Biomolecular profiles of Arctic sea-ice diatoms highlight the role of under-ice light in cellular energy allocation

Arctic sea-ice diatoms fuel polar marine food webs as they emerge from winter darkness into spring. Through their photosynthetic activity they manufacture the nutrients and energy that underpin secondary production. Sea-ice diatom abundance and biomolecular composition vary in space and time. With climate change causing short-term extremes and long-term shifts in environmental conditions, understanding how and in what way diatoms adjust biomolecular stores with environmental perturbation is important to gain insight into future ecosystem energy production and nutrient transfer. Using synchrotron-based Fourier transform infrared microspectroscopy, we examined the biomolecular composition of five dominant sea-ice diatom taxa from landfast ice communities covering a range of under-ice light conditions during spring, in Svalbard, Norway. In all five taxa, we saw a doubling of lipid and fatty acid content when light transmitted to the ice-water interface was >5% but <15% (85%-95% attenuation through snow and ice). We determined a threshold around 15% light transmittance after which biomolecular synthesis plateaued, likely because of photoinhibitory effects, except for Navicula spp., which continued to accumulate lipids. Increasing under-ice light availability led to increased energy allocation towards carbohydrates, but this was secondary to lipid synthesis, whereas protein content remained stable. It is predicted that under-ice light availability will change in the Arctic, increasing because of sea-ice thinning and potentially decreasing with higher snowfall. Our findings show that the nutritional content of sea-ice diatoms is taxon-specific and linked to these changes, highlighting potential implications for future energy and nutrient supply for the polar marine food web.

Structural and Thermal Diffusivity Analysis of an Organoferroelastic Crystal Showing Scissor-Like Two-Directional Deformation Induced by Uniaxial Compression

A two-directional ferroelastic deformation in organic crystals is unprecedented owing to its anisotropic crystal packing, in contrast to isotropic symmetrical packing in inorganic compounds and polymers. Thereby, finding and constructing multidirectional ferroelastic deformations in organic compounds is undoubtedly complex and at once calls for deep comprehension. Herein, we demonstrate the first example of a two-directional ferroelastic deformation with a unique scissor-like movement in single crystals of trans-3-hexenedioic acid by the application of uniaxial compression stress. A detailed structural investigation of the mechanical deformation at the macroscopic and microscopic levels by three distinct force measurement techniques (including shear and three-point bending test), single crystal X-ray diffraction techniques, and polarized synchrotron-FTIR microspectroscopy highlighted that mechanical twinning promoted the deformation. The presence of two crystallographically equivalent faces and the herringbone arrangement promoted the two-directional ferroelastic deformation. In addition, anisotropic heat transfer properties in the parent and the deformed domains were investigated by thermal diffusivity measurement on all three axes using microscale temperature-wave analysis (μ-TWA). A correlation between the anisotropic structural arrangement and the difference in thermal diffusivity and mechanical behavior in the two-directional organoferroelastic deformation could be established. The structural and molecular level information from this two-directional ferroelastic deformation would lead to a more profound understanding of the structure-property relationship in multidirectional deformation in organic crystals.

Linearly Polarized Infrared Spectroscopy for the Analysis of Biological Materials

The analysis of biological samples with polarized infrared spectroscopy (p-IR) has long been a widely practiced method for the determination of sample orientation and structural properties. In contrast to earlier works, which employed this method to investigate the fundamental chemistry of biological systems, recent interests are moving toward "real-world" applications for the evaluation and diagnosis of pathological states. This focal point review provides an up-to-date synopsis of the knowledge of biological materials garnered through linearly p-IR on biomolecules, cells, and tissues. An overview of the theory with special consideration to biological samples is provided. Different modalities which can be employed along with their capabilities and limitations are outlined. Furthermore, an in-depth discussion of factors regarding sample preparation, sample properties, and instrumentation, which can affect p-IR analysis is provided. Additionally, attention is drawn to the potential impacts of analysis of biological samples with inherently polarized light sources, such as synchrotron light and quantum cascade lasers. The vast applications of p-IR for the determination of the structure and orientation of biological samples are given. In conclusion, with considerations to emerging instrumentation, findings by other techniques, and the shift of focus toward clinical applications, we speculate on the future directions of this methodology.

