Home About us Contact
|
Home About us Contact | ||
|
|
||
Spectral Profiles (spectral + profile)
Selected AbstractsSpectrum separation resolves partial-volume effect of MRSI as demonstrated on brain tumor scansNMR IN BIOMEDICINE, Issue 10 2008Yuzhuo Su Abstract Magnetic resonance spectroscopic imaging (MRSI) is currently used clinically in conjunction with anatomical MRI to assess the presence and extent of brain tumors and to evaluate treatment response. Unfortunately, the clinical utility of MRSI is limited by significant variability of in vivo spectra. Spectral profiles show increased variability because of partial coverage of large voxel volumes, infiltration of normal brain tissue by tumors, innate tumor heterogeneity, and measurement noise. We address these problems directly by quantifying the abundance (i.e. volume fraction) within a voxel for each tissue type instead of the conventional estimation of metabolite concentrations from spectral resonance peaks. This ,spectrum separation' method uses the non-negative matrix factorization algorithm, which simultaneously decomposes the observed spectra of multiple voxels into abundance distributions and constituent spectra. The accuracy of the estimated abundances is validated on phantom data. The presented results on 20 clinical cases of brain tumor show reduced cross-subject variability. This is reflected in improved discrimination between high-grade and low-grade gliomas, which demonstrates the physiological relevance of the extracted spectra. These results show that the proposed spectral analysis method can improve the effectiveness of MRSI as a diagnostic tool. Copyright © 2008 John Wiley & Sons, Ltd. [source] NMR and Luminescence Binding Studies of Ytterbium, Thulium, and Europium Macrocyclic Complexes with Phosphorus(V) Oxy AnionsHELVETICA CHIMICA ACTA, Issue 3 2005Paul Atkinson The binding of a series of phosphate anions to coordinatively unsaturated macrocyclic complexes of Yb, Tm, and Eu was studied by 1H-NMR, emission and circularly polarized luminescence (CPL) spectroscopy. Each ternary adduct was distinguished by its spectral profile. With O -phosphorylated amino acids and peptides, chemoselective ligation of the phosphate moiety was favored by Eu over chelation involving the terminal amino group, which was competitive for Tm and Yb. A preference for binding O -phosphono- L -tyrosine sites was found with various Eu complexes, and was signalled by ratiometric changes in metal-based emission and CPL spectra. [source] Discrimination of cyanobacterial strains isolated from saline soils in Nakhon Ratchasima, Thailand using attenuated total reflectance FTIR spectroscopyJOURNAL OF BIOPHOTONICS, Issue 8-9 2010Somchanh Bounphanmy Abstract A method was developed whereby high quality FTIR spectra could be rapidly acquired from soil-borne filamentous cyanobacteria using ATR FTIR spectroscopy. Spectra of all strains displayed bands typical of those previously reported for microalgae and water-borne cyanobacteria, with each strain having a unique spectral profile. Most variation between strains occurred in the C,O stretching and the amide regions. Soft Independent Modelling by Class Analogy (SIMCA) was used to classify the strains with an accuracy of better than 93%, with best classification results using the spectral region from 1800,950 cm,1. Despite this spectral region undergoing substantial changes, particularly in amide and C,O stretching bands, as cultures progressed through the early-, mid- to late-exponential growth phases, classification accuracy was still good (,80%) with data from all growth phases combined. These results indicate that ATR/FTIR spectroscopy combined with chemometric classification methods constitute a rapid, reproducible, and potentially automated approach to classifying soil-borne filamentous cyanobacteria. