Intermolecular/intramolecular interactions spectra

Dielectric measurements are carried out on PPOA and PPODG. The dielectric spectrum of PPOA in the bulk presents a prominent glass-rubber relaxation followed by a subglass absorption. The low-molecular-weight compound only exhibits a prominent glass-liquid absorption followed by a diffuse and weak subglass relaxation. This behaviour cannot be explained in terms of only intramolecular interactions, and therefore intermolecular interactions must play an important role in this process. 

A vibrational (infrared or Raman) spectrum of a molecule consists of vibrational modes (resulting from the interaction of two or more different vibrations of neighboring bonds). These absorption (IR) or scattering (Raman) modes provide information about features such as the chemical nature (e.g. bond types and functional groups) and molecular conformation (e.g. irons and gauche). They also provide information about the individual molecular bonds (intramolecular interactions) and the interactions between molecules (intermolecular effects). 

Two-dimensional infrared (2D IR) spectroscopy is a recent novel technique based on time-resolved IR spectroscopy. The spreading out of IR spectra over two dimensions simplifies complex spectra with overlapping peaks. Correlation of such peaks may identify or eliminate specific intermolecular and intramolecular interactions. Such correlations can assist in assigning peaks to particular vibrational modes. In 2D IR, a system is excited by an external perturbation, which induces a dynamic fluctuation of the IR spectrum. A correlation analysis is applied to the... 

Both intramolecular force constants are lowered somewhat through complex formation (Table 6). As expected this effect is larger in the proton-donor than in the proton-acceptor molecule. In Table 7 we present calculated and experimental data on the vibrational spectrum of (HF)2. General agreement is obtained. The most remarkable feature is the strict separation of intra- and intermolecular modes on the frequency axis. Hydrogen bond formation is a weak interaction compared to the formation of a chemical bond hence, the normal frequencies are well separated. However, Hartree-Fock calculations of bond stretching force constants... 

Fluorescence resonance energy transfer (FRET) is a technique that has been used to measure distances between pairs of proximal fluorochromes. A suitable pair consists of a donor fluorochrome, which has an emission spectrum that significantly overlaps with the absorption spectrum of an acceptor fluorochrome (2). With the availability of monoclonal antibodies to many cell-surface determinants, intramolecular distances between nearby epitopes and intermolecular distances between adjacent cell-surface macromolecules can be investigated to analyze molecular interactions influencing important cellular events. Such monoclonal antibodies can be conjugated to fluorescein-isothiocyanate (FITC) as the donor, and either tetramethyl-rhodamine-isothiocyanate (TRITC) or phycoerythrin (PE) as the acceptor. 

The vibrational spectrum of a molecule is determined by its three-dimensional structure and its vibrational force field. An analysis of this [usually infrared (IR) and Raman] spectrum can therefore provide information on the structure and on intramolecular and intermolecular interactions. The more probing the analysis, the more detailed is the information that can be obtained. 

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