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Spectroscopic Signature (spectroscopic + signature)
Selected AbstractsTriplex Au,Ag,C Core,Shell Nanoparticles as a Novel Raman LabelADVANCED FUNCTIONAL MATERIALS, Issue 6 2010Aiguo Shen Abstract Monodispersed, readily-grafted, and biocompatible surface-enhanced Raman spectroscopic (SERS) tagging materials are developed; they are composed of bimetallic Au@Ag nanoparticles (NPs) for optical enhancement, a reporter molecule for spectroscopic signature, and a carbon shell for protection and bioconjugation. A controllable and convenient hydrothermal synthetic route is presented to synthesize the layer-by-layer triplex Au,Ag,C core,shell NPs, which can incorporate the Raman-active label 4-mercapto benzoic acid (4-MBA). The obtained gold seed,silver coated particles can be coated further with a thickness-controlled carbon shell to form colloidal carbon-encapsulated Aucore/Agshell spheres with a monodisperse size distribution. Furthermore, these SERS-active spheres demonstrated interesting properties as a novel Raman tag for quantitative immunoassays. The results suggest such SERS tags can be used for multiplex and ultrasensitive detection of biomolecules as well as nontoxic, in vivo molecular imaging of animal or plant tissues. [source] A near-infrared spectroscopic investigation of relative density and crushing strength in four-component compactsJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 3 2009Steven M. Short Abstract Near-infrared spectroscopy (NIRS) is commonly employed for the analysis of chemical and physical attributes of intact pharmaceutical compacts. Specifically, NIRS has proven useful in the nondestructive measurement of tablet hardness or crushing strength. Near-infrared (NIR) reflectance and transmittance spectra were acquired for 174 13-mm compacts, which were produced according to a four-constituent mixture design (29 points) composed of anhydrous theophylline, lactose monohydrate, microcrystalline cellulose, and soluble starch. Six compacts were produced for each design point by compacting at multiple pressures. Physical testing and regression analyses were used to model the effect of variation in relative density (and crushing strength) on NIR spectra. Chemometric analyses demonstrated that the overall spectral variance was strongly influenced by anhydrous theophylline as a result of the experimental design and the component's spectroscopic signature. The calibration for crushing strength was more linear than the relative density model, although accuracy was poorer in comparison to the density model due to imprecision of the reference measurements. Based on the consideration of reflectance and transmittance measurements, a revised rationalization for NIR sensitivity to compact hardness is presented. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:1095,1109, 2009 [source] Study of the ,Raman spectroscopic signature of life' in mitochondria isolated from budding yeastJOURNAL OF RAMAN SPECTROSCOPY, Issue 1 2010Liang-da Chiu Abstract The ,Raman spectroscopic signature of life' is a Raman band at 1602 cm,1 that sharply reflects the metabolic activity of cell mitochondria. Here we report the study of thissignature in isolated yeast mitochondria. The existence and behaviour of the 1602 cm,1 band in isolated mitochondria have been confirmed to be the same as in living yeast cells: the intensity of the band decreases with timewhen a respiration inhibitor, sodium azide, is added. The present study shows the significance of isolated mitochondria in elucidating the origin of this still unassigned Raman band. Copyright © 2009 John Wiley & Sons, Ltd. [source] Raman spectroscopic signature of life in a living yeast cellJOURNAL OF RAMAN SPECTROSCOPY, Issue 7 2004Yu-San Huang Abstract We have discovered a Raman spectroscopic signature that sharply reflects the metabolic activity of a mitochondrion in a living yeast cell. Raman mapping experiments on a GFP-labeled yeast cell showed that this signature originated exclusively from mitochondria. Addition of KCN caused a rapid decrease and subsequent disappearance of the signature followed by gradual changes of the phospholipid Raman bands, indicating that respiration was first inhibited by KCN and then lowered metabolic activity gradually deteriorated the double-membrane structure of a mitochondrion. We can now monitor the life and death of a single cell by time- and space-resolved Raman spectroscopy. Copyright © 2004 John Wiley & Sons, Ltd. [source] Solvent dependent study of carbonyl vibrations of 3-phenoxybenzaldehyde and 4-ethoxybenzaldehyde by Raman spectroscopy and ab initio calculationsJOURNAL OF RAMAN SPECTROSCOPY, Issue 8 2009Veerabahu Ramakrishnan Abstract A Raman spectroscopy investigation of the carbonyl stretching vibrations of 3-phenoxybenzaldehye (3Phbz) and 4-ethoxybenzaldeheyde (4Etob) was carried out in binary mixtures with different polar and nonpolar solvents. The purpose of this study was twofold: firstly, to describe the