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Angiotensin I-converting enzyme (ACE) is a peptidase widely presented in human tissues and biological fluids. ACE is a glycoprotein containing 17 potential N-glycosylation sites which can be glycosylated in different ways due to post-translational modification of the protein in different cells. For the first time, surface-enhanced Raman scattering (SERS) spectra of human ACE from lungs, mainly produced by endothelial cells, ACE from heart, produced by endothelial heart cells and miofibroblasts, and ACE from seminal fluid, produced by epithelial cells, have been compared with full assignment. The ability to separate ACEs' SERS spectra was demonstrated using the linear discriminant analysis (LDA) method with high accuracy. The intervals in the spectra with maximum contributions of the spectral features were determined and their contribution to the spectrum of each separate ACE was evaluated. Near 25 spectral features forming three intervals were enough for successful separation of the spectra of different ACEs. However, more spectral information could be obtained from analysis of 50 spectral features. Band assignment showed that several features did not correlate with band assignments to amino acids or peptides, which indicated the carbohydrate contribution to the final spectra. Analysis of SERS spectra could be beneficial for the detection of tissue-specific ACEs. [ABSTRACT FROM AUTHOR]

Angiotensin I‐converting enzyme (ACE) is a glycoprotein, consisting of two homologous domains within a single polypeptide chain. ACE concentration in biological fluids is an important parameter of clinical observation; its increase or decrease may accompany various pathologies. Currently, the exact crystal structure of the two‐domain ACE form is still unknown because of microheterogeneity and intensity of the enzyme glycosylation. Raman spectroscopy provides the qualitative and quantitative analysis of many compounds, including proteins. For the first time, surface‐enhanced Raman scattering (SERS) spectra of native and thermo‐denatured human ACE have been demonstrated with full assignment. Denaturation leads to SERS intensity increase and bands shifting. Detailed band assignment and discussion are included to elucidate the potential site of ACE interaction with the silver surface. Based on SERS spectra, we characterized the region on the ACE molecule in contact with the substrate and demonstrated the model of the two‐domain ACE adsorbed on a silver matrix. [ABSTRACT FROM AUTHOR]

Original multiscale flaked silver SERS-substrate (MFSS substrate) was applied for glycated albumin (GA) biosensing. The substrate is composed from silver flakes that have three orders of magnitude size dispersion: from 50 nm to 2 μm. The multiscale silver structure refracts the incident light and various surface plasmons are excited. Some of the internal plasmons are localized and give rise of the large local electric field. It was demonstrated that Raman scattering signal strongly depends: a) on "hot spots" formation at the edges and points of contact of silver plates, and b) on the angle of incidence. As a result the silver structure operates as an effective SERS substrate. To achieve the selectivity to glycated part, the surface of SERS-substrate was modified with 4-mercaptophenylboronic acid (4-mPBA). Various saccharides (Fru, Glc, Suc, Dex) were taken as model compounds for the glycated proteins determination. The saccharides contain cis -diol groups that form five- or six-membered ethers with boronic acid. Spectrum of SERS-substrate changes after sugar/glycated albumin treatment. Main differences in the SERS-spectra of sugar/glycated albumin treated SERS-substrate and control are referred to phenylboronic acid vibrations (999, 1021, 1072 and 1589 cm−1). Principal component analysis (PCA) and Partial Least Squares Regression (PLS-R) were used to discriminate spectra and to construct calibration curve, as well as to measure GA values in real samples of human plasma. Multiscale flaked silver SERS-substrate modified with 4-mPBA allows quantitative one-step biosensing of glycated albumin in 15 μl of human plasma. Image 1 • Silver SERS-substrate was used for glycated human albumin biosensing. • The main differences in spectra are observed at 416, 470, 999, 1021, 1072, 1572 and 1589 cm−1. • SERS-effect depends on "hot spots" formation at the edges of silver plates, and on the angle of incidence. • Quantitative one-step biosensing of glycated albumin in 15 μl of human plasma had been done. [ABSTRACT FROM AUTHOR]

Laser light, illuminating surface‐enhanced Raman scattering‐active nanostructured CeO2/Al/Al2O3 thin‐film samples with reporter molecules/Au nanoparticle conjugates on the CeO2 surface, may cause irreversible modifications of the conjugates and of the surface structure field‐enhancing properties. As a result, the observed Raman signal decreases or vanishes. The limits of the laser light intensity suitable for nondestructive spectroscopic studies have been assessed using continuous and quasi‐continuous wave (mode‐locked ps‐pulse) laser radiation at different wavelengths. This radiation was used as a pump for linear and nonlinear Raman microspectroscopy of reporter molecules adsorbed on the surface of such a plasmonic metamaterial. Reducing laser power below certain levels allowed reproducible mapping of surface‐enhanced Raman scattering and surface‐enhanced coherent anti‐Stokes Raman scattering signal strengths at the reporter molecule Raman shifts. [ABSTRACT FROM AUTHOR]

Virus detection is often performed using antibody-based and polymerase chain reaction-based techniques. Such methods have major deficiencies, caused by time-consuming and labor-intensive incubation and purification steps. In this contribution, a novel SERS substrate for qualitative virus detection was developed and described. The substrate is composed of a thin silver film with folded surface structure containing pore-like nanoscale cavities and indentations, deposited on mica substrate by electron beam physical vapor deposition method. Pore-like structures are semi-regularly arrayed, with a rough surface in between, allowing for SERS activity, and their size and periodicity can be manipulated in the manufacturing process. It was speculated that viral particles could be trapped in these structures and would generate easily detectable enhanced Raman signals. The SERS substrate was tested against detection of four virus species – rabbit myxomatosis virus, canine distemper virus, tobacco mosaic virus and potato virus X. Specific spectra were obtained and analyzed for each virus. Data analysis demonstrated successful differentiation between tested species. The reported results demonstrate that novel SERS substrate is suitable for detection and identification of viral particles. [ABSTRACT FROM AUTHOR]