Identification of reddish pigments in octocorals by Raman spectroscopy

The nature of the pigments in octocorals has been investigated by Raman spectroscopy, where laser excitation at 632.8 and 1064 nm were used to characterize the colored components present in the skeleton of the exotic pink‐yellow soft coral Chromonephthea braziliensis, the reddish purple sea fan Leptogorgia punicea and the endemic deep violet red Leptogorgia violacea from the southeastern coast of Brazil. The observed positions of two major Raman bands at ca 1500 cm⁻¹ [ν(CC)] and 1130 [ν(C C)] for all specimens strongly suggest the presence of a mixtureof conjugated polyenes belonging to a class of compounds named parrodienes. The hemiketal steroidal feeding deterrent, 23‐keto‐cladiellin‐A, isolated from C. braziliensis was identified in the crude extracts by the Raman analysis using 1064 nm excitation. The observation of the most important vibrational bands of this compound can be useful in future investigations to monitor its presence in crude extracts of C. braziliensis and or other species. Copyright © 2010 John Wiley & Sons, Ltd.     

Carotenes and carotenoids in natural biological samples: a Raman spectroscopic analysis

Raman spectroscopic studies of a range of naturally occurring carotenoids in over 50 specimens of plant tissue and a range of standard extracts have been undertaken, and the characteristic bands of CC and C C stretching and C CH bending have been recorded. Comparison of the spectroscopic data with the chemical assignment of the carotenoids from chemical extraction of the plant tissues reveals that there is a problem in the interpretation of the spectroscopic data which can be attributed to significant wavenumber shifts, particularly in the CC stretching band wavenumber, for carotenoids in the organic tissues arising from molecular interactions between the carotenoid and its host matrix. The simple identification of carotenoids in biological tissues on the basis of comparison with the standard spectra of extracted material must be made with caution; the progressive shift in wavenumber of the CC stretching band in the conjugated polyene chain of carotenoids with the number of CC groups, and hence the identification of the carotenoid, cannot be unambiguously interpreted for the range of materials studied here. Copyright © 2009 John Wiley & Sons, Ltd.     

Raman spectroscopic investigations on intermolecular interactions in aggregates and crystalline forms of trans‐astaxanthin

Astaxanthin is a carotenoid naturally found in microbial organisms, microalgae, and many crustaceans. Its consumption has led to beneficial effects such as pigmentation of marine animals, and it favorably addresses several human health issues as a result of its high important antioxidant property. Several companies produce synthetic trans‐astaxanthin for dietary purposes in aquaculture, where it is mainly used for pigmentation. It is known that trans‐astaxanthin manifests itself as a monomer in organic solvents, as aggregates in aqueous solutions of organic solvents, or as crystalline solids. These forms display unique optical and structural properties, which have an impact on biological systems. In this work, we report on detailed Raman investigations, in conjunction with optical absorption spectroscopy, of monomer, aggregates, and crystalline forms of trans‐astaxanthin. The Raman and optical absorption spectroscopic investigations of trans‐astaxanthin aggregates were performed as a function of time, showing the formation of card‐packed aggregates after 2 h, and head‐to‐tail aggregates after 24 h in a 10% acetone–water astaxanthin solution. For the crystalline trans‐astaxanthin, a pointwise Raman mapping evidenced the presence of two distinct crystal structures. The Raman modes of these crystal structures (A and B) were correlated with the intermolecular interactions present in chloroform solvated (AXT‐Cl) and unsolvated (un‐AXT) trans‐astaxanthin single crystals. Both crystal structure A and the card‐packed aggregates have similar intermolecular π stacking interactions as AXT‐Cl. The crystal structure B and the head‐to‐tail aggregates showed linear chain features as in un‐AXT. This work also clearly demonstrates that Raman spectroscopy is a powerful tool to distinguish the crystal structures present in crystalline powder of trans‐astaxanthin. Copyright © 2012 John Wiley & Sons, Ltd.     