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Ionic and electronic processes in non-linear optical crystalsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2005Igor N. Ogorodnikov Abstract The paper presents the results of a study of the formation and decay of lattice defects in nonlinear optical crystals of NH4H2PO4 (ADP), KH2PO4 (KDP), Li2B4O7 (LTB) and LiB3O5 (LBO) with a sublattice of mobile hydrogen (ADP, KDP) and lithium (LTB, LBO) cations. By means of the luminescent and absorption optical spectroscopy with (the) a nanosecond time resolution under excitation with an electron beam, it was revealed that the optical absorption of these crystals in the visible and UV spectral ranges is produced by optical hole-transitions from the local defect level to the valence band states. The valence band density of the states determines the optical absorption spectral profile, and the relaxation kinetics is rated by the interdefect radiationless tunnel recombination between the trapped hole center and the H0 and Li0 electron trapped centers. At 290 K, the H0 and Li0 centers are subject to thermally stimulated migration. All manifestations of a radiative recombination observed in these crystals are accounted for by the involvement of additional electronic and hole centers of a different nature in the recombination process. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Tris-Cyclometalated Iridium(III) Complexes of Carbazole(fluorenyl)pyridine Ligands: Synthesis, Redox and Photophysical Properties, and Electrophosphorescent Light-Emitting DiodesCHEMISTRY - A EUROPEAN JOURNAL, Issue 5 2007Sylvia Bettington Dr. Abstract Using ligands synthesized by Suzuki cross-coupling methodology, new phosphorescent homoleptic tris-cyclometalated complexes have been obtained, namely fac -[Ir(Cz-2-FlnPy)3] (1,d,f) and fac -[Ir(Cz-3-FlnPy)3] (2,d,f), which are solution-processible triplet emitters (Cz denotes N -hexylcarbazole, n is the number of 9,9,-dihexylfluorene (Fl) units (n=0,1,2) and Py is pyridine). In all cases, Py and Fl are substituted at the 2- and 2,7-positions, respectively, and Cz moieties are substituted by either Py or Fl at the 2- or 3-positions, in series 1 and 2, respectively. The oxidation potential of 1,d studied by cyclic voltammetry (=0.14,V, versus Ag/AgNO3, CH2Cl2) is less positive (i.e. raised HOMO level) compared to that of the isomer 2,d (=0.30,V), where the Cz-nitrogen is meta to the Ir center. Ligand-centered oxidations occur at more positive potentials, leading to 7+ oxidation states with good chemical reversibility and electrochemical quasi-reversibility, for example, for 2,f =0.45 (1e), 0.95 (3e), 1.24,V (3e). Striking differences are seen in the solution-state photophysical data between complexes [Ir(Cz-2-Py)3] (1,d) and [Ir(Cz-3-Py)3] (2,d), in which the Cz moiety is bonded directly to the metal center: for the latter there is an 85,nm blue-shift in emission, a decrease in the luminescence lifetime and an increase in the PLQY value. Organic light emitting devices were made by spin-coating using polyspirobifluorene:bis(triphenyl)diamine (PSBF:TAD) copolymer as host and the complexes 1,d or 2,d as dopants. Turn-on voltages are low (3,4,V). With 1,d orange light is emitted at ,max=590,nm with an EQE of 1.3,% (at 7.5,mA,cm,2) and an emission intensity (luminance) of 4354,cd,m,2 (at 267,mA,m,2). The green emission from 2,d devices (,max=500,nm) is due to the reduced electron-donating ability of the carbazole unit in 2,d. Recording the EL spectra of the 1,d device at 6,V (current density, 100,mA,cm,2) established that the time to half brightness was about 9,h under continuous operation with no change in the spectral profile, confirming the high chemical stability of the complex. [source] A study on the spectral changes of reactive textile dyes and their implications for online control of dyeing processesCOLORATION TECHNOLOGY, Issue 1 2009Jorge G Santos Evidence is presented that confirms the colour changes of a widely used trichromatic mixture of bifunctional reactive dyes (Levafix CA) under alkaline conditions, showing that they occur slowly and throughout the dyeing time, and not instantly after alkali addition to the dyebath. Thus, it is impossible to determine the specific absorptivity of the dyes at each moment of the dyeing process. An investigation into the relationship of the type of reactive group to the dye and the visible spectral changes over time was undertaken. Model reactive dyes were studied. The samples collected from the simulated dyebaths were monitored online using an automated system and their absorption on the whole of the visible spectrum was measured. The studies of dyes that included halo- s -triazinyl groups revealed the existence of hypochromic shifts in the spectra of the dyes in the presence of an electrolyte (sodium chloride or sodium sulphate) and bathochromic and hyperchromic shifts, when evaluated in the presence of alkaline agents. However, the vinylsulphonyl derivatives present a more stable spectral profile. The use of buffer solution at pH 5 was an efficient method to stabilise the absorption profile of Levafix CA trichromatic