Synchrotron-Infrared Microspectroscopy of Live Leishmania major Infected Macrophages and Isolated Promastigotes and Amastigotes

The prevalence of neglected tropical diseases (NTDs) is advancing at an alarming rate. The NTD leishmaniasis is now endemic in over 90 tropical and sub-tropical low socioeconomic countries. Current diagnosis for this disease involves serological assessment of infected tissue by either light microscopy, antibody tests, or culturing with in vitro or in vivo animal inoculation. Furthermore, co-infection by other pathogens can make it difficult to accurately determine Leishmania infection with light microscopy. Herein, for the first time, we demonstrate the potential of combining synchrotron Fourier-transform infrared (FTIR) microspectroscopy with powerful discrimination tools, such as partial least squares-discriminant analysis (PLS-DA), support vector machine-discriminant analysis (SVM-DA), and k-nearest neighbors (KNN), to characterize the parasitic forms of Leishmania major both isolated and within infected macrophages. For measurements performed on functional infected and uninfected macrophages in physiological solutions, the sensitivities from PLS-DA, SVM-DA, and KNN classification methods were found to be 0.923, 0.981, and 0.989, while the specificities were 0.897, 1.00, and 0.975, respectively. Cross-validated PLS-DA models on live amastigotes and promastigotes showed a sensitivity and specificity of 0.98 in the lipid region, while a specificity and sensitivity of 1.00 was achieved in the fingerprint region. The study demonstrates the potential of the FTIR technique to identify unique diagnostic bands and utilize them to generate machine learning models to predict Leishmania infection. For the first time, we examine the potential of infrared spectroscopy to study the molecular structure of parasitic forms in their native aqueous functional state, laying the groundwork for future clinical studies using more portable devices.

Single Shot Lensless Interferenceless Phase Imaging of Biochemical Samples Using Synchrotron near Infrared Beam

Phase imaging of biochemical samples has been demonstrated for the first time at the Infrared Microspectroscopy (IRM) beamline of the Australian Synchrotron using the usually discarded near-IR (NIR) region of the synchrotron-IR beam. The synchrotron-IR beam at the Australian Synchrotron IRM beamline has a unique fork shaped intensity distribution as a result of the gold coated extraction mirror shape, which includes a central slit for rejection of the intense X-ray beam. The resulting beam configuration makes any imaging task challenging. For intensity imaging, the fork shaped beam is usually tightly focused to a point on the sample plane followed by a pixel-by-pixel scanning approach to record the image. In this study, a pinhole was aligned with one of the lobes of the fork shaped beam and the Airy diffraction pattern was used to illuminate biochemical samples. The diffracted light from the samples was captured using a NIR sensitive lensless camera. A rapid phase-retrieval algorithm was applied to the recorded intensity distributions to reconstruct the phase information. The preliminary results are promising to develop multimodal imaging capabilities at the IRM beamline of the Australian Synchrotron.

Microspectroscopic visualization of how biochar lifts the soil organic carbon ceiling

The soil carbon (C) saturation concept suggests an upper limit to the storage of soil organic carbon (SOC). It is set by the mechanisms that protect soil organic matter from mineralization. Biochar has the capacity to protect new C, including rhizodeposits and microbial necromass. However, the decadal-scale mechanisms by which biochar influences the molecular diversity, spatial heterogeneity, and temporal changes in SOC persistence, remain unresolved. Here we show that the soil C storage ceiling of a Ferralsol under subtropical pasture was raised by a second application of Eucalyptus saligna biochar 8.2 years after the first application—the first application raised the soil C storage ceiling by 9.3 Mg new C ha⁻¹ and the second application raised this by another 2.3 Mg new C ha⁻¹. Linking direct visual evidence from one-, two-, and three-dimensional analyses with SOC quantification, we found high spatial heterogeneity of C functional groups that resulted in the retention of rhizodeposits and microbial necromass in microaggregates (53–250 µm) and the mineral fraction (<53 µm). Microbial C-use efficiency was concomitantly increased by lowering specific enzyme activities, contributing to the decreased mineralization of native SOC by 18%. We suggest that the SOC ceiling can be lifted using biochar in (sub)tropical grasslands globally.