Raman spectroscopic identification of fullerene inclusions in polymer/fullerene blends

Thin films of the conjugated polymer poly(3‐hexylthiophene) (P3HT) and blends of the soluble fullerene derivative[6,6]‐phenyl C₆₁‐butyric acid methyl ester (PCBM) with P3HT—a well studied but not completely understood donor–acceptor system for organic solar cells—have been studied by means of UV–visible absorption and resonant Raman spectroscopy. Additionally, we have employed atomic force microscopy phase imaging to characterize the nanomorphology of the P3HT : PCBM thin film, revealing a close intermixing of two phases with domain sizes ranging from a few to several tens of nanometers. A systematic analysis of pristine polymer and blend Raman spectra provides evidence that features attributable to PCBM, possibly even depending on the charge state of the fullerene molecule, can be observed. Hence our results suggest that fullerene inclusions in polymer/fullerene blends can be identified via Raman spectroscopy. Copyright © 2011 John Wiley & Sons, Ltd.     

Lichen colonization of an active volcanic environment: a Raman spectroscopic study of extremophile biomolecular protective strategies

The Raman spectra of some sixteen lichen specimens from eight genera growing on basaltic lava and wood substrates on new lava fields on the Kilauea volcano, Kona, Hawaii, have been analysed in therms of the pigments and biomolecules produced in this extreme environment. Chlorophyll and a carotenoid, probably lutein or astaxanthin, are ubiquitous, but otherwise, a range of protective pigments have been identified, including atranorin, usnic acid, gyrophoric acid, parietin and pulvinic acid dilactone. In addition, some species were observed to produce calcium oxalate monohydrate and dihydrate. Clearly, several strategies for survival were being adopted by the lichens to combat radiation insolation, desiccation and high temperatures; in one case, of the same lichen species colonizing wood and lava in the same location, a different survival strategy could be detected related to their substrate, but further long‐term ecological experiments would be indicated to derive more detailed information on this aspect. Copyright © 2009 John Wiley & Sons, Ltd.     

激光镊子拉曼光谱法优化红法夫酵母合成虾青素条件

用激光镊子拉曼光谱法优化红法夫酵母生产虾青素的条件。首先,将红法夫酵母细胞拉曼光谱与虾青素标准品溶液拉曼光谱进行对比,找出定量虾青素的拉曼特征峰;然后对照红法夫酵母生长曲线与不同时间点红法夫酵母细胞内虾青素含量曲线,进行发酵时间的优化;最后将红法夫酵母分别用不同氮源、碳源培养基培养,对比其细胞的虾青素拉曼特征峰强度,最终优化培养基。由实验可得,适宜定量虾青素的拉曼特征峰是1520cm-1峰;最佳发酵时间为72h;最佳优化培养基氮源含硫酸铵4g/L+硝酸钾4g/L,碳源含蔗糖60g/L。从上述结果可知,用激光镊子拉曼光谱法对红法夫酵母合成虾青素的条件进行优化,充分发挥了其操作简便、耗时短、样品用量少、对样品无损伤等优势,使所得结果更准确可信。因此,激光镊子拉曼光谱法是红法夫酵母细胞合成虾青素条件优化的理想选择。     

Raman spectroscopic analysis of cataract lens: A compendious review

Age-related cataracts is a pressing health issue with the increase in elderly populations. This creates an imminent demand for the development of an early, noninvasive method of cataracts diagnosis. Early detection of cataracts will improve quality of life and may prevent morbidity associated with advanced cataracts and surgery. Raman spectrum of proteins provides characteristic information regarding molecular interactions of peptide residues. Hence Raman spectroscopy is a promising tool for the study of protein-related diseases, such as cataracts. We surveyed the literature to assess the use of Raman technology in the studies of human lens and animal models. These studies included analysis of amino acids (i.e., cysteine, tryptophan, and tyrosine, etc.) and secondary protein structures (i.e., α-helix and β-sheet) in various Raman profiles. Other studies used Raman spectroscopy to analyze and monitor the development of cataracts in lens. Technological advances in the instrumentation of laser Raman spectroscopy, including Fourier transform Raman spectroscopy, Raman microspectroscopy, and confocal Raman microspectroscopy have improved the performance of Raman spectroscopic analysis. How to take advantage of these developments and make it closer to reality using Raman spectroscopic methods to diagnose cataracts in a timely manner is a key challenge for the scientific community of Raman spectroscopy.     

