Orientation fluorescence spectroscopy

Polarized Raman and fluorescence spectroscopies, NMR and X-ray diffraction allow the determination of at least (P2) and (P4) for uniaxial systems. This is a great advantage since the shape of the orientation distribution can then be estimated [7], even if not all the coefficients of the ODF s expansion are known. While P2 has fixed boundary limits, those of (P4) depend on the (P2) value such as... 

In fluorescence spectroscopy, the orientation distribution of the guest probe is not necessarily identical to the actual orientation of the polymer chains, even if it is added at very small concentrations (i.e., a probe with high fluorescence efficiency). As a matter of fact, it is generally assumed that long linear probes are parallel to the polymer main chain, but this is not necessarily the case. Nevertheless, if the relation between the distribution of the probe axes and those of the polymer axes is known, the ODF of the structural units can be calculated from that of the probe thanks to the Legendre s addition theorem. Finally, the added probe seems to be mainly located in the amorphous domains of the polymer [69] so that fluorescence spectroscopy provides information relative to the noncrystalline regions of the polymeric samples. 

It should be noted that the dynamics studied by fluorescence methods is the dynamics of relaxation and fluctuations of the electric field. Dipole-orientational processes may be directly related to biological functions of proteins, in particular, charge transfer in biocatalysis and ionic transport. One may postulate that, irrespective of the origin of the charge balance disturbance, the protein molecule responds to these changes in the same way, in accordance with its dynamic properties. If the dynamics of dipolar and charged groups in proteins does play an important role in protein functions, then fluorescence spectroscopy will afford ample opportunities for its direct study. 

It is anticipated that orientational dynamics of a host-guest complex produced by molecular recognition are different from those of a host or guest. Therefore, time-resolved fluorescence spectroscopy under TIR conditions has a possibility to sense molecular recognition at a water/oil interface. The system studied is a model of flavoenzymes as shown in Figure 12.9. 

In order to understand the dynamics of the solvent fluctuation, many experimental as well as theoretical efforts have been made intensively in the last decade. One of the most convenient methods to observe solvent reorganization relaxation processes within the excited state molecule is time resolved fluorescence spectroscopy. By using time resolved techniques a time dependent fluorescence peak shift, so ( ed dynamic Stokes shift, has been detected in nanosecond picosecond >, and femtosecond time regions. Another method to observe solvent relaxation processes is time resolved absorption spectroscopy. This method is suitable for the observation of the ground state recovery of the solvent orientational distribution surrounding a solute molecule. 

Studies of TM residue accessibility to water-soluble sulfhydryl-reactive compounds has allowed Javitch and coworkers to gain evidence that P2-AR activation also involves a conformational rearrangement of TM VI (123), whereas detailed fluorescence spectroscopy studies by Kobilka and coworkers indicated that the helical movements occurring with P2-AR activation are almost identical to those for rhodopsin, that is, a counterclockwise rotation (when viewed from the extracellular surface of the receptor) of both TM III and TM VI, with a tilting of the cytoplasmic end of the latter toward TM V (74,124). The importance of the orientation of TM VI, which is stabilized by interhelical interactions with TM V, comes from studies of the arARs, which showed that mutation of either the... 

A completely different behaviour is observed for evaporated films on oxidic substrates at room temperature [21,22]. UV-Vis, IR, and fluorescence spectroscopy show, that the long axes of 4T molecules are oriented mainly perpendicular to the (silica) surface normal for monolayer coverages. This can be deduced from a dichroism D = = 3 with e as molar absorption... 

The application of total internal reflection fluorescence spectroscopy (TIRF) by this laboratory to the study of protein adsorption at solid-liquid interfaces is reviewed. TIRF has been used to determine adsorption isotherms and adsorption rates from single-and multi-component protein solutions. Initial adsorption rates of BSA can be explained qualitatively by the properties of the adsorbing surface. Most recently, a TIRF study using monoclonal antibodies to probe the conformation of adsorbed sperm whale myoglobin (Mb) elucidated two aspects of the Mb adsorption process 1) Mb adsorbs in a non-random manner. 2) Conformational changes of adsorbed Mb, if they occur, are minor and confined to local regions of the molecule. Fluorescence energy transfer and proteolytic enzyme techniques, when coupled with TIRF, can characterize, respectively, the conformation and orientation of adsorbed Mb. 

C and PMMA at +105°C. Also called transition. See orientation and glassy state processing via fluorescence spectroscopy thermomechanical analysis. 

Electron spectroscopy for chemical analysis (ESCA) [9] and Fourier transform infrared (FTIR) spectroscopy [10] with attenuated total reflectance (ATR) can also be used for routine surface studies. FTIR spectroscopy is known to have the sensitivity to determine the average orientation and reorientation of interfacial chains. But it does not directly provide information on the motion itself. The mobility of a solute in the neighborhood of an alkyl chain can be measured by fluorescence spectroscopy [11]. 

In a large portion of routine and discovery-oriented analyses, mass spectrometry (MS) is used as a qualitative technique. The obtained qualitative data enable detection and structural elucidation of molecules present in the analyzed samples. However, modern chemistry and biochemistry heavily rely on quantitative information. In biochemistry it is often sufficient to conduct quantification of analytes in biofluids every few hours, days, or even weeks. In the real-time monitoring of highly dynamic samples, it is necessary to collect data points at higher frequencies. When it comes to selection of techniques for quantitative analyses, especially in the monitoring of dynamic samples, MS has not generally been favored. In fact, the performance of MS in quantitative analysis is worse than that of optical spectroscopies - especially, ultraviolet-visible (UV-Vis) absorption and fluorescence spectroscopy. 

Holt A, Koehorst RBM, Killian JA (2009) Tilt and rotation angles of a transmembrane model peptide as studied by fluorescence spectroscopy. Biophys J 97(8) 2258-2266 Monticelli L, Tieleman DP, Fuchs PFJ (2010) Interpretation of H-NMR experiments on the orientation of the transmembrane helix WALP23 by computer simulations. Biophys J 99(5) 1455-1464... 

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