A decadal-scale field trial revealed 1.01 Mg of rhizodeposit and necromass C was stored in soil microaggregate and mineral fractions per Mg biochar-C applied. Microspectroscopic analyses visualize mechanisms for this elevated soil C storage ceiling.

Magnetic field induced alignment of macroradical epoxy for enhanced electrical properties

Improving the electrical performance of macroradical epoxy thermosets to surpass the semiconductor threshold requires a comprehensive understanding of the electrical charge transport mechanisms and characteristics. In this study, we investigate the electrical properties of a non-conjugated radical thermoset in a rigid, three-dimensional (3D) motif cured under an external magnetic field. The outcomes of the four-angle analysis of the synchrotron IRM beamline provide for the first time quantitative insights into the molecular orientation at the atomic-scale level. These insights, in turn, were utilized to apply Quantum Computational modeling theories and Monte Carlo simulation to study the effect of the magnetic field-induced molecular alignment on tuning electrical charge transport characteristics. The results explored the impact of radical density on forming percolation networks, showing a robust protocol for designing polymers with high electrical/thermal conductivity.

"Wax On, Wax Off": In Vivo Imaging of Plant Physiology and Disease with Fourier Transform Infrared Reflectance Microspectroscopy

Analysis of the epicuticular wax layer on the surface of plant leaves can provide a unique window into plant physiology and responses to environmental stimuli. Well-established analytical methodologies can quantify epicuticular wax composition, yet few methods are capable of imaging wax distribution in situ or in vivo. Here, the first report of Fourier transform infrared (FTIR) reflectance spectroscopic imaging as a non-destructive, in situ, method to investigate variation in epicuticular wax distribution at 25 µm spatial resolution is presented. The authors demonstrate in vivo imaging of alterations in epicuticular waxes during leaf development and in situ imaging during plant disease or exposure to environmental stressors. It is envisaged that this new analytical capability will enable in vivo studies of plants to provide insights into how the physiology of plants and crops respond to environmental stresses such as disease, soil contamination, drought, soil acidity, and climate change.

Exploiting spatio-spectral aberrations for rapid synchrotron infrared imaging

The Infrared Microspectroscopy Beamline at the Australian Synchrotron is equipped with a Fourier transform infrared (FTIR) spectrometer, which is coupled with an infrared (IR) microscope and a choice of two detectors: a single-point narrow-band mercury cadmium telluride (MCT) detector and a 64 × 64 multi-pixel focal plane array (FPA) imaging detector. A scanning-based point-by-point mapping method is commonly used with a tightly focused synchrotron IR beam at the sample plane, using an MCT detector and a matching 36× IR reflecting objective and condenser (NA = 0.5), which is time consuming. In this study, the beam size at the sample plane was increased using a 15× objective and the spatio-spectral aberrations were investigated. A correlation-based semi-synthetic computational optical approach was applied to assess the possibilities of exploiting the aberrations to perform rapid imaging rather than a mapping approach.

Infrared Based Saliva Screening Test for COVID-19

Severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) has resulted in an unprecedented need for diagnostic testing that is critical in controlling the spread of COVID‐19. We propose a portable infrared spectrometer with purpose‐built transflection accessory for rapid point‐of‐care detection of COVID‐19 markers in saliva. Initially, purified virion particles were characterized with Raman spectroscopy, synchrotron infrared (IR) and AFM‐IR. A data set comprising 171 transflection infrared spectra from 29 subjects testing positive for SARS‐CoV‐2 by RT‐qPCR and 28 testing negative, was modeled using Monte Carlo Double Cross Validation with 50 randomized test and model sets. The testing sensitivity was 93 % (27/29) with a specificity of 82 % (23/28) that included positive samples on the limit of detection for RT‐qPCR. Herein, we demonstrate a proof‐of‐concept high throughput infrared COVID‐19 test that is rapid, inexpensive, portable and utilizes sample self‐collection thus minimizing the risk to healthcare workers and ideally suited to mass screening.

