bluuebunny/crossref_metadata_2025 huggingface dataset:
Time-resolved step scan FTIR spectroscopy and DFT investigation on triplet formation in peridinin–chlorophyll-a–protein from Amphidinium carterae at low temperature
Authors: Mezzetti Alberto , Spezia Riccardo
Published: April 2012

We have used time-resolved step-scan FTIR spectroscopy to investigate the process of triplet formation in the peridinin–chlorophyll-a–protein (PCP) at 100 K. Results have led to the identification of possible marker bands for peridinin (Per) and3Per. Band assignment has been carried out performing a DFT investigation on Per,3Per and on model molecules. The main spectral feature is a couple of bands at 1746 (negative) and 1719 (positive) cm–1. The assignment of these two bands to the lactonic C═O of Per in (respectively) its fundamental S0 and tripletT1state is based on: (1) comparison with FTIR spectra of isolated Per in literature; (2) good agreement with DFT calculations for Per and3Per; (3) the downshift of the band upon triplet formation as predicted by DFT calculations in Per and similar lactonic systems; (4) the kinetic of band disappearance, in agreement with literature data. Another possible band for Per in its fundamental state has been identified at 1523 cm–1.

The results are in overall agreement with a recent step-scan FTIR study on PCP at 298 K (Alexandre et al.,Biophys. J. 93 (2007), 2118–2128) even though some small discrepancies emerge, probably related to the different temperature at which experiments were carried out. Further DFT calculations have been performed to rationalise these spectral discrepancies. From a methodological point of view, the work demonstrates the potential of a combined step-scan FTIR/DFT approach in the study of photophysical processes in proteins. Furthermore, it has been shown that, when small differential IR signals are concerned, nagging photothermal effects can interfere and can possibly lead to misleading interpretations.
FTIR-ATR biosensor based on self-assembled phospholipids surface: Haemophilia factor VIII diagnosis
Authors: Aamouche Ahmed , Goormaghtigh Erik
Published: April 2012

We report a new generic device suitable for the investigation of biological interactions by means of Fourier Transform Infrared (FTIR) spectroscopy. The research is focused on multi reflected evanescent optical radiation through a chemically modified surface of the attenuated total reflection (ATR) element (silicon or germanium). Using a wet chemistry approach, the original method is based on grafting of a bifunctional binding molecule (N-hydroxysuccinimidyl ester forms) at the surface of the Si or the Ge crystals. The functionalized surface permits then the foundation of different types of self-assembled phospholipid membranes. The obtained sensors allow the detection, in infrared spectral domain, of any perceptible molecular interaction or structural changes. The key experimental result concerns the coagulation factor VIII(FVIII). The principle of the diagnostic is related to the ability of FFVIIImolecules to bind specifically to phosphatidylserine (PS) membrane.
Electronic coherence transfer in photosynthetic complexes and its signatures in optical spectroscopy
Authors: Mančal Tomáš , Valkunas Leonas , Read Elizabeth L. , Engel Gregory S. , Calhoun Tessa R. , Fleming Graham R.
Published: April 2012

Effects of electronic coherence transfer after photoexcitation of excitonic complexes and their manifestation in optical spectroscopy are discussed. A general excitonic model Hamiltonian is considered in detail to elucidate the origin of energy relaxation in excitonic complexes. We suggest that the second-order quantum master equation for the reduced density matrix of electronic degrees of freedom provides the most suitable theoretical framework for the study of coherence transfer in photosynthetic bacteriochlorophyll complexes. Temperature dependence of the absorption band maximum of a simple excitonic dimer is interpreted in terms of coherence transfer between two excited states. The role of reorganization energy of the transitions in the magnitude of the effect is discussed. A large reorganization energy difference between the two states is found to induce significant band shift. The predictions of the theory are compared to experimental measurements of the bacterial reaction center absorption spectra ofRhodobacter sphaeroidesAs an example of a time-dependent spectroscopic method sensitive to coherences and possibly to their transfer, we present recent two-dimensional photon echo measurements of energy relaxation in the so-called Fenna–Matthews–Olson complex ofChlorobium tepidum, where distinct oscillatory patters predicted to be signatures of electronic coherence have been observed.
Metabolomics relative quantitation with mass spectrometry using chemical derivatization and isotope labeling
Authors: O'Maille Grace , Go Eden P. , Hoang Linh , Want Elizabeth J. , Smith Colin , O'Maille Paul , NordstrÖm Anders , Morita Hirotoshi , Qin Chuan , Uritboonthai Wilasinee , Apon Junefredo , Moore Richard , Garrett James , Siuzdak Gary
Published: April 2012

Comprehensive detection and quantitation of metabolites from a biological source constitute the major challenges of current metabolomics research. Two chemical derivatization methodologies, butylation and amination, were applied to human serum for ionization enhancement of a broad spectrum of metabolite classes, including steroids and amino acids. LC-ESI-MS analysis of the derivatized serum samples provided a significant signal elevation across the total ion chromatogram to over a 100-fold increase in ionization efficiency. It was also demonstrated that derivatization combined with isotopically labeled reagents facilitated the relative quantitation of derivatized metabolites from individual as well as pooled samples.
Identification betweenStephania tetrandraS. Moore andStephania cepharanthaHayata by CWT–FTIR–RBFNN
Authors: Zhang Chang-Jiang , Cheng Cun-Gui
Published: April 2012

