Resonance raman, ultraviolet

Ultraviolet resonance Raman Wide-line separation Wild type... 

Mo2(02CCH2).. Metal compounds with multiple metal-metal bonds such as Mo2(02CCH3)4 of symmetry, have attracted much experimental and theoretical attention focussed on the description of bonding and bond strength (46-48). Their electronic structure has been investigated experimentally by various methods such as resonance Raman, photoelectron spectroscopy, ultraviolet absorption and polarization studies of the matrix isolated sample (49-56). 

NMR, EPR, EXAFS, infrared, resonance Raman, and ultraviolet-visible spectroscopy should follow. Kinetic and thermodynamic information about the model complexes in comparison to that known for natural systems should be gathered. These concepts were updated in 1999 by Karlin, writing in reference 49. Model studies should provide reasonable bases for hypotheses about a biological structure and its reaction intermediates. Researchers should determine the model s competence in carrying out reactions that mimic metalloprotein chemistry. Using these methods and criteria, researchers may hope to exploit Cu-oxygen systems as practical dioxygen carriers or oxidation catalysts for laboratory and industrial purposes. 

Probing Metalloproteins Electronic absorption spectroscopy of copper proteins, 226, 1 electronic absorption spectroscopy of nonheme iron proteins, 226, 33 cobalt as probe and label of proteins, 226, 52 biochemical and spectroscopic probes of mercury(ii) coordination environments in proteins, 226, 71 low-temperature optical spectroscopy metalloprotein structure and dynamics, 226, 97 nanosecond transient absorption spectroscopy, 226, 119 nanosecond time-resolved absorption and polarization dichroism spectroscopies, 226, 147 real-time spectroscopic techniques for probing conformational dynamics of heme proteins, 226, 177 variable-temperature magnetic circular dichroism, 226, 199 linear dichroism, 226, 232 infrared spectroscopy, 226, 259 Fourier transform infrared spectroscopy, 226, 289 infrared circular dichroism, 226, 306 Raman and resonance Raman spectroscopy, 226, 319 protein structure from ultraviolet resonance Raman spectroscopy, 226, 374 single-crystal micro-Raman spectroscopy, 226, 397 nanosecond time-resolved resonance Raman spectroscopy, 226, 409 techniques for obtaining resonance Raman spectra of metalloproteins, 226, 431 Raman optical activity, 226, 470 surface-enhanced resonance Raman scattering, 226, 482 luminescence... 

Most of the early gas lasers emitted in the visible region. Continuous-wave (CW) lasers such as Ar+ (351.1-514.5 nm), Kr+ (337.4-676.4 nm), and He-Ne (632.8 nm) are now commonly used for Raman spectroscopy. More recently, pulsed lasers such as Nd YAG, diode, and excimer lasers have been used for time-resolved and ultraviolet (UV) resonance Raman spectroscopy. 

I. Harada and H. Takeuchi, Raman and ultraviolet resonance Raman spectra of proteins and related compounds, in Advances in Spectroscopy (R. A. H. Clark and R. E. Hester, eds.), Vol. 13, John Wiley, New York, 1986. 

Palaniappan V, Temer J (1989) Resonance Raman spectroscopy of horseradish peroxidase derivatives and intermediates with excitation in the near ultraviolet. J Biol Chem 264 16046-16053... 

Infrared spectroscopy is an important technique for studying acidity. Acidic OH groups can be studied directly. Probe molecules such as pyridine may be used to study both Bronsted and Lewis acidity since two forms of adsorbed probes are easily distinguished by their infrared spectra. Quantitative infrared spectroscopy may be performed by measuring the spectrum of acidic OH or probes adsorbed on thin, self-supporting wafers of the acidic solid. Other spectroscopic methods which may provide information in specific cases include Fourier Transform Raman spectroscopy, electron spin resonance spectroscopy, ultraviolet spectroscopy, and nuclear magnetic resonance spectroscopy. 