Mapping sub-cellular protein aggregates and lipid inclusions using synchrotron ATR-FTIR microspectroscopy

Visualising direct biochemical markers of cell physiology and disease pathology at the sub-cellular level is an ongoing challenge in the biological sciences. A suite of microscopies exists to either visualise sub-cellular architecture or to indirectly view biochemical markers (e.g. histochemistry), but further technique developments and innovations are required to increase the range of biochemical parameters that can be imaged directly, in situ, within cells and tissue. Here, we report our continued advancements in the application of synchrotron radiation attenuated total reflectance Fourier transform infrared (SR-ATR-FTIR) microspectroscopy to study sub-cellular biochemistry. Our recent applications demonstrate the much needed capability to map or image directly sub-cellular protein aggregates within degenerating neurons as well as lipid inclusions within bacterial cells. We also characterise the effect of spectral acquisition parameters on speed of data collection and the associated trade-offs between a realistic experimental time frame and spectral/image quality. Specifically, the study highlights that the choice of 8 cm^-1 spectral resolutions provide a suitable trade-off between spectral quality and collection time, enabling identification of important spectroscopic markers, while increasing image acquisition by ∼30% (relative to 4 cm^-1 spectral resolution). Further, this study explores coupling a focal plane array detector with SR-ATR-FTIR, revealing a modest time improvement in image acquisition time (factor of 2.8). Such information continues to lay the foundation for these spectroscopic methods to be readily available for, and adopted by, the biological science community to facilitate new interdisciplinary endeavours to unravel complex biochemical questions and expand emerging areas of study.

Co-delivery of inhalable therapies: Controlling active ingredients spatial distribution and temporal release

The management of respiratory diseases relies on the daily administration of multiple active pharmaceutical ingredients (APIs), leading to a lack of patient compliance and impaired quality of life. The frequency and dosage of the APIs result in increased side effects that further worsens the overall patient condition. Here, the manufacture of polymer-polymer core-shell microparticles for the sequential delivery of multiple APIs by inhalation delivery is reported. The microparticles, composed of biodegradable polymers silk fibroin (shell) and poly(L-lactic acid) (core), incorporating ciprofloxacin in the silk layer and ibuprofen (PLLA core) as the antibiotic and anti-inflammatory model APIs, respectively. The polymer-polymer core-shell structure and the spatial distribution of the APIs have been characterized using cutting-edge synchrotron macro ATR-FTIR technique, which was correlated with the respective API sequential release profiles. The APIs microparticles had a suitable size and aerosol properties for inhalation therapies (≤4.94 ± 0.21μm), with low cytotoxicity and immunogenicity in healthy lung epithelial cells. The APIs compartmentalization obtained by the microparticles not only could inhibit potential actives interactions but can provide modulation of the APIs release profiles via an inhalable single administration.

Bone loss markers in the earliest Pacific Islanders

Kingdom of Tonga in Polynesia is one of the most obese nations where metabolic conditions, sedentary lifestyles, and poor quality diet are widespread. These factors can lead to poor musculoskeletal health. However, whether metabolic abnormalities such as osteoporosis occurred in archaeological populations of Tonga is unknown. We employed a microscopic investigation of femur samples to establish whether bone loss afflicted humans in this Pacific region approximately 3000 years ago. Histology, laser confocal microscopy, and synchrotron Fourier-transform infrared microspectroscopy were used to measure bone vascular canal densities, bone porosity, and carbonate and phosphate content of bone composition in eight samples extracted from adult Talasiu males and females dated to 2650 BP. Compared to males, samples from females had fewer vascular canals, lower carbonate and phosphate content, and higher bone porosity. Although both sexes showed evidence of trabecularised cortical bone, it was more widespread in females (35.5%) than males (15.8%). Our data suggest experiences of advanced bone resorption, possibly as a result of osteoporosis. This provides first evidence for microscopic bone loss in a sample of archaeological humans from a Pacific population widely afflicted by metabolic conditions today.

