Infrared spectroscopy biochemical applications

The application of NIR spectroscopy has been further stimulated by the development of NIR diffuse reflectance techniques which are widely used in the analysis of agricultural, pharmaceutical, biochemical and synthetic polymer materials (Siesler, 1991). The rapidly increasing use of NIR spectroscopy is illustrated in the book Making Light Work Advances in Near infrared spectroscopy , edited by Murray and Cowe (1992) as well as in the Handbook of Near-Infrared Analysis by Bums and Ciurcak (1992). 

T. Theophanides (Ed.), Fourier Transform Infrared Spectroscopy Industrial, Chemical and Biochemical Applications, D. Riedel Publishing Company, Dordrecht, The Netherlands, 1984. 

Y. Nishimura, A.Y. Hirakawa and M. Tsuboi, in R.J.H. Clark and R.E. Hester, (Eds.) Advances in Infrared and Raman Spectroscopy, Heyden Son, London, 1978 P.R. Carey, Biochemical Applications of Raman and Resonance Raman Spectroscopies, Academic Press, New York, 1982 (and references therein). 

All these advantages explain why today most infrared experiments on biological samples are performed with FT-IR spectrometers. Partial exceptions are time-resolved studies, and the specied techniques employed there are discussed elsewhere in this volume (see [19]). Apart from the book already mentioned on FT-IR spectroscopy in which a special chapter is dedicated to biochemical and biomedical applications including instrumental and sampling aspects, several other useful guides for both the general application of infrared spectroscopy and the more specialized field of biomedical infrared spectroscopy have appeared. " ... 

The phenomenon of surface-enhanced infrared absorption (SEIRA) spectroscopy involves the intensity enhancement of vibrational bands of adsorbates that usually bond through contain carboxylic acid or thiol groups onto thin nanoparticulate metallic films that have been deposited on an appropriate substrate. SEIRA spectra obey the surface selection rule in the same way as reflection-absorption spectra of thin films on smooth metal substrates. When the metal nanoparticles become in close contact, i.e., start to exceed the percolation limit, the bands in the adsorbate spectra start to assume a dispersive shape. Unlike surface-enhanced Raman scattering, which is usually only observed with silver, gold and, albeit less frequently, copper, SEIRA is observed with most metals, including platinum and even zinc. The mechanism of SEIRA is still being discussed but the enhancement and shape of the bands is best modeled by the Bruggeman representation of effective medium theory with plasmonic mechanism pla dng a relatively minor role. At the end of this report, three applications of SEIRA, namely spectroelectrochemical measurements, the fabrication of sensors, and biochemical applications, are discussed. 

Most of our knowledge of cuticle-surface structure and ultrastructure has been derived from the application of physical techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS), secondary ion mass spectroscopy (SIMS), and infrared spectroscopy (IR). In addition, recent biochemical studies have provided the essential chemical data (lipids and proteins) required for modeling the surface structure [42,43]. 

This volume presents a cross section of recent advances in the development of novel chemical and biochemical sensors for on-line monitoring and control applications in the environmental, clinical, and bioprocess areas. These chapters illustrate how many of the key challenges for continuous monitoring are being addressed. The methods discussed include optical techniques ranging from near-infrared spectroscopy to lifetime-based phase fluorometry biosensors ranging from optical immu-nosensors to enzyme-electrodes as well as electrochemical, acoustic, and plasmon resonance techniques. 

McKelvie, 2008). Detection methods have included UV/Vis spectroscopy (the largest number of applications for its robustness, versatility, simplicity, and low cost), luminescence and chemiluminescence (CL) (which offer low detection limits and high sensitivity, being therefore especially favored for biological, biochemical, and trace analysis), atomic absorption and emission spectroscopy (which benefit enormously from automated sample pretreatment, used for matrix removal and analyte accumulation), electrochemistry (pH, fluoride ion selective electrodes, stripping voltammetry and conductivity), turbidimetry, vibrational spectroscopy (Fourier transform infrared spectroscopy [FTIR] and Raman) and mass spectrometry. 

Raman spectroscopy failed to live up to its original expectation when the technique was discovered. This was due to instrumental problems, high cost of the instrument, and the fluorescence problem. However, with improvement in instrumentation, the use of a near infrared laser with FT-Raman, the introduction of fiber optics, the number of applications (some of which were discussed in Chapter 3) has escalated. The applications are expanded in this chapter, which deals with materials applications involving structural chemistry, solid state, and surfaces. Additional applications are presented in Chapter 5 (analytical applications), Chapter 6 (biochemical and medical applications) and Chapter 7 (industrial applications). 

As mentioned above, the most informative method to study biochemical reactions would be time-resolved infrared difference spectroscopy. However, because the spectral changes are very small, all techniques require signal averaging over many reaction cycles. This limits application of the techniques to thermally reversible photoreactions. If such systems are in addition stable enough, the photoreaction can be triggered by thousands of flashes. 

Near-infrared absorption spectroscopy is increasingly used in agriculture, food science, medicine, fife sciences, pharmaceuticals, textiles, general chemicals, polymers, process monitoring, food quality control and in clinical in vivo measurements [215, 216]. The increase in popularity is largely due to the availability of miniaturised NIR-spectrometers by a variety of vendors (e.g. Ocean Optics Inc.). The most promising applications of NIR-absorbance spectroscopy clearly lie in process control, because of the relatively low complexity of the sample in chemical and biochemical processes, e.g. compared to biological tissues. Also in food quality control... 

This article will concern itself only with devices that involve a chemical or biochemical transduction mechanism to generate the analytical information, with the processes occurring in a membrane or layer attached to the probe in such a manner that the analytical information can be accessed electronically from the outside world. This covers sensors that are for single use and for continuous monitoring because the basic chemistry and sensor configuration used are very similar for a particular application. Hence, the article does not cover techniques such as open-cell Fourier transform infrared or remote fiber spectroscopy, which can be used to sense the chemical nature of the environment without involving the use of a bona fide sensor. 

Rinnan, R. and Rinnan, A. (2007). Application of near infrared reflectance (NIR) and fluorescence spectroscopy to analysis of microbiological and chemical properties of arctic soil. Soil Biol. Biochem., 39,1664-1673. 

---