Horizontal attenuation total reflection–Fourier transform infrared spectroscopy (HATR–FTIR) is used to measure the FTIR ofStephania tetrandraS. Moore andStephania cepharanthaHayata. Because they belong to the same family and the same genus Chinese traditional medicinal materials, their chemical components are very similar. In order to extrude the difference betweenStephania tetrandraS. Moore andStephania cepharanthaHayata, continuous wavelet transform (CWT) is used to decompose the FTIR ofStephania tetrandraS. Moore andStephania cepharanthaHayata. Three main scales are selected as the feature extracting space in the CWT domain. According the distribution of FTIR ofStephania tetrandraS. Moore andStephania cepharanthaHayata, three feature regions are determined at every spectra band at selected three scales in the CWT domain. Thus nine feature parameters form the feature vector. The feature vector is input to the radius basis function neural network (RBFNN) to train so as to accurately classify theStephania tetrandraS. Moore andStephania cepharanthaHayata. 128 couples of FTIR are used to train and test the proposed method, where 78 couples of data are used as training samples and 50 couples of data are used as testing samples. Experimental results show that the accurate recognition rate betweenStephania tetrandraS. Moore andStephania cepharanthaHayata is respectively 99.8 and 99.9% by using the proposed method.
Complexation of Cd(SeCN)2with imidazolidine-2-thione and its derivatives: Solid state, solution NMR and anti-bacterial studies
Authors: Al-Maythalony Bassem A. , Wazeer Mohammed I. M. , Isab Anvarhusein A. , Nael M. T. , Ahmad Saeed
Published: April 2012

Reactions of imidazolidine-2-thione (Imt), 1,3-diazinane-2-thione (Diaz) and 1,3-diazipane-2-thione (Diap) with Cd(SeCN)2in acetonitrile resulted in the formation of 2:1 tetrahedral complexes. Both solid state and solution NMR, confirm the exocyclic thione atom to be the donor in all cases.113Cd shielding tensors and anisotropies were calculated from the solid-state NMR spectra. Based on the solid NMR data, a distorted tetrahedral dispositions of ligands around cadmium is proposed for the Imt complex. However, when the Imt ligand is substituted with one or two R groups (where R=Me, Et ori-Pr) forming RImt or R2Imt, a five coordinate complex with polymeric structure [(RImt)Cd(SeCN)2]∞or [(R2Imt)Cd(SeCN)2]∞is observed. Antibacterial studies of some of the complexes were carried out.
The investigations of bioactive copper(II) complexes with reduced low-molar dextran
Authors: Cakić Milorad , Mitić Žarko , Nikolić Goran S. , Ilić Ljubomir , Nikolić Goran M.
Published: April 2012

The optimization of the reaction conditions (pH,T,t) to obtain stable copper(II) ion complexes with dextran derivatives were investigated in this paper. A complete synthesis of stable aqueous complexes can be realized with reduced low-molar polysaccharides, at an average molar mass 5000 g mol–1and pH 7.5–8. Fourier-transform IR spectra of polysaccharide dextran and its compounds with copper(II) ion, recorded at room temperature, were analyzed in order to obtain the information about the structure and the conformation of these polymer compounds. The ESR parameters of the spectra indicate the square-planar coordination of Cu(II) ion with four O atoms. Copper(II) complex formation with dextran and its derivatives were analyzed by physicochemical methods. Synthesized complexes of Cu(II) ion with reduced low-molar dextran in comparison with commercial preparations showed the considerably lower acute toxicity (LD501705).
Phase behaviour of DPPC/Lyso-PPC mixtures by spin-label ESR and spectrophotometry
Authors: Pantusa Manuela , Sportelli Luigi , Bartucci Rosa
Published: April 2012

The influence of lysopalmitoylphosphatidylcholine (Lyso-PPC) on lamellar dispersions of dipalmitoylphosphatidylcholine (DPPC) has been investigated by spectrophotometry and electron spin resonance (ESR) of spin-labelled phosphatidylcholine at the C-5 or at the C-16 positions in thesn-2 acyl chain (5- and 16-PCSL). On increasing the concentration of Lyso-PPC up to 10 mol%, the spectral anisotropy of 5-PCSL is slightly reduced whereas that of 16-PCSL is markedly increased. This effect of the lysolipid on the DPPC lipid chain mobility is evident from 10 to 50 mol% at low temperature in the gel phase, disappears in the fluid phase, is associated with the lack of the pre-transition in the mixed lipid dispersions and it is interpreted as interdigitation of the DPPC lipid chains. At intermediate concentrations and for temperatures in the gel phase, the ESR spectra of both labels in DPPC and Lyso-PPC mixtures are the superposition of an anisotropic lamellar component and of an isotropic micellar signal, suggesting the coexistence of lamellar and micellar aggregates. Chain interdigitation and lamellar-micellar coexistence are not evident for temperature above the melting transition temperature. At high Lyso-PPC content (≥60 mol%) the mixed lipid dispersions reach the optical clarity, the main transition is no more detected and spin-label ESR spectra typical of micellar dispersions are detected in the whole temperature range investigated.
Hydration structure analysis of lysozyme amyloid fibrils by thermally stimulated depolarization currents (TSDC) technique
Authors: Bridelli Maria Grazia , Capelletti Rosanna
Published: April 2012

Thermally stimulated depolarization currents technique has been employed to investigate the conformation of hen egg white lysozyme in native and amyloid form, in the state of powder at very low hydration level. The technique, able to detect the current generated by thermally activated reorientation of water dipoles previously oriented by an electric field, exploits H2O dipoles, belonging to the solvation shell, as a probe to gain information on the protein conformation.