Correction: Synchrotron macro ATR-FTIR microspectroscopy for high-resolution chemical mapping of single cells

Correction for 'Synchrotron macro ATR-FTIR microspectroscopy for high-resolution chemical mapping of single cells' by Jitraporn Vongsvivut et al., Analyst, 2019, 144, 3226-3238, DOI: 10.1039/C8AN01543K.

Design of polymeric core-shell carriers for combination therapies

Particle engineering for co-delivery of drugs has the potential to combine multiple drugs with different pharmaceutical mechanisms within the same carrier, increasing the therapeutic efficiency while improving patient compliance. This work proposes a novel approach for producing polymer-polymer core-shell microparticles by multi-step processing of emulsion and spray drying. The particle core was obtained by an oil-in-water emulsion of poly(ε-caprolactone) (PCL) loaded with curcumin (CM), followed by the resuspension in poly(vinyl alcohol) (PVA) containing ciprofloxacin (CPx) forming the shell layer by spray-drying. The obtained core-shell particles showed an average size of 3.8 ± 1.2 μm, which is a suitable size for inhalation therapies. The spatial distribution of the drugs was studied using synchrotron-based macro attenuated total reflection Fourier transform infrared (macro ATR-FTIR) microspectroscopy to map the chemical distribution of the components within the particles and supported the presence of CM and CPx in the core and shell layers, respectively. The formation of the core-shell structure was further supported by the differences in the release profile of CM from these particles, when compared to the release profile observed for the single particle structure (PCL-CM). Both empty and drug-loaded carriers (up to 100 μg.mL^-1) showed no cytotoxic effects on A549 cells while exhibiting the antibacterial activity of CPx against Gram-positive and Gram-negative bacteria. These polymer core-shell microparticles provide a promising route for the combination and sequential drug release therapies, with the potential to be used in inhalation therapies.

Asymmetric midshaft femur remodeling in an adult male with left sided hip joint ankylosis, Metal Period Nagsabaran, Philippines

OBJECTIVE

This study investigated microstructural changes of the right and left midshaft femur in an archaeological individual afflicted with left-sided hip joint ankylosis to assess whether increased cortical porosity was present as a result of leg disuse.

MATERIALS

The individual is a middle-aged adult male excavated from the Metal Period (∼2000 BP) Nagsabaran, Luzon Island, Philippines.

METHODS

Following standard examination of femur gross anatomy and differential diagnosis of the hip joint fusion, ∼1 cm thick posterior midshaft femur samples were removed for microstructural examination. Using static histomorphometry, bone multi-cellular unit activity from Haversian canal (vascular pore) density, area, and circularity was reconstructed. Spatial positioning of Haversian canals was mapped using Geographic Information Systems software. Phosphate, carbonate, and carbonate:phosphate ratios were obtained using synchrotron-sourced Fourier transform infrared microspectroscopy.

RESULTS

The left femur had greater cortical pore density, with smaller and rounder vascular canals, in addition to lower matrix levels of phosphate and carbonate, when compared to the right femur.

CONCLUSIONS

Our data indicate compromised bone tissue in the left femur, and conform to expected bone functional adaptation paradigms of remodeling responses to pathological and biomechanical changes.

SIGNIFICANCE

The preservation of this individual's hip abnormality created a unique opportunity to evaluate intra-skeletal bone health asymmetry, which may help other researchers evaluate the presence of limb disuse in archaeological samples.

LIMITATIONS

A lack of lower limb data limits our interpretations to femur remodeling only.

SUGGESTIONS FOR FURTHER RESEARCH

Future research efforts should aim to examine the presence of remodeling changes in all bones of the lower limb.

