Isolation and structure elucidation of ovatoxin-a, the major toxin produced by Ostreopsis ovata

Since 2005, the benthic dinoflagellate Ostreopsis cf. ovata has bloomed across the Mediterranean basin, provoking serious toxic outbreaks. LC/MS studies have identified a number of palytoxin-like compounds, termed ovatoxins, along with trace amounts of putative palytoxin as the causative agents of the O. cf. ovata -related human sufferings. So far, any risk assessment for ovatoxins as well as establishment of their allowance levels in seafood has been prevented by the lack of pure toxins. The present paper reports on the isolation, NMR-based structural determination, and preliminary mouse lethality evaluation of ovatoxin-a, the major toxic compound contained in O. cf. ovata extracts. Availability of pure ovatoxin-a will open the double prospect of fully evaluating its toxicity and preparing reference standards to be employed in LC/MS quantitative analyses. Elucidation of ovatoxin-a's complex structure will ultimately herald the understanding of the molecular bases of ovatoxins bioactivity.     

Putative palytoxin and its new analogue,ovatoxin-a,in <Emphasis Type="Italic">Ostreopsis ovata</Emphasis> collected along the ligurian coasts during the 2006 toxic outbreak

In this article we report on the liquid chromatography tandem mass spectrometry (LC-MS) investigation of plankton samples collected in the summer of 2006 along the Ligurian coasts, coinciding with a massive bloom of the tropical microalga Ostreopsis ovata. LC-MS analyses indicated the occurrence of putative palytoxin along with a much more abundant palytoxin-like compound never reported so far, which we named ovatoxin-a. On the basis of molecular formula, fragmentation pattern, and chromatographic behavior, the structure of ovatoxin-a appeared to be strictly related to that of palytoxin. We report also on the analysis of cultured O. ovata, which was necessary to unequivocally demonstrate that putative palytoxin and ovatoxin-a contained in field samples were actually produced by O. ovata itself.     

ATR and transmission analysis of pigments by means of far infrared spectroscopy

In the field of FTIR spectroscopy, the far infrared (FIR) spectral region has been so far less investigated than the mid-infrared (MIR), even though it presents great advantages in the characterization of those inorganic compounds, which are inactive in the MIR, such as some art pigments, corrosion products, etc. Furthermore, FIR spectroscopy is complementary to Raman spectroscopy if the fluorescence effects caused by the latter analytical technique are considered. In this paper, ATR in the FIR region is proposed as an alternative method to transmission for the analyses of pigments. This methodology was selected in order to reduce the sample amount needed for analysis, which is a must when examining cultural heritage materials. A selection of pigments have been analyzed in both ATR and transmission mode, and the resulting spectra were compared with each other. To better perform this comparison, an evaluation of the possible effect induced by the thermal treatment needed for the preparation of the polyethylene pellets on the transmission spectra of the samples has been carried out. Therefore, pigments have been analyzed in ATR mode before and after heating them at the same temperature employed for the polyethylene pellet preparation. The results showed that while the heating treatment causes only small changes in the intensity of some bands, the ATR spectra were characterized by differences in both intensity and band shifts towards lower frequencies if compared with those recorded in transmission mode. All pigments' transmission and ATR spectra are presented and discussed, and the ATR method was validated on a real case study. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

A comparative study of diesel analysis by FTIR, FTNIR and FT-Raman spectroscopy using PLS and artificial neural network analysis

Diesel properties determined by ASTM reference methods as cetane index, density, viscosity, distillation temperatures at 50% (T50) and 85% (T85) recovery, and the total sulfur content (%, w/w) were modeled by FTIR-ATR, FTNIR, and FT-Raman spectroscopy using partial last square regression (PLS) and artificial neural network (ANN) spectral analysis. In the PLS models, 45 diesel samples were used in the training group and the other 45 samples were used in the validation. In the ANN analysis a modular feedforward network was used. Sixty diesel samples were used in the neural network training and other 30 samples were used in the validation. Two different ATR configurations were compared in the FTIR, a conventional (ATR1) and an immersion (ATR2) cell. The ATR1 cell presented the best results, with smaller prediction errors (root mean square error of prediction, RMSEP). The comparison of the three PLS models (FTIR-ATR1, FTNIR, and FT-Raman) shows that reasonable values of R² and RMSEP were obtained by the FTIR-ATR1 and FTNIR models in the evaluation of density, viscosity, and T50. The PLS/FT-Raman models presented reasonable results only for the T50 property. None of the techniques was able to generate suitable PLS calibration models for the determination of sulfur content. The ANN/FT-Raman models presented the best performances, with all models presenting R²-values above 85% some of them with RMSEP values significantly smaller than those obtained with FTIR-ATR and FTNIR. The ANN/FT-Raman and ANN/FTIR-ATR1 models were able to estimate the total sulfur content of diesel with 0.01% (w/w) accuracy.     

