choose lithium-ion hybrid supercapacitors (HSC) as a model system. The AEE enables the HSC to provide exceptional high-rate cell performance over broad temperature ranges (−40°C ~ 100°C) without incurring fire or explosion.

Subzero temperature dependence of electrical conductivity for permafrost geophysics

Temperature dependence of the electrical conductivity of natural waters due to viscosity-based reduction in ionic mobility is well-established for unfrozen conditions. For cold regions, a model for the temperature dependence of electrolyte conductivity at subzero temperatures is required for geophysical studies of permafrost terrain, for which salinity and tension forces may result in freezing-point depression. Extension of the linear temperature model for unfrozen conditions has been applied to geophysical studies of permafrost, but has not been experimentally validated. The temperature dependence of electrical conductivity is measured at subzero temperatures, but above the depressed freezing point for NaCl solutions at a range of concentrations from seawater to brine. Measurements show near-linear dependence of electrical conductivity on temperature down to the lowest experimental temperature of ˗9 °C with no distinct change in behavior observed for subzero temperatures. Given the observed temperature dependence, the linear temperature-conductivity compensation equation is extended to ˗9 °C with a temperature compensation coefficient of 0.019 °C˗1 for a reference temperature of 20 °C with subzero prediction errors of 1–6%. This equation can be used to compensate for temperature dependence of electrical conductivity with reasonable accuracy for geophysical experiments in permafrost terrain. Subzero accuracy is improved by adopting a quadratic temperature compensation equation that accounts for an observed increase in nonlinear behavior at lower temperatures distant from the reference.

Freezing point depression and freeze-thaw damage by nanofluidic salt trapping

A remarkable variety of organisms and wet materials are able to endure temperatures far below the freezing point of bulk water. Cryo-tolerance in biology is usually attributed to "anti-freeze" proteins, and yet massive supercooling ($< -40^\circ$C) is also possible in porous media containing only simple aqueous electrolytes. For concrete pavements, the common wisdom is that freeze-thaw damage results from the expansion of water upon freezing, but this cannot explain the large pressures ($> 10$~MPa) required to damage concrete, the observed correlation between pavement damage and de-icing salts, or the damage of cement paste loaded with benzene (which contracts upon freezing). In this Letter, we propose a different mechanism -- nanofluidic salt trapping -- which can explain the observations, using simple mathematical models of dissolved ions confined to thin liquid films between growing ice and charged surfaces. Although trapped salt lowers the freezing point, ice nucleation in charged pores causes enormous disjoining pressures via the rejected ions, until their removal by precipitation or surface adsorption at a lower temperatures releases the pressure and allows complete freezing. The theory is able to predict the non-monotonic salt-concentration dependence of freeze-thaw damage in concreter and provides a general framework to understand the origins of cryo-tolerance.