Environmental Engineering Reference
In-Depth Information
• While charge transfer complexes also give rise to colors, the colors are often too
intense to be used for quantitative measurement [
11
].
13.2.10 Dual Polarization Interferometry (DPI)
Dual polarization interferometry (DPI) is a highly versatile, powerful analytical
technique for biophysical characterization of proteins and other biomolecules. It
extends the typical dynamic measurements of conventional biosensors by including
an additional quantitative, submolecular, conformational measurement. DPI
delivers a unique perspective on biochemistry, linking conformational changes to
biochemical activity at a resolution normally associated with “big physics.”
DPI is an interferometry technique to derive dynamic information concerning
the thickness, density, and mass of a molecular layer. As well as mass-based affinity
and kinetic determinations possible with other label-free optical and acoustic
biosensor technologies, DPI additionally provides real-time data on the orientation
of the surface immobilized layer and any conformational changes involved upon
binding.
13.2.11 Nuclear Magnetic Resonance (NMR)
Nuclear magnetic resonance spectroscopy (NMR) was first developed in 1946 by
research groups at Stanford and M.I.T., in the USA. The radar technology devel-
oped during World War II made many of the electronic aspects of the NMR
spectrometer possible. With the newly developed hardware physicists and chemists
began to apply the technology to chemistry and physics problems. Over the next
50 years NMR developed into the premier organic spectroscopy available to
chemists to determine the detailed chemical structure of the chemicals they were
synthesizing. Another well-known product of NMR technology has been the Mag-
netic Resonance Imager (MRI), which is utilized extensively in the medical radi-
ology field to obtain image slices of soft tissues in the human body. In recent years,
NMR has moved out of the research laboratory and into the on-line process
analyzer market. This has been made possible by the production of stable perma-
nent magnet technologies that allow high-resolution 1H NMR spectra to be
obtained in a process environment.
NMR is a spectroscopic technique which relies on the magnetic properties of the
atomic nucleus. When placed in a strong magnetic field, certain nuclei resonate at a
characteristic frequency in the radio frequency range of the electromagnetic spec-
trum. Slight variations in this resonant frequency give us detailed information about
the molecular structure in which the atom resides.
The NMR phenomenon is based on the fact that nuclei of atoms have magnetic
properties that can be utilized to yield chemical information. Quantum mechanical
