Type I spectrum

Another spectral change was found w hen a cast film of C AzoCgN+Br was annealed and then moistened (Figure 13). The type I spectrum of the as-cast film changed to the type V spectrum (the broken-line spectrum in Figure 13) after heating above its phase transition (115°C[22]), and then immediately shifted to the type III spectrum within 30 sec in a 75% humidity condition at room temperature. The type III state seemed to be another metastable state in the annealed film because the moisture induced isothermal transition from the type III to the type I required a long period (e.g. 13 hours even at 75% humidity). 

The spectrum of di-cyclopentadienyltitanium dichloride is the simple type I spectrum that might be expected of a hypothetical hydrated divalent titanium salt. 

Another system that has received recent intensive study by both diffraction and spectroscopic methods is that of ethene on Pt(lll). In recent papers, Somorjai et al. have investigated the adsorption of ethene by diffuse LEED to give the unexpected result that the di-cr species [which on Pt(lll) gives an extreme type I spectrum] is adsorbed across threefold sites with... 

A recent study of ethene adsorbed on Fe(100) by Hung and Bernasek (48) showed adsorption as a di-cr species (type I spectrum) at 100 K, but with a soft-mode component at ca. 2720 cm-1 in addition to the stronger 2985-cm 1 absorption in the vCH2 region. When the temperature had been raised to 253 K, the spectrum largely changed to that probably indicative of a mixture of CH and a(CCH) species (see also Section IV.D). At 523 K, only adsorbed carbon remained on the surface. 

Additional work on Ru(0001) to that previously reviewed (17) includes a VEELS study on C2H4 and C2D4 by Sakakini et al. (218, 218a), which shows a type I spectrum at 170 or 130 K, either representing a mixture of di-tr and n species (two absorptions at 850 and 945 cm 1 for C2H4 raise the possibility of two adsorbed species) or a (no) metallocyclopropane structure. The spectrum is clearly that of ethylidyne at 220 K, as shown by VEELS (2890, 1360, 1120, 420 cm" ) (218), and at 240 K by RAIRS (2877 and 1340 cm" ) (219a). Similar VEEL spectra have been obtained in the presence of coadsorbed CO (220). The 300 K spectrum on Ru/A1203 (2888, 1350/1344, 1131 cm" ) is equally clearly from ethylidyne. 

The type I spectrum of the di-cr species has been found at low temperatures on most investigated crystal planes of Fe (234, 235), Ni, Ru, and Pt (Tables V and VI). The intermediate type I spectrum, which we have related to the (7ia) species, occurs on Fe(lll), Rh(lll), Ru(0001), and Pd(100). In the Ru(0001) and Pd(100) cases, however, different spectra have been obtained in different laboratories (17), leading to some uncertainty as to whether these type I patterns may alternatively arise from superimposed component spectra from di-rx and n species (17), or to experimentally variable contributions from impact-excited features (Section IV.B). Such species could therefore profitably be reinvestigated, and the higher resolution of RAIRS would be particularly valuable in this respect. 

Type I Cu(II) is the blue copper responsible for the unusually intense absorption at 614 nm in laccase. Its EPR spectrum is unusual with low g values and very small hyperfine splittings. Type II Cu(II) shows a more normal EPR spectrum and is thus responsible for the so called low field line in the EPR spectrum of laccase (in spite of considerable overlap with the type I spectrum). There are no optical absorptions which strongly depend on the oxidation state of the type II copper in laccase and it is thus considered transparent. It is well established89 that anions such as F- and N3 strongly bind to type II Cu(II) in laccase. In the case of F- binding91, the low field EPR line was split by the 19F nucleus, the enzyme was inactivated, and a very high binding constant measured. 

Using the data from the model systems above we found that the type-I spectrum (Figure 13.4a, heavy lines), based on its spectral shape and the sharply defined high absorptions (at 2925, 2852, and 1745 1465, 1375,... 

