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Raman Signatures (raman + signature)
Selected AbstractsRaman spectroscopy of nanostructures and nanosized materialsJOURNAL OF RAMAN SPECTROSCOPY, Issue 6 2007Gwénaël Gouadec Abstract The interest in micro and tip-enhanced Raman spectroscopy in analyzing nanosized and nanostructured materials, chiefly semiconductors, oxides and pristine or functionalized carbon nanotubes, is reviewed in the light of contributions to this Special Issue. Particular attention is paid to the fact that chemical reactions, size or shape distribution, defects, strain and couplings may add to nanodimensionality in defining the Raman signature. Copyright © 2007 John Wiley & Sons, Ltd. [source] Extent of thermal ablation suffered by model organic microparticles during aerogel capture at hypervelocitiesMETEORITICS & PLANETARY SCIENCE, Issue 10 2009M. J. Burchell Commercial polystyrene particles (20 ,m diameter) were coated with an ultrathin 20 nm overlayer of an organic conducting polymer, polypyrrole. This overlayer comprises only 0.8% by mass of the projectile but has a very strong Raman signature, hence its survival or destruction is a sensitive measure of the extent of chemical degradation suffered. After aerogel capture, microparticles were located via optical microscopy and their composition was analyzed in situ using Raman microscopy. The ultrathin polypyrrole overlayer survived essentially intact for impacts at ,1 km s,1, but significant surface carbonization was found at 2 km s,1, and major particle mass loss at ,3 km s,1. Particles impacting at ,6.1 km s,1 (the speed at which cometary dust was collected in the NASA Stardust mission) were reduced to approximately half their original diameter during aerogel capture (i.e., a mass loss of 84%). Thus significant thermal ablation occurs at speeds above a few km s,1. This suggests that during the Stardust mission the thermal history of the terminal dust grains during capture in aerogel may be sufficient to cause significant processing or loss of organic materials. Further, while Raman D and G bands of carbon can be obtained from captured grains, they may well reflect the thermal processing during capture rather than the pre-impact particle's thermal history. [source] New structural insights from Raman spectroscopy of proteins and their assembliesBIOPOLYMERS, Issue 4-5 2002George J. Thomas Jr.Article first published online: 9 MAY 200 Abstract Protein structure and stability are sensitive to and dependent on the local interactions of amino acid side chains. A diverse and important type of side-chain interaction is the hydrogen bond. Although numerous hydrogen bonds are resolved in protein 3-dimensional structures, those of the cysteine sulfhydryl group (S H) are elusive to high-resolution X-ray and NMR methods. However, the nature and strength of sulfhydryl hydrogen bonds (SH,X) are amenable to investigation by Raman spectroscopy. The power of the Raman method for characterizing SH,X interactions is illustrated by resolving the Raman SH stretching band for each of the eight cysteines per 666-residue subunit in the trimeric tailspike of icosahedral bacteriophage P22. The Raman sulfhydryl signatures of the wild-type tailspike and eight single-site cysteine to serine mutants reveal a heretofore unrecognized diversity of SH hydrogen bonds in a native protein. The use of Raman spectroscopy to identify the non-hydrogen-bonded state of the tyrosine phenoxyl group is also described. This unusual and unexpected state occurs for all tyrosines in the assembled capsids of filamentous viruses Ff and Pf1. The Raman spectral signature of the non-hydrogen-bonded tyrosine phenoxyl, which is characterized by an extraordinary Raman Fermi doublet intensity ratio (I850/I830 = 6.7), extends and refines the existing correlation for hydrogen-bonded tyrosines. Finally, a novel Raman signature for tryptophan in the Pf3 filamentous virus is identified, which is proposed as diagnostic of "cation,, interaction" involving the guanidinium group of Arg 37 as a cation donor and the indolyl ring of Trp 38 as a ,-electron acceptor. These studies demonstrate the power of Raman spectroscopy for investigating the interactions of key side chains in native protein assemblies. © 2002 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy) 67: 214,225, 2002 [source] Optical probing and imaging of live cells using SERS labelsJOURNAL OF RAMAN