Structural Probes of Complex Fluids

The photonic force microscope may yield a means for proximal probe imaging within fluid-containing voids and structures such as vesicles and living cells. Some current limitations of the photonic force microscope include the potential for incorporation of optical artifacts when internal structures of optically complex samples (such as cells) are to be studied. Coupling of optical features into the images of such a microscope arises via the dependence of the optical trapping... 

Since many metal complexes bind to DNA, those that show luminescence in fluid media have the potential to act as probes of biological structure. Such a feature is particularly useful if the luminescent probe is site specific on the DNA chain. Complexes that can be chemically modified at the ligand periphery, or whose photophysical properties are sensitive to medium effects, have the best potential for use in biological applications. 

Flow (or streaming) birefringence is a non-destructive optical method, which may be used to indicate stress patterns in a flowing fluid or to probe the structure of the fluid. In certain classes of flows e.g. simple shearing) values of stress may be accurately determined by this method for more complex flows the matter is not quite as simple, as we shall discuss below. Stresses in deforming solids can also be measured by an analogous technique. ... 

We have seen that NMR can provide detailed molecular structure information. It is possible to join together or couple an HPLC instrument with an NMR spectrometer. The HPLC performs the separation of a complex mixture, and the NMR spectrometer takes a spectrum of each separated component to identify its structure. We now have a new instrument, an HPLC-NMR instrument. We call a coupled instrument like this a hyphenated instrument. The coupling of two instruments to make a new technique with more capabilities than either instrument alone provides results in a hyphenated technique or hybrid techniqne. HPLC-NMR is made possible with a specially designed flow probe instead of the standard static probe. For example, Bruker Corporation (www.brukerbiospin.com) has a flow probe for proton and C NMR with a cell volume of 120 pL. Complex mixtures of unknown alkaloids extracted from plants have been separated and their structures completely characterized by HPLC-NMR using a variety of 2D NMR experiments (Bringmann et al.). Only a simple aqueous extraction of the plant leaves, lyophilization, and dissolution in D2O were required for injection into the HPLC-NMR, saving time and resonrces. HPLC-NMR has been used for the analyses of metabolites in body fluids body fluid samples are very complex mixtures and are usnally of limited volume (Lindon et al.). 

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