| 1. |
- Ahlinder, Linnea, et al.
(författare)
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Noise Removal with Maintained Spatial Resolution in Raman Images of Cells Exposed to Submicron Polystyrene Particles
- 2016
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Ingår i: Nanomaterials. - : MDPI AG. - 2079-4991. ; 6:5
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Tidskriftsartikel (refereegranskat)abstract
- The biodistribution of 300 nm polystyrene particles in A549 lung epithelial cells has been studied with confocal Raman spectroscopy. This is a label-free method in which particles and cells can be imaged without using dyes or fluorescent labels. The main drawback with Raman imaging is the comparatively low spatial resolution, which is aggravated in heterogeneous systems such as biological samples, which in addition often require long measurement times because of their weak Raman signal. Long measurement times may however induce laser-induced damage. In this study we use a super-resolution algorithm with Tikhonov regularization, intended to improve the image quality without demanding an increased number of collected pixels. Images of cells exposed to polystyrene particles have been acquired with two different step lengths, i.e., the distance between pixels, and compared to each other and to corresponding images treated with the super-resolution algorithm. It is shown that the resolution after application of super-resolution algorithms is not significantly improved compared to the theoretical limit for optical microscopy. However, to reduce noise and artefacts in the hyperspectral Raman images while maintaining the spatial resolution, we show that it is advantageous to use short mapping step lengths and super-resolution algorithms with appropriate regularization. The proposed methodology should be generally applicable for Raman imaging of biological samples and other photo-sensitive samples.
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| 2. |
- Andersson, Per Ola, et al.
(författare)
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Towards Fingermark Dating : A Raman Spectroscopy Proof-of-Concept Study
- 2017
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Ingår i: ChemistryOpen. - : Wiley. - 2191-1363. ; 6:6, s. 706-709
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Tidskriftsartikel (refereegranskat)abstract
- Fingermarks have, for a long time, been vital in the forensic community for the identification of individuals, and a possibility to non-destructively date the fingermarks would of course be beneficial. Raman spectroscopy is, herein, evaluated for the purpose of estimating the age of fingermarks deposits. Well-resolved spectra were non-destructively acquired to reveal spectral uniqueness, resembling those of epidermis, and several molecular markers were identified that showed different decay kinetics: carotenoids > squalene > unsaturated fatty acids > proteins. The degradation rates were accelerated, less pronounced for proteins, when samples were stored under ambient light conditions, likely owing to photo-oxidation. It is hypothesized that fibrous proteins are present and that oxidation of amino acid side chains can be observed both through Raman and fluorescence spectroscopy. Clearly, Raman spectroscopy is a useful technique to non-destructively study the aging processes of fingermarks.
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| 3. |
- Näsström, Thomas, et al.
(författare)
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Amyloid fibrils prepared using an acetylated and methyl amidated peptide model of the alpha-Synuclein NAC 71-82 amino acid stretch contain an additional cross-beta structure also found in prion proteins
- 2019
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 9, s. 1-14
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Tidskriftsartikel (refereegranskat)abstract
- The 71-82 fragment of the non-amyloid-beta component (NAC) region of the Parkinson's disease (PD) and dementia with Lewy bodies (DLB) related protein alpha-Synuclein, has been reported to be important during protein misfolding. Although reports have demonstrated the importance of this fragment for the aggregation properties of the full-length protein, its exact role in pre-fibrillar oligomerisation, fibrillar growth and morphology has not yet been fully elucidated. Here, we provide evidence that fibrils prepared from an acetylated and methyl amidated peptide of the NAC 71-82 amino acid stretch of alpha-Synuclein are amyloid and contain, in addition to the cross-beta structure detected in the full-length protein fibrils, a cross-beta structure previously observed in prion proteins. These results shed light on the aggregation propensity of the NAC 71-82 amino acid stretch of the full-length protein but also the roles of the N- and C-terminal domains of alpha-Synuclein in balancing this aggregation propensity. The results also suggest that early aggregated forms of the capped NAC 71-82 peptide generated structures were stabilised by an anti-parallel and twisted beta-sheet motif. Due to its expected toxicity, this beta-sheet motif may be a promising molecular target for the development of therapeutic strategies for PD and DLB.
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