samples. [source] Noise propagation and error estimations in multivariate curve resolution alternating least squares using resampling methodsJOURNAL OF CHEMOMETRICS, Issue 7-8 2004Joaquim Jaumot Abstract Different approaches for the calculation of prediction intervals of estimations obtained in multivariate curve resolution using alternating least squares optimization methods are explored and compared. These methods include Monte Carlo simulations, noise addition and jackknife resampling. Obtained results allow a preliminary investigation of noise effects and error propagation on resolved profiles and on parameters estimated from them. The effect of noise on rotational ambiguities frequently found in curve resolution methods is discussed. This preliminary study is shown for the resolution of a three-component equilibrium system with overlapping concentration and spectral profiles. Copyright © 2004 John Wiley & Sons, Ltd. [source] Resolution of two-way data from spectroscopic monitoring of reaction or process systems by parallel vector analysis (PVA) and window factor analysis (WFA): inspection of the effect of mass balance, methods and simulationsJOURNAL OF CHEMOMETRICS, Issue 3 2003Jian-Hui Jiang Abstract The effect of mass balance on the analysis of two-way data of reaction or process systems is investigated. It is shown that the rank-deficient species-related bilinear model can be converted to a full-rank reaction-related bilinear model, and in general situations the chemical rank for a system is the number of reactions plus one. Two slightly modified procedures are thus suggested to extract the spectral subspaces essential for resolution and to ascertain the number of reactions in different time domains. Based on the reaction-related bilinear model, a procedure of window factor analysis (WFA) is implemented for resolving the extent curves of reactions. A new two-way resolution approach, parallel vector analysis (PVA), is also developed. The idea of PVA is to construct a set of subspaces comprising only one common (spectral) component and then find a vector that is in parallel with a series of vectors coming from different subspaces. With suitably constructed subspaces the PVA procedure offers a versatile avenue to approach the unique resolution of spectral profiles. A four-component system which comprises four different processes or reactions is simulated. Results obtained reveal that favorable resolution is achieved for the spectral and concentration profiles by the suggested procedures of WFA and PVA. Copyright © 2003 John Wiley & Sons, Ltd. [source] Comparison of basis set effects and the performance of ab initio and DFT methods for probing equilibrium fluctuationsJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 2 2007Ross C. Walker Abstract The electronic absorption and emission spectra of large molecules reflect the extent and timescale of electron-vibration coupling and therefore the extent and timescale of relaxation/reorganization in response to a perturbation. In this paper, we present a comparison of the calculated absorption and emission spectra of NADH in liver alcohol dehydrogenase (LADH), using quantum mechanical/molecular mechanical methods, in which we vary the QM component. Specifically, we have looked at the influence of basis set (STO-3G, 3-21G*, 6-31G*, CC-pVDZ, and 6-311G**), as well as the influence of applying the DFT TD-B3LYP and ab initio TD-HF and CIS methods to the calculation of absorption/emission spectra and the reorganization energy (Stokes shift). The ab initio TD-HF and CIS methods reproduce the experimentally determined Stokes shift and spectral profiles to a high level of agreement, while the TD-B3LYP method significantly underestimates the Stokes shift, by 45%. We comment on the origin of this problem and suggest that ab initio methods may be naturally more suited to predicting molecular behavior away from equilibrium geometries. © 2006 Wiley Periodicals, Inc. J Comput Chem 28: 478,490, 2007 [source] Rapid Profiling of Swiss Cheese by Attenuated Total Reflectance (ATR) Infrared Spectroscopy and Descriptive Sensory AnalysisJOURNAL OF FOOD SCIENCE, Issue 6 2009N.A. Kocaoglu-Vurma ABSTRACT:, The acceptability of cheese depends largely on the flavor formed during ripening. The flavor profiles of cheeses are complex and region- or manufacturer-specific which have made it challenging to understand the chemistry of flavor development and its correlation with sensory properties. Infrared spectroscopy is