鞋底材料的傅立叶变换红外光谱类型分析

利用傅立叶变换红外光谱技术对收集的29种皮鞋类黑色鞋底样品进行了测定分析,其中24种样品来自不同品牌或型号,5种样品来自同一品牌同一厂家同一批次.从红外光谱图中可以看出,依据红外光谱图中特征峰的峰数、峰位、峰形可将29个鞋底样品分为3大类.同一大类的部分鞋底样品有着相似的红外光谱特征,但在相对峰高比和指纹区中一些弱吸收峰上仍然存在明显差异.同一品牌同一厂家同一批次的鞋底样品红外光谱特征基本一致.这表明傅立叶变换红外光谱法是鉴别鞋底材料的有效方法,可以为案件现场遗留的各种鞋底材料残渣及其擦痕提供种属鉴别及比对分析.     

Investigation of biodeteriorated historical textiles by conventional and synchrotron radiation FTIR spectroscopy

We have examined specimens of historical biodeteriorated cellulose textiles using synchrotron radiation and conventional source FTIR spectroscopy. The main aim of our research was to investigate structural changes caused by ageing and biodeterioration in different types of cellulose fibres. We compared the results, obtained with both methods regarding spectral quality and information obtained with each method. Additionally, we obtained mapping images of the cross sections of the investigated specimens using synchrotron FTIR in order to analyze structural changes in cross sections, caused due to biodeterioration.     

Earth pigments in painting: characterisation and differentiation by means of FTIR spectroscopy and SEM-EDS microanalysis

Analytical characterisation of natural earths (ochres, siennas, umbers and green earths) has been carried out using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) coupled to an energy dispersive X-Ray spectrometer (EDS). The study of these pigments, which are found in works of art, is very important since it can shed light on their source or the pictorial technique used. FTIR spectroscopy is suitable for the identification and differentiation of ochres and siennas. According to the matrix of the sample, FTIR allows the classification of ochres into ochres containing kaolinite and ochres containing sulphate. One of the goals of this research has been to establish a relationship between the matrix and the source of the samples tested. SEM-EDS is probably a better technique than FTIR for characterising umbers and green earths since they do not exhibit significant differences when FTIR studies are performed.     

傅里叶变换中红外光谱技术用于人体胃镜样品检测的新方法

应用傅里叶变换红外光谱(FTIR)测定了184例胃镜样品,总结不同病变类型组织的光谱特征,并与病理结果进行比较.实验结果表明,由于不同类型病变组织会在其分子组成和结构上发生相应改变,浅表性胃炎、萎缩性胃炎和胃癌组织具有不同的FTIR光谱,可据此进行胃镜样品疾病类型和病变程度的判别.研究结果表明,FTIR技术有望发展成为一种用于胃镜样品无创、快速、准确的在体临床诊断的新方法.     

Continuous nondestructive monitoring of <Emphasis Type="Italic">Bordetella pertussis</Emphasis> biofilms by Fourier transform infrared spectroscopy and other corroborative techniques

This work describes the application of several analytical techniques to characterize the development of Bordetella pertussis biofilms and to examine, in particular, the contribution of virulence factors in this development. Growth of surface-attached virulent and avirulent B. pertussis strains was monitored in continuous-flow chambers by techniques such as the crystal violet method, and nondestructive methodologies like fluorescence microscopy and Fourier transform (FT) IR spectroscopy. Additionally, B. pertussis virulent and avirulent strains expressing green fluorescent protein were grown adhered to the base of a glass chamber of 1-μm thickness. Three-dimensional images of mature biofilms, acquired by confocal laser scanning microscopy, were quantitatively analysed by means of the computer program COMSTAT. Our results indicate that only the virulent (Bvg⁺) phase of B. pertussis is able to attach to surfaces and develop a mature biofilm. In the virulent phase these bacteria are capable of producing a biofilm consisting of microcolonies of approximately 200 μm in diameter and 24 μm in depth. FTIR spectroscopy allowed us not only to follow the dynamics of biofilm growth through specific biomass and biofilm marker absorption bands, but also to monitor the maturation of the biofilm by means of the increase of the carbohydrate-to-protein ratio.     

