March's Paper of the Month

 An optical image of black phosporus mid-IR photodetector. 

An optical image of black phosporus mid-IR photodetector. 

The element phosphorus has several different allotropes, including the thermodynamically stable form, black phosphorus (BP). BP has interesting properties which make it useful for the optoelectrical field, such as its layered structure, bandgap in the mid-infrared range and high carrier mobility. 

HgxCd(1-x)Te (MCT) is generally regarded as the most popular mid-infrared material, whose composition can be tuned by in material growth process. However dynamical, in-situ tuning of its optical properties has never been achieved, limiting its ability. 

The Paper of the Month for March, discovered black phosphorus could be useful for in-situ tunable mid-infrared applications. They leveraged a thin layer of black phosphorus sandwiched between hexagonal boron nitride (HBN) and applied an electric field to tune its optical properties. This expanded the photo-response of the mid-infrared photodetectors from 3.7 to 7.7 µm. Other than photodetectors, high speed mid-infrared modulators can be readily constructed using the same concept. 

They used the heating and cooling probe stage, the HFS600E-PB4, together with an FTIR spectrometer for the temperature-dependent photo-response measurements. 

Their results prove promising. The layered nature of BP, the high intrinsic mobility and strong photo-response in the broad mid-IR wavelength range make it an ideal material for high-speed mid-IR photodetectors, modulators and spectrometers. 
 

By Tabassum Mujtaba

Xia et al., Widely tunable black phosphorus mid-infrared photodetector. (2017) Nature Communicationsvolume 8, Article number: 1672 doi:10.1038/s41467-017-01978-3

Studying Phase Transitions in Pharmaceuticals with the Linkam DSC450

Dr Asma Buanz

UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London, WC1N 1AX

Background

Polymorphism in pharmaceutical solids has great implications on both the processing and the performance of solid pharmaceutical products. It is the ability of a substance to exist in more than one molecular arrangement and the result is more than one polymorphic forms which differ in their physiochemical properties such as solubility, stability, melting point etc.1 Depending on these arrangements the polymorphic forms could vary in their relative stabilities; with the metastable forms eventually converting to the most stable form.1,2. Studying these phase transformations is important in understanding the properties of these polymorphic forms. Various techniques could be employed for this purpose but Differential Scanning Colorimetry is the most common and efficient technique as it allows following these transformations as a function of temperature or time, in addition to its high sensitivity.3 Nonetheless, sometimes it is difficult to build a clear picture of what is happening to the sample as it goes through a phase transition from just the heat flow signal provided by the DSC, and thus visualising these processes would be valuable. In addition, subtle transitions such as solid-solid transitions could be missed in the DSC if they happen over a wide temperature range.

Method

The Linkam DSC450 stage allows visualisation of the sample during a DSC experiment. Therefore, this system was used in studying flufenamic acid, one of the most polymorphic pharmaceuticals with a record of nine known polymorphic forms2. The aim was to study crystallisation from the amorphous phase obtained by melt quenching. Form I was obtained by spray drying and was first heated in the DSC450  up to the melt, then it was allowed to cool down to room temperature before re-heating at a 10 °C/min heating rate.

Results

As shown in Figure 1, form I melted at ca. 132 °C while the re-heated sample melted at a lower temperature (onset of ca. 122 °C). No re-crystallisation was observed in the second heating cycle, which indicated that upon cooling a metastable form recrystallised from the melt. 

Asma graph 1.jpg

The effect of adding a polymer (PVP) is evident in Figure 2 where it appeared that the sample did not crystallise upon cooling but rather formed an amorphous phase. Heating the amorphous phase caused there-crystallisation of FFA followed by a solid-solid transition and then a melt. These events appear as two exothermic transitions followed by a sharp endotherm. The solid-solid transition is subtle in the DSC thermogram but is very clear from the signal obtained from employing an image analysis technique (Thermal Analysis by Surface Characterization, TASC) shown in Figure 2c. The melting peak has an onset temperature of ca. 119 °C, which is lower than that of the form crystallised from the melt without the presence of the polymer. The TASC signal also shows that melting is detected visually before the DSC signal starts to change.

Asma graph 2.jpg

Conclusion

In this work polymorphic transitions in the pharmaceutical active flufenamic acid were studied with Linkam DSC450 stage, which combines optical microscopy with differential scanning calorimetry. The power of the complementary technique was evident with the increased sensitivity for detecting subtle transitions such as solid-solid transition by analysing the optical images.