Large differences are detected between the TSDC spectra related to the two different protein conformations, for what concerns the number and position of the main peaks, the native form displaying two peaks, atTM=175 K and atTM=297 K, and the amyloid one, only one at intermediate temperature (TM=235 K). The spectra have been compared with those monitored for poly-L-lysine (MW 80400), as received and prepared in different ways, i.e.α-helix,β-sheet, and coil conformation, respectively. The poly-L-lysine spectra show specific features that can be attributed to water texture around the secondary structure adopted by the macromolecule: the results stress how TSDC technique is a tool of great potential value in the conformational analysis of proteins.
Inelastic neutron scattering spectroscopy of amino acids
Authors: Parker Stewart F. , Haris Parvez I.
Published: April 2012

A combination of infrared, Raman and inelastic neutron scattering (INS) spectroscopies are used to provide complete vibrational spectra of several amino acids and dipeptides. The amino acids studied were glycine, alanine, glutamine, cysteine, methionine and phenylalanine and the dipeptides studied were Gly–Gln and Gly–Ala. The findings of this study have shown how the complementarity of infrared, Raman and INS spectroscopies can be exploited to provide complete vibrational spectra of amino acids and peptides. In particular, the strengths of INS spectroscopy are highlighted: the absence of selection rules, that hydrogenic motions are emphasised, the ready access to the low energy regime (<400 cm−1) and the straightforward calculation of intensities. In the future, it should be possible to apply this approach to the study of larger peptides as well as proteins.
Influence of extremely low energy radiation on artificial tissue: Effects on image quality and superficial dose
Authors: Al-Akhras M.-Ali H. , Aljarrah K. , Al-Omari A. , Al-Khateeb H. M. , Albiss B. A. , Azez K. , Makhadmeh G.
Published: April 2012

The design and slicing technique of artificial soft tissue are presented. Artificial soft tissue has optical penetration properties similar to biological tissues. The soft tissues are made of agar dissolved in water as a transparent tissue (control) incorporated with scatter materials such as polystyrene microspheres and absorbers such as artificial dairy substitute, coffee mate (Carnation Co.). The radiation's interaction with 20 and 40 keV X-ray, and visible light (400–800 nm) with different types of tissue phantoms has been investigated. The half value layer (HVL), attenuation coefficient, energy density and penetration depth through the artificial tissues has been calculated. X-ray radiation depth show significant reduction in soft tissue incorporated with polystyrene microspheres. At extremely low energy (E), the half value layer decreases with increasing the energy, while the attenuation coefficient increase. The calculated values of the half value layers are in very good agreement with experimental results. The calculated values of effective linear attenuation coefficient, are found to be µeff(0.22–0.42). Significant reduction in superficial dose with clear image is found with 10 mm soft tissue filter used. These results suggests: possible enhancement in diagnostic imaging and reduction in excess dose to patients; artificial soft tissue can be used as filter substitute.
Human breast tissue cancer diagnosis by Raman spectroscopy
Authors: Abramczyk H. , Placek I. , Brozek-Pluska B. , Kurczewski K. , Morawiec Z. , Tazbir M.
Published: April 2012

Differences between Raman spectra of normal, malignant and benign tissues have been recorded and analyzed as a method for the early detection of cancer. To the best of our knowledge, this is one of the most statistically reliable research (67 patients) on Raman spectroscopy-based diagnosis of breast cancers among the world women population. The paper demonstrates that Raman spectroscopy is a promising new tool for real-time diagnosis of tissue abnormalities.
Infrared investigation of hard human teeth tissues exposed to various doses of ionizing radiation from the 1986 Chernobyl accident
Authors: Darchuk L. A. , Zaverbna L. V. , Bebeshko V. G. , Worobiec A. , Stefaniak E. A. , Grieken R. Van
Published: April 2012

Infrared spectroscopy (IR) was applied to study changes in solid teeth tissues of persons exposed to low (0.12–0.20 Gy) and high (0.5–1.7 Gy) doses of ionizing radiation during their work in the Chernobyl zone after the accident. Changes in the inorganic and organic matrix of teeth were noted for both high and low radiation doses. The obtained results demonstrated that high doses of radiation lead to imbalance between phosphate–carbonate phases level (because of increasing of CO32−content) and accumulation of soluble phosphates in the mineral part of the teeth. These changes have an effect on dental matrix strength. Low doses of radiation do not induce appreciable negative changes in the mineral part of all tooth tissues but lead to changes in organic matrix of teeth (in collagen).

The present results demonstrated that pathological effect of radiation touches upon all dental tissue and obviously all bone systems of irradiated people.
Molecular relaxation processes in calf-thymus DNA, in the presence of Mn2+and Na+ions: A Raman spectroscopic study
Authors: Muntean Cristina M. , Bratu Ioan
Published: April 2012

In this paper the Raman total half bandwidths of calf-thymus DNA vibrations have been measured as a function of Mn2+ion concentration (0–600 mM), in the presence of two concentrations of Na+cations, respectively. The dependencies of the half bandwidths and of the global relaxation times on DNA molecular subgroup structure, on Mn2+and Na+ions concentrations, respectively, are reported. It is shown that changes in the (sub)picosecond dynamics of molecular subgroups in calf-thymus DNA can be monitored with Raman spectroscopy.