Spectroscopic analysis of roman wall paintings from Casa del Mitreo in Emerita Augusta, Mérida, Spain

The use of visible spectroscopy, applied to chromatic characterization of Roman wall paintings, allows an easy and trustworthy grouping of the samples studied. The use of other spectroscopic techniques such as Fourier transform infrared spectroscopy (FTIR) and energy-dispersive X-ray spectroscopy (EDS) in conjunction with X-ray diffraction (XRD) allows a good identification of the substances present in the pictorial layers that define and differentiate each chromatic group. In this paper, a study of 40 Roman wall painting samples, from Pinturas Báquicas of Casa del Mitreo in Emerita Augusta (Mérida, Spain), is described. In these samples, some pigments of high quality and cost, as well as some unusual mixtures, not described in the bibliography, have been found.     

Vibrational spectroscopy differentiates between multipotent and pluripotent stem cells

Over the last few years, there has been an increased interest in the study of stem cells in biomedicine for therapeutic use and as a source for healing diseased or injured organs/tissues. More recently, vibrational spectroscopy has been applied to study stem cell differentiation. In this study, we have used both synchrotron based FTIR and Raman microspectroscopies to assess possible differences between human pluripotent (embryonic) and multipotent (adult mesenchymal) stem cells, and how O(2) concentration in cell culture could affect the spectral signatures of these cells. Our work shows that infrared spectroscopy of embryonic (pluripotent) and adult mesenchymal (multipotent) stem cells have different spectral signatures based on the amount of lipids in their cytoplasm (confirmed with cytological staining). Furthermore, O(2) concentration in cell culture causes changes in both the FTIR and Raman spectra of embryonic stem cells. These results show that embryonic stem cells might be more sensitive to O(2) concentration when compared to mesenchymal stem cells. While vibrational spectroscopy could therefore be of potential use in identifying different populations of stem cells further work is required to better understand these differences.     

UPLC-UV-MSE analysis for quantification and identification of major carotenoid and chlorophyll species in algae

A fast method for quantification and identification of carotenoid and chlorophyll species utilizing liquid chromatography coupled with UV detection and mass spectrometry has been demonstrated and validated for the analysis of algae samples. This method allows quantification of targeted pigments and identification of unexpected compounds, providing isomers separation, UV detection, accurate mass measurements, and study of fragment ions for structural elucidation in a single run. This is possible using parallel alternating low- and high-energy collision spectral acquisition modes, which provide accurate mass full scan chromatograms and accurate mass high-energy chromatograms. Here, it is shown how this approach can be used to confirm carotenoid and chlorophyll species by identification of key diagnostic fragmentations during high-energy mode. The developed method was successfully applied for the analysis of Dunaliella salina samples during defined red LED lighting growth conditions, identifying 37 pigments including 19 carotenoid species and 18 chlorophyll species, and providing quantification of 7 targeted compounds. Limit of detections for targeted pigments ranged from 0.01?ng/mL for lutein to 0.24?ng/mL for chlorophyll a. Inter-run precision ranged for of 3 to 24 (RSD%) while inter-run inaccuracy ranged from ?17 to 11.

Spectroscopic study of trypsin, heat and triton X-100-induced denaturation of the chlorophyll-binding protein CP43

Trypsin-, heat- and Triton X-100-induced denaturation of CP43, the core antenna complex of photosystem II purified from spinach, has been investigated using absorption, fluorescence and circular dichroism spectroscopy. Triton X-100 was found to bring about considerable dissolution of pigments from the protein to the monomeric state in solution and destruction of the interactions among the chlorophyll, carotene and protein. Heat induced significant unfolding of the protein secondary structure and loss of excitonic interactions of the pigments, but no apparent dissolution of the pigments from CP43. Trypsin caused structural changes in the extrinsic part of the protein but no change of the native state of the pigments. Trypsin, heat and Triton X-100 treatments increased the light sensitivity of chlorophyll in CP43 to different extents. The results suggest that the protein and beta-carotene can protect the chlorophyll from light-induced destruction in CP43.     