an attractive technology for the rapid, sensitive, and high-throughput analysis of foods, providing information related to its composition and conformation of food components from the spectra. Our objectives were to establish infrared spectral profiles to discriminate Swiss cheeses produced by different manufacturers in the United States and to develop predictive models for determination of sensory attributes based on infrared spectra. Fifteen samples from 3 Swiss cheese manufacturers were received and analyzed using attenuated total reflectance infrared spectroscopy (ATR-IR). The spectra were analyzed using soft independent modeling of class analogy (SIMCA) to build a classification model. The cheeses were profiled by a trained sensory panel using descriptive sensory analysis. The relationship between the descriptive sensory scores and ATR-IR spectra was assessed using partial least square regression (PLSR) analysis. SIMCA discriminated the Swiss cheeses based on manufacturer and production region. PLSR analysis generated prediction models with correlation coefficients of validation (rVal) between 0.69 and 0.96 with standard error of cross-validation (SECV) ranging from 0.04 to 0.29. Implementation of rapid infrared analysis by the Swiss cheese industry would help to streamline quality assurance. [source] A SERS probe of adenyl residues available for intermolecular interactions.JOURNAL OF RAMAN SPECTROSCOPY, Issue 11 2001Part I, adenyl, fingerprint' This work validated a SERS probe able to compare adenyl reactivity in DNA and RNA. A Creighton silver colloid including adenine (A) [or 2, -deoxyadenosine 5, -phosphate (pdA)] from 2 × 10,3 to 2 × 10,8M is stabilized in the absence or presence of chloride. Concentration-dependent SER spectral profiles reveal how A may interact with (Ag)n+ sites. At concentration ,2 × 10,5M adsorption of (A)n clusters prevents the colloid from undergoing salt effects. Adsorption via N1/N3 is allowed whereas C6NH2 is involved in self-association. At [A] <2 × 10,5M with chloride, hydrogen bonding between chloride and the C6NH2 group enhances C6N electronegativity, which assists C6N/N7 cooperative adsorption. Complex A(Cl,) entities compete with individual chloride ions for adsorption on silver. Very similar C6N/N7 adenyl adsorption occurs for pdA but only above 2 × 10,5M. Chloride,adenyl bonding is reduced and pdA self-association is weaker than adenine self-association. Steric factors, repulsive electrostatic forces and phosphate competitive reactivity with respect to chloride may explain the much higher pdA concentration needed to saturate the silver surface compared with A. Mg2+,phosphate complexation entails concentration-dependent opposite effects on adenyl reactivity with (Ag)n+ sites. Cytosine, thymine and guanine base or corresponding nucleotides deliver weaker SER spectra and much higher SERS responses for chloride adsorption compared with A or pdA. This reveals a weaker adsorption of the oxo bases, assumed to result from alternative oxo and nitrogen interactions with the (Ag)n+ sites. Copyright © 2001 John Wiley & Sons, Ltd. [source] Medium molecular weight polar substances of the cuticle as tools in the study of the taxonomy, systematics and chemical ecology of tropical hover wasps (Hymenoptera: Stenogastrinae)JOURNAL OF ZOOLOGICAL SYSTEMATICS AND EVOLUTIONARY RESEARCH, Issue 2 2010David Baracchi Abstract The Stenogastrinae wasps have been proposed as a key group for an understanding of social evolution in insects, but the phylogeny of the group is still under discussion. The use of chemical characters, in particular cuticular hydrocarbons, for insect taxonomy is relatively recent and only a few studies have been conducted on the cuticular polar substances. In this work, we ascertain, by the matrix-assisted laser desorption ionization-time of flight mass spectrometry technique, that different species of primitively eusocial hover wasps have different compositions of the epicuticular polar compounds ranging from 900 to 3600 Da. General linear model analysis and discriminant analysis showed that the average spectral profiles of this fraction can be diagnostic for identification of the species. Moreover, for the first time we show population diversification in the medium MW polar cuticular mixtures in insects. In conclusion, the results demonstrate that the chemical characters are consistent with the physical characters and the study support the importance of medium MW polar substances as powerful tools