In this study the Raman band parameters for the vibrations at 729 cm-1(dA), 787 cm-1(dC), 1094 cm-1(PO2-), 1376 cm-1(dA, dG, dT, dC), 1489 cm-1(dG, dA) and 1578 cm-1(dG, dA) of calf thymus DNA are presented. The full-widths at half-height (FWHH) of the bands in calf-thymus DNA are typically in the wavenumber range from 9 to 33.5 cm-1. It can be observed that the molecular relaxation processes studied in this work, have a global relaxation time smaller than 1.179 ps and larger than 0.317 ps.

Mn2+-induced DNA structural changes result for the vibrations at 729 cm-1and 787 cm-1in smaller global relaxation times, and larger half bandwidths, respectively, as compared to the starting value of 0 mM Mn2+. The vibrational energy transfer processes of these two subgroups (dA, dC), respectively, are slower in the case of DNA samples at 10 mM NaCl, as compared to the corresponding DNA samples at 150 mM NaCl. However, the behaviour of the global relaxation times characteristic to the bands at 729 and 787 cm-1is similar with respect to manganese(II) ions concentration, in the case of the two values of Na+ions content, respectively.

On the contrary, the molecular dynamics is slower for the base vibrations at 1376, 1489 and 1578 cm-1, in the case of DNA samples at 150 mM NaCl, as compared to the corresponding samples at lower Na+concentration, in almost all Mn2+ions concentration range. The molecular relaxation processes in these three cases, respectively, are quite different for the corresponding samples with different Na+ions content, upon increasing divalent manganese ions concentration.

The molecular dynamics characterizing the band near 1094 cm-1of the DNA backbone PO2-symmetric stretching vibration is faster upon increasing the Mn2+ions concentration between 0–600 mM and seems not to be influenced by the Na+ions content, specific to our experimental conditions.
FTIR spectroscopic studies of bacterial cellular responses to environmental factors, plant-bacterial interactions and signalling
Authors: Kamnev Alexander A.
Published: April 2012

Modern spectroscopic techniques are highly useful in studying diverse processes in microbial cells related to or incited by environmental factors. Spectroscopic data for whole cells, supramolecular structures or isolated cellular constituents can reflect structural and/or compositional changes occurring in the course of cellular metabolic responses to the effects of pollutants, environmental conditions (stress factors); nutrients, signalling molecules (communication factors), etc. This information on the molecular level, often obtained using non-destructive techniques with minimal sample preparation, is of importance for basic studies on mechanisms of bacterial tolerance to stresses and their impact on bacterial metabolism, as well as for applied multidisciplinary research in the fields related to biotechnology, bioremediation, agriculture, biogeochemistry, etc. In the present communication, some recent examples are reviewed and discussed which illustrate the applicability of Fourier transform infrared (FTIR) spectroscopy for monitoring metabolic changes in soil bacteria, using the examples of intensively studied plant-growth-promoting rhizobacteria of the genusAzospirillum. Compositional and structural changes occurring in whole bacterial cells in response to different stress factors and plant signals, as well as spectroscopic images of relevant biospecific interactions are considered from the viewpoint of the possibilities provided by this versatile and easy-to-use technique and its methodology.
The proximal and distal pockets of the H93G myoglobin cavity mutant bind identical ligands with different affinities: Quantitative analysis of imidazole and pyridine binding
Authors: Du Jing , Sono Masanori , Dawson John H.
Published: April 2012

His93Gly sperm whale myoglobin (H93G Mb) has the proximal histidine ligand removed to create a cavity for exogenous ligand binding, making it a versatile template for the preparation of model heme complexes. In this study, we have measured the first and second ligand binding affinities of imidazole and pyridine to form mono- and bis-ligated ferric and ferrous H93G Mb complexes. Electronic absorption spectroscopy has been utilized to determine the binding affinities for the proximal (Kd1, first ligand) and distal (Kd2, second ligand) pockets of H93G Mb. Magnetic circular dichroism spectroscopy has been used to confirm the identity of the complexes. The binding affinities for the first ligand are one hundred- to one thousand-fold higher than those for the second ligand (Kd1«Kd2) for the same exogenous ligand. This is entirely opposite to what is seen with free heme in organic solvents whereKd1»Kd2. Thus, the proximal pocket is the high affinity binding site. The lower affinity for the distal pocket can be attributed to steric hindrance from the distal histidine. This report provides quantitative evidence for differential ligand binding affinities of the proximal and distal pockets of H93G Mb, a unique property that facilitates generation of heme iron derivatives not easily prepared with other heme model systems.
Analysis of postmortem metabolic changes in rat kidney cortex using Fourier transform infrared spectroscopy
Authors: Huang Ping , Ke Yong , Lu Qinyang , Xin Bo , Fan Shuanliang , Yang Guangde , Wang Zhenyuan
Published: April 2012

Estimation of the time since death (postmortem interval, PMI) is one of the most difficult problems in forensic investigations and many methods currently are utilized to estimate the PMI. The aim of this study was to investigate the changes of Fourier transform infrared (FT-IR) spectra of rat kidney cortex from time zero to 168 h postmortem at molecular level. The spectra of rat kidney cortex displayed the prominent changes with increasing postmortem interval. (1) Significant increase in the intensity of the C–H stretching bands at 2958, 2925, 2871, 2852 cm–1, the ═C–H stretching band at 3012 cm–1, the CO2–symmetric stretching band at 1396 cm–1and the N–H bend, C–N stretching at 1541 cm–1; (2) significant decrease in the intensity of the PO2–stretching band at 1238, 1080 cm–1; (3) the intensity of at 3303, 1652 and 1170 cm–1remained relatively stable. The linear regression analysis of the various absorption intensity and area ratios against the PMI shows a close correlation, maximum forA1541/A1396ratio (R2═ 0.95) and minimum forI1080/I1396ratio (R2═ 0.70). Our results indicate that FT-IR spectroscopy may be a useful technique for estimating the short- and long-term PMI.
Lymph node pathology using optical spectroscopy in cancer diagnostics
Authors: Isabelle M. , Stone N. , Barr H. , Vipond M. , Shepherd N. , Rogers K.
Published: April 2012