Molecular structure of Mg-Al, Mn-Al and Zn-Al halotrichites-type double sulfates--an infrared spectroscopic study

Near infrared (NIR), X-ray diffraction (XRD) and infrared (IR) spectroscopy have been applied to halotrichites of the formula MgAl(2)(SO(4))(4)·22H(2)O, MnAl(2)(SO(4))(4)·22H(2)O and ZnAl(2)(SO(4))(4)·22H(2)O. Comparison of the halotrichites in different spectral regions has shown that the incorporation of a divalent transition metal into the halotrichite structure causes a shift in OH stretching band positions to lower wavenumbers. Therefore, an increase of the hydrogen bond strength of the bonded water is observed for divalent cations with a larger molecular mass. XRD has confirmed the formation of halotrichite for all three samples and characteristic peaks of halotrichite have been identified for each halotrichite-type compound. It has been observed that Mg-Al and Mn-Al halotrichite are very similar in structure, while Zn-Al showed several differences particularly in the NIR spectra. This work has shown that compounds with halotrichite structures can be synthesised and characterised by infrared and NIR spectroscopy.     

Optimization and infrared spectrometric evaluation of the mechanical properties of PLA-based biocomposites

In this work polylactic acid (PLA)/starch biocomposite samples with optimized mechanical properties and suitable cost have been prepared by extrusion and thermal mixing. The variables to be optimized were PLA, corn starch, ethyl vinyl acetate (EVA), carboxy methyl cellulous (CMC) and glycerol mono- stearate (GMS) contents. The experiments were carried out based on the experimental design using D-optimal mixture methods. The analysis of variance indicated accuracy of the model. It was observed that biocomposite sample with PLA 59.5%, Starch 20%, EVA 10%, CMC 6.5%, GMS 2% and CaCO₃ 2% would be attained noticeable improvement in the mechanical properties. Fourier transform infrared spectroscopy (FTIR) in combination with partial least square (PLS) chemometric technique was used to estimate the mechanical properties in five different spectral regions. Results show good accuracy between calibration and validation sets also denoted that O-C?=?O stretching and C?=?O stretching functional groups of PLA, EVA, CMC and GMS have the most positive effect on tensile strength and hydrogen bonded hydroxyl group of starch has the minimum positive effect. This research provided a method to improve the mechanical properties of biocomposite samples by using the D-optimal design and PLS chemometric techniques and Obtained results demonstrated that PLS could accurately predict mechanical properties in these spectral regions.     

Influence of Hydration on the Structure and Interactions of Ethaline Deep-Eutectic Solvent: A Spectroscopic and Computational Study

Deep-eutectic solvents (DESs) are regarded as alternative green solvents to ionic liquids. In this work we report the structural properties and hydrogen bonding (H-bonding) interactions of an aqueous DES system. The used DES, ethaline (ETH), is composed of choline chloride and ethylene glycol (EG) in 1 : 2 molar ratio. The investigations were carried out by FTIR spectroscopy combined with quantum chemical calculations. Excess spectroscopy and two-dimensional correlation spectroscopy (2D-COS) were used to explore the data in detail. The results showed that, upon mixing, ETH transforms to EG dimers and trimers and D₂O clusters transform to various ETH-D₂O complexes. Theoretical calculations show that water molecules insert between the anion and cation of ETH, break the strong doubly ionic Cl^{− …} H−O_Ch+ H-bond, share charges of the ions and form H-bond with them, thus modulate the interaction properties of ETH. This study deepens our molecular-level understanding of the system and would shed light on its applications.     

