Display omitted
•Glucosamine binds to gold nanoparticles obtained from laser ablation in liquid.•Aggregation of glucosamine at 10 mM concentration causes new UV–VIS band at 625 nm.•SERS spectra of ...glucosamine in clean gold colloid were obtained for 0.1 mM and 1 mM glucosamine concentrations.•Strongest SERS bands are at 1563, 1586 and 1652 cm−1 (fron C-NH3+ bending modes), at 1165 cm−1 (C-N stretching coupled with C-C stretching motion) and at 1075 cm−1 (C-O stretching coupled with ring C-C stretching mode)
The binding of glucosamine to gold in water solutions of glucosamine hydrochloride mixed with clean colloidal gold nanoparticles obtained by laser ablation in liquid was studied using surface-enhanced Raman scattering (SERS), dynamic light scattering (DLS) and UV–VIS spectroscopy. The purpose of this study was to establish whether the binding of charged aminogroup to gold nanoparticles (AuNPs) is taking place, and if it does, how can it be identified by means of SERS.
The average size of dried gold nanoparticles was (20 ± 4) nm determined by averaging the sizes observed in transmission electron microscopy micrographs, which is smaller than the average size of gold nanoparticles in water solution as determined by DLS: (52 ± 2) nm. Upon adding the glucosamine solutions to gold colloid, average hydrodynamic diameter of ions was slightly larger for 0.1 mM glucosamine solution (55 ± 2 nm), while it increased to (105 ± 22) nm in the case of 1 mM solution, and was (398 ± 54) nm when 10 mM glucosamine solution was added.
Most prominent Raman bands observed both for 0.1 mM and 1 mM glucosamine solutions were located at 1165 cm−1, 1532 and 1586 cm−1 and assigned to C-N coupled with C-C stretching, and C-NH3+ deformation angles bending. In SERS spectrum of 1 mM GlcN+ solution, two strong bands at 999 and 1075 cm−1 were found and attributed to C-Oring stretching coupled with C-NH3+ bending (999 cm−1) and to dominantly C-O stretching vibration. The differences in SERS spectra are attributed to different number of glucosamine molecules that attach to gold nanoparticles and their orientation with respect to the metal particle surface, partly due to presence of beta anomers protonated at anomeric oxygen position. The assignment of glucosamine bands was further corroborated by comparison with vibrational spectra of alpha and beta glucose and of polycrystalline powder of glucosamine hydrochloride. For all three substances comprehensive calculation of vibrational density of states was conducted using density functional theory. Benchmark bands for polycrystalline glucose anomers distinction are 846 and 915 cm−1 for alpha glucose, and 902 cm−1 for beta glucose. However, the bands observed in SERS spectra of 0.1 mM glucosamine solution at 831, 899, and 946 cm−1 or in 1 mM solution at 934 cm−1 cannot be easily identified as belonging either to alpha or beta glucosamine anomer, due to complexity of atomic motions involved. The identification of vibrational bands associated with –CNH3+ group will aid SERS studies on amino acids, especially in cases when several atomic groups could possibly bind to AuNPs.
Advanced imaging techniques can noninvasively characterise, monitor, and evaluate how conservation treatments affect cultural heritage objects. In this specific field, hyperspectral imaging allows ...nondestructive characterisation of materials by identifying and characterising colouring agents, binders, and protective coatings as components of an object’s original construction or later historic additions. Furthermore, hyperspectral imaging can be used to monitor deterioration or changes caused by environmental conditions. This paper examines the potential of hyperspectral imaging (HSI) for the evaluation of heritage objects. Four cameras operating in different spectral ranges were used to nondestructively scan a beehive panel painting that originated from the Slovene Ethnographic Museum collection. The specific objective of this research was to identify pigments and binders present in the samples and to spatially map the presence of these across the surface of the art piece. Merging the results with databases created in parallel using other reference methods allows for the identification of materials originally used by the artist on the panel. Later interventions to the original paintings can also be traced as part of past conservation campaigns.
Glutathione is the most abundant low molecular weight thiol-containing molecule in biological cells with a strong tendency to interact with metal ions. Among the eight possible glutathione binding ...sites, only two are determined as groups that interact with the Cd2+ ion. Analysis of vibrational spectra and 13C and 1H NMR spectra revealed that thiol and glutamyl's carboxylic groups are groups that cooperate in interaction with Cd2+ ions. The coordination of Cd2+ with those groups was supported by the application of auxiliary molecules (D-penicillamine, glycine, cysteine and glutamic acid dipeptides, mercaptosuccinic acid and N-acetyl-L-cysteine). These molecules provide a reliable assignment of the fundamental vibrations in the glutathione vibrational spectra. Concentration-dependent measurements of Cd2+ ions showed that the optimal stoichiometry of coordination with the glutathione molecule is 1:1. The analysis of 3J (Halpha, H(N)) coupling constants and conformational sensitive bands in the glutathione vibrational spectra suggest that interaction with Cd2+ ions significantly alters glutathione backbone conformation. The binding of ions induced the conformational change of the cysteine backbone from a predominantly beta structure to P(II).
PDF
