Laser photo-CIDNP technique

Some features of the laser photo-CIDNP method will now be summarized. We have shown that hy employing a dye as sensitizer nuclear spin polarization can be generated in native proteins. When flavins are used as dyes nmr lines of Tyr, His, and Trp residues can be selectively enhanced when these residues are accessible to the photo-excited dye. Thus, the method constitutes a "surface probe" with the very high resolution of the nmr technique, which is capable of resolving lines due to individual residues. Large enhancements, often of the order of a magnitude or more, are translated in considerable time savings. 

R133 S. W. Homans, Conformational Analysis in Solution by NMR , p. 947 R134 J. F. G. Vliegenthart and H.-C. Siebert, Carbohydrate-Protein Interactions Use of the Laser Photo Chemically Induced Dynamic Nuclear Polarization (CIDNP) - NMR Technique , p. 1025... 

Important mechanistic insights have been obtained in the last 5 years, particularly owing to the availability of such modern techniques as laser-flash time-resolved transient absorption spectroscopy [22,23], photo-CIDNP [21c, 24], and so on. It is thus the particular purpose of this review to analyze this recent work on mechanisms for photodecomposition of iodonium and sulfonium salts, and to evaluate its implications for practical applications of onium salt photochemistry. 

Carbohydrate-Protein Interactions Use of the Laser Photo Chemically Induced Dynamic Nuclear Polarization (CIDNP)-NMR Technique... 

In 1960 s, CIDEP was less popular than CIDNP because CIDEP did need much faster measuring techniques than CIDNP. This is due to much faster relaxation times (usually less than 1 /r s) of polarised electron spins than those (usually a few second for protons) of nuclear spins. In 1968, Smaller et al. [2] observed a population inversion for the cyclopentyl radical with a 2-MHz ESR apparatus coupled with a 15 MeV electron beam with pulse duration of 0.5 -4.0 /z s. The response time of the system corresponded to a time constant of 1.6/z s. In 1970, Atkins et al. [3] obtained the photo-CIDEP for the ketyl radical from benzophenone in paraffin solvents with a 2-MHz ESR apparatus coupled with a 20-ns laser flash. Under favorable chemical conditions, Wong and Wan [4] demonstrated that the photo-CIDEP for some semiquinone radicals in alcohol solvents could be observed with a commercial ESR spectrometer having a 100-kHz modulation unit and a custom-designed rotating sector giving light pulses. 

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