LAYUNIN

Gamit ang buto ng magkabilang pemur ng isang taong natagpuan sa isang archaeological site na may sakit na ankylosis sa kaliwang balakang, pinag-aralan ang iba't-ibang microstructures galing sa gitnang bahagi o midshaft ng pemur upang malaman kung may makikitang mataas na cortical porosity ang buto dahil hindi ito malimit gamitin.

GAMIT

Ang pinag-aaralang buto ay galing sa isang indibidwal na tinatayang middle-age na lalaki na namuhay noong Panahon ng Metal (∼2000 BP) sa Nagsabaran, Cagayan, Republika ng Pilipinas.

PAMAMARAAN

Matapos ang unang pagkilatis sa femur at ang pagkilala ng sakit sa balakang, kumuha ng ∼1 sentimetro ng buto galing sa midshaft ng pemur upang lalong mapag-aralan ang kanyang microstructure. Gamit ang static histomorphometry, napag-aralan ang mga naiwang bakas ng multi-cellular unit activity ayon sa kapal, laki at pagkakabilog ng Haversian canal (vascular pore). Gumamit din ng Geographic Information Systems (GIS) software upang mapag-aralan ang kaugnayan ng posisyon ng Haversian canal. Panghuli, gumamit din ng synchroton-sourced Fourier transform infrared (sFTIR) microspectroscopy upang makuha ang bilang ng phosphate, carbonate, at carbonate:phosphate ratio.

RESULTA

Napag-alaman na ang kaliwang pemur ay mayroong higit na maraming cortical pores, maliit at mabilog na vascular canals, at mababang bilang ng phosphate, carbonate kung ihahambing sa kanang pemur.

KONKLUSYON

Ayon sa aming datos, ang kaliwang pemur ay umaayon sa mga katangian ng isang butong may sakit. Sumunod din ito sa inaasahang bone functional adaptation paradigms of remodeling ng buto dahil may sakit at hindi nagamit.

KAHALAGAHAN

Dahil maganda ang pagkakalibing ng buto ng balakang, nagkaroon ng pagkakataong makilatis ang kalusugan ng sinaunang-tao sa pamamagitan ng pag-aaral ng kalusugan ng buto. Dagdag pa, makakatulong din ito upang malaman kung ibang mananaliksik ang pag-aaral ng ibang butong hindi nagagamit mula sa archaeological site.

LIMITASYON

Dahil walang nakuhang ibang buto mula sa binti at paa, ang pemur lang ang naimbestigahan.

MUNGKAHI PARA SA MGA SUSUNOD NA PAG-AARAL

Kung magkakaroon ng pagkakataon sa susunod, dapat maimbistigahan ang lahat ng buto ng binti (lower limb).

Investigation of molecular mechanisms of experimental compounds in murine models of chronic allergic airways disease using synchrotron Fourier-transform infrared microspectroscopy

The ovalbumin-induced (OVA) chronic allergic airways murine model is a well-established model for investigating pre-clinical therapies for chronic allergic airways diseases, such as asthma. Here, we examined the effects of several experimental compounds with potential anti-asthmatic effects including resveratrol (RV), relaxin (RLN), l-sulforaphane (LSF), valproic acid (VPA), and trichostatin A (TSA) using both a prevention and reversal model of chronic allergic airways disease. We undertook a novel analytical approach using focal plane array (FPA) and synchrotron Fourier-transform infrared (S-FTIR) microspectroscopic techniques to provide new insights into the mechanisms of action of these experimental compounds. Apart from the typical biological effects, S-FTIR microspectroscopy was able to detect changes in nucleic acids and protein acetylation. Further, we validated the reduction in collagen deposition induced by each experimental compound evaluated. Although this has previously been observed with conventional histological methods, the S-FTIR technique has the advantage of allowing identification of the type of collagen present. More generally, our findings highlight the potential utility of S-FTIR and FPA-FTIR imaging techniques in enabling a better mechanistic understanding of novel asthma therapeutics.

