Raman Spectroscopic Analysis

Most commonly, the units chosen for expressing wave munber in Raman spectra is inverse centimetres (cm ). Since wave length is often expressed in units of nanometres (nm), the formula above can scale for this imits conversion explicitly, giving 

The basic parts of Raman spectrometer are (i) excitation source, a laser beam, (ii) sample illumination system (usually an intense, polarized and coherent laser beam in the UV, visible, or near-infrared range) and light collection optics (collected with a lens and is sent through interference filter or spectrophotometer), (iii) wave length selector i.e. filter spectrophotometer and (iv) detector system. 

In the experimental arrangement, the sample is exposed to laser beam of suitable energy and the scattered light is collected. The wave lengths of these scattered light yield information about the status of the chemical functional group and hence the bond features of the sample under study. This nondestructive technique can analyse solid, liquid and gaseous samples. Needed sample amoimt is about 10 mg and in some specific cases the amount is as low as 10 to 50 ng. Liquid samples can run in aqueous solutions. 

---

It is a supposition that the )9-sheet structure of neurotoxin is an essential structural element for binding to the receptor. The presence of -sheet structure was found by Raman spectroscopic analysis of a sea snake neurotoxin (2). The amide I band and III band for Enhydrina schistosa toxin were at 1672 cm and 1242 cm" respectively. These wave numbers are characteristic for anti-parallel -sheet structure. The presence of -sheet structure found by Raman spectroscopic study was later confirmed by X-ray diffraction study on Laticauda semifasciata toxin b. 

The one residue most extensively studied is tryptophan. It is very easily modified, indicating that tryptophan residue is exposed 5-8). Raman spectroscopic analysis of a sea snake neurotoxin indicated that a single tryptophan residue is indeed exposed (2). The tryptophan residue lies in the important loop consisting of segment 4. Modification of the tryptophan residue induces the loss of AChR binding ability as well as the loss of toxicity 5-8). 

Vandenabeele, P., Bode, S., Alonso, A. and Moens, L. (2005). Raman spectroscopic analysis of the Maya wall paintings in Ek Balam, Mexico. Spectro-chimica Acta Part A 61 2349-2356. 

PA. Anquetil, C.J.H. Brenan, C. Marcolli and l.W. Hunter, Laser Raman spectroscopic analysis of polymorphic forms in microliter fluid volumes, J. Pharm. ScL, 92, 149-160 (2003). 

The evolution of lasers and detectors has enabled Raman spectra of high signal-to-noise ratio to be acquired in shorter time frames with lower laser powers, thus opening up new possibilities for Raman spectroscopic analysis of biological samples. Some applications have evolved to the point that it is no longer necessary to excise out the sample and bring it to the spectrometer for analysis. Rather, with fibre-optic probe technology, it is now possible... 

Anquetil, P.A. Brenan, C.J.H. Marcolli, C. Hunter, I.W. Laser Raman Spectroscopic Analysis of Polymorphic Forms in Microliter Fluid Volumes /. Pharm. Sci. 2003, 92, 149-160. 

Chan JW et al (2005) Raman spectroscopic analysis of biochemical changes in individual triglyceride-rich lipoproteins in the pre- and postprandial state. Anal Chem 77(18) 5870-5876... 

The inner volume and maximum working pressure of the high-pressure optical cell for the Raman spectroscopic analysis were 0.2 cm and 400 MPa, respectively. The cell had a pair of sapphire (or quartz) windows on both the upper and lower sides. The thermostated water was circulated constantly in the exterior jacket of the high-pressure optical cell. A ruby ball was enclosed to agitate the contents by the vibration from outside. 

T Takei, T Kato, T lijima, and M Higaki. Raman Spectroscopic Analysis of Wood and Bamboo Lignin. Mokuzai Gakkaishi 41 229-236, 1995. 

Raman spectrometers are used to carry out Raman spectroscopic analysis. The scheme of a Raman spectrometer defers from that of an infrared spectrometer. First of all is the sequence of light source and detector. These are not arranged in a parallel format as was done in infrared spectrometers. Instead the light source is built perpendicular to the detector. The scheme of the Raman spectrometer is shown in Figure 2.46. 

RAMAN SPECTROSCOPIC ANALYSIS OF THE MICROSTRUCTURES OF BUTADIENE-ACRYLONITRILE COPOLYMERS... 

R625 A. Hachikubo, Raman Spectroscopic Analysis of Natural Gas Hydrate , Jasco Report, 2011, 53, 6. 

Abrantes, L.M., Fleischmann, M., HUl, I.R. et al. (1984) An investigation of copper acetyhde films on copper electrodes. Part I electrochemical and Raman spectroscopic analysis of the film formation. Journal of Electroarudytical Chemistry, 164, 177. 

Fissure fillers have two characteristic Raman spectroscopic areas, which do not interfere with the emerald spectrum 1200-1700 cm (Fig. 18) and 2800-3100 cm The major Raman spectroscopic area for emerald lies between 100 and 1100 cm . The second area, although it displays more intense peaks than the first, may, however, be masked by a strong Raman fluorescence of the emerald. Therefore, when conducting a Raman spectroscopic analysis on emerald fillers, more emphasis should be given to the analytical area between 1200 and 1800 cm . In this area, interference with the emerald spectrum is minimized and good spectra of fissure fillers are obtained (Fig. 18). 

---