Anna Tinti

Recent applications of vibrational mid-Infrared (IR) spectroscopy for studying soil components: a review

The present review highlights the recent applications of mid-infrared spectroscopy and in particular of diffuse reflectance spectroscopy (DRIFT) and attenuated total reflectance (ATR) and processing methods (e.g., deconvolution, derivative and chemometrics) to rapidly provide valuable information on soil composition and organic geochemistry. Research has demonstrated that both DRIFT and ATR techniques can be considered useful tools for the analysis of a large number of soil samples, giving not only typical spectral patterns but permitting an accurate prediction of quantitative parameters such as, e.g., total carbon, total nitrogen, C/N ratio, lignin, dissolved OC, carbonyl-C, aromatic-C, O-alkyl-C, and alkyl-C contents. Based on literature results, infrared spectroscopy can be recognized as one of the most promising analytical techniques for investigating soil science.

Characterization of polymorphic ampicillin forms

In this work polymorphs of α-aminobenzylpenicillin (ampicillin), a β-lactamic antibiotic, were prepared and investigated by several experimental and theoretical methods. Amorphous monohydrate and three crystalline forms, the trihydrate, the crystal form I and the crystal form II, were investigated by FT-IR and micro-Raman. Also data obtained by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray powder diffraction (XRPD) and hot-stage Raman spectroscopy are reported. Finally, quantum mechanical calculations were performed by density functional theory (DFT) to assist the assignment of spectroscopic experimental bands. For the first time, the ampicillin molecule in its zwitterionic form was studied at the B3LYP/aug-cc-pVDZ level and the corresponding theoretical vibrational spectra were computed. In fact, ampicillin in the crystal is in zwitterionic form and concentrations of this same form are quite relevant in solutions at physiological pH. Experimental and theoretical results allowed identification of specific features for polymorph characterization. Bands typical of the different polymorphs are identified both in IR and Raman spectra: in particular in the NH stretching region (IR), in the amide I+δNH region (both techniques), in the 1520-1490cm(-1) region (IR), in the 1320-1300cm(-1) and 1280-1220cm(-1) (IR), in the 1200-1170cm(-1) (Raman), in the amide V region (IR), and, finally, in the 715-640cm(-1) and 220-200cm(-1) (Raman). Interconversion among different polymorphs was investigated by hot-stage Raman spectroscopy and thermal analysis, clarifying the complex pattern of transformations undergone as a function of temperature and heating rate. In particular, DSC scans show how the trihydrate crystals transform into anhydrous forms on heating. Finally, stability tests demonstrated, after a two years period, that no transformation or degradation of the polymorphs occurred.

DSC and Raman study of DMPC liposomes in presence of Ibuprofen at different pH

Ibuprofen (IbuH), 2-(4-isobutylphenyl) propionic acid, is a well-known nonsteroidal anti-inflammatory drug and is a promising antiatherosclerotic agent. Since IbuH has demonstrated to affect cell membranes structure, the study of the interaction between the membrane components, like phospholipids, and the drug, is of paramount interest. Moreover, liposomes can be used as drug carriers. In this paper, the effect of increasing amounts of Ibuprofen at neutral and acidic pH on the behaviour of dimyristoylphosphatidylcholine (DMPC) liposomes was investigated by means of Raman and differential scanning calorimetry (DSC) techniques. The results showed that pH influenced noticeably the liposome structure. A simple ‘solution-like’ model can explain the system when small or high IbuH or IbuNa (IbuH sodium salt forming at neutral and basic pH) amounts are present (IbuH/DMPC molar ratio ≤1/8.3 or ≥1/2.2 or IbuNa/DMPC molar ratio ≤1/17.5 or ≥1/4), whereas at intermediate amounts, two DSC peaks appeared: these systems could be described as a mixture of ‘phase II’ domains inserted within a structure of smaller and further ramified ‘phase I’ domains. Both DSC and Raman data suggested IbuH can penetrate within the apolar bilayer at pH 3, while at pH 7, the setting up of polar interactions of different strength between the carboxylic groups of IbuNa and the choline head of the DMPC, hamper a further penetration of the drug. Similar results were obtained both inserting directly IbuH molecules into liposomes as well as acidifying IbuNa water solutions, suggesting a possible use of liposomes as drug carriers when polarity is pH dependent.

Biological Activity of Vegetal Extracts Containing Phenols on Plant Metabolism.

The influence of vegetal extracts derived from red grape, blueberry fruits and hawthorn leaves on Zea mays L. plant growth and the activity of phenylalanine ammonia-lyase (PAL), a key enzyme of the phenylpropanoid pathway, was investigated in laboratory experiments. The extracts were characterized using FT-IR and Raman spectroscopies in order to obtain a pattern of the main functional groups. In addition, phenols content was determined by HPLC, whereas the content of indoleacetic acid and isopentenyladenosine hormones was determined by ELISA test and the auxin and gibberellin-like activities by plant-bioassays. The treated maize revealed increased root and leaf biomass, chlorophyll and sugars content with respect to untreated plants. Hawthorn, red grape skin and blueberry at 1.0 mL/L induced high p-coumaric content values, whilst hawthorn also showed high amounts of gallic and p-hydroxybenzoic acids. PAL activity induced by hawthorn at 1.0 mL/L had the highest values (11.1-fold UNT) and was strongly and linearly related with the sum of leaf phenols. Our results suggest that these vegetal extracts contain more than one group of plant-promoting substances.