Low‐temperature Raman spectroscopic studies in NaNbO3

Raman spectroscopic measurements were carried out in the temperature range 10–300 K to understand the low‐temperature antiferroelectric (AFE)–ferroelectric (FE) phase transition in NaNbO₃. Several modes in the low wavenumber range were found to disappear, while some new modes appeared across the transition. The temperature dependence of mode wavenumbers suggests that, during cooling, the AFE–FE phase transition begins to occur at 180 K, while the reverse transition starts at 260 K during heating. During cooling, the two phases were found to coexist in the temperature range of 220–160 K. Upon heating, the FE phase is retained up to 240 K and both FE and AFE phases coexist in the temperature range 240–300 K. In contrast to the earlier reports, the present results suggest a different coexistence region and the reverse transition temperature. The reported relaxor‐type FE behaviour over a broad temperature is consistent with the observed coexistence of phases during cooling and heating cycles. Copyright © 2010 John Wiley & Sons, Ltd.     

Possibilities for human skin characterization based on strongly reduced Raman spectroscopic information

Loss‐of‐function mutations in the gene coding for filaggrin are the single most important risk factor for development of atopic dermatitis and associated allergic rhinitis and asthma. Filaggrin is enzymatically degraded to natural moisturizing factor (NMF) in the stratum corneum (SC). In vivo Raman spectra of human skin can be used to quantify the NMF concentration in SC and thereby identify carriers of a loss‐of‐function mutation in the gene coding for filaggrin, which results in decreased NMF content. Here, we demonstrate that strongly reduced Raman spectral information is sufficient to make this differentiation. This is an important step towards development of a dedicated diagnostic device of reduced complexity, size and cost as compared to current state‐of‐the‐art Raman equipment. A genetic algorithm was used to select the spectral regions needed to classify skin based on normal or reduced NMF content in SC. Using the NMF content based on full spectral information as gold standard, only four Raman regions were required to create a linear discriminant analysis model that can differentiate between skin with low NMF and skin with normal NMF with a prediction accuracy of 93 %. Copyright © 2013 John Wiley & Sons, Ltd.     

Raman spectroscopic diagnosis of breast cancers: evaluation of models

Breast cancer is the leading cancer affecting women. Conventional screening and diagnostic methods are shown to suffer from well‐described limitations. The aim of this study was to evaluate Raman spectroscopic models, which were developed earlier, by blinded tissue samples. We have recorded Raman spectra of 69 blinded tissue samples. In each sample, six or more spectra were recorded at different locations. Pretreated spectra were matched against normal, malignant and benign standard sets to obtain a match/mismatch status, which in turn was correlated with histopathology. Among 69 samples analyzed, 61 could be unambiguously diagnosed as 29 normal, 17 malignant and 15 benign, as their spectra matched with only one standard set and mismatched against the others. In the cases of the remaining tissue samples, matching them against pathological sets was the determining criteria. These samples were diagnosed as pathological since at least one of the spectra of these tissues had matched with pathological sets. Thus, we demonstrate a good correlation between histopathology and Raman spectroscopic diagnosis. Therefore, findings of the study further support the efficacy of Raman spectroscopic models that were developed by us. Prospectively, by developing models for as many pathological conditions as possible followed by rigorous validation, objective/unambiguous Raman spectroscopic diagnosis of breast pathologies can be realized. Copyright © 2008 John Wiley & Sons, Ltd.     

Surface enhanced Raman spectroscopic readout on heavy metal ions based on surface self assembly

A new method is reported for detecting heavy metal ions by using the self assembled monolayer (SAM) technique and surface enhanced Raman spectroscopy (SERS). The p‐mercaptobenzoic acid (MBA) served as the SERS readout molecule and the modified tag to attach on the smooth gold substrate as well as the tag of nanoparticles by the SAM method. Two carboxyl groups from MBA molecules which were attached respectively to gold substrate and gold nanoparticles were linked through the heavy metal ions (Cu²⁺, Pb²⁺ and Zn²⁺) as bridge, and thus sandwich structure of ‘MBA modified gold substrate/heavy metal ions/MBA modified gold nanoparticles’ was built for detection. The observation of the oxidation peak of metal nanoparticles from cyclic voltammetry (CV) curve, gold nanoparticles from scanning electron microscopy (SEM) images and SERS signal of MBA from the sandwich structure indicated the existence of heavy metal ions. The difference in the wavenumbers of vibrational modes from MBA in the sandwich structure constructed by different could be used to identify different heavy metal ions. The assembled structure was rinsed by strong chelator of EDTA solution to remove the heavy metal ions from the sandwich structure and thus to obtain a fresh gold substrate modified with MBA for the cyclic detection. Copyright © 2007 John Wiley & Sons, Ltd.     