References

1. Rodrı́g uez-Spong, B., Price, C. P., Jayasankar, A., Matzger, A. J. and Rodrı́guez-Hornedo, N. r. 2004. General principles of pharmaceutical solid polymorphism: A supramolecular perspective. Advanced Drug Delivery Reviews 56(3): 241-274.

2. López-Mejías, V., Kampf, J. W. and Matzger, A. J. 2012. Nonamorphism in flufenamic acid and a new record for a polymorphic compound with solved structures. Journal of the American Chemical Society 134(24): 9872-9875.

3. Gaisford, S. and Saunders, M. 2012. Physical form i – crystalline materials. Essentials of pharmaceutical preformulation, John Wiley & Sons, Ltd: 127-155.

February's Paper of the Month

Nanomaterials have been found to have interesting electronic, magnetic and optical properties. They can manipulate electromagnetic fields through localised surface plasmon resonance to modulate light interactions. Such plasmonic phenomena are popular in application for the biomedical field. 

February’s Paper of the Month comes from the University of California, Merced and Stanford University. They developed a micro-scale delivery module for various organic and inorganic compounds using nanomaterials. 

Their aim was to create something that would be versatile and capable of encapsulating a range of different materials (drugs, dyes, cells, bacteria, etc.) for many different applications. These could include drug delivery for cancer treatment, releasing dyes in vivo for fluorescence imaging, or tissue engineering. The problem with most current platforms is that they are either leaky, unable to hold the contents without loss for any prolonged period, or they are incapable of releasing contents in a spatially and temporally controlled manner. For example, other cargo delivery systems that use light to activate the release of the cargo need several milliwatts of power over several minutes to achieve the required effect, therefore creating significant localised heating. The group managed to reduce the power required to less than 2 mW and the release time to under 5 seconds. As a result, the total temperature increase at the vicinity of the capsules is only to ~ 40°C, which is well within tolerable limits for many biological systems.

They used an LTS350* for their experiments. When asked on the importance of the hotstage, Dr Ghosh said: “One of the most critical parameters that determine whether a cargo delivery system is viable in vivo is the thermal gradient that is produced because of the photothermal effect when optical excitation used to rupture the shells is in resonance with the plasmonic response of the nanoparticles that make up the shell walls. To estimate this, the first step was to use heat to rupture the shells instead of light. That is where we used the heating stage.”
 

 Fluorescence microscopy images of a Nano-Assembled Microshell loaded with a fuorescent dye on the LTS350 stage. 

Fluorescence microscopy images of a Nano-Assembled Microshell loaded with a fuorescent dye on the LTS350 stage. 

 Their method has proved to be exciting and advantageous. No leakage was seen for over five months after encapsulation, promising a long shelf life. Furthermore, a lower optical intensity was required for shell disintegration compared to other methods. 

Although more work is required to improve future in-vivo applications (such as actuation by near infra-red and reducing overall size of capsule), their work is a promising result for future cargo delivery systems. 

By Tabassum Mujtaba

Ghosh et al., Plasmon-actuated nano-assembled microshells. Sci. Rep. 7. doi:10.1038/s41598-017-17691-6

*The LTS350 has been superseded by the LTS420 offering a large temperature range and better temperature control to 0.01°C.
 

January's Paper of the Month

The efficiency of lead halide perovskites has increased significantly since their introduction in 2009. The high performance as well as cost-effective manufacture make them ideal for photovoltaic applications. However, lead halide perovskites are known for their instability when subjected to changes in light, oxygen, temperature as well as issues with homogeneity. As such it becomes important to test their stability in a practical situation, such as in a device stack, to better understand the degradation mechanics. 

Raman spectroscopy is a powerful probing tool to study the degradation of individual perovskite layers as well as the degradation kinetics. Raman mapping techniques can also be used to investigate the homogeneity of the perovskite film. 

January’s Paper of the Month comes from the University of Swansea. They used a Linkam RH95 and THMS600-H to conduct in-situ Raman Spectroscopy and further understand the degradation kinetics of perovskite materials when temperature and humidity were altered. 

The device stack was first tested for thermal degradation by heating to 150°C. While photo-degradation was found to be dependent on top and bottom layers, thermal degradation was shown to be non-reversible and affects the entire MAPI film. It is determined by the homogeneity of the film rather than structural layers. Raman signals from in-situ humidity experiments show the dihydration of the perovskite to be almost completely reversible once drying occurs. However further analysis of the raman peaks showed dihyration remained in the Au region, suggesting some moisture remained trapped in this region. Device performance may be fully recovered if trapped moisture can be removed.
 

