Fatty Acids Reverse the Supramolecular Chirality of Insulin Fibrils.

Long-chain unsaturated and polyunsaturated fatty acids (LCUFAs and LCPUFAs, respectively) are the essential components of phospholipids and sphingolipids, major building blocks of plasma and organelle membranes. These molecules are also involved in cell signaling and energy metabolism. Hence, both LCUFAs and LCPUFAs are broadly used as food supplements. However, the role of these fatty acids (FAs) in the self-assembly of misfolded proteins remains unclear. In this study, we investigated the effect of LCUFAs and LCPUFAs, as well as their saturated analogue, on insulin aggregation. Using vibrational circular dichroism, we found that all analyzed FAs reversed the supramolecular chirality of insulin fibrils. Molecular dynamics simulations showed that strong hydrophobic interactions were formed between the long aliphatic tails of FAs and hydrophobic amino acid residues of insulin. We infer that such insulin:FA complexes had different self-assembly mechanisms compared to that of insulin alone, which resulted in the observed reversal of the supramolecular chirality of the amyloid fibrils.

Unsaturated fatty acids uniquely alter aggregation rate of α-synuclein and insulin and change the secondary structure and toxicity of amyloid aggregates formed in their presence.

Docosahexaenoic (DHA) and arachidonic acids (ARA) are omega-3 and omega-6 long-chain polyunsaturated fatty acids (LCPUFAs). These molecules constitute a substantial portion of phospholipids in plasma membranes. Therefore, both DHA and ARA are essential diet components. Once consumed, DHA and ARA can interact with a large variety of biomolecules, including proteins such as insulin and α-synuclein (α-Syn). Under pathological conditions known as injection amyloidosis and Parkinson's disease, these proteins aggregate forming amyloid oligomers and fibrils, toxic species that exert high cell toxicity. In this study, we investigate the role of DHA and ARA in the aggregation properties of α-Syn and insulin. We found that the presence of both DHA and ARA at the equimolar concentrations strongly accelerated aggregation rates of α-Syn and insulin. Furthermore, LCPUFAs substantially altered the secondary structure of protein aggregates, whereas no noticeable changes in the fibril morphology were observed. Nanoscale Infrared analysis of α-Syn and insulin fibrils grown in the presence of both DHA and ARA revealed the presence of LCPUFAs in these aggregates. We also found that such LCPUFAs-rich α-Syn and insulin fibrils exerted significantly greater toxicities compared to the aggregates grown in the LCPUFAs-free environment. These findings show that interactions between amyloid-associated proteins and LCPUFAs can be the underlying molecular cause of neurodegenerative diseases.

Raman Spectroscopy Enables Non-invasive and Confirmatory Diagnostics of Salinity Stresses, Nitrogen, Phosphorus, and Potassium Deficiencies in Rice.

Proper management of nutrients in agricultural systems is critically important for maximizing crop yields while simultaneously minimizing the health and environmental impacts of pollution from fertilizers. These goals can be achieved by timely confirmatory diagnostics of nutrient deficiencies in plants, which enable precise administration of fertilizers and other supplementation in fields. Traditionally, nutrient diagnostics are performed by wet-laboratory analyses, which are both time- and labor-consuming. Unmanned aerial vehicle (UAV) and satellite imaging have offered a non-invasive alternative. However, these imaging approaches do not have sufficient specificity, and they are only capable of detecting symptomatic stages of nutrient deficiencies. Raman spectroscopy (RS) is a non-invasive and non-destructive technique that can be used for confirmatory detection and identification of both biotic and abiotic stresses on plants. Herein, we show the use of a hand-held Raman spectrometer for highly accurate pre-symptomatic diagnostics of nitrogen, phosphorus, and potassium deficiencies in rice (Oryza sativa). Moreover, we demonstrate that RS can also be used for pre symptomatic diagnostics of medium and high salinity stresses. A Raman-based analysis is fast (1 s required for spectral acquisition), portable (measurements can be taken directly in the field), and label-free (no chemicals are needed). These advantages will allow RS to transform agricultural practices, enabling precision agriculture in the near future.

Non-invasive identification of potato varieties and prediction of the origin of tuber cultivation using spatially offset Raman spectroscopy.

High starch content, simplicity of cultivation, and high productivity make potatoes (Solanum tuberosum) a staple in the diet of people around the world. On average, potatoes are composed of 83% water and 12% carbohydrates, and the remaining 4% includes proteins, vitamins, and other trace elements. These proportions vary depending on the type of potato and location where they were cultivated. At the same time, the chemical composition determines the nutritional value of potato tubers and can be proved using various wet chemistry and spectroscopic methods. For instance, gravity measurements, as well as several different colorimetric assays, can be used to investigate the starch content. However, these approaches are indirect, often destructive, and time- and labor-consuming. This study reports on the use of Raman spectroscopy (RS) for completely non-invasive and non-destructive assessment of nutrient content of potato tubers. We also show that RS can be used to identify nine different potato varieties, as well as determine the origin of their cultivation. The portable nature of Raman-based identification of potato offers the possibility to perform such analysis directly upon potato harvesting to enable quick quality evaluation. Graphical abstract.

Non-invasive diagnostics of Liberibacter disease on tomatoes using a hand-held Raman spectrometer.

MAIN CONCLUSION: Hand-held Raman spectroscopy can be used for confirmatory, non-invasive and non-destructive detection and identification of two haplotypes of Liberibacter disease on tomatoes. Using this spectroscopic approach, structural changes in carotenoids, xylan, cellulose and pectin that are associ-ated with this bacterial disease can be determined. 'Candidatus Liberibacter solanacearum' (Lso) is a phloem-limited Gram-negative bacterium that infects crops worldwide. In North America, two haplotypes of Lso (LsoA and LsoB) are transmitted by the potato psyllid, Bactericera cockerelli (Sulc), and infect many solanaceous crops such as potato and tomato. Infected plants exhibit chlorosis, severe stunting, leaf cupping, and scorching. Polymerase chain reaction (PCR) and potato tuber frying are commonly used methods for diagnostics of the plant disease caused by Lso. However, they are time-consuming, costly, destructive to the sample, and often not sensitive enough to detect the pathogen in the early infection stage. Raman spectroscopy (RS) is a noninvasive, nondestructive, analytical technique, which probes chemical composition of analyzed samples. In this study, we demonstrate that Lso infection can be diagnosed by non-invasive spectroscopic analysis of tomato leaves three weeks following infection, before the development of aerial symptoms. In combination with chemometric analyses, Raman spectroscopy allows for 80% accurate diagnostics of Liberibacter disease caused by each of the two different haplotypes. This diagnostics approach is portable and sample agnostic, suggesting that it could be utilized for other crops and could be conducted autonomously.