Fluorescence spectroscopy, characterisation

Kazarian et al. [281-283] have used various spectroscopic techniques (including FUR, time-resolved ATR-FHR, Raman, UV/VIS and fluorescence spectroscopy) to characterise polymers processed with scC02. FTIR and ATR-FTIR spectroscopy have played an important role in developing the understanding and in situ monitoring of many SCF processes, such as drying, extraction and impregnation of polymeric materials. 

Analytical absorption spectroscopy in the ultraviolet and visible regions of the elechomagnetic spectrum has been widely used in pharmaceutical and biomedical analysis for quantitative purposes and, with certain limitations, for the characterisation of drugs, impurities, metabolites, and related substances. By contrast, luminescence methods, and fluorescence spectroscopy in particular, have been less widely exploited, despite the undoubted advantages of greater specificity and sensitivity commonly observed for fluorescent species. However, the wider availability of spectrofluorimeters capable of presenting corrected excitation and emission spectra, coupled with the fact that reliable fluorogenic reactions now permit non-fluorescent species to be examined fluorimetrically, has led to a renaissance of interest in fluorimetric methods in biomedical analysis. 

The structural properties of the samples were characterised by X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRFS), nitrogen adsorption and 27Al MAS NMR. The acid properties of the zeolite were also investigated using n-butane cracking as a test reaction. 

The first is based on the structural evolution of the organic matrix with the characterisation of functional or structural groups. Fluorescence spectroscopy, infrared spectroscopy or RMN measurement have been developed to follow humic-like-substances in soil, and to study urban compost [8-13],... 

Aladan substitution of internal core amino-acid residues provides an approach to characterise the physical characteristics of protein cores. Steady-state fluorescence alone can provide initial insight to the immediate environment of Aladan in the protein core. However, time-resolved fluorescence spectroscopy can be used to understand variations in protein core composition and structure as a function of time through the characterisation of Aladan fluorescence intensity and /max changes that are caused by small fluctuations in the relative permittivity, e, of the protein interior with time (fs-ps timescale). Such spectroscopy is possible since fluorescence lifetimes, Tr, are typically in the ns range (see Section 4.5). Also, time-resolved fluorescence spectroscopy can be performed with non-covalently linked extrinsic fluorophores such as ethidium bromide (EtBr). This fluorophore intercalates between the bases of DNA or RNA double helix and in so doing acquires a substantial increase in (j) and hence fluorescence intensity at /max (595 nm). Should there be a disruption or collapse in double-helical structure, then intercalation fails and fluorescent intensity drops... 

Physicochemical characterisation was characterised of self-assembled nanoparticles based on glycol chitosan-bearing 5p-cholanic acid and their surfactant activity . Fluorescence spectroscopy and pulsed field gradient NMR (PFG-NMR) revealed information concerning the polydispersity of micelle polymers - chiral polymeric surfactants developed over the past decade for use as chiral selectors in the analytical separation of enantiomers . The authors suggest that polydispersity is a crucial factor in understanding the chiral interactions of these species. 

D. Baneijee, H. Rho, H. E. Jackson and R. N. Singh, Characterisation of Residual Stresses in a Sapphire-Fiber-Reinforced Glass-Matrix Composite by Micro-Fluorescence Spectroscopy, Comp. Sci. Technol. 61, 1639-1647(2001). 

A.M.K. Nilsson, D. Heinrich, J. Olajos, S. Andersson-Engels Near-infrared diffuse reflection and laser-induced fluorescence spectroscopy for myocardial tissue characterisation. Spectrochim. Acta A 53, 1901 (1997)... 

Fluorescence spectroscopy with lasers has been reviewed [3], in particular also the use of LIF for the characterisation of chemical systems [10]. 

S. Madhuri, N. Vengadesan, P. Aruna, D. Koteeswaran, P. Venkatesan and S. Ganesan, Native fluorescence spectroscopy of blood plasma in the characterisation of oral malignancy, Photochem. and Photobiol, 2003, 78(2), 197-204. 

Le Moigne M, Dufour E, Bertrand D, Maury C, Seraphin D, Jourjon F. Front face fluorescence spectroscopy and visible spectroscopy coupled with chemometrics have the potential to characterise ripening of Cabernet Franc grapes. Anal Chim Acta 2008 621 8-18. 

A new imidazolium functionalised cholestane-based receptor has been synthesised and characterised by Kim et al. A binding study of receptor (22) with various anions was assessed by UV-Vis and fluorescence spectroscopy in dry CH3CN and aqueous CH3CN solutions. Receptor (22) showed the highest selectivity toward H2PO4 which was a biologically vital... 