Raman and infrared spectroscopy are optical spectroscopic techniques that use light scattering (Raman) and light absorption (infrared) to probe the vibrational energy levels of molecules in tissue samples. Using these techniques, one can gain an insight into the biochemical composition of cells and tissues by looking at the spectra produced and comparing them with spectra obtained from standards such as proteins, nucleic acids, lipids and carbohydrates. As a result of optical spectroscopy being able to measure these biochemical changes, diagnosis of cancer could take place faster than current diagnostic methods, assisting and offering pathologists and cytologists a novel technology in cancer screening and diagnosis.

The purpose of this study is to use both spectroscopic techniques, in combination with multivariate statistical analysis tools, to analyze some of the major biochemical and morphological changes taking place during carcinogenesis and metastasis in lymph nodes and to develop a predictive model to correctly differentiate cancerous from benign lymph nodes taken from oesophageal cancer patients.

The results of this study showed that Raman and infrared spectroscopy managed to correctly differentiate between cancerous and benign oesophageal lymph nodes with a training performance greater than 94% using principal component analysis (PCA)-fed linear discriminant analysis (LDA). Cancerous nodes had higher nucleic acid but lower lipid and carbohydrate content compared to benign nodes which is indicative of increased cell proliferation and loss of differentiation.

With better understanding of the molecular mechanisms of carcinogenesis and metastasis together with use of multivariate statistical analysis tools, these spectroscopic studies will provide a platform for future development of real-time (in surgery) non-invasive diagnostic tools in medical research.
Catheter with dielectric optical filter deposited upon the fiber optic end for Ramanin vivobiospectroscopy applications
Authors: de Lima Carlos José , Pacheco Marcos Tadeu T. , Villaverde Antonio Balbin , Zângaro Renato Amaro , Moreira Leonardo Marmo , Damião Álvaro José
Published: April 2012

Raman spectroscopy (RS) is a powerful tool that allows obtaining significant biochemical information from biological tissue. The fiber optic catheter permits applicationsin vivothat present wide clinical employment. This biochemical analysis is developed through a guide light that furnishes to Raman spectroscopy system the data obtained from tissue. These Raman signals represent the modes of vibration of molecular groups that are present in the biological molecules. Raman measurements undergo the optical influence of the material that constitutes the catheter, mainly Raman scattering of the silica that composes the fiber optic, decreasing signal to noise ratio (SNR) of the resultant spectra. In this work, a dielectric optical filter called “bandpass” was deposited upon the surface of the tip of the central fiber optic (distal probe). Indeed, other six fibers without any optical filter are disposed around this central optical fiber with “bandpass”. This prototype of catheter presented significant decrease of the silica Raman scattering when compared with unfiltered catheters. The biomedical applications of this new catheter are auspicious, involving biochemical analysis and diagnosisin vivo, since the SNR improvement obtained propitiates a much more informative Raman spectrum.
Structural lesion to ribonuclease A caused by reductive stress: Assessment by Raman spectroscopy
Authors: Torreggiani Armida
Published: April 2012

The damages induced by reductive radical stress on bovine pancreatic ribonuclease A (RNAse A) were investigated by Raman spectroscopy. Gamma-irradiation was used to simulate the endogenous formation of reductive species, in particular•H atom that is a simple one-electron equivalent reducing agent. Specific damages occur at sensitive amino acid sites, selectively, rather than indiscriminately, leading to the structure modification of the protein. Sulfur-containing residues (Met and Cys) and aromatic residues are appreciably attacked. In particular, extensive changes in the disulfide bridge conformations are induced as well as conformational changes of the protein secondary structure; a gradual conversion ofα-helical to pleated-sheet geometry was evidenced, indicating a higher ability of reducing radicals in denaturing the protein structure compared with that of oxidizing radical species.
Role of H-bond formation in the photoreactivity of curcumin
Authors: Nardo Luca , Paderno Roberta , Andreoni Alessandra , Másson Már , Haukvik Tone , TØnnesen Hanne Hjorth
Published: April 2012

Curcumin is the main constituent of curry. In its ground state it shows chemo-preventive, chemo-therapeutic and anti-inflammatory effects. For its immunostimulating action it has been considered for the development of drugs suitable for treating AIDS and cystic fibrosis. Further biological action is induced in curcumin by photoactivation: in suitable environmental conditions electronically excited curcumin can act as a singlet oxygen generator. Moreover, cytotoxicity is enhanced by light exposure and antibacterial effects are photosensitized. This work is aimed to understand the photobiological action of curcumin by elucidating the deactivation mechanisms of its first excited singlet state. In particular we find evidence of the role of tautomerization in the excited state by measuring fluorescence lifetimes and quantum yields for such compound dissolved in solvents of different polarity and H-bonding capability. Degradation quantum yield and singlet oxygen generation efficiency were also measured in acetonitrile and methanol. The results emphasize the strong dependence of the deactivation processes from the environment. The deactivation phenomenology can be fully explained by postulating intramolecular proton transfer in thecisenol conformer to be the leading non-radiative deactivation pathway.
Interaction of metal ions with glutaminase interacting protein (GIP): A potential role of GIP in brain diseases
Authors: Ward Priscilla , Huang Chengdong , Banerjee Monimoy , Mohanty Smita
Published: April 2012