An IBSCA-spectrum (Fig. 4.48) consists of many peaks in the visible range (250-900 nm). Every peak can be related to an process of electron de-excitation of a sputtered particle from a higher to a lower state, for the more dominant peaks to the ground state. There are, in principle, two major types of peak family type I - photons emitted from excited sputtered secondary neutrals and type II - photons emitted from excited sputtered secondary ions (single charged). 

There are four disulfide bonds in short-chain (Type I) neurotoxins. This means that there are eight half-cystines. However, all Hydrophiinae toxins have nine halfcystines with one cysteine residue. An extra cysteine residue can be readily detected from the Raman spectrum as the sulfhydryl group shows a distinct S-H stretching vibration at 2578 cm" Some Laticaudinae toxins do not have a free cysteine residue as in the cases of L. laticaudata and L. semifasciata toxins. In long toxins (Type II) there are five disulfide bonds (Table III). 

In their pursuit of modeling Type I copper proteins, Kitajima et al. reported112 a rare, tetrahedrally coordinated complex (105), which displayed an EPR spectrum consistent with the presence of the unpaired electron in the dz2 orbital.1 They also isolated a square-pyramidal DMF adduct (complex (106)). They were successful in providing structural proof of a copper(II) complex (trigonal pyramidal) with C6F5S -coordinated complex (107), with CuN3S chromo-phore.113 The X-ray analysis (poor data set) of a closely similar complex with Ph3CS as the... 

Now for the next big step forward if they are not equivalent, then there is no reason for them to have the same chemical shift. Another big step and if they have different chemical shifts, they will couple to each other. In fact, in molecules of this type (i.e., that have an isolated CH2 in the region of a chiral centre) the likelihood is that the CH2 will be observed as a pair of doublets (see Spectrum 6.1). 

Many multiple copper containing proteins (e.g., laccase, ascorbate oxidase, hemo-cyanin, tyrosinase) contain so-called type III copper centers, which is a historical name (cf. Section 5.8 for type I and type II copper) for strongly exchange-coupled Cu(II) dimers. In sharp contrast to the ease with which 5=1 spectra from copper acetate are obtained, half a century of EPR studies on biological type III copper has not produced a single triplet spectrum. Why all type III centers have thus far remained EPR silent is not understood. 

The importance of P0 in PNS myelin has been clearly demonstrated. In P0 gene knockout experiments in mice [40], severe hypomyelination and a virtual absence of compact myelin in the PNS is observed. In humans, there are two disease states associated with mutations in the P0 gene Charcot-Marie-Tooth type I disease (see Ch. 38) and Dejerine-Sottas disease, both dysmyelinating diseases that exhibit a spectrum of severity depending on the particular mutation. 

Type I copper enzymes are called blue proteins because of their intense absorbance (s 3000 M-1 cm- ) in the electronic absorption spectrum around... 

Figure 12. Spectral change of the annealed film by moisture treatment, (a) CgAzoCioN+Br film was sealed in a quartz cell with 62% humidity after annealing. The type V spectrum (broken line) immediately moved to the type VI spectrum and then shifted to the type I absorption, (b) Humidity effect on time courses of the spectral change. Ao and A, are absorbance of 370 nm immediately and l min after stored in a sealed quartz cell, respectively.

Structural polymorphism has been already reported as a peculiar solid-solid phase transition with a large spectral shift in the cast film of CgAzoCioN+ Br (chapter 4). The type 1 spectrum was thermally transformed to the type VI spectrum and then backed to the type I by the isothermal moisture treatment. The reversible spectral change between the type I and VI is a good experimental evidence of Okuyama s prediction on the molecular packing. Since the type VI state is assumed to be a metastable state, the isothermal phase transition to the type I state is expected to be induced by some external stimuli. Water molecules adsorbed to cast bilayer films might act as an accelerator of the phase transition. 

Decisive informations on the mass-to-radius ratio can be provided by measuring the gravitational redshift of lines in the spectrum emitted from the compact star atmosphere. Very recently, redshifted spectral lines features have been reported for two different X-ray sources (Cottam et al. 2002 Sanwal et al. 2002). The first of these sources is the compact star in the low mass X-ray binary EXO 0748-676. Studying the spectra of 28 type-I X-ray bursts in... 

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