 Figure 1: The in situ raman spectra highlights the reversible dihydration when relative humidity is decreased but also indicates the presence of a dehydrated species in the Au region. 

Figure 1: The in situ raman spectra highlights the reversible dihydration when relative humidity is decreased but also indicates the presence of a dehydrated species in the Au region. 

Understanding how humidity affects perovskite layers differentially within a stack has led to the conclusion that targeted drying would help improve and regain device performance. Optimising such performances will have great benefits for the future development of microelectronics and telecommunication.

By Tabassum Mujtaba

Tsoi et al., Probing the degradation and homogeneity of embedded perovskite semiconducting layers in photovoltaic devices by Raman spectroscopy. Phys.Chem.Chem.Phys. 19, 5246 (2017). 

December's Paper of the Month

 Fluorescent labelled E. coli can be seen in the swollen pharynx of some dying C. elegans (P, left) but not others with an atrophied pharynx (p, right). 

Fluorescent labelled E. coli can be seen in the swollen pharynx of some dying C. elegans (P, left) but not others with an atrophied pharynx (p, right). 

With improving healthcare humans are living longer than ever before, but with longer life comes ever more senescence-related pathologies. Understanding the role genes and environment play in the development of such pathologies in the complex system of our bodies is difficult.  The nematode Caenorhabditis elegans is a great model organism and has been used extensively to study the biology of ageing because just like more complex animals, C. elegans also develop senescent pathologies.

Researchers from the University College London and Washington University, MO studied age-related pathologies in C. elegans and their role in limiting lifespan. Understanding these processes in a simple organism may in turn help to further understand the origins of human age-related pathologies.

To investigate the causes of death, the group analysed the corpses of recently expired wildtype C. elegans and found two particular forms with different pharyngeal pathologies. One type, named P ("big P") death, occurred earlier than the other and had increases in the posterior bulb size of 20-120%. The other, named p ("small p") death, showed a shrinking of the posterior bulb by up to 70%.

 The figures above show the age distribution and percentage survival of P and p deaths. 

The figures above show the age distribution and percentage survival of P and p deaths. 

Dissections and RFP labelling of the E. coli food source established that the enlarged posterior bulb in P death individuals was due to E. coli infection in elderly C. elegans. The high pharyngeal pumping rates typical of young nematodes is thought to mechanically damage the cuticle, creating vulnerability to invasion. Their findings suggest there is a narrow time frame in which young nematodes are thus susceptible. Consistent with this, the group found that mutants with reduced pumping rate had fewer P deaths, and lived longer.  However, it was also found that worms dying with P and p death previously had similar pumping rates, so why did some worms but not others get an infected pharynx? 

The difference appeared to be due to the ability of some nematodes (p death type) to heal the cuticle thereby preventing invasion. 

When asked about their work and the role of the PE120 stage, Professor David Gems stated, “to help identify old age pathologies that limit life, we watched nematodes as they aged, measuring a range of pathologies, and then measured their lifespan. By measuring how well each pathology correlated with lifespan we could identify pathologies likely to cause death. But to do this required repeatedly putting immobilized nematodes under the microscope, and we needed to do this in a way that wasn’t so stressful that it shortened their lifespan. By using the PE120 Linkam stage to gently cool the worms, we were able to avoid using stressful anaesthetics. We were able to confirm that repeated viewing of nematodes using the PE120 Linkam stage in this way did not shorten their lifespan.”

The group used a novel approach to understand ageing by analysing and combining pathology and mortality profiles. Further work can now be conducted with a view to understanding how genes that affect lifespan differentially affect worms dying from different causes.

By Tabassum Mujtaba

Zhao, Y. et al. Two forms of death in ageing Caenorhabditis elegans. Nat. Commun. 8, 15458 doi: 10.1038/ncomms15458 (2017).

November's Paper of the Month

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Solution printing is a novel technique which uses an ink solution, containing semi-conductor precursors or nanoparticles, and deposits these on substrates with desirable characteristics. This offers a cost-effective method of creating large area thin film optoelectronics whilst also offering precise control over the stoichiometry and adaptability of the material. Metal halide perovskites have superb optoelectronic properties and the last few years has seen their power conversion efficiency increase rapidly, largely through the optimisation of the crystal morphology. 