Glutaminase interacting protein (GIP), a PDZ domain containing protein, mediates the distribution and clustering of proteins/peptides in membranes, acting as a scaffold where signaling molecules are linked to a multi-protein complex. GIP has been shown to play a key role in the glutamate signaling system. Some metals, particularly Pb2+, Cu2+and Zn2+, have been implicated in a wide range of neurological disorders including Alzheimer's disease and Parkinson's disease, whose etiologies have been associated with dysfunction of the glutamate signaling system. Here, for the first time, the effects of lead, copper, and zinc on GIP were determined by using circular dichroism and fluorescence spectroscopy. All three metal ions significantly affected the conformational properties of GIP. The deconvolution of CD data showed that, with increasing amounts of Pb2+/Cu2+/Zn2+, theα-helix percentage decreased while theβ-sheet content increased. The binding constants of GIP to Pb2+, Cu2+and Zn2+determined by fluorescence were found to be 1.4, 2.38 and 2.85 μM respectively, which indicated strong bindings between GIP and all three metal ions. We propose that the metal ion binding site of GIP is located onα-2 helix, where residues His90, Asp91 and Arg94 may coordinate the metal ions. The conformational change of GIP upon metal ion binding possibly results from the disruption of a salt bridge between Asp91 and Arg94.
Raman spectroscopy: A powerful technique for biochemical analysis and diagnosis
Authors: Moreira Leonardo M. , Silveira Jr. Landulfo , Santos Fábio V. , Lyon Juliana P. , Rocha Rick , Zângaro Renato A. , Villaverde Antonio Balbin , Pacheco Marcos T. T.
Published: April 2012

The present work focuses on the recent applications of Raman spectroscopy (RS) on biochemical analysis and diagnosis of several biological materials with or without pathological alterations. Important published works about Raman spectroscopy and its use for medical applications were critically reviewed, including articles form our group in order to evaluate the state of the art of the subject. The potential for sample characterization with RS associated to the possibility of analysisin situmakes this instrumental technique in a very auspicious tool of biochemical analysis. RS can promote a significant improvement in the chemical identification and characterization of biological systems, clinical diagnosis and prognosis regarding several diseases and quality of life of innumerous patients. The spectroscopic evaluation is based on the analysis of the Raman spectrum regarding the identification of fingerprint bands of main biological macromolecules, such as nucleic acids, proteins and fat, present in the tissue structure. This review evaluates the employment of RS in diagnosing such pathological manifestations as well as the efforts focused on the instrumental development to biomedical applications. Furthermore, advantages and limitations of this kind of approach are discussed in order to improve the biochemical analysis and diagnosis of several diseases.
Mechanism of tiron as scavenger of superoxide ions and free electrons
Authors: Taiwo Fatai A.
Published: April 2012

Sodium 4,5-dihydroxybenzene-1,3-disulfonate (tiron) has been reported to be an efficient chelator of certain metal ions, and a substrate in several enzyme reactions. Its small size facilitates cell entry and therefore modulates intracellular electron transfer reactions as an antioxidant by scavenging free radicals. Its reduction by electrochemical and enzymatic methods gives identical products; a semiquinone detectable by EPR spectroscopy. In a test of its use as a spin trap, in comparison with DMPO, tiron does not form a molecular spin-adduct but proves more functional as an electron trap. Electron addition to tiron is more facile than reduction of dioxygen as observed by the non-formation of DMPO-OOH spin-adduct in the system XO/HPX/O2/DMPO/tiron. Rather, it is the tiron semiquinone radical which is formed quantitatively with increasing concentration of hypoxanthine independent of oxygen concentration. These results offer explanation for the action of tiron and its suitability for measuring electron release in hypoxic conditions, and also for mitigating redox-induced toxicity in drug regimes by acting as an electron scavenger.
ATR-FTIR, FT-NIR and near-FT-Raman spectroscopic studies of molecular composition in human skinin vivoand pig ear skinin vitro
Authors: Greve Tanja M. , Andersen Kristine B. , Nielsen Ole F.
Published: April 2012

ATR-FTIR, FT-NIR and near-FT-Raman spectroscopy were used to characterize the molecular composition of human skinin vivoand pig ear skinin vitro. Due to different measurement depths the spectroscopic techniques reveal the characteristics of different layers of the skin. Tape stripping was used with the ATR-FTIR technique. Spectral differences concerning lipid content and conformation, protein secondary structure or content of water were found with respect to both gender and species (i.e. human versus pig ear) at all measured skin depths. New assignments of so far unassigned lipid and protein peaks in the FT-NIR and ATR-FTIR spectra of skin were made. PCA and PLS models were used to investigate the division of the recorded spectra into groups. With respect to classification of male and female subjects, the PLS discriminant analysis provided a classification accuracy of 64–93% based on the ATR-FTIR spectra and 83–89% based on the Raman spectra. With respect to classification of human skinin vivoand pig ear skinin vitro, the PLS discriminant analysis provided a classification accuracy of 75–100% based on the Raman spectra and 100% based on the ATR-FTIR spectra.
Raman study of HIV TAR structural stability
Authors: Vachoušek Jan , Štěpánek Josef
Published: April 2012