A novel Raman spectroscopic approach to identify polymorphism in leflunomide: a combined experimental and theoretical study

Polymorphism is an important characteristic which affects the activity, solubility and other physical properties of a compound and can be induced by varying temperature, pressure and solvent. The presence and conversion of α to β polymorphic forms of an anti‐rheumatic drug leflunomide have been studied by temperature‐dependent and in situ Raman observations. Both α and β polymorphs were found to co‐exist in the temperature interval 367–372 K. The α form alone exists below 367 K and the β form alone above 373 K. The CO stretching band clearly demonstrates the α → β conversion because of breaking of N–H···O bond and formation of N–H···N bond. On cooling the Raman spectra suggest the irreversibility of this conversion. Thermodynamic stability, crystal parameters and surface morphology of both forms in the leflunomide powder used for the present study have been verified by differential scanning calorimetry, X‐ray powder diffraction and scanning electron microscopy. Copyright © 2015 John Wiley & Sons, Ltd.     

A Raman spectroscopic study of the uranyl carbonate rutherfordine

The molecular structure of the uranyl mineral rutherfordine has been investigated by the measurement of its Raman spectra at 298 and 77 K and complemented with infrared spectra. The infrared spectra of the (CO₃)²⁻ units in the anti‐symmetric stretching region show complexity with three sets of carbonate bands observed. This, combined with the observation of multiple bands in the (CO₃)²⁻ bending region in both Raman and IR spectra, suggests that both monodentate and bidentate (CO₃)²⁻ units are present in the structure in accordance with the X‐ray crystallographic studies. Complexity is also observed in the IR spectra of (UO₂)²⁺ anti‐symmetric stretching region and is attributed to non‐identical UO bonds. Both Raman and infrared spectra of the rutherfordine show the presence of both water and hydroxyl units in the structure, as evidenced by IR bands at 3562 and 3465 cm⁻¹ (OH) and 3343, 3185 and 2980 cm⁻¹ (H₂O). Raman spectra show the presence of four sharp bands at 3511, 3460, 3329 and 3151 cm⁻¹. Copyright © 2007 John Wiley & Sons, Ltd.     

A resonance Raman spectroscopic study of the protonation of Disperse Orange 25 in solution and adsorbed on oxide surfaces

The protonation of Disperse Orange 25 (DO25) in aqueous solution, and upon adsorption on oxide surfaces, was studied by resonance Raman (RR) spectroscopy. The neutral and protonated forms of DO25 were modelled by DFT calculations of the isolated molecules in the gas phase at the B3‐LYP/DZ level, enabling calculation of the vibrational spectra of these species, together with vibrational assignments. RR spectra show that DO25 is physisorbed on the SiO₂ surface, but its adsorption on SiO₂ Al₂O₃ or H‐mordenite results in protonation. This observation indicates the presence of Brønsted acidic sites on these oxide surfaces with pK_a values ⩽2.5. RR studies of the adsorption of DO25 can therefore provide useful information on the nature of surface acidity on oxides, which is complementary to that obtained from other probe molecules. Copyright © 2007 John Wiley & Sons, Ltd.     

表面增强拉曼光谱生物成像技术及其应用

基于表面增强拉曼光谱的成像分析方法具有频带窄,水溶液背景弱,稳定性好,高特异性等优势已成为生物成像领域的优良选择。拉曼成像技术拓展了拉曼光谱的应用范围,使其不再只是检测单点化学成分的手段,而进一步用于对评价区域内化学物质成分、分布及变化进行整体统计和描述。本文探讨了表面增强拉曼散射的原理及增强机制,介绍了基于表面增强拉曼光谱的拉曼成像技术,并对其在无标记成像及带标记成像中的细胞成像、活体成像,特别是其在生物医学方面的应用进行了详细论述,最后讨论了表面增强拉曼光谱生物成像技术存在的问题,展望了该项技术的研究和应用前景。     

Numerical simulations of confocal Raman spectroscopic depth profiles of materials: a photon scattering approach

We present a simple model that uses a novel photon scattering approach to predict the depth profile response obtained when confocal Raman spectroscopy is applied both to silicon and to a number of related polymeric materials of varying optical clarity. This paper first provides an overview of the models proposed to date to demonstrate the evolution in understanding of the confocal Raman response of semi‐transparent materials, based upon geometrical optics. A new model is then described that is based upon the twin notions of a permanent extended Raman illuminated volume and the degree of extinction of the incident and Raman scattered photons from the whole of the illuminated volume as it is gradually moved further into, or defocused above, the sample. The model's predictions are compared with empirical data from previous studies of a range of semi‐crystalline polymers with different scattering properties and, by means of contrast, with that of a silicon sample. We show that, despite its inherent simplicity, the physics this model utilizes is able successfully to predict the form of the depth profile for each material, something that has not been achieved by any model previously proposed, and that the parameters used in the model scale with independent physical measurements. Finally the model is used to account for the fact that useful Raman spectra can be obtained when the laser is focused as much as 40 µm above the sample surface. Copyright © 2007 John Wiley & Sons, Ltd.     

