Cystine ultraviolet absorption

The ultraviolet absorption spectra of cysteine, cystine, and methionine are shown in Figs. 2, 3, and 11. The lowest energy (long-wave absorption band) transitions have been assigned (Mulliken, 1935 Walsh, 1953) as n — (f transitions. Transition assignments for disulfide spectra have been critically discussed in a recent paper by McGlynn et al. (1962). The... 

The ultraviolet absorption of these three sulfur-containing amino acids is of interest since that of cystine is appreciable in the 2500-3100 A,... 

Similar results were obtained with urinary albumin, the cystine content of which was found to vary with that of the plasma albumin of individual nephrotic subjects, although the decrease in cystine content of urinary albumin was distinctly less marked. Alving and Mirsky emphasized the importance of working with sufficiently purified fractions in studies on nephrotic albumin, citing Hewitt (141,1 ), who was unable to differentiate urinary albumin from normal serum albumin by specific rotations, refractive indices, or ultraviolet absorption spectra in highly purified preparations, and Widdowson (377), who also found no distinct differences on the basis of racemization curves, osmotic pressures, and specific refractions. 

Side chains of the three aromatic amino acids phenylalanine, tyrosine, and tryptophan absorb ultraviolet light in the 240- to 300-nm region, while histidine and cystine absorb to a lesser extent. Figure 3-13 shows the absorption spectrum of a "reference compound" for tyrosine. There are three major absorption bands, the first one at 275 nm being a contributor to the well-... 

In these and other papers by Anslow and coworkers the frequency at which absorption is complete, is used to calculate the energy required for the presumed related dissociation process (e.g. of a proton from a carboxyl group, fission of the S—S bond in cystine), using an equation relating the mass of the ion produced to the frequency of complete absorption (see also Anslow, 1932a, b). As the frequency at which complete dissociation commences has been obtained with complete disregard for the well-established selective absorption of saturated carboxylic acids and aminocarboxylic acids in the vacuum ultraviolet below 2000 A. (see Platt and Klevens, 1944, for a review of the available data), and the more easily accessible short wave bands of the aromatic amino acids (see Section III, 1), and as the theoretical basis of the equation concerned is open to serious criticism, this particular aspect of the work will not be considered further. 

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