Fig. 11.10. Schematic illustration of fluorescence correlation spectroscopy. The autocorrelation function characterises the fluctuations of the fluorescence intensity its decay time expresses the average duration of a...

The application of analytical methods to speciation measurements in complicated systems has remained rather limited, despite the considerable technological progress during the past 25 years. The characterisation methods (e.g. spectroscopy, nuclear magnetic resonance) are often limited to the study of isolated compounds at relatively high concentrations. They, therefore, necessitate the prior employment of sophisticated separation and pre-concentration methods which introduce severe risks of perturbation. The trace analysis methods are often insensitive to the chemical form of the elements measured (e.g. atomic absorption, neutron activation). Those which possess sufficient element specificity (e.g. electron spin resonance, fluorescence, voltammetry) still require significant development before their full potential can be realised. 

Rhenium(I) pyrazolyl-diamine complexes appended with an anthracen-9-yl group (21) have been isolated and characterised [59], The binding of these complexes to double-stranded calf-thymus DNA has been investigated with absorption, fluorescence, circular dichroism, and linear dichroism spectroscopy. The results indicate that the complexes bind to the DNA molecules by intercalation of the... 

Weyermann, J., et al. (2004), Physicochemical characterisation of cationic polybutyl-cyanoacrylat—Nanoparticles by fluorescence correlation spectroscopy, Eur. J. Pharm. Biopharm., 58(1), 25-35. 

The latest experiments have used tunable laser induced fluorescence techniques to monitor the CN(A 2 ) fragments produced through photodissociation of ICN by a frequency quadrupled NdrYAG laser (X = 266.2 nm) or a flash lamp (X > 220 nm) ). They each concluded that virtually all the CN(JT) fragments are formed without vibrational excitation (Nj,=o-No= i > 1.00 0.02) but that they are rotationally excited with a distriTtution characterised approximately by a rotational temperature of 3000 K. While earlier time-of-fl ht photofragment spectroscopy experiments had been rationalised by assuming that CN(A 2 ) and CN(4 II)... 

The general principles involved in Raman spectroscopy are described in section 2.6. This method for characterising orientation is very similar to the fluorescence method, in that it involves both incident and emerging radiation, but the Raman process is a scattering process the re-radiation is essentially instantaneous. It is also similar to the infrared method in that it is associated with molecular vibrations and it has the same advantages of potential selectivity to a part of the polymer molecule or a phase of the polymer. 

In Table 3 the orientation information which can be obtained from these various structural techniques is summarised. This table also shows the part of the molecular structure which is being characterised, and some of the theoretical and experimental limitations of each method. A further technique, that of polarised fluorescence has been added. This technique is exactly analogous in its orientation aspects to Raman spectroscopy. The distinction between the two techniques lies in the fact that in the Raman effect, the lifetime of the process is of the order of the vibrational period ( 10 s) whereas fluorescence occurs after much longer occupancy of the transition state ( 10 s). 

If values of cos 0p and cos 0p are required, the relationship between the two distributions of orientations niust be known. This can only be established initially by comparison of the fluorescence results with those of other methods which give direct information about cos 0p and cos 0p, such as infra-red and Raman spectroscopy, and studies along these lines are in progress (see Section 5.3.2). If the relationship can be satisfactorily established the fluorescence method could become a much simpler method of quantitatively characterising molecular orientation in amorphous polymers than any of the other methods that offer information about both cos 0p and cos 0p. 

These monolayers (SAMs) are characterised by UV-Vis, fluorescence and Raman spectroscopy. This is made easy because of the presence of benzene cores within the acetylene and linker chains, these being made of poly(l,4-phenylene-l,3-butadiynylene) polymers. AFM then provides the topology, i.e. shapes (contours), thicknesses and aspect ratios (length and width), of the 2D S.AMs. This is done at all stages including those described below. 

Of the first 31 chlorina mutants characterised in the Copenhagen mutant collection, 9 were found to be characterised by unusually high F680/F740 and Fm/Fo ratios, when examined by low temperature fluorescence emission spectroscopy and room temperature fluorescence induction kinetics (1). Of these nine, four showed these properties when grown in the glasshouse at 17°C, but not at 22°C. This paper describes one of these temperature-sensitive mutants, chlorina- y which is the first barley mutant in which mutant leaf tissue returns to normal as the result of being shifted from the restrictive temperature. 

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