The requirement to control morphology has posed a problem for solution printing. The understanding of crystallisation in dynamic flow of perovskite inks is quite limited, thus imposing restrictions in achieving high-quality perovskite films by the solution-printing technique.

A group from the Georgia Institute of Technology and the University of Nebraska-Lincoln used a meniscus-assisted solution printing method to elucidate the crystallisation kinetics of perovskite inks and help create high efficiency perovskite solar cells. The thin-films were created with preferred crystal orientation with micrometre-scale grains. 

When discussing their work Professor Lin said, “through integrating the meniscus effect within the solution printing, we found that the solvent evaporation could be largely promoted by the meniscus effect instead of the thermal evaporation as in conventional doctor-blade coatings, thus leading to the low-temperature solution-based deposition of high-quality perovskite films with preferred crystal orientations. This low temperature feature circumvents thermal degradations and thermomechanical fatigues on perovskite and electrode materials, as well as decreases energy consumptions. Our technique paves the pathway for depositing perovskite thin films on flexible polymer substrates, and is anticipated to promote the future development and applications of perovskites in low-cost, large-area, and flexible optoelectronic devices.”

The group used an LTS350* to control the substrate temperature during the meniscus-assisted solution printing process, due to its capability of precisely controlling the temperature at ±0.1oC. Their investigation on the crystallisation kinetics of perovskite films revealed that a large temperature fluctuation would seriously impact the crystallisation kinetics of perovskite films during the meniscus-assisted printing process. The LTS350* was ideal for maintaining the substrate at a constant temperature and focusing on the exploration of the meniscus effect on the perovskite crystallisation process. 

Their study helped to uncover the crystallisation kinetics of perovskites during the printing process, providing rational guides to precisely control the crystallisation morphology of printed perovskite films. By improving the control over morphology, the group’s work helps to pave a route to large-area optoelectronic devices for commercial applications.

*The LTS350 has been superseded by the LTS420 offering a large temperature range and better temperature control to 0.01°C.

Lin et al., Meniscus-assisted solution printing of large-grained perovskite films for high-efficiency solar cells. Nat. Commun. 16045, doi:10.1038/ncomms16045 (2017).

October's Paper of the Month

 Partly fossilized mycelium of fungal hyphae on a zeolite crystal from 740 m depth in fractured granite. Back-scattered Environmental Scanning Electron Microscopy image. Width of view 600 µm. Photo credit: Henrik Drake, Magnus Ivarsson.

Partly fossilized mycelium of fungal hyphae on a zeolite crystal from 740 m depth in fractured granite. Back-scattered Environmental Scanning Electron Microscopy image. Width of view 600 µm. Photo credit: Henrik Drake, Magnus Ivarsson.

Despite being considered vital for energy cycling of the earth; the deep biosphere is one of the least understood ecosystems. It is thought to have approximately 19% of the earth’s biomass yet samples are hard to come by, making their study difficult. Microorganisms from the deep biosphere that have been studied are generally prokaryotes, with microeukaryotes being largely ignored.

Recently samples were taken from a 740m deep drill core sample in Sweden after the site was investigated for its suitability for deep nuclear waste repositories. Findings have shown the presence of fossil and active fungi in these deep ecosystems, but little work has gone into understanding them.

Drake et al., studied the microorganisms in these deep crystalline fractured rock samples. Their aim was to gain a better understanding of the microbial processes in the continental crust. The knowledge of this vast realm is very scarce and tells us more about life forms and processes under extreme conditions which may also have important implications for nuclear waste storage. 

Their analyses found the microorganisms belonged to the Kingdom Fungi and were found to be anaerobic. The closest systems studied were that of anaerobic fungi in the rumina of ruminant animals. It was proposed that the fossilised fungi also shared a symbiotic relationship with bacteria in the deep biosphere. 

The group used a THMS600 to help indicate the approximate age of the fungi. Dr Drake said, “The THM600 was used to investigate fluid inclusions in calcite crystals that were spatially related to the fungi. The fluid inclusion signatures gave us information about past conditions (e.g. salinity) in the fracture void. Because no radiometric dating could be made of the fungi, the fluid inclusion signatures (when put in a paleohydrogeological context) serve as an important temporal indicator for when the fungi were active.” 

Their work highlighted an intimate relationship between the fungi and sulphate reducing bacteria, further drawing attention to the richness of the deep oligotrophic biosphere which is often neglected. These fungi were found to provide significant amounts of H2 to autotrophic microorganisms in the crystalline continental crust.

