1162 BLYTH : TXE ULTRA-VIOLET ABSORPTION SPECTRUM OF CXX.-Thc Ultrcc-violct rlbsoiptiou SpectrwL of Protez'ds in Relcction to Tyrosiiie, By A. JvYNTEIl BLYTH. T m apparatus employed in the investigation of the ultra-violet absorption spectrum of proteids consists of a large quartz prism made of two halves of right and left hand rotation respectively. A double quartz slit is used, as it possesses the advantage that two spectra are taken one above the other, one with a wide, the other with a narrow slit, so that when it is necessary to use a slit wide enough to blur the lines, the narrower slit will give the metallic lines sharply defined, and thus enable the position of any absorption bands to be measured. The source of light is a powerful spark produced by a large coil charged either from storage batteries or from the main, the coil is provided with a Wehnelt's brea.k, and one Leyden jar is used as a condenser.The optical train is quartz, and the image is thrown by a lens of 12 inches focal length on to a photographic film placed at aPROTEIDS IN RELATION TO TYROSINE. 1163 proper angle. The tube bearing the slit is passed through a hole in the door of a dark room in which the instrument is placed. The poles used have been various : cadmium, cadmium and nickel, nickel and iron, nickel and copper. To obtain an interpolation curve, poles made of an alloy of mercury, zinc, mdmium, and tin were em- ployed, n photograph being taken of the metal under examination with tho centre of the slit blotted out by a screen; on the same film, the spectrum of the alloy was nest taken, using a second screen so nrrnnged that the spectrum would occupy the blank space left by the first.Since all the wave-lengths of cadmium, mercury, zinc, and tin in the ultra-violet are well known, the spectrum of the alloy with its very numerous lines acted as a nntural scale. The liquids under examination have been ex- amined in ordinary cells closed 1)y quartz plates, but as the cleansing of these cells was found to be troublesome and tedious, the author devised a special absoiaption cell which promises to furnish important aid in researches of this kind. The cell consists of a block of quartz (a) cut into suc- cessive steps, the faces of the steps and the back are perfectly parallel and highly polished, the cell is completed by a quartz plate in front (b), the sides being of ground glass, a metal frame pro- vided with screws acting on small plates of instal, ,securely presses the plates of glass and quartz together, the top is closed with a glass plate, b J which is kept in place by a screw.The steps in the preseut cell are cut so as to give successive thicknesses of 1, 2, 4, 8, and 16 mm. The cell is supported on a stand capable of moving by rack-work. The photographic slide is similarly moved by rack-work. Five photographs on the same film can thus be taken in less than 5 minutes. If other thicknesses are required, they can be obtained in the ordinary way. According to Soret, diluted eggalbumin gives a single absorption band of wave-lengths 2880-2650. Hartley (Trans., 1887, 51, 69) confirms this statement, giving the band in wave-lengths as 2948-2572.The author has investigated the absorption spectrum of egg-albumin, ~erum-albumin, animal casein, and vegetable casein, as well as. of Witte's peptone, and also finds a single band. * The cell was constructed by Mr. Hilger, of Stanhope Street.1164 BLYTH : THE ULTRA-VIOLET ABSORPTION SPECTRUM OF 3439-3766 3509-3784 3509 -3766 3509-3766 The egg-albumin, purified by frequent precipitation, was diluted and filtered through several hardened filter papers, and ultimately an almost limpid solution obtained. A fractional part of the solution was evaporated on a platinum dish until i t ceased to lose weight, and the residue ignited and weighed; the solution was then diluted until it attained the strength desired. A similar process was adopted with both vegetable casein, legurnin, and sernm-albumin.It mas found that the absorption bands of these substances differed quantitatively rather than essentially in character. The following are the measurements obtained with solutions of egg-albumin and Witte's peptone, it being understood that, although mave-lengths in four 29SO- 2655 28 50-26 13 2850-2655 2850-2655 0 figures are given, the wave-length is taken from a definite metallic line bordering the absorption band ; in point of fact, the bands are never so definite, being diffuse a t the edges, Solution of egg-albumin in wcctei. (1 C.C. = 1.52 nzilligrccm of nlbzcmin). Oscillation Absorption Spcc trulll lmud. ellds. I in mm. 20 15 10 5 2415 2405 2385 2360PROTEIDS IN RELATION TO TYROSINE.1165 Solution of Witte's peptone in water (1 C.C. = 3.14 nzilligrccrns of p@one). Thickness of film i n mm. 20 35 10 5 ~ ~~ Oscillation fr equc n cie s . l / A . ~~ Absorption band. A. 3478-3783 3478-3538 3478-3538 34n-353a 2875-2643 2875-2826 2875-2826 2875-2826 ~~ Spectrum ends. A. 2260 2260 2258 2256 There are, however, quantitative differences between the different absorption spectra. Solutions containing equal amounts of nitrogen give absorption spectra of unequal length, Witte's peptone extending farthest into the ultra-violet, then come, in succession, legumin, egg- albumin, serum-albumin, and an alkaline solution of casein. Each of these substances may be made to yield tyrosine by appro- priate treatment.Solution of tplrosine ivt water (1 C.C. = 0.256 9?ziUiqmm of tyrosine). Thickness of film in n i m 16 8 4 2 1 Oscillation frequencies. 1/A. 3471-3na 3551-3731 Absorption band. A. Spectrnm ends. A. 2405 2360 2305 2272 2272 Solution of tyrosine in watw (I c,c. = 0.126 nailligrana of tglrosine). Thickness of film in nim. 16 10 8 5 4 2 1 Oscillation frequencies. 1 /A. Absorption band. A. 3470-3784 3509-3571 3558-3676 3558-3676 2882-2643 2850-2680 2810-2720 2810-2750 Faint baud Spectrum ends. A. 2377 2345 2335 2335 2315 2315 2305 The chief features of these absorption bands are indicated in the VOL LXXV. 4 1 curves on p. 1164.1166 THE ULTRA-VIOLET ABSORPTION SPECTRUM OF PROTEIDS. It is thus seen that the absorption spectrum of tyrosine is practically identical with that of the proteids enumerated.The author has little doubt that the single absorption band given by the various vegetable and animal albumins is due to the fact that tyrosine enters into their structure. Albumoses and Gelatin. Schrotter (Monatsh., 1893, 14, 612) has described an albumose possessing very definite properties, Briefly, it is prepared by acting on an acidified solution of Witte’s peptone with zinc dust, filtering, evaporating to dryness in a vacuum at the ordinary temperature, taking up with methylic alcohol, in which it is soluble, and reprecipi- tating with ether. The albumose may be obtained pure by precipi- tating several times. It contains C = 51.0, N = 16.8, H = 6.4, S = 1.1 per cent., and gives all the ordinary reactions of an albumin. This substance was dissolved in water, diluted, and a series of absorp- tion spectra taken from extinction of most of the ultra-violet to almost perfect transparency, but no selective absorption could be discovered. A pathogenic toxalbumin from diphtheria, submitted to the author by Prof. Sidney Martin, gave the usual absorption band of albumin. A toxalbumin from a case of ulcerative endocarditis, also strongly poisonous, and submitted by Prof. Martin, gave a continuous spectrum. Gelatin from various sources also failed to show selective absorption. It therefore seems to the author that proteids might be divided conveniently, from a chemical standpoint, into those which show the tyrosine absorption band and those in which the band is absent-a division which is correlated with a profound difference in molecular composition.