Far-UV region

The majority of detectors, which are employed for the measurement of absorption, employ UV glass (e.g. Suprasil). AU type S-5 photomultiphers possess sheaths of this material, so that they ought to be usable in the far UV region if N2 purging IS employed (to remove O2) (Tab. 4). 

The energy of electronic transitions corresponds to light in the visible, UV, and far-UV regions of the spectrum (Fig. 7.1). Absorption positions are normally expressed in wavelength units, usually nanometers (nm). If a compound absorbs in... 

The effect of formalin-treatment on the structural properties of RNase A was examined using circular dichroism (CD) spectropolarimetry. A brief introduction to CD spectropolarimetry is provided in Section 15.15.2 for those readers unfamiliar with this biophysical method. The secondary structure of RNase A consists of one long four-stranded anti-parallel p-sheet and three short a-helixes,44 which places RNase A in the a + p structural class of proteins. The effect of a 9-day incubation of RNase A (6.5mg/mL) in 10% formalin on the protein secondary structure was examined with CD spectropolarimetry in the far-UV region (170-240nm) as shown in Figure 15.6a. The resulting... 

The effect of heating on the structure of formalin-treated RNase A is shown in Figure 15.7a (far-UV region) and 15.7b (near-UV region). In both Figures 15.7a,b, trace 1 is the spectrum of RNase A (6.5 mg/mL) kept in 10% buffered formalin (pH 7.4) for 9 days and then analyzed at 23°C following removal of excess formaldehyde by fast dialysis. Trace 2 is the same sample after heated to 95°C at a rate of 5°C/min and allowing 10 min for temperature equilibration. 

The spectrum of tin emitted from a triggered spark source in the far UV region (17.5-200 nm) has been analysed26. The emission lines in this region may be useful for development of new analytical methods. 

A relative ratio between the 4/ and 4/ 5d-configuration levels energies specifies a sharply distinctive position of broad bands in the spectra of trivalent and divalent rare-earth ions, hi the TR + spectra, with the exception of Ce +, broad bands fall into a relatively far UV region and they yield only fine spectra in the visible and adjacent regions. In the spectra broad bands fall into the visible and near-UV regions. Thus in the case of TR + the f-d and /-/ transitions he close to each other and overlap. Three individual cases are distinguished in the TR + liuninescence spectra, namely broad bands due to d-f transitions, line IR spectra and a combination of bands and fines. 

In case there is a need to perform wavelength accuracy and photometric accuracy measurements for the far-UV region below 240 nm, there are new certified reference standards available from Stama Cell [18]. The wavelength standard is a solution of rare earth oxides solvated in dilute sulfuric acid. The standard exhibits well-characterized absorption bands at 210, 211, 222, 240, and 253 nm (Figure 10.13). The photometric accuracy standard consists of a series... 

The CD spectra in the far-UV region revealed that the pro-tyrosinase and acid-activated tyrosinase had similar secondary structures (Figure 40). On the other hands, the CD signal of acid-activated tyrosinase in the range of 280-290 nm, indicating that the tertiary and/or quaternary structure of the protyrosinase was changed by acid-treatment. On the basis of these results, we deduce that the intersubunit polar interaction is disrupted at pH 3.0, and that the tetrameric protyrosinase dissociates to dimmers. 

Figure 1. CD spectrum of SBA in the (a) far-UV and (b) near-UV regions. The lectin concentration was 0.046 mg/ml in the far-UV region and 0.48 mg/ml in the near-UV region. The light path length was 1 mm below 250 nm and 1 cm above 250 nm. The solid curves were constructed from four recordings each. The far-UV region was resolved into gaussian bands using the curve resolver. Solvent, CMF-PBS, pH 7.5. Bars indicate maximum deviation from mean. Comparable CD patterns were obtained using SBA, prepared by the method of Lotan et al.

Only peptide chromophores contribute to the far UV region of the CD spectra of proteins. 

While the far UV region has received the most attention in the study of protein CD, there are intrinsic chromophores in proteins which give nse to signals in the near U V (A. = 250-350 nm). These include the side chains of aromatic amino acids (tryptophan, Trp, tyrosine, Tyr, and phenylalanine, Phe) and the disulfide moiety of cystine. The exact position of these bands depends on the extent of exposure to the solvent, the solvent polarity and pH, and their proximity to other groups. The analysis of the near UV CD spectra of proteins has been reviewed [7, 8],... 

With many organic compoimds it reacts like OH (see below), abstracting H from alkyl groups and adding to centers of unsaturation. Because it absorbs only in the far-UV region, many of its rate constants have been measured by competition kinetics [7]. 

---