Structural characteristics of a central segment of the HIV RNA trans-activation response element (TAR) have been studied in aqueous solution. The investigated segment (TAR-14), comprising nucleotides 26–39 of the wild-type HIV genome (GAGC-CUGGGA-GCUC sequence), forms the TAR apical hairpin with a six-base loop and a stem of 4 base pairs. Raman spectra were recorded in a wide temperature range and the spectral series analyzed by means of factor analysis (FA) and a consequent fit to a thermodynamic model. The model was applied for temperatures above 20°C because of spectroscopic indication of possible intermolecular complexes at lower temperatures. FA results corresponded to a monomolecular reaction of the hairpin opening characterized by a melting temperature of 71°C and ∆G37= −3.2 kcal/mol. Besides the process of the hairpin opening, the FA revealed also substantial, approximately linear, temperature induced changes of the closed hairpin Raman spectrum. Spectral changes attributed to this effect indicated partial disordering of the A-type duplex geometry of the stem, opening of intraloop hydrogen bonds, weakened conformational regularity of the loop guanosines and release of the loop uracil.
FT-Raman signatures of genomic DNA from plant tissues
Authors: Muntean Cristina M. , Halmagyi Adela , Puia Mircea D. , Pavel Ioana
Published: April 2012

The vibrational spectra of eight genomic DNAs from leaf tissues (sword fern (Nephrolepis exaltataL.), chrysanthemum (Dendranthema grandifloraRamat.), redwood (Sequoia sempervirensD. Don. Endl.), orchids (Cymbidium × hybrida), common sundew (Drosera rotundifoliaL.), potato (Solanum tuberosumL.) and scopolia (Scopolia carniolicaJacq.)) have been analyzed using FT-Raman spectroscopy, in the wavenumber range 500–1800 cm–1.

FT-Raman signatures, spectroscopic assignments and structural interpretations for these plant genomic DNAs are reported. Spectral differences among two genomic DNAs, independently extracted from chrysanthemum leaves, are to be observed between 1000–1200 cm–1. Besides, similarities in the FT-Raman spectra of genomic DNAs from potato and scopolia leaves, respectively, have been found. This might be explained by their belonging to the same family (Solanaceae). Other spectral differences among genomic plant DNAs have also been observed.

These findings demonstrate that Raman spectroscopy may be exploited to distinguish different plant genomic DNAs.

The present study provides a basis for future use of Raman spectroscopy to analyze specific plant DNA–ligand interactions or DNA structural changes induced by plants' stress conditions associated with their natural environment.
Structural analysis of DNA and RNA interactions with antioxidant flavonoids
Authors: Kanakis C. D. , Nafisi Sh. , Rajabi Mehdi , Shadaloi Azadeh , Tarantilis P. A. , Polissiou M. G. , Bariyanga J. , Tajmir-Riahi H. A.
Published: April 2012

Flavonoids are natural polyphynolic compounds with major antioxidant activity that can prevent DNA damage. The anticancer and antiviral activities of these natural products are attributed to their potential biomedical applications. In this review we are examining how the antioxidant flavonoids bind DNA and RNA and what mechanism of action is involved in preventing DNA damage. Detailed spectroscopic data on the interactions of morin (mor), apigenin (api), naringin (nar), quercetin (que), kaempferol (kae) and delphinidin (del) with DNA and transfer RNA in aqueous solution at physiological conditions were analysed. The structural analysis showed flavonoids mainly intercalate into DNA and RNA duplexes with minor external binding to the major or minor groove and the backbone phosphate group with overall binding constants for DNA adducts Kmor═5.99×103M–1, Kapi═7.10×104M–1, and Knar═3.10×103M–1, Kque═7.25×104M–1, Kkae═3.60×104M–1and Kdel═1.66×104M–1, and for tRNA adducts Kmor═9.15×103M–1, Kapi═4.96×104M–1, and Knar═1.14×104M–1, Kque═4.80×104M–1, Kkae═4.65×104M–1and Kdel═9.47×104M–1. The stability of adduct formation is in the order of que > api > kae > del >mor > nar for DNA and del > api > que > kae > nar > mor for tRNA. Low flavonoid concentration induces helical stabilization, whereas high pigment content causes helix opening. Flavonoids induce a partial B to A–DNA transition at high pigment concentration, while tRNA remains in A-family structure upon flavonoid complexation. The antioxidant activity of flavonoids changes in the order delphinidin > quercetin > kaempferol > morin > naringin > apigenin. The results show intercalated flavonoid molecule can act as an antioxidant and prevent DNA damage.
Inclusion compound of Fosinopril withβ-cyclodextrin
Authors: Bratu I. , Kacso Irina , Borodi Gh. , Constantinescu Daniela E. , Dragan Felicia
Published: April 2012