for systematics (chemosystematics) and chemical ecology (fertility signal and population characterization) in a primitively social insect taxon. Riassunto Le vespe primitivamente eusociali della sottofamiglia delle Stenogastrinae sono state proposte come gruppo chiave per lo studio dell'evoluzione della socialità negli insetti. Ancora oggi, però, la filogenesi del gruppo rimane incerta e discussa. Sebbene l'uso dei caratteri chimici, e in particolare degli idrocarburi cuticolari, negli studi tassonomici sugli insetti sia ben noto, seppur di recente applicazione, sono ancora pochi gli studi condotti sulle sostanze cuticolari di natura polare. In questo lavoro abbiamo saggiato, mediante tecniche di spettrometria di massa (MALDI-TOF MS), la presenza di composti polari cuticolari di massa compresa tra i 900 e i 3600 (probabilmente provenienti dal veleno) sulla cuticola di alcune specie di vespe stenogastrine. Analisi statistiche multivariate hanno dimostrato che lo spettro medio dei profili chimici nel range da noi indagato può essere utilizzato per l'identificazione delle specie e la nostra ricerca propone questo metodo come un potente strumento non solo per studi di tassonomia (chemotassonomia) ma anche per studi di sistematica e di ecologia chimica (es. segnali di fertilità e differenze intra-popolazioni) nei taxon di insetti primitivamente eusociali. [source] Comparative analysis of virulence determinants and mass spectral profiles of Finnish and Lithuanian endodontic Enterococcus faecalis isolatesMOLECULAR ORAL MICROBIOLOGY, Issue 2 2007A. Reynaud af Geijersstam Introduction:, Putative virulence factors of Enterococcus faecalis have been proposed by several workers and, by analogy, these have been linked to strains of endodontic origin. However, their distribution within the cell population is unknown. In the present study, isolates were taken from the dental root canals of two defined human populations, Lithuanian and Finnish, and examined for a range of virulence properties. In addition, surface-associated molecules and intracellular proteins were compared using matrix-assisted laser desorption-ionization/mass spectrometry (MALDI-TOF-MS) and ProteinChipTM capture/MS (SELDI-TOF-MS), respectively. Methods:, Twenty-three Lithuanian and 35 Finnish dental root canal isolates were included. The esp, gelE, ace and efaA genes were detected by polymerase chain reaction, and cytolysin and gelatinase phenotypes were determined by hydrolysis of horse blood agar and gelatine agar, respectively. Protein extracts and surface-associated molecules of whole cells were analysed by SELDI-TOF-MS and MALDI-TOF-MS, respectively. Results:, Presence of esp (n = 15), cytolysin (n = 9), ace (n = 55) and efaA (n = 58) was not statistically different in the two samples, whereas gelE and gelatinase production was detected more frequently in the Finnish material (chi-squared, P < 0.01). Analysis of protein profiles by SELDI-TOF-MS showed clustering of cytolysin-producing strains, whereas MALDI-TOF-MS generated profiles that clustered according to the samples' origin and, furthermore, to atypical quinupristin,dalfopristin susceptibility. Conclusion:, A high prevalence of virulence factors was demonstrated in both population types. SELDI-TOF-MS and MALDI-TOF-MS proved useful in distinguishing between different E. faecalis phenotypes and they may be useful technologies for elucidating the eco-distribution of E. faecalis in humans. [source] Preinvasive and invasive cervical cancer: an ex vivo proton magic angle spinning magnetic resonance spectroscopy studyNMR IN BIOMEDICINE, Issue 3 2004Marrita M. Mahon Abstract The aim of this study was to obtain 1H MR spectra using magic angle spinning (MAS) techniques from punch biopsies (<20,mg) of preinvasive and invasive cervical disease and to correlate the spectral profiles with sample classification on the basis of histopathology. Tissue samples were obtained at colposcopic examination, during local treatment of cervical intraepithelial neoplasia (CIN) or at hysterectomy. 1H MAS MRS was performed at 25°C while spinning the sample at 4.5,kHz. After measurement, the tissue was immersed in formalin and the pathology determined. Histological examination after 1H MAS MRS defined 27 samples with squamous cell carcinoma (SCC), 12 with CIN and 39 with only normal tissue. The standardized integrals of the lipid, choline and creatine regions of the spectra were significantly higher in SCC than in normal or CIN tissue. There was no obvious difference in the standardized integral of the region 4.15,3.5,ppm. The acyl fatty acid side-chain length was longer or less unsaturated in SCC than in normal tissue. Normal tissue from patients with SCC showed significantly higher triglycerides than normal tissue from patients with benign uterine disease but significantly lower triglycerides than SCC tissue. 