Effect of pH on the uptake of arsenate and vanadate by hydrotalcites in alkaline solutions: a Raman spectroscopic study

Hydrotalcites have been synthesised using solutions of three different pH values to assess the effect of pH on the uptake of arsenate and vanadate. The ability of these hydrotalcites to remove vanadate and arsenate from solution has been determined by inductively coupled optical emission spectroscopy. Raman spectroscopy was used to monitor changes in the anionic species for hydrotalcites synthesised at different pH values. The results show a reduction in the concentration of arsenate and vanadate anions that are removed in extremely alkaline solutions. Hydrotalcites containing arsenate and vanadate are stable in solutions up to pH 10. Exposure of these hydrotalcites to higher pH values results in the removal of large percentages of arsenate and vanadate from the hydrotalcite interlayer. Copyright © 2010 John Wiley & Sons, Ltd.     

Raman spectroscopy as a tool to the in situ study of three lichens species from Antarctica and Brazil

In this investigation the chemistry of the lichens Gondwania regalis, Teloschistes exilis and Xanthoria candelaria (Teloschistaceae) have been recorded by means of Raman spectroscopy. The non‐destructive analysis provided the recognition of parietin and conjugated polyenes, probably belonging to the carotenoid family for all the investigated specimens. Bands at ca. 1370 and 1600 cm⁻¹, respectively, assigned to the ν(C―O) and ν(CO) modes of the phenyl group of the anthraquinone compound, as well the bands at ca. 1005, 1158 and 1527 cm⁻¹, possibly assigned to the β‐carotene in the FT‐Raman spectra, have provided valuable spectroscopy data for the identification of the biomarkers for these lichen pigments. Thus, this is the first report of parietin and carotenoid in T. exilis and X. candelaria tissues even as the parietin anthraquinone for G. regalis tissues, which are effective pigments against free radicals from UV radiation. Copyright © 2014 John Wiley & Sons, Ltd.     

胞嘧啶分子拉曼光谱研究

本文通过实验测量了胞嘧啶的常规拉曼光谱,有四个弱拉曼峰在以前胞嘧啶的常规拉曼光谱中未检测到。采用密度泛函(Density Function Theory)B3LYP/6-31+G(d,p)计算了胞嘧啶分子的拉曼光谱。结合理论计算结果对实验拉曼光谱振动模式进行了指认,并对其中几个拉曼峰非常弱的原因进行了分析。     

Raman spectroscopic studies of the corrosion of model iron electrodes in sodium chloride solution

We have explored the un‐enhanced Raman spectra of both single and twin electrodes in 3.5% NaCl solution (at ambient temperatures) over a range of applied potentials (between 20 and 200 mV) and times (between 0 and 5 h). Under these conditions, we observed the initial formation of ‘green rust’ (hydroxychlorides and/or hydroxycarbonates), followed by the formation of magnetite (Fe₃O₄) and then a mixture of the α‐ and γ‐FeOOH (goethite and lepidocrocite, respectively). These data are consistent with a model for corrosion during which the initially formed magnetite is either covered, or replaced, by layers of the FeOOH oxidation products. Fitting of the data as a function of time and potential shows that, although the product range is independent of potential, the relative kinetics of formation of magnetite and its subsequent conversion to the γ‐FeOOH were potential and time dependent. Analysis by mapping of the dry corroded surface showed a variety of species, including green rust, some Fe(OH)₃, as well as the γ‐FeOOH, and possibly some β‐FeOOH. But no surface magnetite was found, indicating that this material had been either covered up or converted to FeOOH. We noted several complications during this work, including the interference of resonance effects (on the Raman intensities) and the heterogeneity of the corrosion process (and hence distribution of species on the corroded surface). However, we believe that the use of un‐enhanced Raman methods has led to conclusions more likely to be relevant to ‘real’ corrosion processes. Copyright © 2007 John Wiley & Sons, Ltd.