The group also looked at the biochemistry of these fungi and found they may pose a threat to repositories of toxic waste.  This is through either directly breaking down the barriers holding the waste, or by facilitating the bacterial community into doing so. 

Their work highlights the importance of studying these neglected geological microorganisms. With fossil fuels running out, nuclear energy may be the way forward. But to safely store away waste products, understanding their chemical and geological environment is of utmost importance as illustrated by Drake et al., As such it becomes vital to study ecosystems, such as the deep biosphere, in its entirety. 

By Tabassum Mujtaba

Drake et al., Anaerobic consortia of fungi and sulfate reducing bacteria in deep granite fractures. Nat. Comms 8, Article number: 55 doi:10.1038/s41467-017-00094-6 (2017)

September's Paper of the Month

 Serpentinization is central to many theories of the origin of life. 

Serpentinization is central to many theories of the origin of life. 

The hydrothermal alteration of mantle rocks, referred as serpentinization, occurs when the mantle is exposed to aqueous fluids circulating below 400°C, leading to the formation of serpentine, hydrogen and other minerals. It is a process heavily involved in mass exchange between the mantle and the surface and influences geochemical cycling and fluid-mobile elements. It occurs in various submarine environments including mid-ocean ridges and subduction zones and it affects the physical and chemical properties of the oceanic lithosphere.

 It is also pivotal to current theories on the origin of life. Serpentinization is likely to have provided the crucial chemical gradients required for life to being when the earth was simply rock, water and carbon dioxide. 

Despite being a process vital to our understanding of the origin of life and the Earth´s lithospheric mantle activity, the rates and the environmental factors affecting serpentinization are poorly understood. A collaborative effort from Virginia Tech, The Free University of Berlin, Woods Hole Oceanographic Institution and The University of Texas used synthetic fluid inclusions as micro-reactors in olivine crystals as a model to study the rate of serpentinization. This method allowed them to study mineral precipitation and water activity in real time and in situ.

When discussing their work, Dr. Lamadrid said “We trapped synthetic fluid inclusions (tiny droplets of fluid) with a seawater-like composition in gem quality olivine crystals and then we set the samples to serpentinization conditions (~280ºC). Within a few days, serpentine crystals begin to precipitate inside the synthetic fluid inclusions. Since the inclusions are isolated any changes inside the inclusion can be observed and we can model them as chemical micro-reactors. The serpentinization reaction consumes H2O, so the original salinity starts to increase as more H2O leaves the fluid to form new serpentine crystals. As such, we were able to monitor the amounts of H2O leaving the fluid by measuring changes of the salinity inside the inclusion. The salinity of the fluid inclusions were measured with high precision by measuring changes in the freezing point depression of the fluid inclusions with the Linkam THMSG600 stage.”

Their technique allowed them to study the mineralogy and chemistry of the reaction products. After carrying out experiments with different salinities and fluid compositions, they found the reaction to be highly sensitive to the salinity and chemistry of the fluid. This poses interesting concepts of where serpentinization may occur in the earth’s mantle as well on other planetary bodies. Their novel micro-reactor technique could also be applied to many other minerals, reaction products, and fluid compositions to study fluid-rock reactions in real time and in situ. 
 

By Tabassum Mujtaba

 Lamadrid, H. M. et al. Effect of water activity on rates of serpentinization of olivine. Nat. Commun. 8, 16107 doi: 10.1038/ncomms16107 (2017).

August's Paper of the Month

Bacteria must be able to find food in order to survive. They have evolved various chemotactic strategies to efficiently locate and track nutrient gradients, several of which have been defined. The strategies usually consist of a series of run phases in which the bacteria swim in straight lines followed by phases of tumbles, arcs, stops and reversals. A tight control over these phases allows them to direct and adapt movements towards nutrient sources. 

Their intricate pathways of signalling proteins allow them to detect chemical changes in the environment which in turn will affect their run phase. Bacteria must maintain straight trajectories to pick up vital environmental cues and react appropriately. However due to their size and shape, the lengths of their movements are restricted by Brownian motion. 

The rotation friction (fr) co-efficient is the cell’s resistance to being rotated, which is dependent on both cell size and shape. Several models have been suggested for spherical and ellipsoidal cell types. However, despite theoretical modelling, there has been little empirical evidence. 