Vibrational study of lithium, sodium and potassium complexes with p-halogenbenzoic acids

Abstract Assignments are proposed for infrared and Raman spectra of lithium, sodium and potassium p-halogenbenzoates. The effect of metals on the aromatic system of p-halogenbenzoic acids and effect of halogens on the electronic system of the Li, Na and K salts were studied. In case of the influence of alkali metals, essential differences in frequency and intensity of the bands of the aromatic system have been found within the range for γ(CH) at 850-600 cm−1. On the other hand, change of halogens in the benzoic acid rings brings about marked changes within the ranges for at 1640-1370 cm−1, for β(CH) at 1270-1000 cm−1 and for γ(CH) at 850-600 cm−1. We believe that the important conclusion of our study is that the perturbation of the aromatic system depends mainly on the ionic potential of the metal and the halogen. The wavenumbers and intensities of some vibrational bands of the aromatic system as well as antisymmetric and symmetric vibrations of the carboxylate anion depend systematically on the ionic potentials of the metals and the halogens.

Blood Meal-Based Compound. Good Choice as Iron Fertilizer for Organic Farming

Prevention of iron chlorosis with Fe synthetic chelates is a widespread agronomical practice but implies high costs and environmental risks. Blood meal is one of the main fertilizers allowed to be used in organic farming. Through this work a novel blood meal fertilizer was audited. Measurements such as FTIR, Raman, electron paramagnetic resonance, and Mössbauer spectroscopy, UV-visible properties, stability against pH, and batch experiments were performed to characterize and assess the reactivity on soil constituents and agronomic soils. The spectroscopy findings give clear indications that Fe is in the ferric oxidation state, is hexacoordinated, and has a low-spin form suggesting a similar structure to hemin and hematin. A spectrophotometric method at 400 nm was validated to quantify blood meal concentration at low electrolyte concentrations. Batch experiments demonstrated high reactivity of blood meal fertilizer with soil constituents, mainly in the presence of calcium, where aggregation processes are predominant, and its ability to take Fe from synthetic Fe (hydr)oxides. The beneficial profile of blood meal by a providing nitrogen source together with the capability to keep the Fe bound to porphyrin organic compounds makes it a good candidate to be used as Fe fertilizer in organic farming.

Comparative Raman study of four plant metallothionein isoforms: Insights into their Zn(II) clusters and protein conformations

Four Metallothioneins (MTs) from soybean (Glycine max) were heterologously synthesized and comparatively analysed by Raman spectroscopy. The participation of protein donor groups (S-thiol and N-imidazol) in Zn(II) chelation, as well as the presence of secondary structure elements was comparatively analysed. Metal clusters with different geometry can be hypothesised for the four GmMTs: a cubane-like or an adamantane-like metal cluster in Zn-GmMT1, and dinuclear Zn-S clusters in Zn-GmMT2, Zn-GmMT3 and Zn-GmMT4. The latter have also a similar average Cys/Zn content, whereas a lower ratio is present in Zn-GmMT1. This is possible thanks to the involvement in metal coordination of a greater number of bridging Cys, as well as of some carboxylate groups. As regards secondary structure elements, a large content of β-turn segments is present in all four Zn-GmMTs, especially for isoforms 1 and 4. β-strands give a contribution to the folding of three GmMTs isoforms, and the highest percentage was found in Zn-GmMT2 (~45%). Conversely, the α-helix content is negligible in all the GmMTs except in Zn-GmMT3, where this peculiar feature coincides with the possible involvement of the two His residues in metal coordination. Conversely, His is predominantly free and present as tautomer I in Zn-GmMT4. In conclusion, this work illustrates the attractive potential of Raman spectroscopy, combined with other techniques, to be a very informative tool for evidencing structural differences among in vivo synthesized metal-MT complexes.

A Promising Raman Spectroscopy Technique for the Investigation of trans and cis Cholesteryl Ester Isomers in Biological Samples.

Lipid geometry is an important issue in biology and medicine. The cis–trans geometry conversion of double bonds in lipids is an endogenous process that can be mediated by sulfur-centered free radicals. Trans isomers of polyunsaturated fatty acids can be used as biological markers of free radical stress, and their presence in biological samples can be determined by synthesis and characterization of appropriate reference compounds. Fractions of plasma lipids, such as cholesteryl linoleate and arachidonate esters, are interesting targets because of their connection with membrane phospholipid turnover and their roles in cardiovascular health. In this context, Raman spectroscopy can provide a useful contribution, since Raman analysis can be performed directly on the lipid extracts without any derivatization reaction, is nondestructive, and can rapidly supply biochemical information. This study focused on the build up of Raman spectral libraries of different cis and trans isomers of cholesteryl esters to be used as references for the examination of complex biological samples and to facilitate isomer recognition. Unsaturated cholesteryl esters obtained by chemical synthesis and with different alkyl chain lengths, double bond numbers, or both, were analyzed. The potential of Raman analysis for trans isomer detection in biological samples was successfully tested on some cholesteryl ester lipid fractions from human serum. The data suggest promising applications of Raman spectroscopy in metabolomics and lipidomics.

IR, Raman and SERS spectra of propantheline bromide

The two known propantheline bromide polymorphs (form I and form II) were studied and characterized by a multianalytical approach. In the present work, the identification of propantheline bromide polymorphic forms through vibrational IR spectroscopies are presented and for the first time Raman microscopy and hot stage Raman microscopy (HSRM) studies are reported. Finally, quantum mechanical calculations were performed. For assisting the assignment of the experimental picks, the two IR spectra of the most and least stable representatives of a set of 56 conformers are calculated and studied. DSC thermograms data, are also reported. The surface enhanced Raman scattering (SERS) spectrum was also recorded in a silver colloid; it could be inferred that propantheline bromide is adsorbed on silver colloid through the oxygen atom with the molecular plane perpendicular to the metal surface.