interaction of the carbonyl groups of two solute molecules in terms of a splitting in the isotropic and anisotropic components and secondly, to analyze their spectroscopic signatures in a binary mixture. Changes in wavenumber position, variation in the anisotropic shift and full width half maximum were investigated for binary mixtures with different mole fractions of the reference systems. In binary mixtures, the observed increase in wavenumber with solvent concentration does not show linearity, indicating the significant role of molecular interactions on the occurrence of breaking of the self-association of the solute. In all the solvents, a gradual decrease in the anisotropic shift reflects the progressive separation of the coupled oscillators with dilution. ,i(,c), 3Phbz,solvent mixtures, exhibit a gradual decrease with decrease in the concentration of the solute which is an evidence on the influence of micro viscosity on linewidth. For 4Etob, the carbonyl stretching vibration shows two well-resolved components in the Raman spectra, attributed to the presence of two distinct carbonyl groups: hydrogen-bonded and free carbonyl groups. The intensity ratio of the carbonyl stretching vibration of these two types of carbonyl groups is studied to understand the dynamics of solute/solvent molecules owing to hydrogen bond interactions. Ab initio calculations were employed for predicting relevant molecular structures in the binary mixtures arising from intermolecular interactions, and are related to the experimental results. Copyright © 2009 John Wiley & Sons, Ltd. [source] Establishing the nature of companion candidates to X-ray-emitting late B-type stars,MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2007S. Hubrig ABSTRACT The most favoured interpretation for the detection of X-ray emission from late B-type stars is that these stars have a yet undiscovered late-type companion (or an unbound nearby late-type star) that produces the X-rays. Several faint infrared objects at (sub)arcsecond separation from B-type stars have been uncovered in our earlier adaptive optics imaging observations, and some of them have been followed up with the high spatial resolution of the Chandra X-ray observatory, pinpointing the X-ray emitter. However, firm conclusions on their nature require a search for spectroscopic signatures of youth. Here we report on our recent ISAAC observations carried out in low-resolution spectroscopic mode. Equivalent widths have been used to obtain information on spectral types of the companions. All eight X-ray-emitting systems with late B-type primaries studied contain dwarf-like companions with spectral types later than A7. The only system in the sample where the companion turns out to be of early spectral type is not an X-ray source. These results are consistent with the assumption that the observed X-ray emission from late B-type stars is produced by an active pre-main-sequence companion star. [source] Theoretical resonant Raman spectra of nanotube (7,0) with point defectsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 11-12 2009Valentin N. Popov Abstract The Raman spectra of the nanotube (7,0) with point defects (monovacancy, divacancy, and Stone,Wales defect) were simulated in order to derive spectroscopic signatures of defective nanotubes. First, we calculated the electronic band structure and the phonon dispersion of the defective nanotubes using supercells within a non-orthogonal tight-binding model. We found that new optical transitions and Raman-active phonons appeared in comparison with the perfect nanotube. Secondly, we calculated the resonance Raman excitation profile for all Raman-active phonons of the defective nanotubes and simulated their Raman spectra at specific laser excitation energies. The predicted high-intensity Raman lines can be used as spectroscopic signatures of the defective nanotubes. [source] Identification of hemes and related cyclic tetrapyrroles by matrix-assisted laser desorption/ionization and liquid secondary ion mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 12 2002Hyung-Sun Youn Mass spectrometry has proven to be a powerful technique applicable on trace amounts for the identification of known hemes and cyclic tetrapyrroles, and for providing critical information for the structure of new and novel versions. This report describes investigations of the practical limits of detection for such bioinorganic prosthetic groups, primarily by liquid secondary ion mass spectrometry (LSIMS) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS), including a survey of the utility of common matrices. The lower limit of detection under favorable conditions extends to low picomole amounts. Certain derivatization techniques, such as methyl esterification and chelation to zinc, both increase the sensitivity of analyses and provide spectroscopic signatures that enable heme/cyclic tetrapyrrole ions to be identified in the presence of contaminants. Copyright © 2002 John Wiley & Sons, Ltd. [source] | |||||||||||||