Structural features and hydrogen-bond properties of galanthamine and codeine: an experimental and theoretical study

Structural features of galanthamine and codeine, two allosteric potentiating ligands of nicotinic acetylcholine receptors (nAChRs), have been investigated through experimental studies in solution by FTIR and NMR spectroscopy and by quantum chemical calculations in the isolated state. The infrared spectra accumulated in solvents of various polarities show that the intramolecular OH···O hydrogen bond in galanthamine is stronger than the corresponding interaction in codeine. Molecular electrostatic potential calculations allow rationalisation of the experimental trends. NOE measurements on the two ligands in the same solvent range show significant differences. In apolar solvents, the NMR spectroscopic data indicate the occurrence of CH···O hydrogen-bond interactions, whereas in the more polar solvents, a trans orientation of the methoxy group with respect to the furanyl oxygen atom is favoured. A natural bond orbital (NBO) analysis provides evidence that these stabilising interactions originate in the hyperconjugation between the lone pairs of the furanyl oxygen atoms, n(O), and the methoxy antibonding σ*(C-H) orbitals within the two molecules. Despite the strong structural similarities between the two allosteric modulators, FTIR equilibrium constants measurements of hydrogen-bond complexation combined with quantum chemistry calculations point out the significant increase of hydrogen-bond accepting strength of galanthamine relative to codeine. This increase is mainly assignable to the stronger hydrogen-bond basicity of the hydroxyl group, and to a lesser extent to the higher hydrogen-bond accepting strength of the amino nitrogen of galanthamine in comparison with the corresponding groups of codeine. An analysis of the interactions that occur between the two ligands and acetylcholine esterase (AChE) suggests significant differences with Trp84, a key component of the AChE catalytic active site. In contrast, both ligands appear to interact similarly with acetylcholine binding protein (AChBP).     

Excitation energy transfer in the photosystem II core antenna complex CP43 studied by femtosecond visible/visible and visible/mid-infrared pump probe spectroscopy

Excitation energy transfer in the Photosystem II core antenna complex CP43 has been investigated by vis/vis and vis/mid-IR pump-probe spectroscopy with the aim of understanding the relation between the dynamics of energy transfer and the structural arrangement of individual chlorophyll molecules within the protein. Energy transfer was found to occur on time scales of 250 fs, 2-4 ps, and 10-12 ps. The vis/mid-IR difference spectra show that the excitation is initially distributed over chlorophylls located in environments with different polarity, since two 9-keto C=O stretching bleachings, at 1691 and 1677 cm-1, are observable at early delay times. Positive signals in the initial difference spectra around 1750 and 1720 cm-1 indicate the presence of a charge transfer state between strongly interacting chlorophylls. We conclude, both from the spectral behavior in the visible when the annihilation processes are increased and from the vis/mid-IR data, that there are two pigments (one absorbing around 670 nm and one at 683 nm) which are not connected to the other pigments on a time scale faster than 10-20 ps. Since, in the IR, on a 10 ps time scale the population of the 1691 cm-1 mode almost disappears, while the 1677 cm-1 mode is still significantly populated, we can conclude that at least some of the red absorbing pigments are located in a polar environment, possibly forming H-bonds with the surrounding protein.     

Aragonite in Roman wall paintings of the VIII(a) Regio, Aemilia, and X(a) Regio, Venetia et Histria

In the Roman wall paintings different white colours were used, named Paraetonium, Melinum, Anularia, Eretria, Argentaria, etc. FTIR, Raman spectroscopy and X-Ray diffraction were applied to study different white pigments, such as calcite, aragonite, dolomite and huntite, white carbonates present in archaeological findings from Roman walls in the Mediterranean region. This study showed that it is possible to distinguish and identify these components in white colours. About 450 samples of Roman wall paintings were analysed and it was observed that often aragonite is associated to precious coloured pigments. On the basis of the obtained results some considerations about the period in which the different kinds of white pigments were used are proposed.     

Evaluation by Fourier Transform Infrared Spectroscopy of the different crystalline forms in syndiotactic polystyrene samples

Fourier transform infrared (FTIR) spectra of syndiotactic polystyrene (s-PS) semicrystalline samples have been examined by using the spectral subtraction approach. For the crystalline forms including trans-planar chains (trigonal α and orthorhombic β) a number of conformational and structural order effects, not previously described in the literature, have been identified. A method based on the results of the spectral subtraction analysis has been developed for the determination of the crystallinity degree and compared with the standard method based on the wide-angle X-ray diffraction patterns. The spectral subtraction analysis on FTIR spectra allows also an easy evaluation of the amount of α and β crystalline phases (often simultaneously present in melt-crystallized samples) although both contain chains in a same conformation. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 1055–1066, 1997