Fluorescence spectroscopy hydration

Tits, J., Stumpf, Th., Rabung, Th., Wieland, E. Fanghanel, Th. 2003. Uptake of trivalent actinides (Cm(III)) and lanthanides (Eu(III)) by Calcium silicate hydrates a wet chemistry and time-resolved laser fluorescence spectroscopy (TRLFS) study. Environmental Science and Technology, 37, 3568-3573. 

Protein rate processes are strongly affected by hydration. The dry protein shows greatly reduced internal motions, measured by Moss-liauer spectroscopy, neutron scattering, fluorescence spectroscopy, and other methods. Surface motions, monitored by spin probes or spin or Mossbauer labels, are similarly frozen in the dry protein. The following paragraphs comment on the appearance of motion characteristic of the hydrated protein and on the coupling between protein and solvent motions. 

Robertson EG, Hockridge MR, Jelfs PD, Simrais JP (2001) IR-UV ion-depletirai and fluorescence spectroscopy of 2-phenylacetamide clusters hydration of a primary amide. Phys Chem Chem Phys 3 786... 

Various experimental probes on the hydration-shell structure of Cm (aq) reported in literature have yielded a wide range of coordination numbers. To mention a few, EXAFS experiments measured primary hydration numbers of 9 or 7 (based on the truncation of the EXAFS fitting data) in 1M HCIO4 acid [114] and 10 in 0.25 M HCl acid [115]. High energy X-ray scattering (HEXS) experiments yielded a hydration number of 8.8 [114]. Time-resolved laser fluorescence spectroscopy (TREES) found coordination numbers between... 

Stumpf T, Fanghanel T and Grenthe 1 2002 Complexation of trivalent actinide and lanthanide ions by glycolic acid a trlfs study. J. Chem. Soc., Dalton Trans, pp. 3799-3804. Lindqvist-Reis P, Klenze R, Schubert G and Fanghl T 2005 Hydration of cm3+ in aqueous solution from 20 to 200 c. a time-resolved laser fluorescence spectroscopy study. The Journal of Physical Chemistry BimO), 3077-3083. PMID 16851323. 

Principal component analysis has been used in combination with spectroscopy in other types of multicomponent analyses. For example, compatible and incompatible blends of polyphenzlene oxides and polystyrene were distinguished using Fourier-transform-infrared spectra (59). Raman spectra of sulfuric acid/water mixtures were used in conjunction with principal component analysis to identify different ions, compositions, and hydrates (60). The identity and number of species present in binary and tertiary mixtures of polycycHc aromatic hydrocarbons were deterrnined using fluorescence spectra (61). 

A short excursion into the physics and spectroscopy of intermolecular interactions is intended to illustrate the effects of fluorescence spectra change on the transition of dye molecules from liquid solvents to solid environments, on the change of polarity and hydration in these environments, and on the formation of excited-state complexes (excimers and exciplexes). 

The application of Raman spectroscopy becomes more challenging when samples exhibit significant fluorescence (e.g., sediment samples which are brown in color). Other difficulties occur when hydrate samples contain occluded gas (e.g., the vC-H peak for methane gas overlaps with that for methane in the small cage of structure I hydrate). In this case, care must be given to assignment of the spectra (Hester, 2007). The latter example illustrates the strength of combining Raman and NMR spectroscopy to ensure correct interpretation of the data. 

Femtosecond spectroscopy has an ideal temporal resolution for the study of ultrafast water motions from femtosecond to picosecond time scales [33-36]. Femtosecond solvation dynamics is sensitive to both time and length scales and can be a good probe for protein hydration dynamics [16, 37-50]. Recent femtosecond studies by an extrinsic labeling of a protein with a dye molecule showed certain ultrafast water motions [37-42]. This kind of labeling usually relies on hydrophobic interactions, and the probe is typically located in the hydrophobic crevice. The resulting dynamics mostly reflects bound water behavior. The recent success of incorporating a synthetic fluorescent amino acid into the protein showed another way to probe protein electrostatic interactions [43, 48]. 

The compressibility of a protein may also be obtained from fluorescence line-narrowing spectroscopy at 10 K low temperatures. Under these conditions one does expect the hydrational changes not to play a very prominent role. Nevertheless the compressibilities that are obtained under such conditions are of the same order of magnitude as those obtained at ambient conditions [34]. This points to important contributions from the cavities to the compressibility and the thermal expansion. The observed pressure-induced amorphization in inorganic substances [35], liquid crystals [36], synthetic polymers [37,38] and starch [9] also support this hypothesis. 

In a series of papers (24-29) Eicke and co-workers reported results of thorough studies performed on inverse micellar systems involving hydrocarbons such as benzene or isooctane and surfactants such as AY or AOT aerosols. Dielectric, conductance, ultracentrifugation, NMR, light scattering, fluorescence depolarization and photon correlation spectroscopy techniques were used. The main conclusions arrived at are the following ones, as expressed in C29). For water-to-AOT molar ratios smaller than 10, water-in-isooctane systems consist of dispersions of hydrated soap aggre-... 

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