1H MAS MRS of the uterine cervix ex vivo may be used to differentiate non-invasive from invasive cervical lesions, increase interpretation of in vivo MRS and provide insights into tumor biology. Copyright © 2004 John Wiley & Sons, Ltd. [source] Linkage position and residue identification of disaccharides by tandem mass spectrometry and linear discriminant analysisRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 10 2008Hui Zhang The discrimination of isomeric disaccharides with different linkage types and different monosaccharide residues , glucose (Glc), galactose (Gal), and mannose (Man) at the non-reducing end , was investigated with tandem mass spectrometry (MS/MS) and linear discriminant analysis (LDA). Conventional matrix-assisted laser desorption/ionization (MALDI)-MS has strong interference peaks from matrix ions in the low mass region (<500,Da). This greatly limits the application of MALDI-MS for the analysis of small molecules such as saccharides. We solved this problem by using LDI with acidic fullerene matrix, which gives a very clean background in the low-mass region. Disaccharides with different linkage types give different tandem mass spectral profiles from various cross-ring fragmentation pathways. Disaccharides with the same linkage type but with three different kinds of monosaccharide residues bear the same fragmentation profiles. However, the relative ratios of the fragment ion intensities were found to be distinctly different among the three disaccharide isomers. By employing statistical tools such as LDA to classify the tandem mass spectra, disaccharide isomers with either different linkages or different monosaccharide residues were successfully classified. Copyright © 2008 John Wiley & Sons, Ltd. [source] Mass spectrometry study of hemoglobin-oxaliplatin complexes in colorectal cancer patients and potential association with chemotherapeutic responsesRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 17 2006Rupasri Mandal Oxaliplatin is the most active platinum (Pt)-containing anticancer drug for the treatment of advanced colorectal cancer. We report here the study of potential association of the levels of oxaliplatin-protein complexes in 19 cancer patients with treatment efficacy using size-exclusion high-performance liquid chromatography with inductively coupled plasma mass spectrometry (HPLC/ICPMS) and nanoelectrospray ionization mass spectrometry (nanoESI-MS) techniques. Blood samples from 19 colorectal cancer patients were collected at 1 and 48,h after the first infusion of oxaliplatin. HPLC/ICPMS quantification of the oxaliplatin-protein complexes showed that the levels of Pt-protein complexes in plasma samples at 48,h were reduced by approximately 50% compared to those at 1,h, whereas those in hemolysates did not change significantly. The concentrations of hemoglobin (Hb)-oxaliplatin complexes determined by HPLC/ICPMS ranged from 3.1 to 8.7,µM. NanoESI-MS analysis of the patient hemolysates showed three distinct mass spectral profiles of the Hb-oxaliplatin complexes: (1) 1:1, (2) 1:1 with 1:2, and (3) multiple complexes of 1:1, 1:2, 1:3, and 1:4, corresponding to the Hb-oxaliplatin complex concentrations determined by HPLC/ICPMS. Potential association of variables including Hb-oxaliplatin complex concentrations with time to progress as the treatment efficacy indicator was analyzed using the Cox model. Multivariate analysis of the potential predictors showed that the statistically significant variables were Hb-oxaliplatin complex concentration (p,=,0.02), performance status (p,=,0.02), baseline neutrophil count (p,=,0.05), and the site of the primary cancer (colon vs. rectal, p,=,0.01). The hazard ratio for the concentration of the Hb-oxaliplatin complexes was 2.4, suggesting that the risk of cancer progression significantly increased with increasing of Hb-oxaliplatin complexes in patients. These results demonstrate that the level of the Hb-oxaliplatin complexes in erythrocytes is a potential biomarker for indicating inter-patient variations in oxaliplatin treatment efficacy. Copyright © 2006 John Wiley & Sons, Ltd. [source] | |||||||||||||