August’s Paper of the Month, from the Universities of York and Lincoln, focussed on validating the theoretical understanding of how cell size and shape affect bacteria run phases. 

To create bacteria with different aspect ratios they treated E.coli with cephalexin, which was found to elongate the cell. They compared this form to the normal wildtype E.coli. With increasing cell length, they found an increase in flagella along the cell body.
 

 Flagella are primarily motile appendages, but also sensory, and are found commonly in the cell bodies of bacteria. 

Flagella are primarily motile appendages, but also sensory, and are found commonly in the cell bodies of bacteria. 

Using phase contrast microscopy, they then recorded and tracked both the control and elongated group. Samples were imaged while placed on a Linkam PE-100 ZAL system heated to 33°C. 

Their results indicated the elongated cells had shorter runs but longer tumble phases. This finding agreed with the veto model which suggests an increase in flagella increases the average tumble time. 

Although mechanistically different, they also found elongated E.coli performed a run and reverse strategy. This pattern has been described within natural populations of marine and soil bacteria and has been found to be advantageous within these particular niches. 
When asked about the role of the stage, Dr Oscar Guadayol said, “For this kind of study, the ability to perfectly control the environment at the microscale is critical, and thus the PE100 has become an absolutely essential piece of equipment in our everyday exploration of the microbial behaviour.”

Their work experimentally demonstrated long-standing theoretical predictions about how cell elongation may affect the capability of bacteria to swim and to navigate their chemical landscape and how different morphologies can lead to vital changes in motility patterns. 

They are now taking their results one step further and using microfluidic devices with the PE100 to characterize bacterial chemotaxis.
 

 A microfluidic chip placed on a Linkam PE100 ZAL system. 

A microfluidic chip placed on a Linkam PE100 ZAL system. 

July's Paper of the Month

 A hexagonal ice crystal in the presence of birch pollen molecules. The shape is indicative of ice crystal growth inhibition.

A hexagonal ice crystal in the presence of birch pollen molecules. The shape is indicative of ice crystal growth inhibition.

Ice crystal growth through nucleation is an important natural process for atmospheric and cryobiological processes. For biological organisms, surviving sub-freezing temperatures requires tackling intracellular ice formation. Such organisms have evolved antifreeze proteins to inhibit ice crystal growth, thus preserving structural integrity. 

Ice crystals are formed in clouds triggered by ice nucleating particles. Originally it was believed these particles were forms of mineral dust but recent studies have found them to also include biological agents including pollen, bacteria, fungal spores, cellulose and microalgae. 

Active sites are regions on the ice nucleating particles where critical ice embryo formation occurs. These can be proteins or polysaccharides in the cell membrane although studies have found these are still active when separated from their original particles. 

Yet these biological molecules can act as both ice nucleators and ice inhibitors and consequently there has been much desire to further understand the manner in which these molecules interact with ice. The search for such answers may also help to further explain how biological organisms survive extreme climatic conditions.

July’s Paper of the Month comes from the Bielefeld University. They tested for the presence of antifreeze molecules in various types of known ice nucleating boreal pollen. The group conducted their temperature controlled experiment using the Linkam BCS196.

FTIR spectroscopy of the pollen highlighted two polysaccharides with similar chemical structures which differed in size. The larger (>100kD) of the two was responsible for the ice nucleating ability of the pollen while the smaller (<100kD) exhibited ice inhibiting abilities. 
Analysis of IR spectrum suggests the ice inhibiting molecules are either fragments of ice nucleating molecules, or ice nucleating molecules are clusters of smaller ice inhibiting molecules. The group’s results indicate both to have similar molecular moieties. Complementary findings in studies on boreal pollen suggest this may be a mechanism to protect pollen against springtime frosts. 

When asked about the role of the BCS196 stage, Professor Koop said: “For the ice growth inhibition experiments, we have developed an assay which makes use of the BCS196 stage while attached to a brightfield transmission optical microscope. The stage allows for a rapid cooling to about -50 °C in order to produce a film of polycrystalline ice and, subsequently, an accurate and constant hold temperature at -8 °C, during which we determine how the size of the ice crystals changes over several hours and how this is affected by the pollen molecules.”

Their valuable work better helps us to understand the way molecules may be interacting with ice in natural processes. 

By Tabassum Mujtaba

Dreischmeier, K. et al. Boreal pollen contain ice-nucleating as well as ice-binding ‘antifreeze’ polysaccharides. Sci. Rep. 7, 41890; doi: 10.1038/srep41890 (2017).