Raman spectra of 35 lipids are presented and analyzed in this work. Selected compounds, i.e. saturated/unsaturated fatty acids, triacylglycerols, cholesterol, cholesteryl esters and phospholipids, were chosen to review key lipids involved in cardiovascular disease development. Differences in Raman signatures both between diverse groups of lipids as well as various members of the same family are investigated in detail in order to elucidate marker features enabling detection and discrimination of lipids in complex samples, particularly of biological origin. This work complements our previous review on important biomolecules, i.e. proteins, and presents a comprehensive database of Raman spectra of naturally occurring lipids. Scheme 1. Chemical structure of chosen fatty acids: saturated (a) and unsaturated (b). Raman spectroscopy of lipids

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Atomic force microscopy-infrared (AFM-IR) spectroscopy is a powerful new technique that can be applied to study molecular composition of cells and tissues at the nanoscale. AFM-IR maps are acquired using a single wavenumber value: they show either the absorbance plotted against a single wavenumber value or a ratio of two absorbance values. Here, we implement multivariate image analysis to generate multivariate AFM-IR maps and use this approach to resolve subcellular structural information in red blood cells infected with Plasmodium falciparum at different stages of development. This was achieved by converting the discrete spectral points into a multispectral line spectrum prior to multivariate image reconstruction. The approach was used to generate compositional maps of subcellular structures in the parasites, including the food vacuole, lipid inclusions, and the nucleus, on the basis of the intensity of hemozoin, hemoglobin, lipid, and DNA IR marker bands, respectively. Confocal Raman spectroscopy was used to validate the presence of hemozoin in the regions identified by the AFM-IR technique. The high spatial resolution of AFM-IR combined with hyperspectral modeling enables the direct detection of subcellular components, without the need for cell sectioning or immunological/biochemical staining. Multispectral-AFM-IR thus has the capacity to probe the phenotype of the malaria parasite during its intraerythrocytic development. This enables novel approaches to studying the mode of action of antimalarial drugs and the phenotypes of drug-resistant parasites, thus contributing to the development of diagnostic and control measures.

A new experimental platform for probing nanoscale molecular changes in living bacteria using atomic force microscopy-infrared (AFM-IR) spectroscopy is demonstrated. This near-field technique is eminently suited to the study of single bacterial cells. Here, we report its application to monitor dynamical changes occurring in the cell wall during cell division in using AFM to demonstrate the division of the cell and AFM-IR to record spectra showing the thickening of the septum This work was followed by an investigation into single cells, with particular emphasis on cell-wall signatures, in several bacterial species. Specifically, mainly cell wall components from and containing complex carbohydrate and phosphodiester groups, including peptidoglycans and teichoic acid, could be identified and mapped at nanometre spatial resolution. Principal component analysis of AFM-IR spectra of six living bacterial species enabled the discrimination of Gram-positive from Gram-negative bacteria based on spectral bands originating mainly from the cell wall components. The ability to monitor molecular changes during cellular processes in bacteria at the nanoscale opens a new platform to study environmental influences and other factors that affect bacterial chemistry.

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 aportable infrared spectrometer with purpose-built transflection accessory for rapid point-of-care detection of COVID-19 markers in saliva. Initially,p urified virion particles were characterized with Raman spectroscopy, synchrotron infrared (IR) and AFM-IR. Adata 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.T he testing sensitivity was 93 %( 27/29) with as pecificity of 82 %( 23/28) that included positive samples on the limit of detection for RT-qPCR. Herein, we demonstrate ap roof-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.