Revealing the Elemental Distribution within Latent Fingermarks Using Synchrotron Sourced X-ray Fluorescence Microscopy

Fingermarks are an important form of crime-scene trace evidence; however, their usefulness may be hampered by a variation in response or a lack of robustness in detection methods. Understanding the chemical composition and distribution within fingermarks may help explain variation in latent fingermark detection with existing methods and identify new strategies to increase detection capabilities. The majority of research in the literature describes investigation of organic components of fingermark residue, leaving the elemental distribution less well understood. The relative scarcity of information regarding the elemental distribution within fingermarks is in part due to previous unavailability of direct, micron resolution elemental mapping techniques. This capability is now provided at third generation synchrotron light sources, where X-ray fluorescence microscopy (XFM) provides micron or submicron spatial resolution and direct detection with sub-μM detection limits. XFM has been applied in this study to reveal the distribution of inorganic components within fingermark residue, including endogenous trace metals (Fe, Cu, Zn), diffusible ions (Cl^-, K⁺, Ca²⁺), and exogeneous metals (Ni, Ti, Bi). This study incorporated a multimodal approach using XFM and infrared microspectroscopy analyses to demonstrate colocalization of endogenous metals within the hydrophilic organic components of fingermark residue. Additional experiments were then undertaken to investigate how sources of exogenous metals (e.g., coins and cosmetics) may be transferred to, and distributed within, latent fingermarks. Lastly, this study reports a preliminary assessment of how environmental factors such as exposure to aqueous environments may affect elemental distribution within fingermarks. Taken together, the results of this study advance our current understanding of fingermark composition and its spatial distribution of chemical components and may help explain detection variation observed during detection of fingermarks using standard forensic protocols.

Nanoscale optical and structural characterisation of silk

The nanoscale composition of silk defining its unique properties via a hierarchial structural anisotropy needs to be analysed at the highest spatial resolution of tens of nanometers corresponding to the size of fibrils made of β-sheets, which are the crystalline building blocks of silk. Nanoscale optical and structural properties of silk have been measured from 100 nm thick longitudinal slices of silk fibers with ca. 10 nm resolution, the highest so far. Optical sub-wavelength resolution in hyperspectral mapping of absorbance and molecular orientation were carried out for comparison at IR wavelengths of 2-10 μm using synchrotron radiation. A reliable distinction of transmission changes by only 1-2% as the anisotropy of amide bands was obtained from nanometer-thin slices of silk.

Interaction of Giant Unilamellar Vesicles with the Surface Nanostructures on Dragonfly Wings

The waxy epicuticle of dragonfly wings contains a unique nanostructured pattern that exhibits bactericidal properties. In light of emerging concerns of antibiotic resistance, these mechano-bactericidal surfaces represent a particularly novel solution by which bacterial colonization and the formation of biofilms on biomedical devices can be prevented. Pathogenic bacterial biofilms on medical implant surfaces cause a significant number of human deaths every year. The proposed mechanism of bactericidal activity is through mechanical cell rupture; however, this is not yet well understood and has not been well characterized. In this study, we used giant unilamellar vesicles (GUVs) as a simplified cell membrane model to investigate the nature of their interaction with the surface of the wings of two dragonfly species, Austrothemis nigrescens and Trithemis annulata, sourced from Victoria, Australia, and the Baix Ebre and Terra Alta regions of Catalonia, Spain. Confocal laser scanning microscopy and cryo-scanning electron microscopy techniques were used to visualize the interactions between the GUVs and the wing surfaces. When exposed to both natural and gold-coated wing surfaces, the GUVs were adsorbed on the surface, exhibiting significant deformation, in the process of membrane rupture. Differences between the tensile rupture limit of GUVs composed of 1,2-dioleoyl- sn-glycero-3-phosphocholine and the isotropic tension generated from the internal osmotic pressure were used to indirectly determine the membrane tensions, generated by the nanostructures present on the wing surfaces. These were estimated as being in excess of 6.8 mN m^-1, the first experimental estimate of such mechano-bactericidal surfaces. This simple model provides a convenient bottom-up approach toward understanding and characterizing the bactericidal properties of nanostructured surfaces.