Valuable spectroscopic studies on the dithiolene chelated to Mo in various enzymes have been enhanced by the knowledge of the structure from X-ray diffraction. Plagued by interference of prosthetic groups—heme, flavin, iron-sulfur clusters—the majority of information has been gleaned from the DMSO reductase system. The spectroscopic tools of X-ray absorption spectroscopy (XAS), electronic ultraviolet/visible (UV/vis) spectroscopy, resonance Raman (RR), MCD, and various electron paramagnetic resonance techniques [EPR, electron spin echo envelope modulation (ESEEM), and electron nuclear double resonance (ENDOR)] have been particularly effective probes of the metal site. Of these, only MCD and RR have detected features attributable to the dithiolene unit. Selected results from a variety of studies are presented below, chosen because their focus is the Mo-dithiolene unit and organized according to method rather than to enzyme or type of active site. 

Nevertheless, a few reports of UV resonance Raman spectra of the purine nucleobases and their derivatives have appeared. Peticolas s group has reported the identification of resonance Raman marker bands of guanine, 9-methylguanine and 9-ethylguanine for DNA conformation [118, 144], In the process of doing that work, very rudimentary excitation profiles were measured, which yielded preliminary structures for two of the ultraviolet excited electronic states. Tsuboi has also performed UV resonance Raman on purine nucleobases in an effort to determine the resonance enhanced vibrational structure [94], Thus far, no excited-state structural dynamics for any of the purine nucleobases have been determined. 

Thus far, the only excited-state structural dynamics of oligonucleotides have come from time-resolved spectroscopy. Very recently, Schreier, et al. [182] have used ultrafast time-resolved infrared (IR) spectroscopy to directly measure the formation of the cyclobutyl photodimer in a (dT)18 oligonucleotide. They found that the formation of the photodimer occurs in 1 picosecond after ultraviolet excitation, consistent with the excited-state structural dynamics derived from the resonance Raman intensities. They conclude that the excited-state reaction is essentially barrierless, but only for those bases with the correct conformational alignment to form the photoproducts. They also conclude that the low quantum yields observed for the photodimer are simply the result of a ground-state population which consists of very few oligonucleotides in the correct alignment to form the photoproducts. 

In a sample containing a mixture of compounds, individual species may be resonance enhanced at different wavelengths. In some cases it may be possible to measure resonance Raman spectra from individual components in a mixture by selective excitation of specific absorption bands. Moreover, the assignment of resonance-enhanced vibrations provides detailed information about the local symmetry of the species. RRS has been used widely to characterize biological samples in which electronic transitions occur at visible excitation wavelengths, and commercial continuous wave lasers are readily available. Resonance Raman spectroscopic characterization of solid catalysts and adsorbed species has seen limited application. Many catalytic materials are white, but their electronic transitions often occur at ultraviolet wavelengths. With the availability of continuous wave and tunable, pulsed ultraviolet laser sources, we anticipate the application of RRS to catalysts will increase substantially. This expectation has motivated the present review. 

Li, C. and Stair, P.C. (1995) An advance in Raman studies of catalysts ultraviolet resonance Raman spectroscopy. Studies in Surface Science and Catalysis, 101 (11th International Congress on Catalysis -40th Anniversary, 1995, Pt B), 881-90. 

Since the publication of CHEC-II(1996), there has been little advance, with respect to ring-fused oxiranes, in experimental structural methods (e.g., nuclear magnetic resonance (NMR), ultraviolet (UV), and Raman spectroscopy). However, there has been considerable interest in the use of theoretical computational studies to probe structural and reactivity issues, particularly with regard to highly labile oxiranes fused to small rings. 

Ackers GK, Holt JM. Asymmetric cooperativity in a symmetric tetramer human hemoglobin. J. Biol. Chem. 2006 281 11441-11443. Jayaraman V, Spiro TG. Structure of a third cooperativity state of hemoglobin ultraviolet resonance Raman spectroscopy of cyanome-themoglobin ligation microstates. Biochemistry 1995 34 4511 515. 

Sureau F et al (1990) An ultraviolet micro-Raman spectrometer— resonance Raman-spectroscopy within single living cells. Appl Spectrosc 44(6) 1047-1051... 

Li, Y.-L., Leung, K. H., Phillips, D. L. Time-Resolved Resonance Raman Study of the Reaction of Isodiiodomethane with Cyclohexene Implications for the Mechanism of Photocyclopropanation of Olefins Using Ultraviolet Photolysis of Diiodomethane. J. Phys. Chem. A 2001, 105, 10621-10625. 

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