Solid state interactions of bioactive substance (4-cyclohexyl-1-[2-[(2-methyl-1-propanoyloxy-propoxy)-(4-phenylbutyl)phosphoryl]acetyl]-pyrrolidine-2-carboxylic acid, called Fosinopril), withβ-cyclodextrin (β-CD), the so-called inclusion compounds of a bioactive (cardiovascular) drug is obtained by different preparation methods: kneading, co-precipitation and freeze-drying. The so obtained compounds were investigated by FTIR spectroscopy, X-ray diffraction method, and differential scanning calorimetric measurements (DSC) to evidence their formation. X-ray diffraction patterns show that the inclusion compound was obtained for kneaded, co-precipitation and freeze-dried products. The crystalline/amorphous degree for these compounds was also investigated. Molecular modeling (MM+ molecular mechanics) shows the spatial architecture of the inclusion compound in good agreement with FTIR experimental data: the drug is included with the propanoyloxy-propoxy group insideβ-cyclodextrin cavity. These findings may constitute a direct contribution to the molecular encapsulation of Fosinopril intoβ-cyclodextrin, improving Fosinopril stability and bioavailability of the drug, also.
Determination of sucrose concentration in lemon-type soft drinks by dispersive Raman spectroscopy
Authors: Silveira Jr. Landulfo , Moreira Leonardo Marmo , Conceição Viviane G. B. , Casalechi Heliodora L. , Muñoz Ingrid S. , Da Silva Fabiano Fernandes , Silva Marcos Augusto S. R. , De Souza Renato Aparecido , Pacheco Marcos Tadeu T.
Published: April 2012

The objective of this study was to quantify the sucrose amount in commercial lemon-type soft drinks through dispersive Raman spectroscopy, comparing the amount listed in the nutritional table of each product to the predicted by a least-square model, in order to obtain a method for quality assurance applied to soft drinks. A dispersive Raman spectrometer was employed using 830 nm laser and imaging spectrograph coupled to a CCD camera, and a total of 48 samples from four brands of lemon-type soft drinks were analyzed. A calibration curve using sucrose from refined sugar (sugarcane) diluted in spring water was elaborated in the range between 0 and 15.0 g/100 ml, and a quantification model based on Partial Least Squares (PLS) regression was developed to correlate the Raman spectra and the amount of sucrose in each dilution. Then, the sucrose in each soft drink sample was predicted employing the calibration curve. The mean error of calibration for the PLS method was 0.30 g/100 ml (3.0%). Results indicated that soft drinks samples have predicted sugar content ranging from 8.1 to 10.9 g/100 ml, with an error of the predicted value compared to the nutritional table ranged from 1.1% to 5.5%. Therefore, Raman spectroscopy in association with PLS regression was an effective method for quantifying the sucrose, with small prediction error. Thus, the present work allows to infer auspicious possibilities of Raman spectroscopy application in the quantification of relevant nutritional facts in beverages.
Zn2+–DNA interactions in aqueous systems: A Raman spectroscopic study
Authors: Muntean Cristina M. , Nalpantidis Konstantinos , Feldmann Ingo , Deckert Volker
Published: April 2012

The influence of Zn2+ions on the structure of natural calf thymus DNA was studied by Raman spectroscopy. Measurements were done at room temperature and pH 6.2±0.1, in the presence of 10 mM Na+, and of Zn2+in a concentration range varying between 0 and 250 mM, respectively. No condensation of DNA was observed.

As judging from the marker bands near 681 cm−1(dG), 729 cm−1(dA), 752 cm−1(dT), and 787 cm−1(dC, dT) altered nucleoside conformations in these residues are supposed to occur, in different intervals of Zn2+ions concentration. Changes in the conformational marker centered around 835 cm−1, upon Zn2+binding to DNA, were detected. Binding of zinc(II) ions to the charged phosphate groups of DNA, stabilizing the double helical structure, is indicated in the spectra. We have found that binding of metal ions at N3 of cytosine takes place at zinc(II) concentrations between 150–250 mM and interaction of Zn2+ions with adenine is observed in a concentration range from 10 to 250 mM. Binding of zinc(II) ions to N7 of guanine and, possibly, in a lesser extent to adenine was also observed as indicated by the Raman marker bands near 1490 and 1581 cm−1. There is no intensity change of the band at 1668 cm−1, suggesting no change in their base pairing and no change induced in the structure of water by Zn2+cations. No evidence for DNA melting was identified.
Quantification of isonicotinoyl lactosyl hydrazone in oral pharmaceutical dosage forms
Authors: Córdoba-Díaz D. , Córdoba-Díaz M. , Elorza B.
Published: April 2012

Isoniazid, one of the most important drugs for the chempublisher-idapy of tuberculosis, can react with some widely used pharmaceutical excipients, like lactose, leading to the formation of hydrazones. This interaction can dramatically modify the oral bioavailability of the drug, what could lead to a failure of the treatment. Some analytical methods, including techniques like HPLC, can be used to quantify this type of products, but all of them are tedious and time-consuming. In this sense, the aim of the present work is to develop a sensitive, rapid and cheap alternative to publisher-id published methods. For this reason, two spectrophotometric methods were developed and validated. In the first one, isoniazid and its lactosyl-hydrazone were measured together. The second one involved a reaction between not bound to lactose isoniazid and 2,3-dichloro-1,4-naphthoquinone. Lactosyl-hydrazone is quantified by comparison of the results obtained from both methods. The linearity is confirmed to be within a range of 1.5–30.0 μg/ml of total isoniazid and 0.5–30.0 μg/ml of “free” isoniazid. Limits of quantification of 1.2 μg/ml and 0.3 μg/ml were obtained for bound and free isoniazid respectively. These results indicated that the here described methods are at least, as sensitive and accurate as the vast majority of the previously published chromatographic methods. This methodology shows a good repeatability (RSD below 2.0%) as well as good accuracy (average recoveries of 100.83% and 99.96% for total and free isoniazid respectively). The results obtained from the assay of isoniazid tablets demonstrated that the proposed method constitutes a clear alternative to chromatographic methods and also to the official titration method. It would be of interest for the routine quality control of oral dosage forms containing isoniazid and lactose and for stability studies.