Protein-to-lipid ratio uniquely changes the rate of lysozyme aggregation but does not significantly alter toxicity of mature protein aggregates.

Irreversible aggregation of misfolded proteins is the underlying molecular cause of numerous pathologies, including diabetes type 2, Alzheimer's, and Parkinson's diseases. Such an abrupt protein aggregation results in the formation of small oligomers that can propagate into amyloid fibrils. A growing body of evidence suggests that protein aggregation can be uniquely altered by lipids. However, the role of the protein-to-lipid (P:L) ratio on the rate of protein aggregation, as well as the structure and toxicity of corresponding protein aggregates remains poorly understood. In this study, we investigate the role of the P:L ratio of five different phospho- and sphingolipids on the rate of lysozyme aggregation. We observed significantly different rates of lysozyme aggregation at 1:1, 1:5, and 1:10 P:L ratios of all analyzed lipids except phosphatidylcholine (PC). However, we found that at those P:L ratios, structurally and morphologically similar fibrils were formed. As a result, for all studies of lipids except PC, mature lysozyme aggregates exerted insignificantly different cell toxicity. These results demonstrate that the P:L ratio directly determines the rate of protein aggregation, however, has very little if any effect on the secondary structure of mature lysozyme aggregates. Furthermore, our results point to the lack of a direct relationship between the rate of protein aggregation, secondary structure, and toxicity of mature fibrils.

Confirmatory detection and identification of biotic and abiotic stresses in wheat using Raman spectroscopy.

Wheat is one of the oldest and most widely cultivated staple food crops worldwide. Wheat encounters an array of biotic and abiotic stresses during its growth that significantly impact the crop yield and consequently global food security. Molecular and imaging methods that can be used to detect such stresses are laborious and have numerous limitations. This catalyzes the search for alternative techniques that can be used to monitor plant health. Raman spectroscopy (RS) is a modern analytical technique that is capable of probing structure and composition of samples non-invasively and non-destructively. In this study, we investigate the accuracy of RS in confirmatory diagnostics of biotic and abiotic stresses in wheat. Specifically, we modelled nitrogen deficiency (ND) and drought, key abiotic stresses, and Russian wheat aphid (Diuraphis noxia) infestation and viral diseases: wheat streak mosaic virus (WSMV) and Triticum mosaic virus (TriMV), economically significant biotic stresses in common bread wheat. Raman spectra as well as high pressure liquid chromatography (HPLC)-based analyses revealed drastically distinct changes in the intensity of carotenoid vibration (1185 cm-1) and in the concentration of lutein, chlorophyll, and pheophytin biomolecules of wheat, triggered in response to aforementioned biotic and abiotic stresses. The biochemical changes were reflected in unique vibrational signatures in the corresponding Raman spectra, which, in turn could be used for ~100% accurate identification of biotic and abiotic stresses in wheat. These results demonstrate that a hand-held Raman spectrometer could provide an efficient, scalable, and accurate diagnosis of both biotic as well as abiotic stresses in the field.

Charge of Phospholipids Determines the Rate of Lysozyme Aggregation but Not the Structure and Toxicity of Amyloid Aggregates.

Biophysical properties of plasma membranes are determined by a chemical structure of phospholipids, including saturation of fatty acids and charge of polar heads of these molecules. Phospholipids not only determine fluidity and plasticity of membranes but also play an important role in abrupt aggregation of misfolded proteins. In this study, we investigate the role of the charge of the most abundant phospholipids in the plasma membrane on the aggregation properties of the lysozyme. We found that the charge of phospholipids determines the aggregation rate of lysozyme and the morphology of the protein aggregates. However, the secondary structure and toxicity of these protein specimens are determined by the chemical nature rather than the charge of phospholipids. These findings show that the charge of phospholipids can be a key factor that determines the stability and aggregation mechanism of amyloidogenic proteins.