SPECTROSCOPY, Issue 1 2009Janina Kneipp Abstract During surface-enhanced Raman scattering (SERS), molecules exhibit a significant increase in their Raman signals when attached, or in very close vicinity, to gold or silver nanostructures. This effect is exploited as the basis of a new class of optical labels. Here we demonstrate robust and sensitive SERS labels as probes for imaging live cells. These hybrid labels consist of gold nanoparticles with Rose Bengal or Crystal Violet attached as reporter molecules. These new labels are stable and nontoxic, do not suffer from photobleaching, and can be excited at any excitation wavelength, even in the near infrared. SERS labels can be detected and imaged through the specific Raman signatures of the reporters. In addition, surface-enhanced Raman spectroscopy in the local optical fields of the gold nanoparticles also provides sensitive information on the immediate molecular environment of the label in the cell and allows imaging of the native constituents of the cell. This is demonstrated by images based on a characteristic Raman line of the reporter as well as by displaying lipids based on the SERS signal of the CH deformation/bending modes at ,1470 cm,1. Copyright © 2008 John Wiley & Sons, Ltd. [source] Non-invasive monitoring of commonly used intraocular drugs against endophthalmitis by raman spectroscopyLASERS IN SURGERY AND MEDICINE, Issue 4 2003K. Hosseini MD Abstract Purpose To develop a non-contact and non-invasive method for quantification of the local concentration of certain antibiotic and antifungal drugs in the eye. Study Design/Materials and Methods An integrated CCD-based Raman spectroscopic system designed specifically for ophthalmic applications was used to non-invasively detect the presence of ceftazidime and amphotericin B in ocular media. Specific Raman signatures of the above named drugs were determined for various concentrations that were injected through a needle in the aqueous humor of rabbit eyes in vivo. Raman spectra were subsequently acquired by focusing an argon laser beam within the anterior chamber of the eye. Results Compared to ocular tissue, unique spectral features of ceftazidime appeared near 1,028, 1,506, 1,586, and 1,641 cm,1. Amphotericin B exhibited its characteristic peaks at 1,156.5 and 1,556 cm,1. The amplitude of the spectral peak corresponding to these drugs (acquired by 1 second exposure time and 25 mW of laser power) were determined to be linearly dependent on their local concentration in the anterior chamber of the eye. Conclusions Raman spectroscopy may offer an effective tool to non-invasively assess the local concentration of the delivered drugs within the ocular media. This technique potentially could be used to investigate the pharmacokinetics of intraocular drugs in vivo either from a releasing implant or a direct injection. Lasers Surg. Med. 32:265,270, 2003. © 2003 Wiley-Liss, Inc. [source] Raman signatures of ligand binding and allosteric conformation change in hexameric insulinBIOPOLYMERS, Issue 5 2001Davide Ferrari Abstract Hexameric insulin is an allosteric protein that undergoes transitions between three conformational states (T6, T3R3, and R6). These allosteric states are stabilized by the binding of ligands to the phenolic pockets and by the coordination of anions to the His B10 metal sites. Raman difference (RD) spectroscopy is utilized to examine the binding of phenolic ligands and the binding of thiocyanate, p -aminobenzoic acid (PABA), or 4-hydroxy-3-nitrobenzoic acid (4H3N) to the allosteric sites of T3R3 and R6. The RD spectroscopic studies show changes in the amide I and III bands for the transition of residues B1,B8 from a meandering coil to an , helix in the T,R transitions and identify the Raman signatures of the structural differences among the T6, T3R3, and R6 states. Evidence of the altered environment caused by the ,30 Å displacement of phenylalanine (Phe) B1 is clearly seen from changes in the Raman bands of the Phe ring. Raman signatures arising from the coordination of PABA or 4H3N to the histidine (His) B10 Zn(II) sites show these carboxylates give distorted, asymmetric coordination to Zn(II). The RD spectra also reveal the importance of the position and the type of substituents for designing aromatic carboxylates with high affinity for the His B10 metal site. © 2001 John Wiley & Sons, Inc. Biopolymers (Biospectroscopy) 62: 249,260, 2001 [source] | ||||||||||